用于三相PWM并网逆变器的改进型幅相控制方法_英文_

J Shanghai Univ(Engl Ed),2008,12(6):560–564

Digital Object Identifier(DOI):10.1007/s11741-008-0617-1

The improved PAC method for a three-phase PWM

grid-connected inverter

LI Jie( ),MA Yi-wei( ),CHEN Guo-cheng( ),WANG De-li( ),

YU Jun-jie( )

Shanghai Key Laboratory of Power Station Automation Technology,Shanghai University,Shanghai200072,P.R.China Abstract In this paper,a vector regulating principle of the phase and amplitude control PAC method for three-phase grid-connected inverters is presented.To solve the problem of heavy inrush current and slow dynamic response when system starts up,the starting voltage prediction control and the current feed-forward control are proposed and used,which improve the dynamic performance of the system in the PAC.The experimental results carried out on a three-phase grid-connected inverter proved the validity of the proposed method.

Keywords three-phase pulse width modulation(PWM)grid-connected inverter,phase and amplitude control(PAC),starting voltage prediction control,current feed-forward control

Introduction

Three-phase pulse width modulation(PWM)grid-

connected inverters can realize feeding electric energy to grid with unity power factor without harmonious pollution.Therefore,it can be applied to many situa-

tions,such as solar photovoltaic generation,wind power generation and the energy-regeneration application[1−2]. The current control methods of three-phase PWM grid-

connected inverters can be divided into two sorts,the direct current control and the indirect current control.

The direct current control includes the hysteresis cur-rent control,the space-vector control,etc.[3−4]These methods can obtain faster current response,but the con-

trol structure and algorithm are comparatively complex. The indirect current control is also called the phase and amplitude control(PAC).It has advantages that the

control is simple without current feedback and its cost is low[5−6].However,comparing with the direct current control,its current dynamic response is not very fast. Recent research about PAC mainly involved in improv-ing the dynamic performance of the system in operation

and design of system parameters[2,7].None of them re-fer to improving startup the dynamic performance of the system.However,in some situations(such as eleva-tors and port machines),grid-connected inverters have to start and stop frequently.The dynamic performance of the system in startup makes an important impact on the quality of electric power fed into grid.

In this paper,based on the research concerned[7−8], a15kW three-phase PWM grid-connected inverter us-ing PAC is designed.Moreover,to solve the problem of

heavy inrush current and slow dynamic response when system starts up,the starting voltage prediction control

and the current feed-forward control are presented.The experimental results proved the validity of the proposed methods.

1Structure of main circuit and operat-ing principle

1.1Structure of main circuit

The main circuit structure of a three-phase PWM grid-connected inverter consists of a bridge rectifier made up of six IGBTs with anti-parallel diodes,DC link

capacitance and series inductances.

As shown in Fig.1,The AC output ports of the sys-

tem are directly connected to the gird,while the DC in-put ports are connected to E G(E G is a renewable power supply)in series with an isolation diodes V D which en-

sure the energy can onlyflow into the grid.Before the system runs,all the IGBTs(V1∼V6)are blocked.En-ergy can’t be fed into the grid and the supply-side cur-

rent is zero.After the system runs,the DC link voltage is held on the set voltage by controller and all the IGBTs are switched on or offby the given PWM rule.Then en-ergy is fed into the grid.

Received Nov.21,2007;Revised Apr.15,2008

Project supported by the Shanghai Education Committee Scientific Research Subsidization(Grant No.05AZ30),and the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20060280018)

Corresponding author CHEN Guo-cheng,Prof.,E-mail:gchchen@