Modelling Single-Wire Capacitive Power Transfer System with Strong Coupling to Ground

Abstract

This paper presents the modelling 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 the capacitance between the wire and ground, and the ground equivalent impedance. The maximum power transfer capacity corresponding to the system’s resonant frequency is analyzed using the proposed model to guide the system tuning design. A prototype single-wire CPT system is built, and CST (Computer Simulation Technology) simulation is undertaken to show the electric and magnetic field distributions, as well as the Poynting vector indicating the direction and magnitude of power flow in the system. It is shown that the output voltage and the power predicted by the theoretical model are in a good agreement with the simulation and practical results under frequency and load variations. Different length of the dangling single wire at the secondary side of the CPT system is also investigated to validate the model with different levels of ground effect.