Ing. Michal Košík, Ph.D.

This paper presents a novel bifurcation-based parameter extraction (BBPE) method for inductive power transfer (IPT) systems. The proposed method utilizes only transmitter-side measurements to accurately determine all coil parameters, including the complex coupling coefficient, making it useful for both optimizing power transfer and efficiency, as well as sensorless metal object (MO) detection. The method is based on two primary current frequency responses, one measurement with an open load and the other with a shorted load. The primary current amplitude spectrum for an open load contains one peak, while a shorted load puts the system in a deep bifurcation state, resulting in two peaks and one minimum. The resonant frequencies and primary current amplitudes at the peaks for the two loads are measured and used to solve for the coil parameters. With its ability to extract all coil parameters, this method is an improvement over previous techniques that could only extract a subset of parameters using transmitter-side information. Measurements of an IPT system with and without an MO are used to validate the effectiveness of the BBPE method.

This paper presents a novel estimation method for obtaining primary and secondary self-inductances and the mutual inductance for inductive power transfer (IPT), based only on measuring the input current amplitude. The input current frequency response characterizes the IPT system, if the IPT system is operated in deep bifurcation, which can be achieved by shorting the load. The frequencies of two peaks emerging in deep bifurcation are used to find the coupling coefficient. The frequency of the minimum between the peaks matches the secondary resonance frequency. The relative ratio of the peak values depends on the ratio of primary and secondary resonance frequencies and coupling coefficient. Thus, the resonance frequencies and coupling can be estimated based on measured frequencies and values of local extrema. Assuming known and constant compensation capacities, values of self-inductances and mutual inductance can be estimated from these parameters. The presented method is experimentally validated for an IPT system under the secondary coil displacement.

This work presents a novel, sensorless method of metal object detection (MOD) based on the bifurcation phenomenon in inductive power transfer (IPT). Our method is based on measuring the amplitudes of two peaks of the primary current, which emerge in bifurcation. Bifurcation is achieved by shorting the load; thus, the method is applicable in standby mode, e.g., before initiating power transfer. For a tuned system without a metal object (MO) nearby, these current peaks have equal magnitudes. However, if a MO is coupled to the charging pads, then the magnitudes are generally not equal. When the measured amplitude imbalance exceeds a threshold, the MO is positively detected. The benefit of our approach is that it only requires a relative, primary-side measurement of two resonant peak amplitudes. Assuming the primary and secondary resonators are closely tuned, no additional calibration is necessary. In contrast, traditional sensorless MOD approaches generally require wireless communication between the secondary and primary and/or initial parameter measurements and calibration if certain parameters are not accurately known a priori. After developing the theory, we experimentally verify our bifurcation-based MOD approach using a IPT system with a parasitically coupled coin and compare our results to that of a traditional resonant frequency-based MOD approach.

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.

Series-series compensated inductive power transfer (SSIPT) systems have been widely studied and characterized for constant resistance loads (CRLs) and constant voltage loads (CVLs), but much less so for constant power loads (CPLs), although CPLs have numerous applications. In this work, we address some of the fundamental knowledge gaps for SSIPT/CPL systems that we believe have not been fully explored in the literature. First, we apply Middlebrook’s stability criterion to derive a closed-form impedance-based stability condition for SSIPT/CPL systems. The derivation of the equilibrium solution is based on small-signal analysis and we show its consistency with intuitive results from perturbation-based arguments. Second, we show that the power transfer efficiency is minimum at the resonant frequency of the primary resonator. Third, the stability criterion is used to develop a straightforward approach for finding the operating frequency and input voltage that achieves near-maximum power transfer efficiency. This solution is useful as a starting point for a more meticulous parameter sweep to find the optimum input voltage and frequency values. Our analytical results are validated by performing frequency sweep measurements with two SSIPT experimental setups – one tuned to 165 kHz and the other to 6.78 MHz. We also provide an intuitive description and comparison of voltage-driven and current-driven CPLs. This topic is rarely treated in an intuitive manner and largely ignored, but we believe a solid conceptual understanding of voltage-driven and current-driven CPLs is beneficial for designers.

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.

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.

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.

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.

This article describe the contactless power transfer (CPT) model created and analyzed in softwares Maxwell and Simplorer. There are mentioned basic analytic equations for electric charging device based on contactless electric energy transfer. From analysis of CPT model created and simulated by co-simulation of Maxwell and Simplorer, basic CPT device operational electric parameters were obtained. CPT operational electric parameters such as transferred power, efficiency, inductances, operational frequency and many others.

The charger station utilizing Contactless power transfer (CPT) is auspicious alternative for Electric vehicle (EV) charging. In this paper, the proposed EV charger layout and individual components are discussed. Inverter and rectifier for CPT transformer and load control strategies are considered. Importance of optimal switching principle for high frequency operation is discussed. Additional components necessary for EV charger operation and their influence over CPT system are considered. Finally, CPT charger is compared with cable charger. Proposed system shall be used for further simulations and elaborated in scaled model.

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.