Fault Resilient Soft Switching DC–DC Converter for Modular Solid State Transformer Applications

Abstract

Soft-switched isolated converters are preferred for dc–dc stage in solid state transformer applications, wherein fault resilience is highly desirable. This article presents a fault resilient, soft-switching dc–dc converter and associated integrated controller. The proposed integrated controller ensures smooth and reliable fault resilient operation with simplified reconfiguration of employed voltage restorer rectifier during fault. The integrated controller promotes converter design for operation above resonance to avail soft transition of all power devices, reduced EMI, and deployment of body diode integrated switches. Further, the reconfigurable multiplier-type rectifier increases overall converter gain without increased transformer turns ratio. The converter also favors minimized resonant inductance due to lower equivalent resistance and reduced transformer size resulting from above resonant operation. The converter characteristic curves during normal and fault states are presented. Experimental investigations for 1.25-kW prototype in both dynamic and steady state are presented to demonstrate fault resilient capabilities and performance efficacy. Also, impact of postfault reconfiguration on operation frequency, efficiency, and loss distribution is demonstrated.