Power Electronics Basics: Operating Principles, Design, Formulas, and Applications

Book Preface

Efficiency of the use of electrical energy can be significantly improved  by means of power electronics. The latter is the fastest growing field of  electrical engineering. This book is devoted to the world of power electronics. It presents and explains the basics and the most important concepts of power electronics. It also gives us the fundamental knowledge  for analysis and design in its area. Readers will find many practical  examples that demonstrate the achievements and prospects of developing and using power electronics including mainstream such as renewable  energy production, transferring, and distribution.

This book will be of interest to many readers including graduate students, industry professionals, researchers, and academics.
The authors express their gratitude to all who helped in the creation of this book.
Yuriy Rozanov
Sergey Ryvkin
Evgeny Chaplygin
Pavel Voronin

Power electronics involves the conversion of electrical energy or the  switching (on or off) of an electrical power circuit, with or without con trol of the electrical energy (IEC, 551-11-1). In the Russian literature, power  electronics associated with the conversion of electrical energy is often  referred to as converter engineering.
Electronic power conversion may be defined as the modification of one  or more parameters of electrical energy by means of electronic devices,  without significant power losses (IEC, 551-11-2).

A converter is a device for power conversion, with one or more switching components and also, if necessary, transformers, filters, and auxiliary  devices (IEC, 551-12-01).

A converter for power-supply purposes is often called a secondary  power source, in contrast to primary sources such as batteries, solar cells,  and ac grids.

The main forms of power conversion are as follows (Kassakian et al.,  1991; Mohan et al., 2003; Rozanov, 2007; Zinov’ev, 2012):
1. Rectification (conversion from ac to dc). The corresponding converter is known as a rectifier or an ac/dc converter for rectification.
The energy source for most consumers is a single- or three-phase  general-purpose ac grid. At the same time, dc voltage is required  for control and communications devices and computers. It is also  required for certain components of drives, electrical equipment, and  optical equipment. In autonomous systems, the ac sources are rotary  generators. Rectifiers are the most common power converters.
2. Inversion (conversion from dc to ac). The corresponding converter  is known as an inverter or an ac/dc converter for inversion. The dc  source of an inverter may be a battery, a solar cell, or a dc transmission line or else another converter.
3. Conversion from ac to dc and vice versa. The corresponding converter  is known as an ac/dc converter. Such converters are able to change the direction of the energy flux and may operate either in the rectifier  mode, when the energy is transmitted from an ac grid to a dc circuit,  or in the inverter mode, when the energy is transmitted from a dc  circuit to an ac grid. In an electric drive, changing the direction of the energy flux ensures a recuperative braking of the machine.
4. Conversion from ac to ac. The corresponding converter is known as an  ac converter. Three types exist:
a. The ac voltage converter, with the same number of phases and  the same voltage frequency at the input and output, changes the  voltage amplitude (upward or downward) and/or improves the  voltage by stabilizing the fundamental harmonic or by adjusting the harmonic composition.
b. The frequency converter transforms an m1-phase voltage of frequency f1 to an m2-phase voltage of frequency f2. Many components of drives, electrical equipment, and optical equipment  require alternating current whose frequency is variable or differs from the industrial frequency of 50 (60) Hz. Such components include ac frequency drives, inductive heaters, and power  sources of optical equipment. Rotary generators in autonomous  systems often produce voltage of unstable frequency, whose stabilization requires frequency converters.
c. The phase converter transforms single-phase to three-phase voltage and vice versa. Conversion of single-phase to three-phase  voltage permits power supply to three-phase components in  the absence of a three-phase grid. The connection of highpower single-phase loads to a single phase of a three-phase grid  imposes an asymmetric burden on the grid, and it is expedient to use the appropriate phase converter in that case.
5. Conversion from dc to dc. The corresponding converter is known as a  dc converter. Such conversion improves the power of a dc source and  matches the voltage of the source and consumers. It is most often  employed for components whose power source is a low-voltage  battery.
6. Reactive power conversion. The corresponding converter is known as  a reactive power converter. Such conversion compensates the reactive  power generated or consumed (Section 1.3). Converters of this type  draw active power from the grid only for the compensation of losses.

These are the basic types of power conversion, but others also exist. For  example, in technological systems, units for the generation of powerful  single pulses are employed. As technology develops, the list of powerelectronic components may grow.
As already noted, converters may change the direction of the energy  flux. A converter with one possible direction of power flow transmits energy  Chapter one: Basic concepts and terms in power electronics 3 only in one direction: from the source to the load. Converters in which  the direction of the energy flux may change are known as reversible converters. Two-quadrant converters may change the direction of the energy  flux by changing the polarity of the voltage or current in the load circuit.  Four-quadrant converters may change the direction of the energy flux by  changing the direction of both the voltage and the current. Multiquadrant  converters capable of changing the direction of the energy flux may be  based not only on ac/dc converters, but also on ac converters of different  types and dc converters.

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