Control Strategy for PWM Converter Based on Suppressing the DC-Side Harmonics

A novel control strategy is proposed to suppress the 2nd voltage harmonic in the DC side of a PWM rectifier when the grid supply is unbalanced. The control strategy described in the paper solves the problem of low-order harmonics generated by a PWM rectifier. The control system is divided into two symmetrical double closed-loop systems to control positive and negative-sequence current respectively. The simulation results verify the proposed control strategy in terms of efficiency, reliability and low-harmonics in the DC side. The new control system not only reduces DC-side voltage harmonics, but also improves the quality of the rectifier output voltage, and decreases the degree of asymmetry in the AC-side current of the rectifier.