Compensation of input current distortion in three-phase buck rectifiers

An overlap time for two commutating switches is necessary to prevent current interruption in a three-phase buck rectifier, but it may cause input current distortion. In this paper, a modified pulse-based compensation method is proposed to compensate for the overlap time. In addition to the traditional method which places the overlap time based on the voltage polarity, this new method first minimizes the overlap time to reduce its effect and then compensates the pulse width according to the sampled voltage and current. It is verified by experiments that the proposed method has better performance than the traditional method, especially when the line-to-line voltage crosses zero. Another distortion comes from the irregular pulse distribution when two sectors change in a 12-sector space vector PWM. This paper proposes two compensation methods for that scenario as well, compensating the duty cycle and increasing switching frequency near the boundaries of two sectors. It is shown through experiments that both methods can reduce the input current distortion in the buck rectifier.