A High-Power-Density Reduced-Fringing-Field Multi-MHz Capacitive Wireless Power Transfer System

The paper presents a high-power density multi-MHz capacitive wireless power transfer (WPT) system for wireless charging of mobile robots that implements metasurface-based capacitive couplers (metacouplers) for fringing electric field reduction. A detailed model that includes all the parasitic capacitances present in a practical charging scenario of the metasurface-based capacitive WPT system is presented, and this model is reduced to an equivalent four-capacitance model. Furthermore, the impact of varying the metacouplers' physical dimensions on fringing electric fields and system efficiency is studied. The design of a metacoupler-based capacitive WPT system that achieves 4.5x reduction in fringing electric fields as compared to a conventional coupler-based system is presented. Finally, to experimentally verify the findings of this study, two prototype 13.56-MHz 3-cm air-gap 1.5-kW capacitive WPT systems (one implemented using conventional couplers and the other using metacouplers) are designed and built. A 3.3x reduction in fringing electric fields is experimentally demonstrated.