Instantaneous Power Theory and Applications to Power Conditioning

Occasionally, one comes across a little gem of a book that leaves a mark in your mind. Instantaneous Power Theory and Applications to Power Conditioning, written by Hirofumi Akagi, Edson Hirokazu Watanabe, and Mauricio Aredes, is one of those little gems. This well-written and well-presented book is written by leading experts in this technology. While there are the usual odd typographical errors that exist in any monogram, one learns very quickly to overlook these and focus on the big picture. When I was approached to do this review, I did not hesitate since I was aware of the authors' pioneering volume of work in this field. I certainly do not regret that decision, as the book simply lives every bit up to the mark that I expected.

The instantaneous active and reactive power theory, or the so-called " theory" was introduced by Akagi, Kanazawa, and Nabae in 1982–1984 in four seminal publications, listed on page 104 of the book. This was followed by pioneering research work on modern active filters for power conditioning under the able leadership and guidance of Prof. Nabae at the Nagaoka University of Technology.

Since then, the theory has evolved and been extended by many authors. Its impact within the industry has been noteworthy, and it has redefined the power electronics and power conditioning industry. The theory was, in fact, one of the four pillars largely responsible for the majority of applications based on the workhorse voltage source converter that became popular after 1985. The other three pillars were the development of suitable high-power electronic switches, the microprocessor (or digital signal processors, DSPs) and the pulse-width modulation (PWM) control algorithms.

This book deals with the theory in a complete form for the first time. The book is timely, and it presents an in-depth treatise on the subject. It is destined to be a classic. If you have ever struggled with the very complex question "What is reactive power?" this book is truly your salvation as it provides clear insight into how energy flows from a source to a load, or circulates between phases, within a three-phase circuit. The theory uses the well-known Clarke matrix transformation which transforms three-phase voltages/currents into the reference frame. The mathematical derivation of the active power and the reactive power in terms of the components is easy to follow from thereon. The theory is equally applicable to three-wire as well as three-wire with neutral connection. And since the theory is based on instantaneous voltages/currents, it can be equally applied during steady or transient states.

The book contains only six chapters. However, the contents are clearly divided and competently presented in these chapters over 379 pages. The introductory Chapter 1 presents the problems relating to nonlinear loads and harmonics. Chapter 2 then logically delves into the various electrical power definitions based on conventional theories. Chapter 3 deals with the instantaneous power theory with numerous examples of designing controllers for active filters for power conditioning. Alternative sets of instantaneous power definitions such as the "modified theory" and "abc theory" are also discussed. Chapter 4 discusses shunt active filters with different filter structures. Chapter 5 discusses series active filters, including hybrid configurations of active and passive filters. And finally, Chapter 6 deals with combined series and shunt power conditioners, including the unified power quality conditioner (UPQC) and the unified power flow controller (UPFC). Moreover, this chapter introduces a new power conditioner referred to as the universal active power line conditioner (UPLC). This compensator shows how the theory can be used in a modular form to deal simultaneously with almost all kinds of power compensations. This includes the reactive power compensation as performed by a STATCOM and the power flow control as performed by a UPFC at the fundamental frequency, as well as harmonic compensation as performed by series and shunt active filters.

The figures are professionally drawn and the three-dimensional graphics are quite neat. The references have been judiciously selected, and only the most relevant ones have been included. As an example, the authors even selected relevant material from a doctoral thesis written in German. The earliest reference on the definition of power dates back to the 1920s. Sorting through the volumes of references on the topic and keeping only the most relevant ones is a task in itself, yet the authors seem to have pulled it off.

In a critical review, it is customary to pick at least one item in the book that fails to meets one¹s expectations. I looked long and hard and came up with the maybe trivial‹but still missing‹legend or list of acronyms and an appendix with perhaps a worked-out computer simulated system example. For instance, one example based on the shunt selective harmonic compensation (p. 208) could have been included with many more practical details in the appendix. I would also have preferred to see some biographical notes on the authors. This is not a textbook for undergraduate students, as it does not contain any problems to be answered and it delves deeply into a narrow but focused topic. However, postgraduate students and practicing engineers from the drives, utilities, and hardware manufacturing industries will certainly find it most instructive as a reference tome.

In closing then, for those of you interested in power electronic drives and power conditioners, this reference book is a must-have for your bookshelves.

Reviewed by Vijay K. Sood