Hybrid soft switching converter for DC grid applications

Abstract

A new soft switched DC/DC converter with low circulating current loss in primary side and low voltage stress in secondary side is presented in direct current micro-grid applications. Modular full-bridge circuits with primary-series and secondary-parallel are used in the studied converter for high input voltage and load current applications. Therefore, the voltage stress of active switches in primary side and the current stress of rectifier diodes in secondary side are reduced. Thus, the low voltage rating switches are utilized to reduce the conduction loss. The input split voltages are balanced using flying capacitors connected between each circuit modular without the complexity control scheme. Phase-shift control is used to regulate the output voltage. Resonant circuit is connected to lagging-leg switches of full-bridge circuit in order to achieve soft switching at light load. The output voltage of resonant converter is connected to the secondary side in order to reset the primary current and clamp the voltage spike across the rectifier diodes at freewheeling state so that the circulating loss is improved. A laboratory prototype with 1.8kW rated power is constructed and tested to verify the theoretical analysis.