Harmonics mitigation of dead time effects in PWM converters using a repetitive controller

Abstract

In order to prevent the power switching devices (e.g., the Insulated-Gate-Bipolar-Transistor, IGBT) from shoot-through in voltage source converter during a switching period, a dead time is added either in the hardware drivers of the IGBTs or implemented in the software Pulse-Width Modulation (PWM) scheme. Both methods will lead to a degradation of the injected current power quality. Thus, the harmonics induced by the dead time have to be compensated in order to achieve a satisfactory current as required by the standards. In this paper, a repetitive controller has been introduced to eliminate the dead-time effect in grid-connected PWM converters. The repetitive controller has been plugged into a proportional resonant based fundamental controller. Compared with the traditional dead-time compensation solutions, the repetitive controller can effectively compensate the dead-time harmonics as well as other low-order distortions, and also it is a simple method without hardware modifications. Experimental results are demonstrating the advantages of the proposed dead-time effect mitigation method compared to the resonant based harmonic compensator.