Bi-directional isolated DC-DC converters with reactive power loss reduction for electric vehicle and grid support applications

In this paper, the concept of “reactive power loss” is defined and its mathematical expressions as a function of electrical parameters are derived. The reactive power loss in different cases is discussed and it is proved that soft-switching can always be achieved when reactive power loss is minimal. A novel technique to design the turns ratio of the transformer in bi-directional isolated DC-DC converters based on reactive power loss is proposed. The simulation results verify the effectiveness of the proposed technique in reducing the conduction loss in the switches of bi-directional isolated DC/DC converters. In addition, the simulation results also show that this technique can keep peak currents and RMS of currents of both bridge 1 and 2 small.