Applicability Analysis of Coupled-Mode Theory Model in Capacitive Power Transfer System

Abstract

Capacitive power transfer (CPT) technique has the advantages of negligible eddy-current loss, low cost and low weight, and so on. The circuit theory is currently used to model the CPT system to analyze its transfer characteristics, but the order of the circuit model is high and the analytical solution is complex. Coupled-mode theory model is a universal model that can be used to model coupled systems with low order and simple calculation. However, the coupled-mode theory has not been used to model the CPT system, and its applicability in the CPT system has not been analyzed. Therefore, this paper analyzes the coupled-mode theory model of the CPT system. Firstly, the general coupled-mode model of the CPT system is derived from the circuit theory, and the relationship between coupled-mode parameters and circuit parameters are analyzed. Theoretical analysis shows that the coupled-mode theory model is equivalent to the circuit model when the coupling capacitance is far less than the compensation capacitance and the natural resonance frequencies of the transmitter and receiver are close. Then, the transfer efficiency and power of CPT are also deduced based on the coupled-mode theory model. Finally, the simulated and experimental results verify the correctness of the theoretical analysis and the effectiveness of the coupled-mode theory model of the CPT system.