Power Conversion and Control of Wind Energy Systems

Book Preface

Wind energy is clean and sustainable. It is one of the fastest growing renewable energy resources. The conversion of wind kinetic energy into electric energy is of a multidisciplinary nature, involving aerodynamics, mechanical systems, electric machines, power electronics, control theory, and power systems. In the past, a number of books have addressed some of these subjects. This book explores the power conversion and control of wind energy conversion systems (WECS) from the electrical engineering perspective. It provides a comprehensive and in-depth analysis of wind generators, system configurations, power converters, control schemes, and dynamic/steady-state performance of various practical wind energy systems.

The book contains nine chapters. Chapter 1 provides a market survey and an overview of wind turbine technology, wind energy system classifications, costs, and grid codes for wind power integration. Chapter 2 introduces the fundamentals and control principles of wind energy systems, including wind turbine components, aerodynamics, stall and pitch controls, and maximum power point tracking schemes. Chapter 3 presents commonly used wind generators, including squirrel cage induction generators, doubly fed induction generators, and synchronous generators. The dynamic and steady-state models of these generators are also derived to facilitate the analysis of wind energy systems in the subsequent chapters.

Chapter 4 discusses various power converters and PWM schemes used in wind energy systems. Both voltage and current source converters are presented with an emphasis on high-power wind energy system. Chapter 5 presents a general overview of configurations and characteristics of major practical WECS. Chapter 6 focuses on fixed-speed, inductor generator based wind energy systems; important issues such as grid connection, two-speed operation, and reactive power compensation are discussed.

Chapter 7 deals with wind energy systems with variable-speed, squirrel cage induction generators (SCIG), in which typical system configurations and advanced control schemes such as field oriented controls (FOC) and direct torque control (DTC) are elaborated. Chapter 8 discusses doubly fed induction generator (DFIG) systems, where the subsynchronous and supersynchronous modes of operation are investigated. Chapter 9 is dedicated to variable-speed, synchronous generator wind systems, in which various control schemes, including zero d-axis current (ZDC) control, maximum torque per ampere (MTPA) control, and unity power factor (UPF) control, are analyzed in detail.

To help the reader understand the principle and operation of various wind energy conversion systems, we have developed more than 30 case studies in the body of the book and more than 100 solved problems in Appendix C—Problems and Solutions. Therefore, this book is not only for academic researchers and practicing engineers as a reference book, but also suitable for graduate students and final-year undergraduate students as a textbook.

We would like to express our sincere appreciation to Mr. Venkata Yaramasu, our Ph.D. student in the Laboratory for Electric Drive Applications and Research (LEDAR) at Ryerson University, for his great assistance in preparing the appendices and the first three sections of Chapter 4. We would like to thank our postdoctoral fellows and graduate students in LEDAR, in particular, Dr. Victor F. Liu, Dr. Moya J. Dai, Mr. Ning Zhu, and Mr. Ehsan Al-Nabi, for their kind assistance in preparing the manuscript. Our special thanks go to Wiley/IEEE Press editors for their great help and support. We also wish to acknowledge the support and inspiration of our families during the preparation of this book.

BINWU
YONGQIANG LANG
NAVID ZARGARI
SAMIR KOURO