The Design And Implementation Of PWM Rectifier Control System

The three phase voltage resource rectifiers(VSR) has the features of unitypower factor, dual-direction energy transport and the sinusoidal grid current under thebalanced grid voltage。However, the actual power grid usually operates under theunbalanced situation, it leads to the abnormal situation to and effects the performancethe VSR designed under the balanced control strategy badly. So it’s necessary tostudy the strategy of PWM rectifier under the unbalanced grid voltage。The maincontents of this paper are as follows。To get the solutions of the problems listed above, this paper represents the basicmathematic models,makes detailed descriptions of its basic principles, analyses thecontrol strategy under the balanced grid voltage. According to the features of the VSRdesigned with the balanced control strategy operated under unbalanced voltage, thepaper focus on the dual current control scheme for VSR under the unbalanced voltageconditions, and make relative simulations.This paper analyses the control strategies for restraining the DC ripples and theAC harmonics according to the dual current control scheme. And then,the designprinciples of ac input inductance under unbalanced control scheme has been comparedwith the balanced control scheme.To separate the positive-sequence and the negative-sequence current, the papersmake an analysis of the scheme between the second-order harmonics filter and thetime domain signal delay. To get the phase angle, three kinds of phase soft phase lockloop(spll) have been studied. In the paper, the control system of dual close loopincluding the out voltage loop and the inner current loop is designed,and theparameters of the PI regulator are analysed.In the end,a hardware test platform is designed based on the DSP ofTMS320F2808. The functions of dsp chip,the selection of the IGBT module, thesampling of voltage and current and the design of IGBT driven module are brieflyintroduced. This paper designs a software program under the environment of CCS3.3to test the control scheme proposed in the paper based on this platform, and gives theflow chart of the software program.