A Novel Single-Phase Cascaded Multilevel AC-AC Converter Without Commutation Problem Kim, Sang-hun Department of Electrical Engineering Graduate School, Kyungpook National University Daegu, Korea

ABSTRACT
A Novel Single-Phase Cascaded Multilevel AC-AC Converter Without Commutation Problem Kim, Sang-hun Department of Electrical Engineering Graduate School, Kyungpook National University Daegu, Korea (Supervised by Professor Kim, Heung-Geun) Abstract) This paper presents a novel cascaded multilevel PWM ac-ac converter that can solve commutation problem. By cascading the single-phase PWM ac-ac converter that uses basic switching cell structure and coupled inductors, the proposed converter does not need to sense the voltage or current polarity for safe commutation. When many unit-cells are cascaded, the proposed converter has more output voltage levels and can obtain high ac output voltage by using low voltage rating switching devices. By applying phase-shifted PWM technique, the proposed converter can reduce output filter size significantly. A 2 kW prototype converter having four unit-cell structure is built and tested to verify the performance.