A SeriesParallel Transformer-Based WPT System for 400-V and 800-V Electric Vehicles With Z1 or Z2 Class

Due to the diversity of chassis heights, battery types, and battery capacities, wireless power transfer (WPT) systems for electric vehicles (EVs) have large variations in Z classes, battery voltages, and output power levels. Conventional solutions require different dc-dc converters, compensation circuits, and coupling coils for each specification, which results in weak compatibility, increased cost, and increased difficulty in development and product management. This article analyzes the influence of parameter variations on the EV WPT system mathematically. Then, a series-parallel transformer-based architecture is proposed for the high-power EV WPT system. The generalized power transfer function of the proposed system is derived. In addition, the design principle is demonstrated in detail, which can adapt to different Z classes, battery voltages, and power levels. A 20-kW LCC-LCC WPT prototype with a maximum dc-dc efficiency of 94.2% is built to demonstrate the feasibility of the proposed system. This article is accompanied by a video file demonstrating the 20-kW experiments.