A Start-up Inrush Current Suppression Method Based on Dual Parameters Soft-start for PWM Rectifier

Abstract

At the start-up moment, three-phase PWM rectifier generates a large inrush current on the AC side generally, which may cause electromagnetic interference and overcurrent protection, even damage to the switching device. In order to suppress the inrush current at start-up moment, the reference soft-start methods based DC Voltage and AC current are proposed respectively. However, suppression effects of such method are imperfect, and existing methods can hardly suppress the inrush current in the first few switching cycles after the rectifier is started. To solve the problem, the generation mechanism of inrush current is analyzed deeply in this paper from the perspective of switching mode and modulation ratio of the PWM rectifier, and mathematical model of three-phase PWM rectifier on each switching mode is derived. The impact of initial modulation ratio on amplitude of inrush current is obtained. Therefore, in this paper, a start-up inrush current suppression method based dual parameters soft-start, which are modulation ratio and DC voltage reference respectively, is proposed. Finally, the simulation and experimental results show that the proposed method can effectively eliminate the inrush current during the whole start-up procedure of the PWM rectifier.