Bidirectional LCC–LCC-Compensated 20-kW Wireless Power Transfer System for Medium-Duty Vehicle Charging

This article presents the design and demonstration of a bidirectional 20-kW wireless charging system (WCS) with a significantly large air gap (11 in) and asymmetrical input-output voltage levels. Analytical and experimental sensitivity analyses of the WCS resonant tank were conducted to verify the optimal operating region under the load and frequency variation. The inverter and rectifier were designed with switching components, the charging pads were designed with double-D (DD) coils, and the tuning networks were designed with an LCC - LCC tuning circuit. The grid and vehicle side tuning circuits were designed separately to achieve a ~1:2 gain for the asymmetrical input (800 V _dc ) and output (350 V _dc ) voltages. The proposed WCS was designed, simulated, and tested to verify the efficiency, power transfer capacity, and sensitivity under load variation. The experimental results show that, at 20-kW output power, the achieved grid-to-vehicle dc - dc efficiency was 96.1%, and the vehicle-to-grid dc - dc efficiency was 96.2%. The proposed system is the largest-air gap bidirectional WCS with the highest efficiency and power density.