Hybrid Switched-capacitor Three-phase Direct AC-AC Converter with Adjustable Output Voltage

A switched-capacitor (SC) three-phase direct ac/ac converter is presented in this paper. It includes an additional inductor and two SC cells for each phase. Due to the introduction of the inductor, the output voltage can be adjusted. The proposed converter operates in fixed switching frequency. One of the features of this topology is that the voltage stresses across the switches and capacitors equal half of high-side voltage. In addition, self-balancing capability of capacitor voltages and simple modulation strategy are other characteristics. The main advantage of the proposed converter is the employment of unidirectional switches (a single MOSFET), which avoids the commutation problems in the bidirectional switches. A detailed description of the operation principle, quantitative analysis, and design considerations for the proposed converter is provided. Eventually, a prototype with 55V/220V and 3kW is designed to demonstrate the feasibility and validity of the proposed converter.