Electric Energy Systems and Engineering Series – serie

Numerical methods for solving boundary value problems have developed rapidly. Knowledge of these methods is important both for engineers and scientists. There are many books published that deal with various approximate methods such as the finite element method, the boundary element method and so on. However, there is no textbook that includes all of these methods. This book is intended to fill this gap. The book is designed to be suitable for graduate students in engineering science, for senior undergraduate students as well as for scientists and engineers who are interested in electromagnetic fields. Objective Numerical calculation is the combination of mathematical methods and field theory. A great number of mathematical concepts, principles and techniques are discussed and many computational techniques are considered in dealing with practical problems. The purpose of this book is to provide students with a solid background in numerical analysis of the field problems. The book emphasizes the basic theories and universal principles of different numerical methods and describes why and how different methods work. Readers will then understand any methods which have not been introduced and will be able to develop their own new methods. Organization Many of the most important numerical methods are covered in this book. All of these are discussed and compared with each other so that the reader has a clear picture of their particular advantage, disadvantage and the relation between each of them. The book is divided into four parts and twelve chapters.

This is the final volume in a four-volume series concerning POWER ELEC­ TRONIC CONVERTERS. The first volume studies AC/DC conversion, the second studies AC/ AC conversion, and the third DC/DC conversion. This final volume deals with DC/AC conversion, i.e. with inverters. At the output of an inverter fed by a DC voltage supply, this voltage is alternatively found with one polarity and then with the other; in other words, an AC voltage made up of square pulses is obtained. Filtering must be carried out if, as is normally the case, a virtually sinusoidal voltage is required: this problem of filtering underlies the entire study of inverters. In some applications, the load itself provides the filtering. In others, a filter is installed between the inverter and the load; however, as it will be shown in Chap. 2, in cases where the filtered voltage is at industrial network frequency and comprises only a single square-wave pulse per half-cycle, the filter becomes bulky and costly, and the results obtained are poor. Filtering problems explain the considerable development of inverters during the last years: - Firstly there is increasing use of pulse width modulation: each half-cycle is cut up into several pulses of suitable widths; this greatly simplifies filtering. The use of a chopping frequency which is much greater than the frequency of the fundamental components of the inverter output voltage and current has only been made possible by progress in the field of semiconductor devices.

This book is the third in a series of four devoted to POWER ELECTRONIC CONVERTERS: The first of these concerns AC to DC conversion. The second concerns AC to AC conversion. This volume examines DC to DC conversion. The fourth is devoted to DC to AC conversion. Converters which carry out the DC-DC conversion operate by chopping the input voltage or current: they are called choppers or switch-mode power converters. Their operating frequency is not imposed by either the input or the output, both of which are at zero frequency. A frequency which is much greater than that of the industrial network can be chosen, provided that suitable configurations and semiconductor devices are used. This is the first difference compared to the rectifiers and AC-AC converters, analyzed in the previous volumes and which often operate at the industrial network frequency. The second difference concerns the commutation mode. Choppers operate in forced commutation. The beginning of an operating phase does not auto­ matically turn off the semiconductor devices which were conducting during the previous phase and which have to be brought to the blocking state. This turn-off must be carried out autonomously. These two differences - the higher frequency of commutations and, espe­ cially, the different mode of commutation -justify the first two chapters in this work: - Chapter 1 examines general notions concerning converters, supplies and loads, and more especially, how they can be characterized with regard to commutations.

Power electronics became an identifiably separate area of electrical engineering with the invention of the thyristor about 30 years ago. The growing demand for controllability and conversion of electric energy has made this area increasingly important, which in turn has resulted in new device, circuit and control developments. In particular, new components, such as the GTO and power MOSFET, continue to extend power electronic technology to new applications. The technology embodied by the name "power electronics" is complex. It consists of both power level and signal level electronics, as well as thermal, mechanical, control, and protection systems. The power circuit, that part of the system actually processing energy, can be thought of as an amplifier around which is placed a closed loop control system. The goal of this book is to provide an easily understood exposition of the principles of power electronics. Common features of systems and their behavior are identified in order to facilitate understanding. Thyristor converters are distinguished and treated according to their mode of commutation. Circuits for various converters and their controls are presented, along with a description of ancillary circuits such as those required for snubbing and gate drives. Thermal and electrical properties of semiconductor power devices are discussed. The line-converter and converter-load interfaces are examined, leading to some general statements being made about energy transfer. Application areas are identified and categorized with respect to power and frequency ranges. The many tables presented in the book provide an easily used reference source.

In 1965-66 the authors have given courses for AEG engineers in the area of "Industrial Installations". The purpose of the courses was to enable the parti­ cipants to carry out calculations on feedback control for drive systems. In 1967 these courses were printed under the title "Calculation of Feedback Control Circuits for Drive Systems". This handbook with the same title arises out of the revision of that publication. The scope was extended by the addition of new sections. Today, many specialized books and publications in the area of control technology are available to the reader. Most of them are characterized by a presentation of the mathematical theory of the fundamental concept and pro­ cedures involved. However, there are few instruction books containing worked examples on the practical application of those procedures. This book is intended to introduce the reader to the practical calculation of feed back control circuits without too much theory. Electric drives were chosen as the area of application. In an instruction book with examples of application, the problem arises of reducing the theoretical treatment of fundamentals and the mathematical deriva­ tions without gaps arising and without the necessity for consulting additional works of reference. The chosen way may be briefly explained.