瞬时无功功率理论

Instantaneous Power Theory and Applications to Power Conditioning. By Akagi, Watanabe, & Aredes 1

Copyright © 2007 the Institute of Electrical and Electronics Engineers, Inc.

CHAPTER 1

INTRODUCTION

The instantaneous active and reactive power theory, or the so-called “p-q Theory,”

was introduced by Akagi, Kanazawa, and Nabae in 1983. Since then, it has been

extended by the authors of this book, as well as other research scientists. This

book deals with the theory in a complete form for the first time, including com-

parisons with other sets of instantaneous power definitions. The usefulness of the

semiconductor devices, analog/digital signal processing, voltage/current sensors,

and control theory.

Concepts and evolution of electric power theory are briefly described below.

Then, the need for a consistent set of power definitions is emphasized to deal with

electric systems under nonsinusoidal conditions. Problems with harmonic pollution

in alternating current systems (ac systems) are classified, including a list of the prin-

distribution power systems at the end of the 19th century was based on sinusoidal

without ac power systems with “constant” voltage and frequency.

With the emergence of sinusoidal voltage sources, the electric power network

could be made more efficient if the load current were in phase with the source

er can be delivered or consumed if the voltage and current are sinusoidal and per-

fectly in phase. The power factor gives a relation between the average power ac-

ing the circuit efficiently.

er factor correction, which could be done by using capacitor banks or, in some

power definitions under nonsinusoidal conditions were introduced by Budeanu

[3,4], in 1927 and Fryze [5] in 1932. Fryze defined power in the time domain,

whereas Budeanu did it in the frequency domain. At that time, nonlinear loads were

negligible, and little attention was paid to this matter for a long time.

Chapter 2 presents a review of some theories dealing with nonsinusoidal conditions.

As pointed out above, the problems related to nonlinear loads have significantly

increased with the proliferation of power electronics equipment. The modern equip-

ment behaves as a nonlinear load drawing a significant amount of harmonic current

from the power network. Hence, power systems in some cases have to be analyzed

under nonsinusoidal conditions. This makes it imperative to establish a consistent

soidal conditions.

have a quick response in controlling their voltages or currents, they may draw reac-

tive power as well as harmonic current from power networks. This has made it clear

that conventional power theories based on average or rms values of voltages and

currents are not applicable to the analysis and design of power converters and pow-

er networks. This problem has become more serious and clear during comprehen-

sive analysis and design of active filters intended for reactive-power compensation

as well as harmonic compensation.

From the end of the 1960s to the beginning of the 1970s, Erlicki and Emanuel-

Eigeles [6], Sasaki and Machida [7], and Fukao, Iida, and Miyairi [8] published their

a way as to supply reactive power to the load, the power network will only supply ac-

tive power to the load. Therefore, ideal power transmission would be possible.”

Gyugyi and Pelly [9] presented the idea that reactive power could be compensat-

ed by a naturally commutated cycloconverter without energy storage elements. This

idea was explained from a physical point of view. However, no specific mathemati-

cal proof was presented. In 1976, Harashima, Inaba, and Tsuboi [10] presented,

probably for the first time, the term “instantaneous reactive power” for a single-

phase circuit. That same year, Gyugyi and Strycula [11] used the term “active ac

power filters” for the first time. A few years later, in 1981, Takahashi, Fujiwara,

plained by them.

The p-q Theory in its first version was published in the Japanese language in

1982 [14] in a local conference, and later in Transactions of the Institute of Electri-

cal Engineers of Japan [15]. With a minor time lag, a paper was published in Eng-

lish in an international conference in 1983 [16], showing the possibility of compen-

sating for instantaneous reactive power without energy storage elements. Then, a

more complete paper including experiental verifications was published in the IEEE

Transactions on Industry Applications in 1984 [17].

The p-q Theory defines a set of instantaneous powers in the time domain. Since

no restrictions are imposed on voltage or current behaviors, it is applicable to three-

and currents into the 0-stationary reference frames. As will be seen in this book,

the p-q Theory provides a very efficient and flexible basis for designing control

ELECTRONICS EQUIPMENT

The proliferation of nonlinear loads has spurred interest in research on new power

theories, thus leading to the p-q Theory. This theory can be used for the design of

power electronics devices, especially those intended for reactive-power compensa-

tion. Various problems related to harmonic pollution in power systems have been

investigated and discussed for a long time. These are listed as follows:

앫 Overheating of transformers and electrical motors. Harmonic components in

voltage and/or current induce high-frequency magnetic flux in their magnetic

core, thus resulting in high losses and overheating of these electrical ma-

overcome this problem [19].

causing damage.

앫 Voltage waveform distortion. Harmonic current may cause voltage waveform

This is a common fact when rectifiers are used. Rectifier currents distort the

voltage waveforms with notches that may change the zero-crossing points of

the voltages. This can confuse the rectifier control circuit itself, or the control

circuit of other equipment.

앫 Interference with communication systems. Harmonic currents generated by

nonlinear loads may interfere with communication systems like telephones,

radios, television sets, and so on.

In the past, these problems were isolated and few. Nowadays, with the increased

cannot be tolerated.