Wide voltage gain bidirectional DC/DC converter based on switched-inductors for EV hybrid energy source systems

This paper proposes a novel small film capacitor based bidirectional DC/DC converter (BDC) for the hybrid energy source systems (HESS) in electric vehicles (EVs). In the proposed BDC, an auxiliary booster cell with a switched-inductor cell is added to achieve wide voltage gains in both the boost and buck modes. Therefore, small film capacitors operate with a voltage gain ratio of up to 10, which helps the proposed BDC utilize the vehicle braking energy and improve vehicle dynamics. The forward boost and reverse buck have symmetrical structures, simplifying the BDC parameter design and reducing the voltage stress. The BDC low voltage side (LVS) current is continuous, and the current ripple is zero, improving the efficiency of battery charging and discharging. In addition, the input and output terminals of the converter are absolutely common ground, avoiding serious electromagnetic interference. The paper provides detailed descriptions of the working principle, characteristic analysis, and parameter design of the proposed BDC. A 200 W prototype with a 20–40 V LVS and a 200 V high voltage side (HVS) is developed and tested. Experimental results confirm the effectiveness of the proposed converter with a maximum efficiency of 95.8% in the boost mode and 96.15% in the buck mode.