Електромагнітна сумісність у системах електропостачання

The textbook is devoted to electromagnetic processes connected both with conducted and field electromagnetic interferences. Special attention is paid to interharmonic electromagnetic interference. Questions of electromagnetic compatibility in power networks with wind electric sets, problems of voltage dips and voltage impulses are considered. Active filters are considered as a specific problem of electromagnetic compatibility. Influence of electromagnetic fields on biosphere, of electromagnetic ecology, economic and legal problems of electromagnetic compatibility are presented

Development of reliability methodology for systems engineering. Volume II - Application - Design reliability analysis of a 250 volt-ampere static inverter Final report

Design stage reliability analysis application to static inverte

Energy loss minimising function of variable speed drive filters

With their many benefits, Variable Speed Drives (VSDs) have grown rapidly in their usage in recent years. However, a unfortunate side effect of their usage is the introduction of harmonic distortion in the power system and reduction of true power factor (TPF). Low true power factor means poor electrical efficiency. The lower the true power factor, the higher the apparent power drawn from the distribution network. A filter connected at the input side of a VSD converter reduces energy losses in the power supply system by reducing harmonics and improving the true power factor. In this thesis, a typical three-phase rectifier is used as an example to present a methodology of designing such filters in technical and economic terms. The relationship between the cost of input filters and the energy cost reduction they provide on the power supply side of VSDs is discussed. By extending the same method to different loads, filters are designed and power savings are calculated. The pricing of relevant harmonic filters is also discussed. The basics of harmonics and the power factor are presented in the introduction. The summary of the results and suggestions for further research are contained in the last sections of the thesis

Transients in Power Systems

Power system engineering largely focuses on steady state analysis. The main areas of power system engineering are power flow studies and fault studies - both steady state technologies. But the world is largely transient, and power systems are always subject to time varying and short lived signals. This technical report concerns several important topics in transient analyses of power systems. The leading chapter deals with a new analytical tool-wavelets-for power system transients. Flicker and electric are furnace transients are discussed in Chapters I1 and IV. Chapter 111 deals with transients from shunt capacitor switching. The concluding chapters deal with transformer inrush current and non simultaneous pole closures of circuit breakers. This report was prepared by the students in EE532 at Purdue University. When I first came to Purdue in 1965, Professor El-Abiad was asking for student term projects which were turned into technical reports. I have \u27borrowed\u27 this idea and for many years we have produced technical reports from the power systems courses. The students get practice in writing reports, and the reader is able to get an idea of the coverage of our courses. I think that the students have done a good job on the subject of transients in power systems

Unified Power Quality Conditioner: protection and performance enhancement

The proliferation of power electronics-based equipment has produced a significant impact on the quality of electric power supply. Nowadays, much of the equipment is based on power electronic devices, often leading to problems of power quality. At the same time this equipment is typically equipped with microprocessor-based controllers which are quite sensitive to deviations from the ideal sinusoidal line voltage. Conventional power quality mitigation equipment is proving to be inadequate for an increasing number of applications, and this fact has attracted the attention of power engineers to develop dynamic and adjustable solutions to power quality problems. One modern and very promising solution that deals with both load current and supply voltage imperfections is the Unified Power Quality Conditioner (UPQC). This thesis investigates the development of UPQC protection scheme and control algorithms for enhanced performance. This work is carried out on a 12 kVA prototype UPQC. In order to protect the series inverter of the UPQC from overvoltage and overcurrent during short circuits on the load side of the UPQC, the secondary of the series transformer has to be short-circuited in a reasonably short time (microseconds). A hardware-based UPQC protection scheme against the load side short circuits is derived and its implementation and effectiveness is investigated. The main protection element is a crowbar connected across the secondary of the series transformer and consisting of a pair of antiparallel connected thyristors, which is governed by a very simple Zener diode based control circuit. Also, the software-based UPQC protection approach is investigated, the implementation of which does not require additional hardware

Effects of overvoltage on power consumption

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.In the recent years there is an increasing need of electrical and electronic units for household, commercial and industrial use. These loads require a proper electrical power supply to convey optimal energy, i.e. kinetic, mechanical, heat, or electrical with different form. As it is known, any electrical or electronic unit in order to operate safely and satisfactory, requires that the nominal voltages provided to the power supply are kept within strict boundary values defined by the electrical standards and certainly there is no unit that can be supplied with voltage values above or below these specifications; consequently, for their correct and safe operation, priority has been given to the appropriate electrical power supply. Moreover, modern electrical and electronic equipment, in order to satisfy these demands in efficiency, reliability, with high speed and accuracy in operation, employ modern semiconductor devices in their circuitries or items. Nevertheless, these modern semiconductor devices or items appear non-linear transfer characteristics in switching mode, which create harmonic currents and finally distort the sinusoidal ac wave shape of the current and voltage supply. This dissertation proposes an analysis and synthesis of a framework specifically on what happens on power consumption in different types of loads or equipment when the nominal voltage supply increases over the permissibly limits of operation. A variety of loads have been selected from those used in everyday life, for household needs, office needs, as well as trade and industry. They were classified in two main categories, the passive loads and the non-linear loads. The classification was made on the event that the passive loads do not create harmonic currents but the non-linear loads create harmonic currents. For the above purpose was made practical experimental testings on several loads – equipment of both the categories in the laboratories, summarising the effects of the supplying voltages in power consumption at higher values1 gradually, from the nominal values up to the overvoltages. Also in some cases, for more accurate observation, was used the PSpice simulating program. 1 For a better understanding of the events, some experimental testings was made at lower supplying voltages – undervoltages across the loads. Finally, the results from the experimental testings confirmed that the effects of the overvoltages are: the increased consumption of power, the decrease of the lifespan of electronic components due to overheating, they are different with respect to the nature of the loads, the increased amplitude of the current harmonics in the non-linear loads. For harmonic current reduction, an easy to use Pulse Width Modulation (PWM) method is proposed through booster topology, using a minimum number of components. This electronic circuit (harmonic current reducer) is cheap and easy to use, and can be easily connected between the mains supply and the non-linear load. It reduces, or keeps in low level the amplitudes of the current harmonics of the supplying current (distorted) of a non-linear load, in order to offer an extra protection or relief to the load when the supplying voltage or mains increases from its nominal value to undesired overvoltage values. Also, in order to avoid the undesirable effects on power consumption, due to overvoltages, design of a prototyping electronic circuit is proposed. This circuit (stabiliser), like the above harmonic current reducer, can be easily connected between the mains supply and a load or equipment; despite the mains supply variations, it keeps constant the desired or nominal voltage supply (voltage amplitude, Vpeak to peak) across the load or equipmen

Rectifier power converter for marine applications with compensating capacitor and boost converter stage

Environmental concerns and new emissions regulations, as well as increasing power needs for marine electrical grids, are pushing the development of more efficient power converters for shipboard power systems (SPS). The priorities for SPS design are reliability and power density especially in harsh operating conditions. Safety, space, and weight are of paramount importance requirements on a ship. One factor affecting the design of SPS is the high inductive impedance presented by ac generators, which requires high voltage ratios to compensate for. Therefore, ac-dc converters, sitting as they do between ac generators and the dc bus of the SPS, are identified as a point of potential development to improve the form factor and efficiency of SPS. A novel series capacitor compensation technique is proposed and applied to an ac-dc boost rectifier. Time-averaged equations are derived and compared to simulated waveforms generated using MATLAB/Simulink. Total harmonic distortion (THD) and power factor (PF) are calculated and measured. THD is found to be the limiting factor in designing the proposed compensator. The circuit is simulated in one and three phases, and several input-to-output voltage ratios are compared. To verify the practicality of the compensation method, a single-phase 1 kW rated prototype is implemented and practical results are presented and compared with the simulated waveforms. It is found that the compensation method can control THD to acceptable levels for a large range of inductive impedances, suggesting that this solution should be further developed and investigated for application in SPS.Environmental concerns and new emissions regulations, as well as increasing power needs for marine electrical grids, are pushing the development of more efficient power converters for shipboard power systems (SPS). The priorities for SPS design are reliability and power density especially in harsh operating conditions. Safety, space, and weight are of paramount importance requirements on a ship. One factor affecting the design of SPS is the high inductive impedance presented by ac generators, which requires high voltage ratios to compensate for. Therefore, ac-dc converters, sitting as they do between ac generators and the dc bus of the SPS, are identified as a point of potential development to improve the form factor and efficiency of SPS. A novel series capacitor compensation technique is proposed and applied to an ac-dc boost rectifier. Time-averaged equations are derived and compared to simulated waveforms generated using MATLAB/Simulink. Total harmonic distortion (THD) and power factor (PF) are calculated and measured. THD is found to be the limiting factor in designing the proposed compensator. The circuit is simulated in one and three phases, and several input-to-output voltage ratios are compared. To verify the practicality of the compensation method, a single-phase 1 kW rated prototype is implemented and practical results are presented and compared with the simulated waveforms. It is found that the compensation method can control THD to acceptable levels for a large range of inductive impedances, suggesting that this solution should be further developed and investigated for application in SPS

Modeling and analysis of power processing systems: Feasibility investigation and formulation of a methodology

A review is given of future power processing systems planned for the next 20 years, and the state-of-the-art of power processing design modeling and analysis techniques used to optimize power processing systems. A methodology of modeling and analysis of power processing equipment and systems has been formulated to fulfill future tradeoff studies and optimization requirements. Computer techniques were applied to simulate power processor performance and to optimize the design of power processing equipment. A program plan to systematically develop and apply the tools for power processing systems modeling and analysis is presented so that meaningful results can be obtained each year to aid the power processing system engineer and power processing equipment circuit designers in their conceptual and detail design and analysis tasks