Experimental Verification of Lowest Switching Current Control for Practical ZVS in 400 V/400 V-5 kW Dual-Active-Bridge Converter

This paper makes a detailed analysis of zero-voltage-switching (ZVS) realization in dual-active-bridge (DAB) converters based on extended-phase-shift (EPS) modulation, when the voltage ratio is not matched with the designed transformer turn ratio. Based on the ZVS principle that the charge stored in parasitic capacitance should be totally released, a specific lowest switching current is necessary at critical switching instants to achieve ZVS. A 400 V/400 V-5 kW laboratory prototype was fabricated to verify that the ZVS can be realized with the lowest switching current control, in which the switching current can be corrected as reference value at some instants. As a result, efficiency can be effectively increased in a specific power range with ZVS.