Menu
CS

Search

Persons

prof. Ing. Jiří Lettl, CSc.

All publications

Comparison of Estimation Techniques for Railway Traction Vehicle Wheel Slip Control

  • DOI: 10.1109/PIERS59004.2023.10221240
  • Link: https://doi.org/10.1109/PIERS59004.2023.10221240
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Power semiconductor converters of railway traction vehicles are controlled by sophisticated regulators. They must respond immediately and with high dynamics to changes in adhesion conditions on the track to utilize the available adhesion. This is the task of the wheel slip controller. Wheel slip controllers for railway traction vehicles are developed for many tenths of years, and many methods based on different principles have been developed. The principle of the slip controller that can fulfil the asked requirement estimates an adhesion characteristic slope in an operating point. These types of slip controllers can run at any part of the adhesion characteristic and ensure that the operating point is in the stable area of the adhesion characteristic for most of the operating time.

Efficiency Analysis of the 25 kV / 50 Hz Traction Network with Static Frequency Converters

  • Authors: Mlynařík, L., Hebelka, V., Novák, J., Sadílek, O., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Proceedigs of PIERS 2023 in Prague. Cambridge: Electromagnetics Academy, 2023. p. 1594-1598. ISSN 1559-9450.
  • Year: 2023
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Based on computer simulations, the article shows possible energy savings when supplying a 25 kV/50 Hz railway line from indirect static frequency converters instead of the classic supply from transformers only. One operating situation is analyzed including 37 trains sequentially powered by seven different combinations of both conventional supply stations and stations equipped with indirect static frequency converters.

High-Efficiency and High-Power-Density Semiconductor Converters

  • DOI: 10.1109/PIERS59004.2023.10221401
  • Link: https://doi.org/10.1109/PIERS59004.2023.10221401
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper describes development of high-efficiency and high-power-density semiconductor converters intended for a two-stage charging station equipped with gallium nitride-based transistors. It consists of an input PWM rectifier that includes an active power factor correction (part PFC) and an output DC-DC voltage converter with an AC intermediate circuit, containing a single-phase bridge voltage resonant inverter with a series resonant LLC circuit on the primary side of the isolation transformer and a single-phase bridge synchronous rectifier on the secondary side of the transformer. The use of resonant topology significantly reduces the switching losses of transistors. The converter ensures the output voltage according to the requirements of the traction battery and the demanded galvanic isolating the feeding network from the being charged vehicle battery and other equipment. The maximum efficiency of the functional sample of the charging station is 97 % and the power density is 3.5 kW per liter.

Output Power Change Analysis at Temperature Variation in Case of Synchronous Bi-Directional DC/DC Converter using Wide Band Gap Devices

  • DOI: 10.1109/PIERS59004.2023.10221526
  • Link: https://doi.org/10.1109/PIERS59004.2023.10221526
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper shows the designed converter output power changes with the temperature changes in case of various semiconductor switches. Mostly, wide band gap semiconductor-based switches like silicon carbide and GaN have a higher temperature capability than silicon for high power applications. 20-kW synchronous bi-directional DC/DC converters were designed for the silicon and silicon carbide switches using the LTSPICE simulations at different temperatures. The synchronous bi-directional DC/DC converters were designed for 75 kHz switching frequency having the duty cycle of 30 % to achieve the desired output power.

Time Variable Dead-Time in GaN Based Bridgeless Converter

  • DOI: 10.1109/PIERS59004.2023.10221385
  • Link: https://doi.org/10.1109/PIERS59004.2023.10221385
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Power factor correction (PFC) bridgeless converter in Fig. 1 with GaN transistors achieves better efficiency and power density compared to other solutions in the field of PFC converters. Utilizing GaN transistors brings new challenges in the field of control algorithms. Mainly the high frequency operation demanding high resolution PWM generator timers and precise dead-time setting together with fast control loop calculations and feedback values measurements. This paper presents a software based solution to on-line deadtime adjustment which improves the efficiency of GaN based PFC converters.

Current Collapse Conduction Losses Minimization in GaN Based PMSM Drive

  • DOI: 10.3390/electronics11091503
  • Link: https://doi.org/10.3390/electronics11091503
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The ever-increasing demands on the efficiency and power density of power electronics convert-ers lead to the replacement of traditional silicon-based components with new structures. One of the promising technologies represents devices based on Gallium-Nitride (GaN). Compared to silicon transistors, GaN semiconductor switches offer superior performance in high-frequency converters, since their fast switching process significantly decreases the switching losses. How-ever, when used in hard-switched converters such as voltage-source inverters (VSI) for motor control applications, GaN transistors increase the power dissipated due to the current conduc-tion. The loss increase is caused by the current-collapse phenomenon, which increases the dy-namic drain-source resistance of the device shortly after the turn-on. This disadvantage makes it hard for GaN converters to compete with other technologies in electric drives. Therefore, this paper offers a purely software-based solution to mitigate the negative consequences of the cur-rent-collapse phenomenon. The proposed method is based on the minimum pulse length opti-mization of the classical 7-segment space-vector modulation (SVM) and is verified within a field-oriented control (FOC) of a three-phase permanent magnet synchronous motor (PMSM) supplied by a two-level GaN VSI. The compensation in the control algorithm utilizes an offline measured look-up table dependent on the machine input power.

GaN Based Inverter Current-Collapse Loss Decrease Using 5-segment Modulation

  • DOI: 10.1109/AE54730.2022.9920074
  • Link: https://doi.org/10.1109/AE54730.2022.9920074
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The current collapse phenomenon increases conduction losses in high electron mobility transistors. This paper presents a simple option to decrease these losses in 3 phase hard-switching inverter driving permanent magnet synchronous motor utilizing 5-segment SVPWM modulation. Converter DC-link input power decrease by 2 % was observed compared to classic 7-segment modulation. This decrease results in significant decrease of transistor operating temperature.

Estimation of Stator Voltage of Inverter-Supplied Induction Motor Using Kalman Filter

  • DOI: 10.1007/978-3-030-53021-1_7
  • Link: https://doi.org/10.1007/978-3-030-53021-1_7
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Most of the control algorithms of variable speed drives with induction motor require the knowledge of the stator voltage vector applied to the motor ter-minals. This vector is usually reconstructed from the known microcontroller’s PWM signals or the commanded voltage for the inverter is used within the con-trol algorithm. However, these solutions require a DC-link voltage sensor and compensation of the nonlinear inverter behavior. In this paper, stator voltage es-timator based on the Extended Kalman filter is proposed. This approach requires neither the knowledge of the DC-link voltage nor the nonlinear model of the in-verter. Only the knowledge of the stator currents and the rotational speed is need-ed. The proposed estimator is verified within the simulation of predictive-torque control of induction motor drive in Matlab Simulink where the comparison of the applied and the estimated voltage vector is presented along with their harmonic analysis. The accuracy of the estimated voltage vector shows its suitability for further inverter nonlinearities investigation.

GaN Based Inverter Current-Collapse Behavior with Switching Frequency and Blocking Voltage

  • DOI: 10.23919/AE51540.2021.9542878
  • Link: https://doi.org/10.23919/AE51540.2021.9542878
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Current collapse in gallium nitride based transistors limit their use in high power and high frequency converters. In some cases, it makes the conduction losses to double. This paper investigates the measurement of dynamic on-state resistance for various cases such as blocking voltage and switching frequency. The optimum minimal length of pulses was determined in the case of three phase inverter to minimize the influence of current collapse.

Novel Method of Coupling Coefficient Estimation Based on the Bifurcation Phenomena in Inductive Power Transfer

  • DOI: 10.3390/electronics10202548
  • Link: https://doi.org/10.3390/electronics10202548
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Inductive power transfer (IPT) applications, such as stationary charging of electric vehicles (EVs), at least moderate coupling between the coils to achieve high efficiency, but the coefficient k typically varies between of 0.1 to 0.4, depending on the displacement of the coils according to SAE J2954. Thus, accurate and reliable methods for estimation of k are required for positioning of the EV to achieve optimal alignment with the charging pad. Additionally, in IPT, numerous control strategies are available for regulating output power and optimizing system efficiency that require an accurate estimate of the mutual inductance or k. However, existing estimation methods tend to require detailed a-priori information of a large number of circuit parameters, or they need measurement of currents or voltages in both primary and secondary sides. This paper presents a preliminary evaluation of a novel, primary-side method to estimate k, which is based solely on the frequency response of the input phase while operating the system in bifurcation. The method does not require any additional measurements of the system parameters. The theoretical background of the method is presented together with the description of the measurement procedure. The method is experimentally verified and compared with two currently used estimation methods. According to the presented experimental evaluation, the proposed method estimates k with an error of 3.62% with respect to the reference over the evaluated range of 0.08 to 0.36. In addition, we demonstrate that the presented method is resilient to detuning.

Capability of Predictive Torque Control Method to Control DC-link Voltage Level in Small Autonomous Power System with Induction Generator

  • DOI: 10.1007/978-3-030-14907-9_74
  • Link: https://doi.org/10.1007/978-3-030-14907-9_74
  • Department: Department of Electric Drives and Traction
  • Annotation:
    In a small autonomous power system, the electric power is usually produced by means of an electric machine operated as a generator. The often used one is an in-duction generator. The generator supplies the DC-link through the controlled converter (voltage source inverter – VSI). The appliances connected to the same DC-link consume power and therefore the DC-link capacitor is discharged. To maintain the decreasing DC-link voltage level, the same power amount must be delivered by the generator. In case of the induction generator, its control is specif-ic as no external source for machine excitation is present. To obtain the torque value desired by the DC link voltage PID controller, the generator is usually con-trolled by the field-oriented control (FOC) method or direct torque control (DTC) method. However, the model predictive control (MPC) method has been utilized for electric machine control in recent time. The paper explores the possibility of employing the predictive torque control (PTC), which is often used implementa-tion of MPC in this type of applications. The PTC method ability to control the DC-link voltage in a small autonomous power system has been verified experi-mentally on a laboratory system with induction generator.

Design of High Efficiency and High Frequency GaN DC/DC Converter

  • Authors: Ing. Filipp Frolov, prof. Ing. Jiří Lettl, CSc.,
  • Publication: 2020 21st International Scientific Conference on Electric Power Engineering (EPE). Prague: Czechoslovakia Section IEEE, 2020. p. 1-4. ISBN 978-1-7281-9480-6.
  • Year: 2020
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper presents a design of a high efficiency and high frequency synchronous buck converter based on GaN devices. Gallium Nitride (GaN) FETs are applied in this design to achieve the low power losses at high operation frequency. Synchronous buck topology is used to increase the system efficiency and reduce conduction losses. Converter is tested in several frequencies 100, 200, 400 kHz. The paper also contains the theoretical analysis of power losses in the converter. A synchronous buck converter prototype is designed and tested with peak efficiency of 98.9%.

Influence of Deadtime on Si, SiC and GaN Converters

  • DOI: 10.1109/EPE51172.2020.9269208
  • Link: https://doi.org/10.1109/EPE51172.2020.9269208
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper presents a comparison of three different transistor technologies Silicon Superjunction (Si SJ), Silicon Carbide (SiC) and Gallium Nitride (GaN) in respect to deadtime setting in a typical halfbridge converter. According to the measured results both new fast switching transistors SiC and GaN needs precise deadtime setting compared to the Si SJ devices. With wrong deadtime settings the converter efficiency drops more rapidly for GaN compared to SiC while the Si SJ device is the least affected by the deadtime length. The optimum deadtime in DC/DC converter can be found by tracking the maximum output voltage for given constant and compensated duty cycle and input voltage.

Optimum Flux Search Control on Induction Motor Drive with Predictive Torque Control

  • DOI: 10.1109/EPE51172.2020.9269212
  • Link: https://doi.org/10.1109/EPE51172.2020.9269212
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This work deals with a real-time optimum flux search control (SC). The method is integrated into Predictive Torque Control (PTC) of induction motor drive (IMD). The proposed predictive search control searches the optimum stator flux amplitude, at which the current amplitude is the lowest. The output of the SC is used as a reference for the PTC controller. As the control variable of the proposed SC, the predicted stator current vector amplitude is utilized. The method was verified experimentally on a laboratory drive with a 5.5 kW induction motor. The IMD achieves a current minimization while maintains the working point defined by the speed and load. The experiment shows good results during steady-state and sufficient performance during transients.

Predictive Torque Control of Induction Motor with Integrated DC-Link Voltage Optimisation

  • DOI: 10.1049/iet-pel.2019.1597
  • Link: https://doi.org/10.1049/iet-pel.2019.1597
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper proposes a new method leading to a reduction in the current and torque ripple of an Induction Motor (IM) drive controlled by a Predictive Torque Control (PTC). The method lies within the optimisation of DC-link voltage magnitude by a three-phase thyristor bridge rectifier. Using a controlled rectifier, the DC-link voltage can be adjusted in such way that the ripple of the IM state variables, caused mainly by treating the inverter as a source of only eight voltage vectors, is significantly reduced. Another positive consequence of the proposed algorithm is the reduction of DC-link-dependent switching losses. The DC-link optimisation algorithm is integrated within the PTC that is used for the torque and flux control. The theoretical analysis of the DC-link voltage influence on the drive behaviour is supported by simulation and experimental results conducted on a 5.5 kW IM drive, which confirms the benefits of the PTC with the DC-link voltage optimisation.

Reverse Conduction Loss Minimization in GaN‑Based PMSM Drive

  • DOI: 10.3390/electronics9111973
  • Link: https://doi.org/10.3390/electronics9111973
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Gallium nitride (GaN) devices are becoming more popular in power semiconductor converters. Due to the absence of the freewheeling substrate diode, the reverse conduction region is used in GaN transistors to conduct the freewheeling current. However, the voltage drop across the device in the reverse conduction mode is relatively high, causing additional power losses. These losses can be optimized by adequately adjusting the dead-time issued by the microcontroller. The dead-time loss minimization strategies presented in the literature have the common disadvantage that either additional hardware or specific converter data are needed for their proper operation. Therefore, this paper’s motivation is to present a novel dead-time loss minimization method for GaN-based high-frequency switching converters for electric drives that does not impose additional requirements on the hardware design phase and converter data acquisition. The method is based on optimizing the current controllers’ output with a simple perturb-and-observe tracker. The experimental results show that the proposed approach can minimize the dead-time losses over the whole drive’s operating range at the cost of only a moderate increase in software complexity.

Analysis of Bifurcation in Series-Series and Series-Parallel Compensated Inductive Power Transfer

  • DOI: 10.1109/WoW45936.2019.9030605
  • Link: https://doi.org/10.1109/WoW45936.2019.9030605
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Bifurcation phenomena significantly affects the inductive power transfer. Presented paper analyses influence of the equivalent circuit parameters on the bifurcation, which yields in the boundary condition for each parameter. Typical course of bifurcation is evaluated from the perspective of suitability for the system operation. Used mathematical and methodological apparatus allows easy comparison of different systems with series-series or series-parallel compensation topology.

Experimental Electric Vehicle for Educational Purposes

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Electric vehicle equipped with power electronic system developed on the department of Electrical drives and Traction faculty of Electrical Engineering Czech Technical University in Prague is now used by students in lab classes as well as for qualification studies realizations.

GaN Transistors Cooling Options Comparison

  • DOI: 10.1109/EDPE.2019.8883894
  • Link: https://doi.org/10.1109/EDPE.2019.8883894
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Three methods of cooling gallium nitride (GaN) transistors have been tested and directly compared together. Under similar conditions, top side cooled GaN was compared to the bottom side cooled type; both were of the same electrical parameters and were mounted on FR4 (fibreglass resin) and aluminium printed circuit boards. At equal dissipated power the proposed bottom side cooled transistor on aluminium board reaches half the temperature compared to the top side cooled one and one fourth of the temperature compared to the bottom side cooled GaN on FR4 board. A High speed driver is placed close to the transistor also on the aluminium IMS (Insulated Metal Substrate) board to reduce parasitic inductance of the gate driving path from control board to the high power side on the aluminium board.

Modernization of Drive System of Experimental Electric Vehicle

  • DOI: 10.14311/TEE.2019.1.004
  • Link: https://doi.org/10.14311/TEE.2019.1.004
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Modernization consists of a new compact drive unit for the Citröen Berlingo Electrique electric vehicle. The drive unit integrates a power converter for the traction motor, a DC/DC low voltage converter, an on board charger and an electronic control unit (ECU). The new air-cooled power converter is lightweight and more efficient due to the modern equipment used. The new ECU uses controller area network (CAN) to communicate with the power converters and also collects all the measured data that can be transferred in real-time during drive. This vehicle also currently provides a test and measurement platform for Master’s Degree students.

Tracking Deadtime Algorithm for GaN DC/DC Converter

  • DOI: 10.23919/AE.2019.8866992
  • Link: https://doi.org/10.23919/AE.2019.8866992
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented method automatically adjusts the deadtime of gallium nitride (GaN) transistors in half-bridge to increase the efficiency. This removes the need of manual measuring and setting the deadtime of the finished converter. The developed algorithm was tested and compared with the fixed deadtime case. The obtained results show that the developed algorithm is achieving higher and more stable efficiency compared to selected fixed deadtime.

GaN Quasi Z-Source DC/DC Converter for Electric Vehicles with Redox Flow Batteries

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Redox flow batteries mounted on the vehicle chassis behaves better at low voltage and high current while the tractive system of electric vehicles is more efficient at high voltage and low current. The proposed DC/DC converter provides the necessary tractive system isolation from the flow battery and keeps the voltage ratio while working in two quadrants of the current flow direction. The Z-source converter topology enables the necessary wide range voltage control at high efficiency. The power density is increased using the Gallium Nitride (GaN) transistors. The tested prototype of the converter proves that the topology is suitable for this application.

Induction Motor Drive Direct Torque Control and Predictive Torque Control Comparison Based on Switching Pattern Analysis

  • DOI: 10.3390/en11071793
  • Link: https://doi.org/10.3390/en11071793
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper describes a switching pattern generated in case of induction motor drive predictive torque control (PTC) compared to a switching pattern of direct torque control (DTC). PTC is a modern control method for electric drives based on model predictive control (MPC). DTC is a very powerful method and is today an industrial standard for controlling an induction motor drive. Its usage is wide-spread, mainly in high-power applications. However, the method suffers from a few disadvantages. One of the causes of the control method’s problematic behavior is choosing the switching combinations in the flux sector. Another inconvenience is the common selection table not including all voltage vectors in given sector. By these factors, the ripples of flux vector trajectory and torque waveforms are influenced. The longer the sample time is, the more significant the influence of factors becomes, because only a few steps occur within one turn of the magnetic flux vector. Based on the detailed analysis, the reasons of the different performance of both systems are explained. The analysis performed by simulation in Matlab Simulink environment has proved that, while DTC might choose voltage vector that pushes system away from the reference values, the MPC always chooses the most proper vector. The experimental results measured on the real drive confirm the appropriate vector selection, just in case of the predictive control method.

Loss Reduction in Induction Motor Drive Using Model Predictive Control

  • Authors: Ing. Pavel Karlovský, Ph.D., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Proceedings of the 2018 10th International Conference on Electronics, Computers and Artifical Intelligence. IEEE (Institute of Electrical and Electronics Engineers), 2018. ISBN 9781538649015.
  • Year: 2018
  • DOI: 10.1109/ECAI.2018.8679073
  • Link: https://doi.org/10.1109/ECAI.2018.8679073
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The induction motor drive with variable speed is a very common drive in many applications. To ensure the induction motor drive speed control, the sophisticated control methods must be utilized. In the paper, the Model Predictive Control (MPC) is employed. This method is usually used in order to control the induction motor flux amplitude and torque values. The induction motor is powered by the semiconductor voltage source inverter. Switching the semiconductor devices and current flow cause arise of losses in inverter. To decrease the losses, the modified MPC method is derived in the paper. In the Matlab Simulink environment reached simulation results show a reduction in losses at the newly modified control strategy compared to the conventional MPC method.

Single shunt phase current reconstruction for Sliding Mode Control algorithm driven PMSM

  • DOI: 10.1109/EPE.2018.8395947
  • Link: https://doi.org/10.1109/EPE.2018.8395947
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper presents a method to obtain phase currents of the Permanent Magnet Synchronous Motor (PMSM) fed by three phase bridge converter equipped with single shunt resistor measuring the DC-link current in case the motor is driven by the Sliding Mode Control (SMC) algorithm running at high switching frequency. This method was successfully tested and the measured results are included. The main benefit of the presented design is the cost reduction of small to medium power drives utilizing the modern high efficient motor with simple converter not depending on motor parameters due to the Sliding mode control. This method brings accurate results at high frequency switching application used for motors with small phase inductance.

Study of Bifurcation Evaluation Method for IPT

  • DOI: 10.1109/WoW.2018.8450911
  • Link: https://doi.org/10.1109/WoW.2018.8450911
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The inductive power transfer (IPT) is negatively affected by the bifurcation. Current methods for IPT analysis are general, not designated for the bifurcation analysis - they may be cumbersome or not effective enough. The proposed method describes device operating point (OP) by a combination of load quality factors. The OP is plotted in a diagram and based on its position towards the bifurcation boundary, the bifurcation occurs. Multiple OP joined together to form an operating trajectory suitable for a process evaluation or an operating area, suitable for parameter range analysis in the device design.

Analysis of bifurcation in two-coil inductive power transfer

  • Authors: Ing. Michal Košík, Ph.D., Fajtl, R., prof. Ing. Jiří Lettl, CSc.,
  • Publication: 18th Workshop on Control and Modeling for Power Electronics (COMPEL). IEEE (Institute of Electrical and Electronics Engineers), 2017. p. 1-8. ISSN 2151-0997. ISBN 978-1-5090-5326-1.
  • Year: 2017
  • DOI: 10.1109/COMPEL.2017.8013324
  • Link: https://doi.org/10.1109/COMPEL.2017.8013324
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Operation of two-coil inductive power transfer (IPT) is affected by the bifurcation phenomenon. So far, its dependence on primary and secondary quality factors was examined. However, similar dependencies exist for coupling coefficient and resonance frequency. In this paper, these dependencies and their mutual relationships are examined. This analysis is based on the normalized impedance approach and provides a calculation of all zero phase angle frequencies. IPT system behavior is examined from a perspective of input and output active power and efficiency. Finally, an automated simulation model is proposed as a mean of effective verification.

Application of MRAS algorithm to replace the speed sensor in induction motor drive system

  • DOI: 10.1016/j.proeng.2017.06.073
  • Link: https://doi.org/10.1016/j.proeng.2017.06.073
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Sophisticated control of induction motor drive requires knowledge of the rotor angular velocity. In order to obtain the speed information an optical sensor is usually utilized. However, it is not always advantageous because of the whole drive robustness decrease caused by the speed sensor inclusion. The paper presents some simulation and measurement results in case of the MRAS (Model Reference Adaptive System) method employing in attempt to eliminate the induction motor drive speed sensor. The operation principle is explained and a mathematical model of the drive system is created. The MRAS method influence on the drive behaviour is examined in simulation environment and experimentally. Finally, the experimental results and comparison of the drive behaviour with and without the speed sensor are discussed.

Application of MRAS algorithm to replace the speed sensor ininduction motor drive system

  • DOI: 10.1016/j.proeng.2017.06.073
  • Link: https://doi.org/10.1016/j.proeng.2017.06.073
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Sophisticated control of induction motor drive requires knowledge of the rotor angular velocity. In order to obtain the speed information an optical sensor is usually utilized. However, it is not always advantageous because of the whole drive robustness decrease caused by the speed sensor inclusion. The paper presents some simulation and measurement results in case of the MRAS (Model Reference Adaptive System) method employing in attempt to eliminate the induction motor drive speed sensor. The operation principle is explained and a mathematical model of the drive system is created. The MRAS method influence on the drive behaviour is examined in simulation environment and experimentally. Finally, the experimental results and comparison of the drive behaviour with and without the speed sensor are discussed.

Combined Magnetic Bearing - Magnetic Bearing Using Active and Passive Magnetic Fields

  • Authors: Vitner, J., Pavelka, J., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Journal of Electrical Engineering. 2017, 17 24-27. ISSN 1582-4594.
  • Year: 2017
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper discusses development and rotor stabilization process of the combined magnetic bearing for high speed bearing-less motors. In the first part the paper deals with the various types of magnetic bearings, their characteristics, properties, and principles. The second part presents a detailed view of the combined magnetic bearing placed in the laboratory of the Department of Electric Drives and Traction FEE CTU in Prague. This part includes mathematical concept of the combined magnetic bearing, calculation of the magnetic circuit parameters and design of the 3-phase winding, determination of the force effects of the passive and active magnetic field. In the last part the paper deals with driving methods of the active magnetic field to stabilize the rotor. The computer simulation results and results of the measurements on the real stabilized combined magnetic bearing are presented.

Comparison of sensorless AC drive operation using MRAS method or Luenberger observer

  • Authors: Ing. Pavel Karlovský, Ph.D., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Optimization of Electrical and Electronic Equipment (OPTIM) & 2017 Intl Aegean Conference on Electrical Machines and Power Electronics (ACEMP), 2017 International Conference on. IEEE, 2017. p. 281-286. ISBN 978-1-5090-4489-4.
  • Year: 2017
  • DOI: 10.1109/OPTIM.2017.7974984
  • Link: https://doi.org/10.1109/OPTIM.2017.7974984
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Induction motor is utilized in wide area of electric drive applications. If sophisticated control of speed or torque is required, the actual rotor angular velocity must be known at every time instant. To obtain the speed information, an optical sensor is usually utilized. However, the usage of such sensor brings some undesired effects. The paper compares two very often used methods on a specific induction motor drive. The MRAS (Model Reference Adaptive System) method and Luenberger observer are tested on the drive controlled through the DTC (Direct Torque Control) strategy. Operation principles of both methods are explained and a mathematical model of the drive system is created. These methods promise very precise speed estimation in simulation environments but in real operation they work less accurate. This paper brings the results measured on real drive and shows the limitations of the methods that do not occur in simulations.

Current Limiting Driver for GaN Half-Bridge

  • DOI: 10.23919/AE.2017.8053619
  • Link: https://doi.org/10.23919/AE.2017.8053619
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper presents a GaN transistor half-bridge prototype with robust pulse by pulse current limiting drivers designed to turn off safely the transistor for the rest of the PWM period when the drain current exceeds the set value. The half-bridge is intended as the key part of a DC/AC converter output stage with operating frequency up to 1 MHz. The current limiting circuit is designed to meet the requirements for safe operation of GaN transistors. The proposed current limiting driver is five times faster compared to common integrated drivers with included current limiting circuit.

Improvement of DTC Performance Using Luenberger Observer for Flux Estimation

  • DOI: 10.1109/EPE.2017.7967286
  • Link: https://doi.org/10.1109/EPE.2017.7967286
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Direct torque control (DTC) is one of the best performing strategies for induction motor control in many applications. However, this method suffers from a few disadvantages. Very important one is the presence of ripples in the torque waveform. The main reason of their presence is the inaccurate model of the motor. This paper utilizes Luenberger observer to calculate the model of the motor instead of the classical one. The DTC strategies with its original model and with Luenberger observer are created on dSPACE ds1103 platform. The results from experiment on a specific induction motor drive are shown. The paper shows better performance of the DTC with model based on Luenberger observer. The ripples in torque waveforms were lowered while switching frequency of the transistors remained the same.

Influence of speed and flux estimation by Luenberger observer on IM drive with DTC

  • DOI: 10.23919/AE.2017.8053585
  • Link: https://doi.org/10.23919/AE.2017.8053585
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The direct torque control (DTC) strategy is one of the most performance methods for induction machine (IM) drive torque control. The controlled stator magnetic flux and torque cannot be easily measured and therefore must be calculated using an IM mathematical model. This paper examines the impact of the replacement the original voltage IM model by Luenberger observer on the drive performance. As the original model requires only voltage and current, the observer is implemented in such a way that the same input variables can be used. The models are created and tests are carried out experimentally employing the dSPACE platform on induction motor of power 5.5 kW. The experimental results indicate better performance of the control strategy based on Luenberger observer.

Influence of Switching Frequency on Torque Ripples in Model Predictive Control of Induction Motor Drive

  • DOI: 10.1109/ECAI.2017.8166398
  • Link: https://doi.org/10.1109/ECAI.2017.8166398
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The proper control of induction motor drive is an important task in many applications. Usually, the motor is supplied from voltage source inverter and the required voltage is calculated according to the actual and past states of the motor. Unlike this, the predictive methods calculate also the future state and adjust the voltage accordingly. The model predictive control method calculates the effects of all possible future states in the next step and chooses the best action according to desired criteria. In the paper, this method is employed in the induction motor drive and the influence of the switching frequency on the torque and flux waveform ripples are examined in simulation environment Matlab Simulink.

Modelling of damping and vibration in electrical machines

  • Authors: Vondřich, J., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Sborník 22. odborné konference Aktuální otázky a vybrané problémy řízení elektrizačních soustav. Praha: EGÚ Praha Engineering, a.s., 2017. ISBN 978-80-87774-51-9.
  • Year: 2017
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The aim of the paper is to use modal analysis to investigation of vibration of each part of the machine in transition States. The amplitude and frequency, depending on the time. Examples of vibrating machinery and powering the electric motors and the method is explained.

Modelling of Trolleybuses Škoda 9Tr and 24Tr in MATLAB/Simulink Environment

  • Authors: Klán, M., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Sborník z XXXV konference o elektrických pohonech. Praha: Česká elektrotechnická společnost, 2017. p. 90-95. 1. vol. 1. ISBN 978-80-02-02724-9.
  • Year: 2017
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper deals with two models of trolleybuses created in MATLAB/Simulink environment and it simulates their behaviour during driving cycles SORT. Two types of trolleybuses were chosen for modelling. They are Škoda brand trolleybuses and each of them has got different concept of traction drives. One of them is clas-sical concept of electric vehicle (series DC motor with resistance control – type 9Tr) and the other is currently the most used concept (asynchronous motor controlled by traction converter with IGBT – type 24Tr). Thanks to simulations, it is possible to show the differences in traction properties of two generations of trolleybuses. Simulations can be done within various operating conditions. Energy consumption of modelled types of trolleybuses was evaluated based on the results of the simulations.

Modern converter equipment for Citroën Berlingo Electrique

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The goal was to design modern converter equipment for the electric vehicle bought by the department for research purposes. The new converter equipment consists of DC/DC converters for DC motor with separate excitation, on board electrical system converter and Electronic Control Unit. ARM microcontrollers had been used to control converters connected together with CAN bus. The equipment is built as a modular construc-tion to enable the possibility to be easy rebuilt for AC motor just by replacing the converter output stage and loading a new SW. Keywords: Electric vehicle;

Predictive Control of Induction Motor Drive Using dSPACE Platform

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Recently, the induction motor drives have become very popular in the area of controlled drives. Nowadays, a great effort is put on increasing their efficiency. The most widely used control method is the direct torque control (DTC). However, this method suffers from the torque ripple and current waveform distortion. The modification using predictive algorithms is becoming a popular approach. This paper presents a predictive control on the dSPACE DS1103 system and compares the method with DTC.

Theoretical evaluation of bifurcation in dependence on resonance frequency in two-coil inductive power transfer

  • DOI: 10.23919/AE.2017.8053586
  • Link: https://doi.org/10.23919/AE.2017.8053586
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Operation of two-coil inductive power transfer (IPX) system is affected by bifurcation phenomenon. In this paper, bifurcation in dependency on resonance frequency is examined. At first, voltage equations are analyzed, and impedance and transfer function derived. In next step, condition for resonance frequency is stated, which is followed by bifurcation analysis. Resulting bifurcation map is analytically described. Lastly, impacts of bifurcation on resonance frequency choice are evaluated using impedance and transfer function.

Improvement of induction motor drive performance using predictive control method instead of DTC method

  • DOI: 10.1109/AE.2016.7577255
  • Link: https://doi.org/10.1109/AE.2016.7577255
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Considering the disadvantages of induction motor drive such as torque ripple and current waveform distortion when using direct torque control (DTC) method, the method substitution might improve the drive behaviour. The authors suggest instead of the DTC method using the predictive method based on similar principles. In the paper, both methods are examined. Then on the induction motor drive yet controlled by DTC algorithm, the predictive method is implemented and performances of both control strategies are compared.

Sensorless Determination of Induction Motor Drive Speed Using MRAS Method

  • DOI: 10.1109/ECAI.2016.7861079
  • Link: https://doi.org/10.1109/ECAI.2016.7861079
  • Department: Department of Electric Drives and Traction
  • Annotation:
    In most cases, using of an optical sensor represents the most common solution to obtain the induction motor actual speed. As in some cases the use of the speed sensor carries number of problems, an effort to find a solution that does not require a speed sensor is obvious in recent time. The paper presents some results of employing MRAS (Model Reference Adaptive System) method for sensorless induction motor shaft speed determination. The working principles and the possible algorithm mathematical derivation are described. Results of the drive performance simulation in MatLab/Simulink environment are presented. Finally, the algorithm is verified on the real induction motor drive utilizing dSPACE platform. Obtained results demonstrate good function and performance of the system.

Analysis of predictive method of direct torque control of drive with induction motor in Matlab Simulink environment

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper deals with predictive method of direct torque control of drive with induction motor. There is a theoretical analysis performed, the mathematical description of the system is created and the functionality of the proposed algorithm in Matlab Simulink environment is verified on the model of drive with induction motor. The gained results demonstrate good behavior of the drive in steady states and transients.

Analysis of the Electromagnetic Field of Electric Machines Based on Object-oriented Design Principles

  • Authors: Pliugin, V., Shilkova, L., prof. Ing. Jiří Lettl, CSc., Buhr, K., Fajtl, R.
  • Publication: Proceedings of PIERS 2015 in Prague. Cambridge: Electromagnetics Academy, 2015. pp. 2522-2527. ISSN 1559-9450. ISBN 978-1-934142-30-1.
  • Year: 2015
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The authors propose to work out common principles of synthesis of electromagnetic field models for the main types of electrical machines. The main objective is to create field models of electric machines by inheritance of their characters from the original Maxwell's equations. An inverse problem is being also solved - the synthesis of electric machine electromagnetic field equations using object-oriented design.

Analysis of the Electromagnetic Field of Electric Machines Based on Object-oriented Design Principles

  • Authors: Pliugin, V., Shilkova, S., prof. Ing. Jiří Lettl, CSc., Buhr, K., Fajtl, R.
  • Publication: Proceedings of PIERS 2015 in Prague. Cambridge: Electromagnetics Academy, 2015. p. 2522-2527. ISSN 1559-9450. ISBN 978-1-934142-30-1.
  • Year: 2015
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The authors propose to work out common principles of synthesis of electromagnetic field models for the main types of electrical machines. The main objectiv is to create field models of electric machines by inheritance of their characters from the original Maxwell's equations. An inverse problem is being also solved - the synthesis of electric machine electromagnetic field equations using object-oriented design.

Combined Magnetic Bearing

  • Authors: Vitner, J., Pavelka, J., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Proceedings of PIERS 2015 in Prague. Cambridge: Electromagnetics Academy, 2015. pp. 2506-2509. ISSN 1559-9450. ISBN 978-1-934142-30-1.
  • Year: 2015
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper discusses development and rotor stabilization process of the combined magnetic bearing for high speed bearing-less motors. In the first part the paper deals with the various types of magnetic bearings, their characteristics, properties, and principles. The second part presents a detailed view of the combined magnetic bearing placed in the laboratory of the Department of Electric Drives and Traction FEE CTU in Prague. This part includes mathematical concept of the combined magnetic bearing, calculation of the magnetic circuit parameters, design of the 3-phase winding, determination of the force effects of the passive and active magnetic field. In the last part the paper deals with driving methods of the active magnetic field to stabilize the rotor. The computer simulation results and results of the measurements on the real stabilized combined magnetic bearing are presented.

Compensation of Disturbed Load Currents Using Active Power Filter and Generalized Non-active Power Theory

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The principal and analysis of usage of the generalized non-active power theory for the parallel compensation of periodic and non-periodic load current disturbances is presented in the paper. The effectiveness of the generalized non-active power theory to mitigate non-periodic current disturbances is demonstrated by simulation and laboratory experiments.

Control Strategy of Grid Connected Converter under Unbalanced Conditions

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Current-controlled voltage source converters are widely used in grid-connected applications. The negative sequence component of the grid voltage causes pulsating components in powers transmitted through the converter and ripple of the dc voltage in the intermediate circuit. Two strategies of the current reference calculation for a dual current controller were developed and tested in the Matlab/Simulink environment and experimentally verified as well.

Current Control of the Matrix Converter Fed Induction Motor Drive

  • Department: Department of Electric Drives and Traction
  • Annotation:
    In this paper is described method of realization of rotor flux oriented control of the induction machine fed by matrix converter with current control. Matrix converter belongs to the category of direct frequency converters that produce output voltage by the means of direct switching of proper input phase voltage to the output. This fact can introduce some problems into control algorithm compared to drive fed by conventional voltage source inverter.

Electric Vehicle Drive Control Based On GPS And GSM Path Parametres

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Minimizing of energy consumption is important task which is solved at all vehicles. In the case of electric vehicles (EV), energy stored on board in chemical accumulators must be used very effectively. For this purposes mathematical model of EV and real journey data used for energy consumption calculation must be used. On the basis of journey regime optimization lower energy consumption can be achieved. Optimal journey regime is calculated from the demanded travelling time by means of known road data, obtained by means of GPS and GSM navigation system with the aim to travel with minimum fuel consumption. From the road horizontal and vertical data basic route elements are calculated. Basic route elements are compared with needed torque, generated by driver’s pedal. All this information's are processed, optimized and needed mechanical torque is transmitted to the control unit of electric drive.

Induction Motor Drive Predictive Control Method Analysis and Comparison with Fundamental Direct Torque Control Method

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The authors propose new modification of the direct torque control method based on voltage vector prediction. The principle of the method is explained and the mathematical description of the system is provided. The control algorithm is implemented in simulation environment MatLab / Simulink and its behaviour is tested on the mathematical model of an induction motor drive. Then, the control algorithm is verified on the real drive with induction motor with dSPACE control system. The results from the simulations and measurements are presented and compared with those when using the fundamental direct torque control method.

Induction Motor Drive Predictive Direct Torque Control Method

  • DOI: 10.1109/RADIOELEK.2015.7129045
  • Link: https://doi.org/10.1109/RADIOELEK.2015.7129045
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper deals with development of the induction motor drive direct torque control (DTC) based on the next step voltage vector prediction. The principle of the method is explained and the system mathematical description is provided. The derived control algorithm is implemented both in the simulation software MatLab/Simulink and on the real induction motor drive with dSPACE control system. Simulated and measured results in steady states and transients are presented.

Locomotive Wheel Speed Measurement under Wheel Slip Conditions

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Wheel speed of heavy freight train locomotive under non-ideal traction conditions was measured with very high resolution and fine precision. Many authors published papers in this area over past century, but only recent advance in the information technology enabled measurement in such extent and resolution at the same time. Most modern locomotives have the speed sensor coupled with the traction motor. Unlike many other authors doing research in the area of wheel-slip, in the presented case the wheel speed was measured directly on the wheel, not indirectly on the traction motor. This approach made it possible to observe the wheel speed directly, without the requirement to implement motor – wheel model, which can introduce inaccuracies. Thanks to an independent method of train speed determination using a sensitive GPS receiver, wheel slip speeds were identified accurately regardless of synchronous slip phenomenon. Despite the adhesion theory, three types of operation mode were identified: the stable traction with negligible slip without oscillations, the semi-stable traction with evident slip and oscillations, and the prominent wheel slip. As the wheel speed was measured directly on the wheel, much larger oscillations than ever published were revealed. The source of the oscillations is discussed in the paper. A simple MatLab model of rotational masses was constructed and tuned to match the measurements. Eigen values and eigenvectors of the model are discussed, too. The model of rotational masses is completed with adhesion model to perform simulation. The simulation results are presented and compared with the results of measurement.

Model of Power Electronics Used for Electric Vehicles Contactless Charging

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper deals with power electronics used in contactless power transfer CPT and its operational functions modelled in FEM analysis software. There are mentioned equations for computing basic power electronics parameters. The main part of the paper deals with modelling of CPT power electronics in multiphysics software Simplorer Ansys.

Physical Meaning of an Induction Machine Dynamic Model

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper summarizes the approaches to dynamic description of an induction machine and presents them from the view point of the modern theory of dynamic systems. Great impact has the selection of the particular state variables. It decides about the mutual dependency of calculated values. Despite of the fact that it is still a correct description of the same system, it in°uences the design of control structures. Only the matrix form underlines clearly the particular differences and shows what combinations of state variables are eligible to be employed in hierarchical control structures.

Predictive Control of Induction Motor Drive Using dSPACE

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Since the induction motor drives have gained its popularity among regulated drives area, the great effort is put on increasing their efficiency. The use of predictive algorithm to control their speed is becoming a popular approach that preserves high efficiency. This paper presents implementing predictive control on the dSPACE DS1103 system, where the dSPACE is the control part of the system, drives the outputs of the power IGBTs and provides online communication with computer through ControlDesk.

Railway Traction Vehicle Longitudinal Velocity Estimation by Kalman Filter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Important task of railway traction vehicles is to achieve maximal traction effort at any conditions if required. For this purpose the vehicles have slip controllers. Some types of this controllers need the vehicle longitudinal velocity value as an input. The vehicle longitudinal velocity is difficult to measure directly because the vehicle longitudinal velocity could not be directly determined from wheel velocity. When the wheel is driven its velocity is higher than the vehicle longitudinal velocity because of the slip phenomenon. The paper describes method that provides possibility to estimate the vehicle velocity on base of measured wheel velocity. Estimation of the vehicle longitudinal velocity is enabled by Kalman filtration. The method is verified by MatLab simulation using real measured data.

Some problems of matrix converter switching pattern generation design

  • DOI: 10.1109/RADIOELEK.2015.7129051
  • Link: https://doi.org/10.1109/RADIOELEK.2015.7129051
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Compared matrix converter with indirect frequency converter, the lacking DC-link accumulation element is its cardinal advantage in terms of volume and weight. On the other hand, in case of matrix converter the control system is much more complex. In the design of matrix converter switching pulse sequence generation the complicated IGBT's commutation process as well as modern sophisticated modulation strategies must be taken into account. System reliability is dependent on the selected commutation algorithm and the proposed modulation strategy significantly affects the maximal reachable output voltage amplitude and thus the whole connected drive dynamics. Times of commutation, semiconductor device minimal switch-on and switch-off times play the essential role, too

FEL: Design of locomotive engines and simulators

Testing of the Matrix Converter Induction Machine Drive Control Algorithm in Matlab/Simulink

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Simulation is nowadays common way how to develop and test control algorithm of a drive before its run up on the real converter. The main problem is that because the control algorithm of the drive has to run in real time and it usually calculates and then outputs switching commands for the transistors, debugging and stopping of the algorithm execution is not possible. Therefore the developed code has to be tested in another way before putting to the real controller. This paper describes development and testing of FOC algorithm for IM drive fed by matrix converter.

Universal Embedded Controller for Matrix Converter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    – This paper describes a embedded controller for the matrix converter. Thanks to its computing throughput it is suitable for university use, but it enables operation in the whole industrial rage thank to its construction. Besides the example usage in matrix converter, the control system is generally usable for various control tasks.

Analysis and Construction of Output Capacitance Filter for High Power LLC Resonant Converter

  • Authors: Plhák, O., prof. Ing. Jiří Lettl, CSc.,
  • Publication: PIERS 2013 Taipei Proceedings. Cambridge: Electromagnetics Academy, 2013. pp. 1-4. ISSN 1559-9450. ISBN 978-1-934142-24-0.
  • Year: 2013
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The authors propose capacitive output filter for resonant inverter type DC / DC converter designed for trolley vehicles. There is designed solution based on real sample, which is further discussed, particularly in terms of their volume. Optimal solution of the printed circuit board (PCB) design requires compliance with certain rules. Their non-compliance leads to local overload, etc. Here are summarized the results obtained by measurements on the sample.

Analysis of the Influence of the Rortor Losses on the IM Control

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The rotor resistance can change significantly depending on the mode of operation of the induction motor. It can influence the accuracy of the controller. This paper strives to analyze if it is important to respect the resistance change or not.

Analytical Derivation of Induction Machine Efficiency Map

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Similarly as in field of combustion engines the efficiency map is very convenient tool for comparison of different motor variants. The overall efficiency of the induction machine can be analyzed in this way too. It is well known, that behavior of the induction machine can be easily described by its state space model. However, this description is mostly used in order to analyze the dynamic behavior only. The efficiency of the machine remains mostly out of the scope of the published articles. Moreover, the rotor resistance can change significantly depending on the mode of operation of the induction motor and power loss caused by hysteresis and eddy currents is not included into the consideration at all. Therefore this paper strives first to derive analytically the efficiency of the induction machine and thus prepare the comparison basis for the future impact analysis of changing the machine parameters and respecting the power loss in magnetic yoke.

Comparison of DTC and Sliding Mode Control of IM Drive

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This contribution strives to compare behaviors of the IM drive controlled by classical DTC and modified direct torque control strategy based on state space variable description of the IM and first order sliding mode controller. Simulations on SW Matlab/Simulink were carried out to test proposed control strategy and compare them with model of ST-DTC.

Dynamic Simulation of the Double-Stator Induction Electromechanical Converter with Ferromagnetic Rotor

  • Authors: Zablodskij, N., Pljugin, V., Ing. Stanislav Flígl, Ph.D., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Proceedings of 2013 fourth international conference International Conference on Power Engineering, Energy and Electrical Drives (POWERENG2013). Red Hook: Curran Associates, Inc., 2013. ISSN 2155-5532. ISBN 978-1-4673-6392-1.
  • Year: 2013
  • Department: Department of Electric Drives and Traction
  • Annotation:
    In this paper, the research in the field of double fed, double-stator induction motors with a ferromagnetic rotor is introduced. This machine was designed as a special electromechanical energy converter with a hollow, thin-walled, outer ferromagnetic rotor, aimed to be used in industry desiccative facilities. For this purpose, a dynamic mathematical model was worked out, implemented and executed in the Matlab/Simulink simulation environment. Finally, the theoretical analysis had been supplemented by experimental results measured on an implemented machine prototype.

Efficiency map of IM

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Recently are vehicles with a combination of combustion engine and electric motor beginning to expand more and more. Therefore the motor efficiency starts to be an important factor from the point of view of energy consumed from the batteries. Since the efficiency of the motor depends on its working conditions (flux, torque, speed) it is needed to take these variables into account when designing the controller. This paper deals with the possibilities of analytical calculation of IM efficiency based on the measured equivalent circuit parameters.

Electromobile Drive Diagnostics and Property Prediction

  • Authors: Buhr, K., Fajtl, R., prof. Ing. Jiří Lettl, CSc., Plyugin, V.
  • Publication: XX. International Symposium on Electric Machinery In Prague. Praha: ČVUT FEL, Katedra elektrických pohonů a trakce, 2013. pp. 38-44. ISBN 978-80-01-05377-5.
  • Year: 2013
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Nowdays used GPS / GSM technologies allow not only to locate electromobiles in space and time but also to synchronously monitor different physical values. It is very important for electromobiles with independent traction equiped by electric traction equipment which are handicapped by limited capacity of traction batteries. Limited capacity of traction energy is possibly to partly eliminate by precise dimensioning of the traction equipment of the vehicle. In this case the significant function of the board drive unit can also be range prediction and suggestion of the optimal route and drive style. It can also use the advantage of the fact that the vehicle moving on the same route and with identical conditions should have the same driving features given for example by driving resistances, energy consumption, heat loss emissions. This all could be a part of operational diagnostics. Analysis of the expected route, simulation of the vehicle which moves on the expected route, monitoring and on-line diagnostics of driving parameters can get new and very different quality. In this sense the article deals with basic considerations for later experimental verifications.

Overview and characteristics of resonant DC / DC converters

  • Authors: Plhák, O., prof. Ing. Jiří Lettl, CSc.,
  • Publication: XXXIII. celostátní konference o elektrických pohonech. 2013. pp. 1-4. ISBN 978-80-02-02457-6.
  • Year: 2013
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper is focused onto the classification of types of resonant DC / DC converters with isolation transformer suitable for high power applications. There are discussed pros and cons. It follows comparison of three types of resonant tanks: series, parallel and combination serio-parallel. There is given the basics of selected inverter topologies.

Practical problems with realization of the LLC resonant converter

  • Authors: Plhák, O., prof. Ing. Jiří Lettl, CSc.,
  • Publication: XXXIII. celostátní konference o elektrických pohonech. 2013. pp. 1-6. ISBN 978-80-02-02457-6.
  • Year: 2013
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Papers describe designing problems of LLC resonant converter type DC/DC. Designed converter is objected to high power static converter for trolley application. First part of study introduce readers into basics of LLC topology. Second part contribute simulation of circuit parameters. Last part analyse using of LLC topology and describe problems which occurs in case of using in trolley application.

Stable Adaptive Signal Generation in Current Based MRAS Induction Motor Sensorless Speed Control

  • Authors: Bednář, M., prof. Ing. Jiří Lettl, CSc., Vlček, M.
  • Publication: Progress In Electromagnetics Research Symposium 2013 Taipei. Cambridge: Electromagnetics Academy, 2013. pp. 689-692. ISSN 1559-9450. ISBN 978-1-934142-24-0.
  • Year: 2013
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper deals with generation of adaptive signal in current based MRAS speed estimation scheme. Transformation of machine equivalent impedance in steady state is used. The gained signal fulfils criterion of stability in the whole speed range (excluding situation, when Psir = 0 ) and in both operating modes (motor and generator).

Torque Control of Matrix Converter Fed Induction Machine Employing Fuzzy Logic

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The matrix converter is a very popular topic because of its advantages in comparison with the indirect frequency converter [1]. The modulation strategy and control algorithm used are very important parts of the converter’s controller. Recently modulation strategies based on a virtual DC-link space vector modulation are used, which works as a dependency injection [2]. That is why different approaches can be used to control both the output voltage and the input current at the same time. In this paper phase control of the input current in combination with a machine’s torque fuzzy controller is presented. This enables us to overcome the traditional limitations of the output voltage without resigning from the input current control.

Analysis of induction machine T and G circuit coequality for use in electric drive controllers

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper examines the problem of adequacy in induction machine modeling and attempts to provide a firmer basis for the selection of an appropriate model, to find a possible connection between the two most widespread models and to confirm or disprove their equivalence or differentness as the case may be.

Commutation Time Reduction of Matrix Converter through the Two-Step Methods Combining

  • Authors: Linhart, L., Pošta, P., prof. Ing. Jiří Lettl, CSc.,
  • Publication: ELEN 2012. Praha: vydavatelství ČVUT v Praze, 2012. pp. 11-12. ISBN 978-80-01-05096-5.
  • Year: 2012
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The simulation results, knowledge obtained in the construction of the state machines and comparison of two commutation strategies of a matrix converter will be presented. Used matrix converter is utilizing the FPGA technology for the realization of the modulator. The modulator includes the state machine to ensure the commutation between the input source lines and dead bands of the IGBTs. The FPGA technology is convenient to test different state machines as well as different commutation strategies.

Comparison of Alternative Equivalent Circuits of Induc-tion Motor

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Nowadays in variable speed drives induction machines are widely used. For the understanding and clear specifica-tion of the electromagnetic processes in the induction ma-chines different equivalent circuits can be employed. Traditionally, in order to reduce the complexity of the mathematical model the resistances and inductances are represented as concentrated components and 3 phase wind-ing is assumed to be symmetrical. These equivalent circuits are also used as a starting point for the design of the drive controller. This article strives to compare the two most widely used models and to derive a transformation against each other. In most papers that deal with the problematic of the IM drive control, equation based on the Park's transformation as a T-formed equivalent circuit are used. These models are adequate in many situations. Even though they can seem to be overly simplified, they can serve as a solid basis for an advanced motor control. However other authors tend to use gamma models and there are approaches using both. This paper examines and compares some of the issues of ade-quate machine modeling and attempts to provide a firmer basis for selection of an appropriate model and to confirm or disprove the equivalence of different approaches.

Comparison of Gamma and T Models for Convector Controlled Induction Machine Drives

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Nowadays in variable speed drives induction machines are widely used. For the understanding and clear specification of the electromagnetic processes in the induction machines different equivalent circuits can be employed. Traditionally, in order to reduce the complexity of the mathematical model the resistances and inductances are represented as concentrated components and 3 phase winding is assumed to be symmetrical. These equivalent circuits are also used as a starting point for the design of the drive controller. This article strives to compare the two most widely used models and to derive a transformation against each other.

Low Power Photovoltaic Converter Control and Development

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper focuses on design and simulation of the low power inverter for photovoltaic application. In the paper it is briefly discussed the DC/DC converter design for the tracking MPP of the solar array and then the design of the control algorithm for the output inverter is discussed. Both possible operation modes - work in “island mode” and operation in the supply grid are considered and a control algorithms for them were developed and simulated. Attention is also paid to the design of the output filter for the converter

Optimization of Indirect Space Vector Modulation Strategy for Matrix Converter

  • Authors: Kuzmanovič, D., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Proceedings of PIERS 2012. Cambridge: Electromagnetics Academy, 2012. pp. 918-924. ISSN 1559-9450. ISBN 978-1-934142-20-2.
  • Year: 2012
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Due to the absence of energy storage elements, conventional modulation strategies cannot be applied to the matrix converter. For that reason, a range of modulation strategies specific to the matrix converter have been developed. The selection of the modulation strategy and the switching pattern does not impact only the quality of the input and output quantities, but also the switching losses. In this paper, the analysis of the matrix converter switching losses, when the Indirect Space Vector Modulation (ISVM) is used, is presented. It was shown, how a simple modification of the modulation strategy can lead to a significant decrease of the switching losses. A software tool for the evaluation of the matrix converter losses was designed. The analysis of the matrix converter switching losses performed with this tool has shown that the use of the optimized modulation strategy decreases the switching losses by up to 20%.

Possibilities of Control Method Application to Matrix Converter Induction Motor Drive

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Implementation of the Field Oriented Control and of the Direct Torque Control in matrix converter supplied induction motor drives is analysed in the paper. Comparison with the implementation in drives supplied by the Voltage Source Inverter is carried out. The analysis is accompanied by the results of numerical simulations and experimental implementations of these two control methods

Reduced State Space Induction Motor Analysis

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Electric drive is an electro-mechanics energy converter. The own change of electric energy to the mechanic is done by the electric motor. For the demanded conversion of the energy needs the motor proper voltage, currents and fre-quency on its input terminals. In case of higher demands like, when the high dynamic of the motor is required, a converter is mostly connected in front of the motor. Induc-tion machine needs for its regulation frequency converter and control algorithm. In order to design control strategy for the induction mo-tor, system equations must be established at first. The target point is not given by a value of state variables, but their multiplication (mechanical torque). Moreover, depending on the coordinate system selection the destination point (or the curve) can be steadily moving. In other words, then the aim of the control is not to achieve a certain point in the state space but to produce a never ending movement that delivers the required torque as its side effect. The contribution deals with the analysis of the state space description of the induction motor based on the G-equivalent circuit of the IM. The operational limitations of the IM are mathematically derived based on the state space equations. The state space model of the IM and operational limits are then used as a starting point for the design of the IM drive control strategy based on the sliding mode control theory.

Simulation of the Matrix Converter Drive with Sliding Mode Control

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converter belongs to the direct frequency converter category. In this contribution the name "Matrix Converter" means the symmetrical 3x3 topology made by nine bidirectional switches. Output voltage is produced by direct switching of input phases to output phases. Very important parts of the converter's controller are used modulation strategy and control algorithm. The common modulation strategies from the area of the indirect frequency converters can not be used because of the absence of the DC-link. Therefore the modulation strategies based on virtual DC-link space vector modulation were developed. It works as a dependency injection. That is why different approaches can be used to control both the output voltage and the input current at the same time. In this paper the phase control of the input current in the combination with the sliding mode control of the output voltage is presented. This enables us to overcome the traditional limitation of the output voltage without resigning from the input current control.

Structured System and Software Design of Distributed Control Computer of Mechatronic Facility for Space Research

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The structured system and software design method of the distributed control computer network of the mechatronic scientific facility for automatic high temperature material processing in the space in microgravitation environment is presented in the paper. The facility distributed computer controls special extra low speed vibrationless electric drives, multi-zone high temperature furnace heating system and several measurement devices. The computer is equipped with special technological language to be possible to specify experiment time flow. Computer network nodes have many user processes (threads) so efficient, reliable, self documented, and low overhead scheduler dispatcher is required. The table driven coroutines have been designed.

2nd Generation Matrix Converter Prototype

  • Authors: doc. Ing. Jan Bauer, Ph.D., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Central European School of Doctoral Study In the field of power electrical engineering and automation. Košice: EDIS - vydavateľstvo ŽU, 2011. pp. 111-117. ISBN 978-80-554-0421-9.
  • Year: 2011
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper deals with the development of a matrix converter. Matrix converters belong to the category of direct frequency converters. A converter does not contain DC-link and the output voltage is provided by direct switching of voltage from the input phases. The absence of a DC-link is great advantage of the matrix converter, but it also increases the requirements on the converter control. For this reason a new prototype of a matrix converter is being developed with sophisticated modern components (FPGA, Power PC) equipped in the control part of the converter. The converter will be used for testing new control algorithms and commutation methods

Comparison of Different Filter Types for Grid Connected Inverter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    In order to stabilize the energy output and to give it some defined shape and value, the power converter must be connected to the output of the solar panel. In order to suppress or reduce negative effects the filter is connected between the converter and the network. The filter must be designed precisely, because it must have sufficient attenuation at the inverter's switching frequency and it must not bring oscillations to the whole system. This paper deals with design and simulation of such a filter type. Simulation models of the systems inverter-filter were made.

Comparison of Matrix Converter Induction Motor Drive Control Methods

  • Department: Department of Electric Drives and Traction
  • Annotation:
    In this paper, the implementation of the Field Oriented Control and the Direct Torque Control in matrix converter supplied induction motor drives is analysed, and compared with the implementation in drives supplied by the Voltage Source Inverter. The analysis is accompanied by the results of numerical simulations and experimental implementations of these two control methods

Control Part Design for the 2nd Generation Matrix Converter Prototype

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This article describes the former configuration of the control part for the experimental matrix converter and it introduces proposals for the next configuration generation as well. The former target system consists of a common personal computer, I/O card, rack, and the power circuit. Based on its overall assessment, a new configuration approach is proposed. The new system configuration promises many improvements. The communication between the control computer and the low level logic is based on the industrial PC104 bus. A new FPGA device is employed. It enables to handle all digital signals in the same time

DC-Space Vector Abstraction in the Virtual DC-Link Matrix Converter Theory

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The working principle of the matrix converter has been described by many authors in various ways. Especially, the introduction of the virtual DC link concept was one of the most important milestones in the matrix converter theory. However, the mathematical description is not symmetrical in this case. That is why a new approach presented in this article strives to symmetrize the matrix converter voltage and current transfer functions. For this purpose, new term is defined: DC-space vector.

Matrix Converter Commutation Time Reduction

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The reduction of matrix converter commutation time can be obtained by means of number of steps decreasing. For this purpose the two-step voltage oriented method was developed. But some limitations of this method occurred, so the solution consisted in combining with four-step method that is naturally two times longer. The new developed two-step current oriented method can overtake the function of four-step one and fix the disadvantage of voltage oriented algorithm. Unfortunately both two-step methods are inapplicable separately.

MMF of six phase induction motors for rectangular current supply

  • Authors: Grochowalski, J. M., prof. Ing. Jiří Lettl, CSc., Pavelka, J.
  • Publication: Proceedings of MMAR´2011. Szczecin: Zapadopomorski Uniwersytet Technologiczny, 2011. pp. 345-350. ISBN 978-1-4577-0912-8.
  • Year: 2011
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The problem of diminishing the pulsating torques in high power induction motor drives are investigated. This paper describes analysis and numerical results of MMF in three and six phase AC machines supplying by sinusoidal and nonsinusoidal currents. Analysis of six phase machines are for different angle between three phase stator windings and different time angles between currents in both three phase systems.

Permanent Magnet Synchronous Drive Vector Control Modeling

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper deals with the simulation of the control structure for the drive with the voltage source inverter and permanent magnet synchronous motor. The control structure is designed with the impact on the dynamic of the regulation for traction load. Realized model of the drive simulates the two level voltage fed inverter and mathematical model of the permanent magnet synchronous motor. Two control strategies of the drive are discussed in the paper.

Photovoltaic Inverter Control and Development

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper focuses on design and simulation of the low power inverter for photovoltaic application. In the paper is briefly discussed design of the DC/DC converter for the tracking MPP of the solar array and then is discussed the design of the control algorithm for the output inverter. Both possible operation modes - work in "island mode" and operation on the supply grid are considered and control algorithms for them were developed and simulated. Attention is also paid to the design of the output filter for the converter.

Problematics of the High Compatible Semiconductor Power Converters

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The effort to use renewable energy sources increase in these days. The processing of the energy obtained from the sun, wind or water gets to the forefront. The energy supplied by these sources has not constant values, but it fluctuates according to the surrounding conditions (intensity of the sun rays, water flow, etc.). Therefore these supplies are added with additional converters. The most used are AC / DC inverters or DC / DC converters. The aim of this project is to create the laboratory test bed that will pursue with energy acquisition from alternative energy sources. The attention will be paid both to the efficiency of the converters and to the control algorithm of the converter.

Simulation of the Inverter for solar application

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper focuses on design and simulation of the low power inverter for photovoltaic application. It is discussed the design of the control algorithm for the output inverter. Both possible operation modes - work in "island mode" and operation on the supply grid are considered and control algorithms for them were developed and simulated. Attention is also paid to the design of the output filter for the converter.

Solar Power Station Output Inverter Control Design

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper focuses on design and simulation of the low power inverter that acts as output part of the whole converter. In the paper is discussed the design of the control algorithm of the inverter for both types of inverter application - for islanding mode and for operation on the supply grid. Attention is also paid to the design of the output filter that should reduce negative side effects of the converter on the supply network

Structured System and Software Design of Distributed Control Computer of Mechatronic Facility for Space Research

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The structured system and software design method of the distributed control computer network of the mechatronic scientific facility for automatic high temperature material processing in the space in micro-gravitation environment is presented in the paper. The facility distributed computer controls special extra low speed vibrationless electric drives, multi-zone high temperature furnace heating system and several measurement devices. The computer is equipped with special language to be possible specify experiment time flow. Computer network nodes have many users processes (threads) so efficient, reliable, self documented, and low overhead scheduler-dispatcher is required. The table driven coroutines are designed.

The Use of Prediction to Improve Direct Torque Control

  • Authors: Kuzmanovič, D., prof. Ing. Jiří Lettl, CSc.,
  • Publication: PIERS 2011 Marrakesh Proceedings. Cambridge, MA: The Electromagnetics Academy, 2011. pp. 1411-1415. ISSN 1559-9450. ISBN 978-1-934142-16-5.
  • Year: 2011
  • Department: Department of Electric Drives and Traction
  • Annotation:
    In this paper, an improved Direct Torque Control scheme for induction motor drives, employing prediction, is presented. The DTC is an efficient induction machine control method. However, in order to keep a low torque ripple, it requires a high switching frequency (≥ 20 kHz). If the switching frequency is not sufficiently high, the only way to improve the drive's performance is to increase the switching frequency by modifying the used hardware. In this article, the use of prediction is offered as an alternative, cost effective solution, which doesn't require expensive hardware changes.

Compatibility of Different Types of Frequency Converters with Supply Network

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper compares from point of view of compatibility with the supply network the above mentioned three frequency converter topologies that are being used for supplying of induction machines. The topic of the EMC of the converters becomes very important in these days, because some of the semiconductor converters can be ranked as the worse supply network polluters. These negative side effects of the converters were previously overlooked, but with the widespread of power electronics they can not be ignored more. That is why the test beds of these three frequency converter input parts were realized and experimental results obtained by the measurement were analyzed and discussed.

Construction of Compact Matrix Converter with Nominal Power 20kW

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Presented paper deals with the design and construction of a matrix converter wtih power cca 20kW. During the design a special attention was paid to dimensions and compactness of the converter.Matrix converters belong to the category of direct frequency converters. A converter does not contain DC-link and the output voltage is provided by direct switching of voltage from the input phases. The absence of a DC-link is great advantage of the matrix converter, but it also increases the requirements on the converter control. For this reason a new prototype of a matrix converter is equipped with sophisticated modern components (FPGA, Power PC) in its control part.

Contribution to the Matrix Converter Overmodulation Strategies Based on the Virtual DC-Link Concept

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with modulation strategy of the matrix converter. Attention is paid to the indirect space vector modulation (ISVM) that is based on the virtual dc link concept. The 3D space for selection of the modulation index is being often overlooked. In this article it is discussed in detail.

Design of Inverter for Photovoltaic Application

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The photovoltaic applications spreads in these days fast, therefore they also undergo great development. Because the amount of the energy obtained form the panel depends on the surrounding conditions, as intensity of the sun exposure or the temperature of the solar array, the converter must be connected to the panel output. In general there are two types of converters used in solar applications. The Solar system equipped with inverter can supply small loads like notebooks, mobile chargers etc. in the places where the supplying network is not present. The paper focuses on design and simulation of the low power inverter that acts as output part of the whole converter. In the paper is discussed the design of the control algorithm of the inverter for both types of inverter application - for islanding mode and for operation on the supply grid. Attention is also paid to the design of the output filter that should reduce negative side effects of the converter on the supply network.

Dimensioning Of The Electromobile Drive With The BLDC PM motor in the hub

  • Authors: Buhr, K., prof. Ing. Jiří Lettl, CSc., Sýkora, P.
  • Publication: Elektromobilita v silniční dopravě a 21. století. Praha: ČVUT, FD, Katedra ekonomiky a managementu v dopravě a telekomunikacích, 2010. ISBN 978-80-01-04557-2.
  • Year: 2010
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper deals with the concept of a experimental workplace, which serves to parameters of the drive with the BLDC PM motor in the hub verifying. The HW and SW of the workplace are described. These make it possible to measure a load characteristic, temperature-rise test and retardation test. The aim of the experiments is to receive really data for the design of drive dimension method on the grounds its dynamics behaviour, granding of a track etc.

Experimental Validation of BLDC PM Wheel-hub Motor Drive Parameters for Electric Car

  • Authors: Buhr, K., prof. Ing. Jiří Lettl, CSc., Sýkora, P.
  • Publication: Sborník semináře Rušivé vlivy elektrických trakčních zařízení, jejich eliminace a elektromagnetická kompatibilita. Pardubice: Univerzita Pardubice, Dopravní fakulta Jana Pernera, 2010, ISBN 978-80-7395-255-6.
  • Year: 2010
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper is engaged in methodology of BLDC PM wheel-hub drive tests. There is described HW and SW experimental stand equipment, that enables automatic measurement of loading, warming and rundown characteristics. The outcomes of measurement of mechanics characteristics, warming and moment of inertia are used as a input data for identifying of dynamic behavior of the car.

Filter Design for Photovoltaic Application with Voltage Source Inverter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The acquisition of the electrical energy from renewable sources is very trendy nowadays. That is why the applications for renewable energy generation undergo rapid development. The greatest weakness of the renewable sources can be assumed as the instability and dependence of the delivered energy amount. In order to stabilize the energy output and to give it some defined waveform and value, the power converter must be connected to the output of the solar panel.In order to suppress or reduce these negative effects, the filter is placed between the converter and the network. The filter must be designed precisely because it must have sufficient attenuation on the inverter's switching frequency and it must not bring oscillations to the whole system. This paper deals with such a filter type design and simulation.

Life Cycle Economy Management Of The Distribution Network Transformers

  • Authors: Buhr, K., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Sborník konference ELEN 2010. Praha: ČVUT FEL, Katedra elektroenergetiky, 2010. ISBN 978-80-254-8089-2.
  • Year: 2010
  • Department: Department of Electric Drives and Traction
  • Annotation:
    In the branches of power electrotechnics and energetics the price development forecasts altogether indicate trend of the markedly higher energy price increase than the price increase of the production basic raw materials. Therefore analysing the economic aspects of the distribution network operation, it will be necessary to put the considerably higher accent on the optimal choice of the ratio of the acquisition costs and operational costs of the given component of the system in the whole technical economic life cycle. As regards the distribution network transformers that must ensure reliably the uninterrupted electrical energy supply, the problem consists in the solving of the dilemma to what extent it is efficient to decrease the idle energy consumption at the expense of the higher price of the initial investment. With the analysis of these problems and appreciation of their solving possibilities deals the presented paper.

Matrix Converter Induction Motor Drive Employing Direct Torque Control Method

  • Authors: prof. Ing. Jiří Lettl, CSc., Kuzmanovic, D.
  • Publication: Proceedings of PIERS 2010 in Cambridge. Cambridge, MA: The Electromagnetics Academy, 2010. ISSN 1559-9450. ISBN 978-1-934142-14-1.
  • Year: 2010
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with the implementation of the Switching Table Based Direct Torque Control (ST-DTC) in the matrix converter-fed induction motor drive. In order to improve the control of the matrix converter input power factor, the use of the simplified Indirect Space Vector Modulation (ISVM) was proposed. To verify the feasibility of the proposed solution, experimental results were presented.

Matrix Converter Two-Step Commutation Method Limitations

  • Authors: Linhart, L., prof. Ing. Jiří Lettl, CSc., doc. Ing. Jan Bauer, Ph.D.,
  • Publication: Proceedings of the 14th EPE-PEMC Conference 2010. Skopje: International Council on Large Electric Systems Macedonian National Commitee, 2010. p. T3-53-T3-58. ISBN 978-1-4244-7854-5.
  • Year: 2010
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper describes the basic knowledge about the matrix converter two-step commutation method that was realized on our department. This commutation strategy was implemented in VHDL for FPGA and was simulated in Simulink/Modelsim (cosimulation). The new developed two-step commutation method is two-time faster than the formerly implemented four-step commutation method. But the cosimulation in MatLab and Modelsim has proved that it includes some limitations not respected in theoretical analysis.

Optimization of Indirect Space Vector Modulation Strategy for Matrix Converter

  • Authors: Kuzmaniovic, D., prof. Ing. Jiří Lettl, CSc.,
  • Publication: EDS 2010 Electronic Devices and Systems. Brno: VUT v Brně, FEI, Ústav mikroelektroniky, 2010. pp. 196-201. ISBN 978-80-214-4138-5.
  • Year: 2010
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Due to the absence of energy storage elements, conventional modulation strategies cannot be used for the matrix converter. Therefore, a range of modulation strategies specific to the matrix converter have been developed. The selection of the modulation strategy and the switching pattern does not impact only the quality of the input and output quantities, but also the switching losses. In this paper, the analysis of the matrix converter switching losses when the Indirect Space Vector Modulation (ISVM) is used is presented. It was shown, how a simple modification of the modulation strategy can lead to a significant decrease in the switching losses. A software tool for the evaluation of the matrix converter losses was designed. The analysis of the matrix converter switching losses performed with this tool has shown that the use of the optimized modulation strategy decreases the switching losses by up to 20%.

Possibilities of frequency converter side effects on the supply network reduction

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper deals with the comparison of different frequency converter topologies from the EMC point of wiev. The negative side effects of the semicondutor converters, that were formerly overlooked, can be no longer ignored. Some topologies of semiconductor converters, that are known as worse supply network poluters, are nowadays still used as input parts of the frequency converters. To compare these side effects, test beds for different input parts used for frequency converters were made and results were analysed and compared with the special direct frequency converter topology of matrix converter.

Power Semiconductor Converters in Hybrid Drive Systems

  • Authors: prof. Ing. Jiří Lettl, CSc., Sýkora, P., Buhr, K.
  • Publication: Sborník semináře Rušivé vlivy elektrických trakčních zařízení, jejich eliminace a elektromagnetická kompatibilita. Pardubice: Univerzita Pardubice, Dopravní fakulta Jana Pernera, 2010. ISBN 978-80-7395-255-6.
  • Year: 2010
  • Department: Department of Electric Drives and Traction
  • Annotation:
    In this paper is shown, how the basic types of power semiconductor converters (rectifier, iverter, DC-DC converter, AC-AC converter) could be used in modern hybrid drive systems.

Regular Operation of Electric Bus in Municipal Transport Company of Prague

  • Authors: Sýkora, P., prof. Ing. Jiří Lettl, CSc., Buhr, K.
  • Publication: Sborník semináře Rušivé vlivy elektrických trakčních zařízení, jejich eliminace a elektromagnetická kompatibilita. Pardubice: Univerzita Pardubice, Dopravní fakulta Jana Pernera, 2010. ISBN 978-80-7395-255-6.
  • Year: 2010

Regular Operation of Electric Bus in Municipal Transport Company of Prague

  • Authors: Sýkora, P., Buhr, K., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Elektromobilita v silniční dopravě a 21. století. Praha: ČVUT, FD, Katedra ekonomiky a managementu v dopravě a telekomunikacích, 2010, ISBN 978-80-01-04557-2.
  • Year: 2010
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper deals with creation of Prague Integrated Transport 292 line, its line features and with BredaMenarini M200E ZEUS electric buses used at this line.

Various types power semiconductor converters backward effects comparison

  • Authors: prof. Ing. Jiří Lettl, CSc., Sýkora, P., Buhr, K.
  • Publication: Sborník semináře Rušivé vlivy elektrických trakčních zařízení, jejich eliminace a elektromagnetická kompatibilita. Pardubice: Univerzita Pardubice, Dopravní fakulta Jana Pernera, 2010. ISBN 978-80-7395-255-6.
  • Year: 2010
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper compares a couple of types of power semiconductor converters in the light of backward effects to a supply net. As the referential converter is taken a classical phase-controlled one-phase four-pulses thyristor rectifier. Further, PWM-controlled voltage rectifier and matrix converter are comparised. In both cases is the current waveform sinusoidal, that's why the supply net is not loaded by the current harmonics, the power factor is near to one and the both converters makes the recuperation possible.

Behaviours of the Induction Machine Fed by the Matrix Converter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The advantages of the modern regulated electric drive are not necessary to mention. Recently mostly induction maschines are used for it good behaviours. To use them optimally, the maschine has to be suplemented with frequency converter. The common indirect frequency converters have some disadvantages that can be eliminated by using matrix converters. This paper therefore deals with matrix converter fed induction machine.

Commutation Between Modulator And Superset Regulator of the Matrix Converter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This work deals with modulator of the matrix converter and his communication with superset regulator. Input voltage measurement method is presented. In the last part of the article, the testing of communication between superset regulator and modulator in FPGA technology are also presented.

Commutation Between Modulator And Superset Regulator of the Matrix Converter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This work deals with modulator of the matrix converter and his communication with superset regulator. Input voltage measurement method is presented. In the last part of the article, the testing of communication between superset regulator and modulator in FPGA technology are also presented.

Compact Matrix Converter Prototype

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converter belongs to direct frequency converter category. Output voltage is made by direct switching of input phases to output phases. This fact means that the converter does not need the DC-link capacitor which increases the costs of the converter and volume requirements of the converter. The absence of the DC-link capacitor is one of the main advantages of the matrix converter. On the other hand it means that output voltage amplitude is limited to 86.6% of the input voltage amplitude. Higher output voltage can be achieved with overmodulation which causes input current distortion. The other advantages of the converter compared to conventional indirect frequency converters are: power factor regulation; work in all four quadrants; its high dynamics; sinusoid current consumption; nearly sinusoidal output voltage waveform with low harmonic content, and high efficiency.

Compact Matrix Converter Prototype

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converter belongs to direct frequency converter category. Output voltage is made by direct switching of input phases to output phases. This fact means that the converter does not need the DC-link capacitor which increases the costs of the converter and volume requirements of the converter. The absence of the DC-link capacitor is one of the main advantages of the matrix converter. On the other hand it means that output voltage amplitude is limited to 86.6% of the input voltage amplitude. Higher output voltage can be achieved with overmodulation which causes input current distortion. The other advantages of the converter compared to conventional indirect frequency converters are: power factor regulation; work in all four quadrants; its high dynamics; sinusoid current consumption; nearly sinusoidal output voltage waveform with low harmonic content, and high efficiency.

Compact matrix converter two-step commutation metod realization and implementation

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper describes basic knowledge about two - step commutation method that was realized in our department. This commutation strategy was realized in VHDL for FPGA and was simulated in Simulink. But it was necessary to link Simulink with Modelsim that can simulate VHDL code. So these two sophisticated programs had to cosimulate. By virtue of this cosimulation can be uncovered, that theoretic calculations did not reflect some limitations of this two step algorithm.

Comparison of Different Commutation Strategies of Matrix Converter

  • Authors: Linhart, L., Pošta, P., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Electronic Devices and Systems, IMAPS CS International Conference 2009 Proceedings. Brno: VUT v Brně, FEI, 2009. pp. 479-484. ISBN 978-80-214-3933-7.
  • Year: 2009
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper describes the main difference in commutation behavior of matrix converter based on the four-step and the two-step commutation algorithm. Both commutation algorithms were realized in VHDL for FPGA and were simulated in Simulink. But it was necessary to link Simulink with Modelsim that can simulate VHDL code. The new developed two-step method is two-time faster than the formerly implemented four-step method. But the cosimulation in MatLab and Modelsim has proved that it includes some limitations not respected in theoretical analysis.

Cosimulation of Two-strep Commutation Method of the Matrix Converter In Simulink/Modelsim

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This paper describes basic knowledge about two - step commutation method that was realized in our department. This commutation strategy was realized in VHDL for FPGA and was simulated in Simulink. But it was necessary to link Simulink with Modelsim that can simulate VHDL code. So these two sophisticated programs had to cosimulate. By virtue of this cosimulation can be uncovered, that theoretic calculations did not reflect some limitations of this two step algorithm.

Experimental Results Measured on PWM Rectifier and their Comparison with Thyristor Rectifier

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with comparison of measured waveforms of PWM rectifier and classical phase controlled rectifier is compared on the basis of the input current harmonic analysis.

Matrix Converter Output Voltage Control with Overmodulation

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The matrix converter is a very popular topic today. Many papers about matrix converter deal with modulation strategies and control algorithms. In this paper, special attention is paid to the indirect space vector modulation, which is based on the virtual dc link concept. The entire converter is interpreted as a series connection of two matrix converters (rectifying and inverting virtual matrix converter). Thanks to this insight, it is possible to compose the modu- lation strategy for the entire matrix converter from the inverter and rectier part modulations. The main goal is to achieve the maximal possible output voltage by overmodulation employ- ment. The overmodulation method based on the indirect vector modulation is presented. By means of the square wave modulation the voltage transfer ratio can be increased from 0.866 up to 0.955. Moreover, together with control of the current modulation index, a linear and continuous adjustment of the output voltage can be achieved.

Matrix Converter Two-Step Commutation Method Development

  • Authors: Linhart, L., prof. Ing. Jiří Lettl, CSc., Bauer, P.
  • Publication: CD EDPE 2009. Zagreb: KoREMA, 2009. ISBN 978-953-6037-56-8.
  • Year: 2009
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The matrix converter is a very popular topic in recent years. The paper describes the realized compact matrix converter two-step commutation method. This commutation strategy was implemented in VHDL for FPGA and simulated in Simulink. But it was necessary to link Simulink with Modelsim that can simulate VHDL code. So these two sophisticated programs had to cosimulate. The developed two-step method is two-time faster than the formerly implemented four-step method. But the cosimulation in MatLab and Modelsim has proved that it includes some limitations not respected in theoretical analysis.

PWM Rectifier Contorl Algorithm

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The phase controlled thyristor rectifiers overload the supply network with higher harmonics and reactive power consumption.The modern industrial production demands continuous and lossless conversion of electrical energy parameters. Utilization of PWM control in rectifiers eliminates problems that were caused by phase controlled rectifiers operation. That is why the PWM rectifier is being examined. Comparing to the phase controlled rectifier it can be controlled to consume nearly sinusoidal current with power factor equal to unity. Another advantage of the PWM rectifier is its capability of energy recuperation

PWM Rectifier Control Algorithm

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The modern industrial production demands continuous and lossless conversion of electrical energy parameters. This need leads to wide spread of power semiconductor converters. The rapid development in power electronics and microprocessor technology enables to apply sophisticated control methods that eliminate negative side effects of the power converters on the supply network. The phase controlled thyristor rectifiers overload the supply network with higher harmonics and reactive power consumption. Utilization of PWM control in rectifiers eliminates the problems that were caused by phase controlled rectifiers operation. That is why the PWM rectifier is being examined. In comparison with the phase controlled rectifier it can be controlled to consume nearly sinusoidal current with power factor equal to unity. Another advantage of the PWM rectifier is its capability of energy recuperation

Two-step Commutation Method of the Matrix Converter Based on the Voltage Sign Measurement

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper describes the basic knowledge about two-step commutation method that was realized on our department. This commutation strategy was implemented in VHDL for FPGA and was simulated in Simulink/Modelsim (cosimulation). The new developed two-step method is two-time faster than the formerly implemented four-step method. But the cosimulation in MatLab and Modelsim has proved that it includes some limitations not respected in theoretical analysis.

Analyses of Energy Conservation Possibilities in an Opencast Coal-Mining Conveyor by means of Continuously Controllable Drives

  • Authors: Buhr, K., Tušla, P., Janoušek, J., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Proceedings of Workshop 2008. Praha: Czech Technical University in Prague, 2008. pp. 376-377. ISBN 978-80-01-04016-4.
  • Year: 2008
  • Department: Department of Electric Drives and Traction
  • Annotation:
    It is the well known fact that in the opencast mining systems the inconsiderable part of the expenses is connected with the material transport. In the EU condition as the most widespread-mode of the opencast mining transport systems the long distance belt conveyor with high power electric drives are used. There are two ways of the energy consumption diminution. The first one consists in the movement resistances reduction, the other one consist in the belt velocity adaptation to the belt transport capability. The continuously controlled electric drive is the most suitable solution from the point of view of the energy cost savings.

Basic Utilization of Electric Current Effects

  • Authors: prof. Ing. Jiří Lettl, CSc., Pivoňka, P.
  • Publication: Alphen aan den Rijn: Simulation Research Press, 2008. ISBN 978-90-807898-3-8.
  • Year: 2008
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The book is a monograph that deals with basic electrotechnical rules. It concerns the origin of electric current, contains the description of the effects caused by the current and also practical use of these effects by the production, transmission, conversion and consumption of electricity. The book is aimed to the audience composed of non-electrical engineering educated persons and it should to show them how the theoretival rules and physical laws can be applied on different electronic, electrotechnical and electromechanical equipment.

Current Generator for Circuit Breaker Testing

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Current harmonic distortion is quite usual in industrial mains. Electromagnetic compatibility of circuit breakers must comply with these conditions. Current releases of circuit breakers were adjusted to sinusoidal current waveform in past. Modern circuit breakers have to disconnect current with high harmonic content and their current releases have to dispatch the releasing impulse with respect to the usual current distortion, too. Therefore the release testing procedure is performed with a test current waveform that is defined by standards. In the paper new current generator for testing of releases and circuit breaker for both low and very high current is described.

Design of the Control System of Compact Matrix Converter

  • Authors: Bednář, M., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Proceedings of Workshop 2008. Praha: Czech Technical University in Prague, 2008. ISBN 978-80-01-04016-4.
  • Year: 2008
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This contribution deals with the hardware design for a matrix converter compact version. It is presented a short introduction to the power circuit configuration and control system of the matrix converter. The accent is given on the design of FPGA based switching pattern generation board, which is necessary part of the converter. Further it can be found a description of individual parts of the board, which are needed to meet requirements of the system.

EMC Comparison Of Controlled Rectifiers and PWM Rectifiers

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The electromagnetic compatibility of electrical devices is going to be serious problem in these days. Many electrical devices are fed by diode or thyristor rectifiers. Such devices generate higher harmonics to the supply network and they can cause malfunction of other devices connected to the grid. Therefore, many methods for elimination of harmonics pollution are investigated. One of them is application of "grid friendly devices" as a PWM rectifier

Example of Power Electronic's Education on the Pulse Width Modulated Rectifier

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Department of Electric Drives and Traction on CTU in Prague is trying to use in education own research results adjusted on theoretical basis or as realized functional samples. It has proven useful to divide the education of power electronic to three levels. This contribution describes the laboratory that belongs to the second category, when students are working with built converter and are concentrated on the control algorithm. In this example students are familiarized with the function and the control of the pulse width modulated rectifier. This rectifier consumes nearly sinusoidal current and works with given power factor. By comparison of waveforms and harmonics with the common rectifier is demonstrated the converter's compatibility growth.

Experimental Results Measured on Matrix Converter Drive System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The matrix converter is very popular topic today. Until now it has attracted mainly academic attention. It has many advantages in comparison with indirect frequency converters. As shown in this paper, the matrix converter works at high efficiency and without harmonic distortion both on the input and on the output side. The only problems are caused by the control system and by real-time control algorithms. However, new control strategies are developed, so we expect solving of these problems in recent time period.

Matrix Converter Modulator and Communication with Regulator

  • Authors: prof. Ing. Jiří Lettl, CSc., Pošta, P.
  • Publication: Proceedings of Workshop 2008. Praha: Czech Technical University in Prague, 2008. ISBN 978-80-01-04016-4.
  • Year: 2008
  • Department: Department of Electric Drives and Traction
  • Annotation:
    This work deals with modulator of the matrix converter and his switching algorithm. Communication with superset regulator is briefly introduced.

Measured Properties of Realized PWM Rectifier

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with measured waveforms of realized PWM rectifier with practically sinusoidal input current and controllable phase shift between input current first harmonic and supply voltage first harmonic. Electromagnetic compatibility of PWM rectifier and classical phase controlled rectifier is compared on the basis of the input current harmonic analysis.

Model of Matrix Converter-Fed Asynchronous Motor Drive Controlled by Takahashi Direct Torque Control

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converter belongs to the group of direct AC-AC converters. Direct torque control method is a modern control technology which uses a simple controlling algorithm. It directly controls motor torque and flux without using a modulator and without the need of precise output voltage vectors generating like it is demanded in the case of field oriented control. The article presents a model of an induction motor fed by a matrix converter controlled by Takahashi direct torque control.

Progressive Approach to Matrix Converter Voltage Control

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Much more frequently than in the case of any other converter, the maximum achievable voltage transfer ratio is mentioned in papers concerning matrix converters. This is mainly historical in nature since early methods achieved rather small output voltages and even today the matrix converter is still disadvantageous from this point of view in comparison with indirect frequency converters. It is very important to obtain a voltage of value close to the mains voltage. In the paper is presented a possible overmodulation method. By increasing the current modulation index the output voltage can be enlarged up to the limit 0.955.

PWM Rectifier Realization

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Pulse width modulated rectifier is a very popular topic nowadays. The modern industrial production demands continuous and lossless conversion of electrical energy parameters. This need leads to wide spread of power semiconductor converters. The rapid development in power electronics and microprocessor technology enables to apply sophisticated control methods that eliminate negative side effects of the power converters on the supply network. The phase controlled thyristor rectifiers overload the supply network with higher harmonics and reactive power consumption. That is why the PWM rectifier is being examined. In comparison with the phase controlled rectifier it can be controlled to konsume nearly sinusoidal current with power factor equal to unity. Another advantage is its capability of energy recuperation. The paper drala with the PWM rectifier functional model realization and examination.

Concept of Modulator for Matrix Converter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This work deals with commutation algorithms of the matrix converter. The working principles of the four-step switching algorithm controlled by the line to line voltage are presented. The explanation is accompanied also with tables of switching patterns for different current direction. Switching time calculation approaches are described in detail as well. In the last part of article, the overall circuit of the modulator unit is explained and its implementation in VHDL language is introduced briefly.

Control Design of Matrix Converter System

  • Authors: prof. Ing. Jiří Lettl, CSc.,
  • Publication: International Aegean Conference on Electrical Machines and Power Electronics ACEMP 2007 and ELECTROMOTION 2007 Proceedings. Ankara: Middle East Technical University, 2007. p. 480-484. ISBN 978-975-93410-2-2.
  • Year: 2007
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with matrix converter induction motor drive with emphasis on the PWM modulation strategy design. The special digital control system was used. This system consists of two personal computers. The first one serves for monitoring purposes only, the second one is equipped with a common interface card and works in real time. The most of the contemporary modulation strategies are able to provide practically sinusoidal waveforms of the input and output currents with negligible low order harmonics, and to control the input displacement factor. Sophisticated pulse width modulation strategies in terms of various optimization criteria are known in case of indirect frequency converters, whereas both the inverter and the rectifier can be operated with pulse width modulation.

Design of Matrix Converter Filter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This article describes the matrix converter system filter design. First, some of the most often used filter configurations are described and their properties compared. Then, the example of the practical filter design is presented. In our case the best characteristics offer the parallel damped and the multiple sections filters. Although a little more complicated, the multiple section filter can be smaller and cheaper due to the use of smaller components. However, the parallel damped filter was chosen due to its simplicity.

Experiences in Matrix Converter Induction Motor Drive Implementation

  • Authors: prof. Ing. Jiří Lettl, CSc., Bednář, M.
  • Publication: Liberecké elektrické pohony 2007. Sborník příspěvků z celostátní konference. Liberec: TUL, Fakulta mechatroniky a mezioborových inženýrských studií, 2007. pp. 25-30. ISBN 978-80-7372-272-2.
  • Year: 2007
  • Department: Department of Electric Drives and Traction
  • Annotation:
    In this paper a special attention is paid to the indirect space vector modulation design based on the virtual DC-link concept. The entire converter is interpreted as a series connection of two matrix converters (rectifying virtual matrix converter and inverting virtual matrix converter). Thanks to this insight it is possible to compose the modulation strategy for the entire matrix converter from the rectifier and inverter part modulations. Achievement of the maximum available output voltage was defined as the main goal. Based on the indirect space vector modulation, an overmodulation with square wave output is introduced. It enables to increase the transfer ratio from the common value of 0.866 to the value of 0.955. It is also presented that the output voltage level can be adjusted continuously in an easy way, even in overmodulation.

Experimental Results Measured on Matrix Converter Drive System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The measured results obtained on the built-up experimental test bed have proved the proper function of the designed conception of the matrix converter control system and implemented PWM strategy.

Experimental Results Measured on Matrix Converter Drive System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The measured results obtained on the built-up experimental test bed have proved the proper function of the designed conception of the matrix converter control system and implemented PWM strategy.

Hardware Design for Matrix Converters of Various Nominal Power

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This article describes various matrix converter topologies. It compares them with traditional indirect converters. The new matrix converter topologies are based on generalization of the term "matrix converter." This new point of view brings new solutions and offers interesting alternative topologies towards to the future. The new topologies are illustrated with some practical examples.

Input Filter Design for Matrix Converter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Different types of differential-mode EMC input filters for matrix converters are presented in this paper. Input filter has two main roles: a) to prevent electromagnetic interference generated in the MC from reaching the power line and b) to prevent the noise from the line side from affecting the operation of the MC and electrical equipment connected to the MC output. Besides its positive sides, input filter has its drawbacks: size and price. Matrix converter belongs to the group of direct AC/AC converters, which means it doesn't contain energy storage elements and is therefore considerably smaller than indirect converter. That makes it convenient for applications with limited installation space, like in hybrid vehicles. For that reason the input filter dimensions should be kept as small as possible which makes the filter design a trade-off between good performance and small size and price.

Linearly Controlled Overmodulation for Matrix Converter System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The matrix converter is a very popular topic today. It has attracted not only academic attention. Many papers about matrix converter deal with modulation strategies and control algorithms. The main goal is to achieve the maximal possible output voltage by overmodulation employment. The overmodulation method based on the indirect vector modulation is presented in this paper. By means of the square wave modulation the voltage transfer ratio can be increased from 0,866 up to 0,955. Moreover, together with control of the current modulation index, a linear and continuous adjustment of the output voltage can be achieved.

Matrix Converter - 2nd Generation Test Bed Development

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This article describes the former configuration of the experimental matrix converter and it introduces proposals for the next configuration generation as well. The former target system consists of a common personal computer, I/O card, rack, and the power circuit. Based on its overall assessment, a new configuration approach is proposed. The new system configuration promises many improvements. The communication between the control computer and the low level logic is based on the industrial PC104 bus. A new FPGA device is employed. It enables to handle all digital signals in the same time.

Matrix Converter modulator Design

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This work deals with commutation algorithms of the matrix converter. The working principles of the four-step switching algorithm controlled by the line to line voltage are presented. The explanation is accompanied also with tables of switching patterns for different current direction. Switching time calculation approaches are described in detail as well. In the last part of article, the overall circuit of the modulator unit is explained and its implementation in VHDL language is introduced briefly.

Perspectives of Operational System LINUX for Matrix Converter Control

PWM Strategy Applied to Realized Matrix Converter System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with matrix converter induction motor drive with emphasis on the PWM modulation strategy design. The special digital control system was used. This system consists of two personal computers. The first one serves for monitoring purposes only, the second one is equipped with a common interface card and works in real time. The most of the contemporary modulation strategies are able to provide practically sinusoidal waveforms of the input and output currents with negligible low order harmonics, and to control the input displacement factor.

Realized Matrix Converter Induction Motor Drive Properties

  • Authors: prof. Ing. Jiří Lettl, CSc.,
  • Publication: XV. International Symposium on Electric Machinery in Prague. Praha: ČVUT FEL, Katedra elektrických pohonů a trakce, 2007. pp. 124-130. ISBN 978-80-01-03807-9.
  • Year: 2007
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The matrix converter is a very popular topic today. It has attracted not only academic attention. Many papers about matrix converter deal with modulation strategies and control algorithms. However, not only the modulation or regulation algorithms or other rather theoretical instruments themselves are essential. Hence this article deals with some aspects of the matrix converter system practical realization and demonstrates experimental results obtained on the realized matrix converter induction motor drive.

Results of Experiments on Matrix Converter Drive System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The described measurements were taken for both the motor and generator operation regimes. The measured results obtained on the built-up experimental test bed have proved the proper function of the designed conception of the matrix converter control system and implemented PWM strategy. The realization brought many other additional effects and pieces of experience.

Switching Pattern Generation Board for Matrix Converter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    This contribution deals with the hardware design for a matrix converter compact version. It is presented a short introduction to the power circuit configuration and control system of the matrix converter. The accent is given on the design of FPGA based switching pattern generation board, which is necessary part of the converter. Further it can be found a description of individual parts of the board, which are needed to meet requirements of the system.

The Switching Pattern Generation Board

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The aim of this contribution is to describe the casual design of a compact matrix converter. It puts mind to the switching pattern generating board development. The accent is given on the design of FPGA based switching pattern generation board, which is necessary part of the converter. Further it can be found a description of individual parts of the board, which are needed to meet requirements of the system.

Comparison of Different Types of AC/AC Converters

  • Department: Department of Electric Drives and Traction
  • Annotation:
    An overview of AC/AC converters used in modern electric drives is presented. These converters take energy from one AC power system and deliver it into another one, which can in general have different voltage, frequency, phase, and number of phases. The AC/AC converters can be divided into two main groups: indirect converters with the DC link containing the energy storage and direct converters transforming the energy directly from one AC power system into another one without the energy storage. A special accent is put on some newly developed topologies, such as matrix converters and multilevel converters. Several most promising configurations are presented.

Contribution to vector control with system nonlinearities consideration

  • Authors: prof. Ing. Jiří Lettl, CSc., Ratz, R.
  • Publication: EPVE 2006 Elektrické pohony a výkonová elektronika. Brno: VUT v Brně, Fakulta elektrotechniky a komunikačních technologií, 2006. pp. 30-35. ISBN 80-214-3286-1.
  • Year: 2006
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with the vector controlled induction motor drive behaviour at boundary conditions if the induction motor magnetizing induction nonlinearity is taking into account. The magnetizing current is optimized in order to obtain the minimal stator current at the given torque, which means that the magnetizing flux is not constant. The established boundary condition for reference value of torque, magnetizing current and d-q stator current components are important for implementing vector control of induction motors in real drive.

Electromagnetic Compatibility of Matrix Converter System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converters have attracted an amount of interest over the past 25 years already, but they find time after time once again new utilisation. The presented paper deals with the recent concept of hybrid and power splitting traction drive systems. Special attention is paid to electric power splitting. In the investigated system a traction induction motor is employed. The matrix converter realised on the base of new progressive semiconductor elements is used to treat the electrically transmitted part of the whole drive energy. This solution is advantageous with regard to the reactive component reduction. The special digital control system consisting of two personal computers is used for the realised test bed. The matrix converter IGBTs are controlled by means of the designed indirect pulse width modulation method.

Employment of Power Semiconductor Converters in Hybrid Drives

  • Authors: prof. Ing. Jiří Lettl, CSc.,
  • Publication: Proceedings of the WSEAS International Conferences: 6th International Conference on Power Systems, on Simulation, modelling and Optimalization, on Signal, Speech and Image Processing, on Multimedia, Internet and Video Technologies, on Distance learning. Athens: WSEAS Press, 2006. pp. 2. ISSN 1790-5117. ISBN 960-8457-53-X.
  • Year: 2006
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented lecture deals with power semiconductor converters employable in hybrid drives. Promising is propulsion with electric power splitting based on internal combustion engine power splitting into two parts. One part is converted into electric power in a generator, which supplies a traction motor, mechanically connected to vehicle wheels, and the remaining part is transmitted by electromagnetic forces in the air gap to the wheels mechanically without losses in electric machines. The splitting devices can be realized mechanically by a planetary gear or electrically by a special electric generator. To treat the electrically transmitted part of the whole hybrid drive power, an indirect frequency converter or a matrix converter can be used. A special DC/DC converter is being used to accumulate the braking energy in a super capacitor.

High-level EMC at Matrix Converter AC/AC Energy Conversion

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with matrix converters pulse width modulation strategies design with emphasis on the electromagnetic compatibility. The most of the contemporary dulation strategies are able to provide practically sinusoidal waveforms of the input and output currents with negligible low order harmonics, and to control the input displacement factor. A special digital control system was developed for the realized experimental test bed which makes it possible to achieve greater throughput of the digital control system and its variability.

Improved Induction Motor Vector Control Considering System Non-Linearity

  • Authors: prof. Ing. Jiří Lettl, CSc., Ratz, R.
  • Publication: ELEN 2006 (Elektroenergetika). Praha: České vysoké učení technické v Praze, 2006. pp. 21-24. ISBN 80-239-7650-8.
  • Year: 2006
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with the vector controlled induction motor drive behaviour in case of taking into account the nonlinearity of the induction motor magnetizing inductance. The magnetizing current is optimized in order to obtain the minimal stator current at the given torque, which means that the magnetizing flux is not constant.

Limiting Boundaries of Vector Controlled Drives with Optimized Rotor Flux

  • Authors: Ratz, E., prof. Ing. Jiří Lettl, CSc., Ratz, R.
  • Publication: XIV-th International Symposium on Electric Machinery in Prague. Praha: ČVUT FEL, Katedra elektrických pohonů a trakce, 2006. pp. 191-197. ISBN 80-01-03548-4.
  • Year: 2006
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with the vector controlled induction motor drive behaviour at boundary conditions and optimized rotor flux. Boundary condition for reference value of torque, magnetizing current and d-q stator current components are important for implementing vector control of induction motors in real drive.

Matrix Converter Hybrid Drive System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converters have attracted an amount of interest over the past 25 years already, but they find time after time once again new utilisation. The presented paper deals with the recent concept of hybrid and power splitting traction drive systems. Special attention is paid to electric power splitting. In the investigated system a traction induction motor is employed. The matrix converter realised on the base of new progressive semiconductor elements is used to treat the electrically transmitted part of the whole drive energy. This solution is advantageous with regard to the reactive component reduction. The special digital control system consisting of two personal computers is used for the realised test bed. The matrix converter IGBTs are controlled by means of the designed indirect pulse width modulation method.

Matrix Converter Induction Motor Drive

  • Authors: prof. Ing. Jiří Lettl, CSc.,
  • Publication: 12th International Power Electronics and Motion Control Conference. Maribor: University of Maribor, 2006. pp. 787-792. ISBN 978-1-4244-0120-8.
  • Year: 2006
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converters have attracted an amount of interest over the past 25 years already, but they find time after time once again new utilisation. The presented paper deals with the recent concept of hybrid and power splitting traction drive systems. Special attention is paid to electric power splitting. In the investigated system a traction induction motor is employed. The matrix converter realised on the base of new progressive semiconductor elements is used to treat the electrically transmitted part of the whole drive energy. This solution is advantageous with regard to the reactive component reduction. The special digital control system consisting of two personal computers is used for the realised test bed. The matrix converter IGBTs are controlled by means of the designed indirect pulse width modulation method.

Matrix Converter Induction Motor Drive Control

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The designed concept of the matrix converter induction motor drive control system with emphasis on the PWM modulation strategy employed in the hybrid traction drive with electric power splitting is presented.

Matrix Converter PWM Strategy

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converters have attracted an amount of interest over the past 25 years already, but they find time after time once again new utilisation. The presented paper deals with the recent concept of hybrid and power splitting traction drive systems. Special attention is paid to electric power splitting. In the investigated system a traction induction motor is employed. The matrix converter realised on the base of new progressive semiconductor elements is used to treat the electrically transmitted part of the whole drive energy. This solution is advantageous with regard to the reactive component reduction. The special digital control system consisting of two personal computers is used for the realised test bed. The matrix converter IGBTs are controlled by means of the designed indirect pulse width modulation method.

Power Electronics Practical Education Conception

  • Authors: prof. Ing. Jiří Lettl, CSc.,
  • Publication: XXI. Mezinárodní symposium učitelů elektrických pohonů SYMEP 2006. Plzeň: Západočeská univerzita v Plzni, 2006. pp. 53-58. ISBN 80-7043-455-4.
  • Year: 2006
  • Department: Department of Electric Drives and Traction
  • Annotation:
    It has proved good to divide the practical training in power electronics to three basic levels. The first level is focused on putting together the converter from basic power semiconductor elements and put it into operation with a simple load type. In the second level the students work with the completed universal converter and focus on the control methods, in the third level they already measure the practical exercises with usual commercial converters.

Realized Matrix Converter Drive System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converters have attracted an amount of interest over the past 25 years already, but they find time after time once again new utilisation. The presented paper deals with the recent concept of hybrid and power splitting traction drive systems. Special attention is paid to electric power splitting. In the investigated system a traction induction motor is employed. The matrix converter realised on the base of new progressive semiconductor elements is used to treat the electrically transmitted part of the whole drive energy. This solution is advantageous with regard to the reactive component reduction. The special digital control system consisting of two personal computers is used for the realised test bed. The matrix converter IGBTs are controlled by means of the designed indirect pulse width modulation method.

Realized Matrix Converter PWM Strategy for Hybrid Drive System

  • Authors: prof. Ing. Jiří Lettl, CSc.,
  • Publication: Proceedings of the WSEAS International Conferences: 6th International Conference on Power Systems, on Simulation, modelling and Optimalization, on Signal, Speech and Image Processing, on Multimedia, Internet and Video Technologies, on Distance learning. Athens: WSEAS Press, 2006. pp. 404-409. ISSN 1790-5117. ISBN 960-8457-53-X.
  • Year: 2006
  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converters have attracted an amount of interest over the past 25 years already, but they find time after time once again new utilisation. The presented paper deals with the recent concept of hybrid and power splitting traction drive systems. Special attention is paid to electric power splitting. In the investigated system a traction induction motor is employed. The matrix converter realised on the base of new progressive semiconductor elements is used to treat the electrically transmitted part of the whole drive energy. This solution is advantageous with regard to the reactive component reduction. The special digital control system consisting of two personal computers is used for the realised test bed. The matrix converter IGBTs are controlled by means of the designed indirect pulse width modulation method.

Vector Controlled AC Drive with Induction Motor Nonlinear Model

  • Authors: prof. Ing. Jiří Lettl, CSc., Ratz, R.
  • Publication: Proceedings of Workshop 2006. Praha: České vysoké učení technické v Praze, 2006. pp. 498-499. ISBN 80-01-03439-9.
  • Year: 2006
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The vector controlled induction motor drive behaviour in case of taking into account the nonlinearity of the induction motor magnetizing inductance is presented. The magnetizing current is optimized in order to obtain the minimal stator current at the given torque, which means that the magnetizing flux is not constant.

Asynchronous Motor Vector Control Respecting Magnetic Nonlinearity

  • Authors: prof. Ing. Jiří Lettl, CSc., Rats, R.
  • Publication: TRANSCOM 2005 - 6th European Conference of Young Research and Science Workers in Transport and Telecommunications. Žilina: Žilinská univerzita, 2005. pp. 77-80. ISBN 80-8070-420-1.
  • Year: 2005
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with the vector controlled induction motor drive behaviour in case of taking into account the nonlinearity of the induction motor magnetizing inductance. The magnetizing current is optimized in order to obtain the minimal stator current at the given torque. Drives that count with the magnetically non-linear character of the induction motor in their control conception have much better dynamics.

Contribution to Induction Motor Vector Control

  • Authors: prof. Ing. Jiří Lettl, CSc., Rats, R.
  • Publication: XIII. International Symposium on Electric Machinery in Prague. Praha: ČVUT FEL, Katedra elektrických pohonů a trakce, 2005. pp. 141-145. ISBN 80-01-03328-7.
  • Year: 2005
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with the vector controlled induction motor drive behaviour in case of taking into account the nonlinearity of the induction motor magnetizing inductance. The vector control takes into consideration both successive steady-states and real mathematical equations that describe the motor itself. The obtained control results have a better dynamic for torque variations in a wider speed range. The space phasor theory is used to handle the equations.

Drive with Matrix Converter

  • Authors: prof. Ing. Jiří Lettl, CSc., Rats, R.
  • Publication: XXIX. celostátní konference o elektrických pohonech. Praha: Česká elektrotechnická společnost, 2005. pp. 158-163.
  • Year: 2005
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper deals with the behaviour of the induction motor drive with the rotor flux oriented vector control in case of respecting the induction motor magnetizing inductance nonlinearity caused by saturation. In addition the magnetizing current is optimized in order to be obtained the minimal stator current at the given induction machine torque. As a result of the designed control system concept implementation the shaft torque increasing in transient states and the general drive dynamics improving become evident.

Matrix Converter Control

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The designed concept of the matrix converter control system employed in the hybrid traction drive with electric power splitting is presented. The matrix converter inclusion in the drive is advantageous especially with regard to the reactive component reduction.

Matrix Converter Control System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with the matrix converter control hardware and software conception. The built matrix converter is used to treat the electrically transmitted energy part of the investigated hybrid power splitting drive system. The digital control system used for the realised test bed consists of two personal computers. The first one serves to monitoring purposes only, the second one is equipped with a common interface card and works in real time. All the signals are reprocessed and adjusted in interface cards situated in the control rack. From these cards the necessary electrical and optical signals are sent directly to the power and measure parts of the matrix converter system.

Matrix Converter Control System for Hybrid Drive

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The designed concept of the matrix converter control system employed in the hybrid traction drive with electric power splitting is presented. The matrix converter inclusion in the drive is advantageous especially with regard to the reactive component reduction.

Matrix Converter Drive

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converters possess many advantages compared to the nowadays common indirect frequency changers. Matrix converters do not require energy storage components as a bulky capacitor or an inductance in the DC-link demanding on the room, material, and finance. They enable the bi-directional power flow between the power supply and load. The most of the contemporary modulation strategies are able to provide practically sinusoidal waveforms of the input and output currents with negligible low order harmonics, and to control the input displacement factor. The PWM methods can be divided into two basic groups - direct and indirect methods. The direct methods result from the direct dependences between the input and output quantities of the converter. In case of the indirect methods, the so-called virtual intermediate dc link is being introduced, which makes it possible to derive the switch sequences combination of the matrix converter switching devices on account of the procedures well known

Matrix Converter PWM Strategy

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converters do not require energy storage components as a bulky capacitor or an inductance in the DC-link demanding on the room, material, and finance. They enable the bi-directional power flow between the power supply and load. The most of the contemporary modulation strategies are able to provide practically sinusoidal waveforms of the input and output currents with negligible low order harmonics, and to control the input displacement factor. The PWM methods can be divided into two basic groups - direct and indirect methods. The direct methods result from the direct dependences between the input and output quantities of the converter. In case of the indirect methods, the so-called virtual intermediate dc link is being introduced, which makes it possible to derive the switch sequences combination of the matrix converter switching devices on account of the procedures well known from the classical indirect frequency changers topologies.

Pulse Width Modulation of a Matrix Converter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converters possess many advantages compared to the nowadays common indirect frequency changers. The most of the contemporary modulation strategies are able to provide practically sinusoidal waveforms of the input and output currents with negligible low order harmonics, and to control the input displacement factor. The PWM methods can be divided into two basic groups - direct and indirect methods. The direct methods result from the direct dependences between the input and output quantities of the converter. In case of the indirect methods, the so-called virtual intermediate dc link is being introduced, which makes it possible to derive the switch sequences combination of the matrix converter switching devices on account of the procedures well known from the classical indirect frequency changers topologies.

Simulation and Realization of Matrix Converter Drive System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The paper deals with simulation and realization of the matrix converter control system employed in the hybrid traction drive with electric power splitting. The results obtained by means of the simulation and on the built-up experimental test bed have proved proper function of the designed matrix converter control hardware and software concept.

Vector Control Considering Non-Linearity of an Induction Motor

  • Authors: prof. Ing. Jiří Lettl, CSc., Rats, R.
  • Publication: EDS '05 IMAPS CS International Conference Proceedings. Brno: Vysoké učení technické v Brně, 2005. pp. 456-459. ISBN 80-214-2990-9.
  • Year: 2005
  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with the vector controlled induction motor drive behaviour in case of taking into account the non-linearity of the induction motor magnetizing inductance. Drives that count with the magnetically non-linear character of the induction motor in their control conception have much higher torque overloading capabilities, less torque ripple, and better dynamics than the ones utilizing a linear control model.

Alternative utilisation of a matrix converter

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Alternative utilisation of a matrix converter Annotation: The matrix converter seems to be the final name of one of the older static direct frequency changer power electronics circuit configuration, which finds once again new utilisation. This switch topology has the cycloconverter advantage of lacking a dc link, and hence lacks an energy store, while offering a potentially unlimited frequency range. The presented paper deals with the recent concept of hybrid and power splitting traction drive systems, whereas a special attention is paid to electric power splitting. In the investigated system a traction induction motor is employed, and the matrix converter realised on the base of new progressive semiconductor devices is used to treat the electrically transmitted part of the whole drive energy.

Matrix converter control system for hybrid drive

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with the designed concept of the matrix converter control system employed in the hybrid traction drive with electric power splitting. In the investigated system a traction induction motor is employed. The matrix converter realised on the base of new progressive semiconductor elements is used to treat the electrically transmitted part of the whole drive energy. This solution is advantageous with regard to the reactive component reduction. The special digital control system consisting of two personal computers is used for the realized test bed.

Matrix Converter in Hybrid Drives

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The matrix converters have attracted an amount of interest over the past 25 years already, but they find time after time once again new utilisation. The presented paper deals with the recent concept of hybrid and power splitting traction drive systems. Special attention is paid to electric power splitting. In the investigated systém a traction induction motor is employed. The matrix converter realised on the base of new progressive semiconductor elements is used to treat the electrically transmitted part of the whole drive energy. This solution is advantageous with regard to the reactive component reduction.

Matrix converters

  • Department: Department of Electric Drives and Traction
  • Annotation:
    Matrix converters, initially called direct frequency changers in general only, have attracted an amount of interest over the past twenty-five years already, but with the rapid progress in the semiconductor devices and control circuits they find once again new utilisation. The presented paper deals with the recent concept of hybrid and power splitting traction drive systems. Special attention is paid to electric power splitting. In the investigated system a traction induction motor is employed. The matrix converter realised on the base of new progressive semiconductor elements is used to treat the electrically transmitted part of the whole drive energy. This solution is advantageous with regard to the reactive component reduction. The special digital control system consisting of two personal computers is used for the realised test bed.

Unconventional Application of Matrix Converter System

  • Department: Department of Electric Drives and Traction
  • Annotation:
    The presented paper deals with the matrix converter control system hardware and software conception. The built matrix converter is used to treat the electrically transmitted energy part of the investigated hybrid power splitting drive system. Special attention is paid to electric power splitting. The special digital control system is used for the realised test bed. This system consists of two personal computers. The first one serves for monitoring purposes only, the second one is equipped with a common interface card and works in real time. All the signals are reprocessed and adjusted in interface cards situated in the control rack. From these cards the necessary electrical and optical signals are sent directly to the power and measure parts of the matrix converter system.

Duality of PWM Rectifiers

  • Authors: prof. Ing. Jiří Lettl, CSc.,
  • Publication: Electronic Devices and Systems 03 - Proceedings. Brno: VUT v Brně, FEI, Ústav mikroelektroniky, 2003. pp. 466-470. ISBN 80-214-2452-4.
  • Year: 2003

Duality of PWM Rectifiers

  • Authors: prof. Ing. Jiří Lettl, CSc.,
  • Publication: Electronic Devices and Systems 03 - Proceedings. Brno: VUT v Brně, FEI, Ústav mikroelektroniky, 2003. p. 466-470. ISBN 80-214-2452-4.
  • Year: 2003
  • Department: Department of Electric Drives and Traction
  • Annotation:
    PWM rectifiers make it possible to improve significantly the compatibility of power converter systems. The applied PWM method and control structure should fulfil the requirements for the converter output DC voltage control, converter operation with the desired power factor, elimination of the unwanted converter input current harmonics, minimum ripple of the converter output quantities, and high dynamics of the system transients. As concerns both the power circuit diagrams and performances, the current stiff rectifiers and the voltage stiff rectifiers can be considered to be dual devices. Compatibility with supply mains of these two converter types is compared.

Some Properties of Current Source Inverter Fed Induction Motor Drive

  • Authors: prof. Ing. Jiří Lettl, CSc., Frackiewicz, Z.
  • Publication: Proceedings of the 5th International Electromechanical and Electrical Systems. Szczecin: WUPS, 2001. pp. 657-660. ISBN 83-88764-70-5.
  • Year: 2001

Comparison of PWM Rectifiers Compatibility

  • Authors: prof. Ing. Jiří Lettl, CSc., Chekhet, E.M.
  • Publication: Proceedings of Int. Conf. on Problems of Present-day Electrotechnics - 2000. Kyjev: Kyjevskij polytěchničeskij institut, 2000. pp. 55-58. ISSN 0204-3599.
  • Year: 2000

PWM Voltage Stiff Rectifiers

  • Authors: Žáček, J., prof. Ing. Jiří Lettl, CSc.,
  • Publication: Proceedings of the EDPE 94. Košice: TU Košice, 1994. pp. 219-224. ISBN 80-967131-2-4.
  • Year: 1994

Responsible person Ing. Mgr. Radovan Suk