Modeling Single-Wire Capacitive Power Transfer System With Strong Coupling to Ground

This article presents the modeling of a single-wire capacitive power transfer (CPT) system to reveal its power transfer mechanism with strong coupling to ground. An equivalent circuit is proposed by treating the ground as a quasi-conductive medium. The parameters of the equivalent circuit model are determined, including the capacitance between the coupling plates of the CPT system, the single-wire inductance and capacitance between the wire and the ground, and the ground equivalent impedance. The maximum power transfer capacity corresponding to the system's resonant frequency is analyzed by using the proposed model to guide the system tuning design. A prototype single-wire CPT system is built, and a computer simulation technology (CST) model is undertaken to show the electric and magnetic field distributions, and the Poynting vector indicating the direction and magnitude of the power flow in the system. It is shown that the output voltage and the power predicted by the theoretical model are in good agreement with the simulation and practical results under the frequency and load variations. Different lengths of the dangling single wire at the secondary side of the CPT system are also investigated to validate the model with different levels of ground effects.