AC-side current waveform improvement of single-phase rectifiers using a triple-frequency PWM scheme

This paper proposes and discusses single-phase rectifiers with a triple-frequency pulsewidth modulation (PWM) scheme. The rectifiers consist of high-, medium-, and low-power sub-converters operated at low, medium, and high frequencies, respectively. The proposed rectifier can equivalently operate as one rectifier that delivers the highest power at the highest frequency defined in the triple-frequency PWM rectifier. A parallel type of the rectifier is mainly discussed in this paper. A cascade type is also considered. In both configurations, current harmonics on the ac-side are greatly reduced, and an approximate unity power-factor is obtained. Experimental and simulation results verify the usefulness of the method