Resonant Capacitive Power Transfer Under Misalignment: Modeling and Mitigation

Abstract

A rigorous modeling approach for resonant capacitive power transfer (RCPT) systems employing a six-plate structure is presented. The possibility for common-mode and ground-return (CM-GR) current flow under imbalance-inducing misalignment is fully captured, along with potentially hazardous increases in the associated shield plate and reference conductor voltages. It is demonstrated that this will occur on the receive side with traditional “single-input single-output (SISO) loading,” wherein the rectifier half-circuits are forced to share a common output voltage. The effects can be mitigated by ensuring the shield and reference conductors are “floating”, i.e., very small shield-to-reference and reference-to-ground capacitances, but this may not always be practical. Instead, a dual-input single-output (DISO) loading approach is proposed, wherein the rectifier half-circuits are connected to a DISO DC-DC that draws equal current from each branch. Provided the system is well-tuned, this ensures low CM-GR currents and reference and shield voltages, regardless of shield-to-reference or reference-to-ground impedances. The effectiveness of this approach is demonstrated both numerically and experimentally: at the cost of minor increases in system complexity and power sharing burden, DISO loading mitigates the impact of imbalance-inducing misalignment on safety and electromagnetic compatibility without unduly constraining the design of the RCPT link or high-speed power converters.