Zero-voltage switching bi-directional power electronic transformer

In this study, a bi-directional power flow zero-voltage switching (ZVS) power electronic transformer (PET) with phase shift modulation controller (PSM) is proposed. The PET contains input full-bridge active rectifier (FBAR), full-bridge DC-link inverter (FBDCI), high-frequency isolating transformer (HFIT), cycloconverter and output filter. FBDCI switches operate under ZVS condition. In addition, ZVS commutation of both cycloconverter bi-directional switches and FBAR switches are achieved. Dynamic voltage regulation is obtained without utilising energy storage elements. Therefore good efficiency can be achieved as a result of ZVS operation together with the absence of energy storage elements. The values of output filter are calculated to provide soft switching operation and voltage regulation. Based on the simulation and experimental results, the steady-state operation principles of the PET are described. Experimental results from a laboratory prototype with specification of 110 V/50 Hz input to 24 V/50 Hz output are presented to verify feasibility of the proposed PET.