Detection of misalignment and foreign objects in resonant capacitive power transfer

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University of New Brunswick


Wireless power transfer has gained interest in recent years due to the increase in the number of mobile electronic devices and systems needing to be charged. Capacitive power transfer (CPT) offers a low-cost option for medium- and high-power charging. To ensure safe and reliable power transfer, foreign objects and misalignments must be detected. Furthermore, exposure of living tissue to high electromagnetic fields (EMFs) must be avoided. This work presents CPT detection methods for both lateral misalignment and foreign objects (FOs). Symmetries of capacitance matrices are studied to distinguish between types of misalignment and FOs. Results were generated via simulation and verified with measurements on a laboratory 13.56 MHz CPT link. FO detection also functions under lateral misalignment, is parameter-based, and is achieved without external circuitry or sensors. Results indicate the direction of lateral misalignment. EMF exposure was simulated to ensure kW-range power transmission while meeting international safety guidelines.