Accurate Power Loss Calculation of a Three-Phase Dual Active Bridge Converter For ZVS and Hard-Switching Operations

A three-phase dual active bridge (DAB) topology has been widely applied in high power DC-DC conversion due to its advantages such as bidirectional power transfer, inherent soft switching capability and small filter size. In order to reach the high power density, the volume of the converter must be decreased. The basic idea to reduce the component size is to increase the switching frequency which causes the higher switching loss and reduces the efficiency of the converter. In this paper, the power losses of the three-phase DAB dc/dc converter are formulated and the variation of the efficiency as a function of switching frequency is investigated. In this analysis, the switching loss of the bridges for ZVS and hard switching operation is calculated with consideration the non-linearity of the drain- source capacitors of the switches. The theoretical results are verified using simulation and in a 50 kW experimental setup.