Dual-Active-Bridge Converter With Parallel-Connected Full Bridges in Low-Voltage Side for ZVS by Using Auxiliary Coupling Inductor

A dual-active-bridge (DAB) converter with parallel-connected full bridges in low-voltage side is proposed in this paper. A coupling inductor is integrated into the two low-voltage-side full bridges for zero-voltage-switching (ZVS) operation throughout full-load range. By analyzing the working modes of the converter, the ZVS range of the converter is derived. To compromise the ZVS and the conduction loss caused by the coupling inductor, the modulation trajectory is designed in terms of the boundary conditions of the ZVS range. The conduction loss of the proposed converter is compared with the conventional parallel-connected DAB converter, which illustrates that the conduction loss of the proposed converter is only increased under light loads. Finally, a 1.2-kW experimental prototype is built to verify the proposed converter and the modulation scheme, which demonstrates the remarkable ZVS performance and efficiency improvement.