Energy and Power Engineering, 2013, 5, 121-124

doi:10.4236/epe.2013.54B023 Published Online July 2013 (http://www.scirp.org/journal/epe)

Control of Unit Power Factor PWM Rectifier*

Meifang Xue, Mingzhi He

School of Electrical Engineering, Beijing Jiaotong University, Beijing, China

Email: xuemeifang12@gmail.com

Received March, 2013

ABSTRACT

To solve the problem of harmonic pollution to the power grid that caused by traditional diode rectifier and phase con-

trolled rectifier, the unit power factor PWM rectifier is designed. The topology structure of the rectifier circuit is intro-

duced and the double closed-loop control strategy in three-phase stationary coordinate system is analyzed. For the defi-

ciency of control strategy, the control strategy in two-phase synchronous rotating coordinate system is proposed. This

makes the independent control of active current and reactive current to be realized. The simulation model of the PWM

rectifier is built and the effectiveness of the control method proposed in this paper is verified by simulation.

Keywords: Control; PWM Rectifier; Unit Power Factor; d, q Coordinates

1. Introduction

Unity power factor PWM rectifier has the advantages of

high power factor, low harmonic content of grid side

current, energy bidirectional transmission etc, is widely

used in AC drive, reactive power compensation, active

power filter, unified power flow control, as well as unin-

terruptible power supply, etc[1]. This paper introduces

the topology of three-phase PWM rectifier, and describes

the control method of the rectifier in three-phase static

coordinate system. On the basis of the analysis of the

advantages and disadvantages of this control method, the

control method in two-phase synchronous rotating coor-

dinate system is put forward. Then the mathematical

model of three-phase PWM rectifier in d, q coordinates is

established and the single control of active current and

relative current is realized.

2. The Control Method of Three-phase

Voltage Source PWM Rectifier in

Three-phase Static Coordinate System

Figure 1 shows the topology of three-phase voltage source

PWM rectifier, abc

is three-phase voltage source, C is

the dc side filtering capacity and

eee

R is the load.

In order to realize the control of input current and

output voltage, the traditional method is controlling the

three-phase input current directly. The control of the in-

put current is also the control of the flow of energy, thus

the control of the output voltage can be realized. The

control method of PWM rectifier in the three-phase sta-

tionary coordinate system is shown in Figure 2.

In this control method, the outer loop controls the DC

voltage. The difference value of the command signal and

actual signal of DC side voltage is imported to PI regu-

lator. The output value of PI regulator is DC current sig-

nal m

, m

is proportional to the amplitude of AC input

current. So the command signal of three-phase AC cur-

rent a*

、*

b

、*

c

can be obtained by separately

multiplying m

by sinusoidal signal whose phase is the

same as three-phase voltage. The difference value of

command current and actual current is imported to PI

regulator, and the sinusoidal modulation wave can be

deserved. By comparing the sinusoidal modulation wave

with carrier wave, the PWM wave which can control the

switch can be deserved.

Figure 1. The topology of three-phase voltage source PWM

rectifier.

sin t

2

sin( )

3

t

2

sin( )

3

t

Figure 2. The control method of PWM rectifier in three-

phase stationary coordinate system.

*Project Supported by National Natural Science Foundation of China

(51207008)

Copyright © 2013 SciRes. EPE