Reduced-Fringing-Field Multi-MHz Capacitive Wireless Power Transfer System Using Metasurface-based Couplers with Active Field Cancellation

This paper introduces a novel design for a capacitive wireless power transfer (WPT) system using metasurface-based capacitive couplers (metacouplers) with active field cancellation for electric vehicle (EV) charging application. Unlike conventional metacouplers that transfer all power through the inner plates, this approach strategically divides power transfer between the inner plates and outer rings. Moreover, active phase shift control of the inverters is done to cancel out the electric fields in the surrounding space of metacouplers. An example 6.78-MHz 12-cm air-gap 1.1-kW capacitive WPT system is proposed, designed and optimized. For experimental verification, three experimental setups (a conventional coupler system, a metacoupler system without power transfer from outer ring, and a metacoupler system transferring 10% of the output power through the outer rings) are built. The developed prototype utilizing metacouplers, with 10% of the output power transferred from outer rings, achieves an efficiency of 87.6% with a significantly improved 3.8x experimental electric field reduction compared to a conventional coupler system.