Kilowatt-scale large air-gap multi-modular capacitive wireless power transfer system for electric vehicle charging

This paper introduces a high-performance kilowatt-scale large air-gap multi-modular capacitive wireless power transfer (WPT) system for electric vehicle (EV) charging. This multi-modular system achieves high power transfer while maintaining fringing electric fields within prescribed safety limits. The fringing fields are reduced using near-field phased-array field-focusing techniques, wherein the adjacent modules of the multi-modular system are out-phased with respect to one another. The inter-module interactions in this multi-modular system are modeled, and an approach to eliminate these interactions in a practical EV charging environment is proposed. A prototype 1.2-kW 6.78-MHz 12-cm air-gap multi-modular capacitive WPT system comprising two 600-W modules is designed, built and tested. This prototype system achieves 21.2 kW/m2 power transfer density and a peak efficiency of 89.8%. This multi-modular system also achieves a fringing field reduction of 50% compared to its individual modules.