A reliable cascaded AC-AC converter

This paper presents a new type of cascaded PWM ac-ac converter with phase-shift PWM control. It can reach high output voltage by cascading single-phase units of low voltage rating devices. The proposed converter does not sense current/voltage polarity, and does not require current/voltage sensors and lossy snubbers for commutation, thereby the control complexity can be decreased. It has no shoot-through problem and eliminates the PWM dead times, which leads to greatly enhanced system reliability. The phase shift PWM control is also proposed for the proposed converter to reduce the volume of passive components, and current and voltage ripples. In order to verify the robustness of the proposed converter, a 1 kW hardware prototype converter having two-unit cell structure is fabricated and tested.