A Systematic Approach for Characterization of Capacitive Couplers for Wireless EV Charging

This article proposes a structured method for characterizing the capacitive couplers used in wireless electric vehicle (EV) charging systems. Most of the existing approaches rely on expensive finite-element analysis (FEA) tools for estimating the mutual capacitance between the coupler plates. An experimental technique is found in the literature that relies on a series
$LC$
resonant circuit but suffers from certain limitations. A parallel
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resonance-based approach is introduced in this article to address those issues. The suggested method requires an initial estimate of the mutual capacitance, which is achieved by deriving an empirical formula. Also, a comprehensive algorithm is presented to design an inductor with low interwinding capacitance, which aids the proposed characterization procedure. An experimental prototype of the capacitive coupler is fabricated and characterized for different vertical distances between the coupler plates under both aligned and misaligned conditions. The outcomes of the proposed method are compared with FEA simulation results, and close agreement between these data is noted.