Single-phase unidirectional AC/DC converter with high power factor

A novel single-phase unidirectional power flow rectifier is proposed to achieve power factor correction and DC bus voltage regulation. Four active switches, two power diodes and two DC side capacitors are used in the proposed circuit topology to generate a three-level PWM voltage waveform on the ac terminal of the proposed rectifier. Compared with neutral-point-clamped and capacitor-clamped topologies, no clamping diode or flying capacitor is used in the proposed rectifier. The reference line current is derived from the DC tank voltage controller and a sinewave generator in phase with mains voltage. The carrier-based current controller is used in the inner loop to track the line current command. A neutral-point voltage compensator is adopted in the control scheme such that the capacitor voltages on the DC side are balanced. The effectiveness of the proposed control algorithm is verified by the computer simulations and experimental results.