Ing. Michal Brejcha, Ph.D.

The dominant part of energy performance of a building consists of the consumption of heating and lighting. Both the heating and lighting systems of buildings work at their designed efficiency for most of the buildings’ lifetimes. Interference with existing systems is costly considering replacements and construction adjustments. Therefore, considerable effort must be put into the design of these systems during the building design phase. The article is focused on luminaire layout design strategy, which affects the number of luminaires in a building and therefore their power consumption and the sustainability of the building. A genetic algorithm with radiosity implemented has been used to find suitable placements of luminaires of a single type in a model room to decrease the number of luminaires as much as possible. The use of a genetic algorithm can reduce the number of luminaires by using an irregular grid of luminaire placement, and therefore decrease the power demand and increase the sustainability of the lighting system. Three outcomes of an optimal luminaire layout design are presented in this paper, including the design strategy conclusions. The results of the calculation outcomes were verified by software DIALux that is commonly used for designing lighting systems.

The paper discusses a way to deploy luminaires in a model room to provide required illuminance levels and uniformity of the working plane by using a genetic algorithm. The problems about determining the adequate DNA structure and fitness function are introduced and solved. The reflections from walls, ceiling and floor are taken into account in the calculations and further discussed. The output results of the algorithm are judged by requirements of the standard CSN EN 12464-1 and from the lighting system designer's point of view.

The paper discusses a way to deploy a given number of point light sources in the interior to provide required illuminance levels and uniformity of the working plane by using a genetic algorithm. Furthermore a genetic algorithm has been used to generate a proper luminous intensity distribution curve of multiple luminaires to meet the given criteria for the reference plane of the model room for predefined luminaire positions.

The paper deals with lighting road design. The demands on illuminance are defined in standard ČSN EN 13201 in case of Czech Republic. There are several parameters that a designer can change to get the optimal solution to fulfill the standard. The distance between pillars, their heights, the lamp overlap and tilt have to be defined. Such number of parameters make the optimization difficult. This paper solves the optimization via genetic algorithm. The fitness function that is convergent to good solutions is a vital point for this type of algorithms. The paper shows that solutions found by the genetic algorithm fulfill the demands and it also shows the way, how the fitness function can be created.

Void is defined such as blow hole in the solder joint. Voids may degrade the mechanical and conductive properties of the solder joint and thus decrease the reliability. Article deals with influence of humidity on voids formation inside the solder joint structure. Experimental part was carried on testing samples, where we used three types of solder pastes (Sn62Pb36Ag2, Sn96.5Ag3Cu0.5 and Sn95.5Ag4Cu0.5), three types of reflow technology (hot air, vapor phase and infra radiation reflow technology) and three types of humidity environments. The inspection was made on X-ray and following diagnostic was made by image analysis with special software.

Surface mount technology has many problems during production. One of them is a problem called tombstone effect. Tombstone effect is a well known phenomenon, when one end of the component (commonly small passive devices such as resistor or capacitor), rises up out of the solder pad and breaks conductive contact. This article focus on the problem with tombstone effect, in concrete in this article we studied the influence of type of reflow technology and type of surface finish on tomb stone effect. In our experiments three types of reflow technologies, three sizes of SMD components, one type of solder paste and three types of surface finishes were used.

This volume deals with Xray inspection possibilities for biological samples. There is presented small animalas such as fly and vesp.

The paper is aimed on some types of FACTS controllers, which can be used for improving the power quality in the point of connection with the power network. It is focused mainly on types of controllers interesting in using rather in large buildings than in transmission networks. The goal is to compare the features of the controllers in some tasks and clarify which solution is the best for defined purposes. The comparison was done by matrix diagram, which was the result of mind maps and other analysis tools.

The paper deals with issues of calculating average value of instantaneous active power in control programs of active harmonic conditioners (active harmonic filters). Common methods based on infinite impulse response (IIR) digital filters are not optimal in some cases. The reason could be the computational and memory complexity. The article describes the cases of instabilities of the IIR filters, which leads to malfunction of control program of active filter. The CIC decimator is presented as suitable substitution of IIR filters.

The paper is aimed on some types of FACTS controllers, which can be used for improving the power quality in the point of connection with the power network. It is focused mainly on types of controllers interesting in using rather in large buildings than in transmission networks. The goal is to compare the features of the controllers in some tasks and clarify which solution is the best for defined purposes. The comparison was done by matrix diagram, which was the result of mind maps and other analysis tools.

The article deals with possibilities of X-ray and computerized thomography of voids diagnostics inside solder joints.

The article continues with X-ray nondestructive testing explanation. It focuses to 3D CT technology. It briefly explains the reconstruction principle and also mentions the technologic artifact phenomenas.

This chapter continues with explanation the Xray inspection possibilities for non-electric samples

This paper deals with the solution for a wideband low-pass filter that can be used for filtering the input currents of switching converters, which are distorted by the switching frequency of PWM. Initially, the filter was proposed for the special type of AC converter, which is described in the paper. However, these solutions can also be used in the inputs of active PFC converters and in outputs of PWM converters, where are similar problems with switching frequency.

The article deals with diagnostic equipment of LVR at CTU in Prague. There is a description of the technolgy together with technical characteristics.

The authors deal with the problem of controlling of single phase active filters. Some algorithms for active filters controlling are well known today, but some of them can't be used in case of single phase filters. For example the PQ Theory (Theory of the Instantaneous Reactive Power) is excellent for three phase solutions, but for single phase solutions it can't be implemented. The main challenge in the single phase controlling method is to get the fundamental harmonic function in a proper magnitude and phase. The authors proposed a simple and fast method, which is based on the LMS algorithm ("Least Mean Square" algorithms are a class of adaptive filters). This method can be easily implemented also in 8-bit microcontroller units only with the need of sum and multiplication instructions.

Article deals with technological equipment of LVR at CTU in Prague. In article is a description of own technolgy together with characteristics of own technological equipment.

This paper is first of three articles about technology and realization of passive EMC filters. In this inductory section the authors deals with reasons of faults in frequency response of proposing filters. For this purpose is used the "Fault Tree Analysis". The article describes potential problems arising during proposing of filters and explains their possible solutions. There is also included related standards and publications covering these problems in the article.

This paper deals with realization of low-pass passive filter with low cut-off frequency and high attenuation in the stopband. This type of filters is called "sine filters" and are used in connection with switching power converters. There are usually used 1st order (only inductor) or 2nd order (LC section) three phase filters. Their purpose is to eliminate the fast change of voltage on motors, to reduce distortion of the input current, to reduce the power loss and wliminate the noise made by pulsed moments. The filter, which is described in the paper, is single phase and there are higher requirements for attenuation in stop-band.

This paper deals with the solution of wideband low-pass filter, which can be used for filtering the input currents of switching converters, which are distorted by a switching frequency of PWM. Initially the filter was proposed for the special type of AC converter, which is described in the paper. However such solution can be used also in the inputs of active PFC and in outputs of PWM converters, where the problems with the switching frequency are similar.

This project deals with the solution of AC/ AC converter based on buck-converter circuit. The circuit has interesting features in AC circuits, which were hardly described before. First of all it doesn't need a rectifier for its run. The conversion is made direct from AC circuit to AC circuit. The distortion of input current can be removed by simple passive filters without need any complicated PFC. The output voltage can be also easy sinusoidal if it is wanted. The control of the converter is also very easy, because the switches work with static duty-cycle. Behavior of the converter is very similar to regulated transformer. That can be utilize to construct an active compensator cos(φ). Unfortunately there are some catches in construction of the converter. This article tries to describe all of the main features and problems of the AC buck-converter.

The authors deal with the problem of zero-crossing detection in power mains voltage which is highly distorted by harmonics. The zero-crossing detection in such system can be difficult due to multiple zero cross in measured signal for example. Simple filtering of the signal can solve the problem of the distortion but it also adds a phase error between input and output signal. So the zeros both signals aren't synchronized. The authors proposed a solution based on adaptive filtering, which extracts the fundamental harmonic from the input signal. So the zero detection can be done according to the zero crossing in the fundamental harmonic.

This paper contains an idea of the freeform use of buck-converter in AC circuit. The buck-converter can be used as an AC/ AC converter or as a series active filter without any DC conversion. There is also briefly described a device with such solution in the paper. Device based on AC buck-converter should have output voltage waveform theoretically similar to the harmonic spectrum of the input voltage. Similar dependency is also between output and input current. These features easy satisfy EMC demands.

This paper deals with idea of extracting first harmonic function of input signal. This signal can be then use as a reference signal in active filtering. The paper is aimed especially on getting first harmonic function from power network voltage. Since the first harmonic frequency is relatively low the passive filters cannot be used for this purpose. It is also necessary that there isn´t any phase shift between the input and output signal.

There are many electrical devices connected to the mains requiring reliable synchronization with the mains voltage. These devices are for example thyristor-controlled rectifiers, uninterruptible power supplies or power converters returning electrical power to the mains. The voltage phase difference between the mains and the output of the converter is typically obtained by detecting zero voltage crossings. This is why a reliable zero voltage crossing detection is becoming so important affecting the converter's operation and the quality of the supplied or consumed energy. Suitable detection can be achieved with signal processing making use of fast signal processors or programmable gate arrays. But it makes the detection more complex and expensive. Therefore the authors try to find a simple and reliable solution even in the case of high distorted mains using only a simple microcontroller

This paper deals with well known buck-converter circuit which is mostly used in DC circuits. However the principle can be used also in AC circuits. In such case we obtain four-quadrant converter. Its behavior is similar to a regulated transformer. Unlike the transformer the converter has some other advantages. For example it can be used also as compensator cos(fi) or it can filter the output waveform. However it is not easy to make such converter. There are problems with voltage peaks on switching parts on one side and danger of short circuit on another side. Because the snubbers increase the losses the use of the converter is limited.

Zero-crossing detection is needed for synchronization of power switching devices. There are many possibilities, how it could be accomplished. This project has been testing an implementation of FIR-based zero crossing detection, which uses an adaptive filter based on algorithm LMS (Least Mean Square). This method is based only on signal processing and needs just a little of hardware components. The detection has been implemented in universal module made by ELFIS spol. s.r.o which is used to control power converters. There haven't been any other parts in the program, which for instance would control the switching, for the purpose of testing zero-crossing detection.

This paper deals with construction of a wall dimmer based on transistor IGBT. There are solved two solutions of the dimmer with designed PCBs in the paper. The results were compared with comon solutions based on triacs.