T31.3 - A 10.4-kW High-Power-Transfer-Density Multi-MHz Capacitive Wireless Power Transfer System for EV Charging Utilizing Stacked-Inverter Stacked-Rectifier Architecture

This paper introduces a high-frequency capacitive wireless power transfer (WPT) system suitable for high-power electric vehicle (EV) charging. The system uses a stacked inverter and stacked rectifier architecture, where multiple high-frequency inverters and rectifiers can be paralleled using transformers with a parallel-in series-out and series-in parallel-out configuration, respectively, thereby increasing the power transfer capability of a capacitive WPT system. Furthermore, a novel symmetric layout to directly parallel two gallium nitride (GaN) transistors in a full-bridge inverter at multi-MHz frequencies using six-layer printed circuit board is proposed. Experimental validation shows the proposed inverter design handles nearly twice the output current of a single GaN transistor-based inverter, supporting up to 4 kW per inverter. Finally, a 6.78-MHz 12-cm air-gap 10-kW scale capacitive WPT system prototype utilizing the proposed power scaling approaches is designed, built and tested. This system achieves record-breaking performance for a capacitive EV charging system, transferring 10.4 kW at a peak efficiency of 85.3%, corresponding to a power transfer density of 136.8 kW/m2.