Highly Efficient Bidirectional Series-Resonant DC/DC Converter over Wide Range of Battery Voltages

This article introduces a highly efficient bidirectional resonant dc/dc converter over wide range of battery voltages for vehicle-to-grid (V2G) capable electric vehicles (EVs). It operates as a pulsewidth-modulation (PWM) full-bridge series-resonant converter in the forward direction and a half-bridge resonant boost converter in the backward direction. One advantage of the proposed converter is that it has a wide voltage gain range in the backward operation. Also, it requires only six active switches. To achieve high efficiency, SiC mosfet s are used for two bottom switches in the primary side, because only these switches suffer hard switching turn- off in both forward and backward directions. Since it operates with fixed-frequency and with PWM control, the magnetic components and passive filters can be optimally designed with respect to the volume and the loss. Thus, the proposed converter achieves low-cost, high-conversion ratio, and high efficiency over a wide range of battery voltages. Detailed analysis of the converter operation is presented along with the design procedure. A 3.3-kW/400-V prototype of the proposed converter has been built to operate for 250–415 V primary source voltages and tested to demonstrate its circuit design.