A new control strategy for voltage type PWM rectifiers to realise zero steady-state control error in input current

Abstract

In this paper, a new simple control strategy for AC input current of voltage type PWM rectifiers which can eliminate the steady state control error completely is proposed. This control method requires neither the instantaneous value of the supply voltage nor any accurate circuit parameters on the AC side of the rectifier. Thus, a robust operation against the variation of the circuit parameters can be achieved. In the proposed control system, a digital resonant element implemented by a digital signal processor is introduced as a feedback controller. The digital resonant element exhibits a function similar to an integrator for the fundamental frequency components. Thus, it can eliminate the steady state control error of the input current completely. The principle of the proposed control method is discussed and its effectiveness is shown theoretically. The detailed method of the implementation of the loss-less digital resonant element is explained. The effects of the harmonics in the supply voltage on the AC input current waveform are clarified. To confirm the effectiveness of the proposed control method, some experimental results from two laboratory test systems are shown.