We developed a dynamic capacitive WPT system suitable for charging in-motion electric vehicles (EVs). We introduced the Active Variable Reactance (AVR) rectifier—a new approach to maintaining constant output power in both capacitive and inductive WPT systems under varying coupling conditions. This new rectifier architecture can enable delivery of high power to vehicles of different ground clearances even when the vehicle-side charging pad is misaligned from the roadway-side charging pad. The concept is validated through a 13.56-MHz 12-cm nominal-gap prototype which maintains constant output power for up to 45% coupler misalignment, and for road clearances ranging from 12 cm to 17.4 cm.

We developed a new analytical approach to design multistage matching networks for capacitive WPT systems that maximizes the network efficiency while ensuring effective and safe power transfer. This method also enables the maximum possible efficiency in a capacitive WPT system to be expressed in terms of a single factor that embodies all the electrical and geometrical parameters of the system, enabling direct insights into various design tradeoffs. The analytical predictions are experimentally validated using three 6.78-MHz capacitive WPT prototypes comprising single-stage, two-stage and three-stage matching networks. The two-stage prototype is also shown to achieve 67% lower losses than a conventionally designed prototype.

We developed a split-inductor based matching network that can absorb the parasitic capacitances present in the coupling environment of large air-gap capacitive WPT systems (such as those in EV charging) and allows them to be utilized in the power transfer mechanism of the WPT system, preventing their severe adverse effect on both power transfer and efficiency. We further developed a simple four-capacitance model of the coupling environment, and techniques to measure these small (pF level) capacitances in a way such that any measurement errors minimally impact the system’s power transfer capability. The development of the four-capacitance model also enables the matching networks of the capacitive WPT system to be realized entirely using the parasitics of the charging environment, thereby eliminating the need for discrete on-board capacitor and enhancng the efficiency and reliability of the system.