Design and Analysis of a CPT System With Extendable Pairs of Electric Field Couplers

The demand for wireless power transfer systems at different power levels has been increasing for various applications, and this requires power converters with different capacities. This article proposes a capacitive power transfer (CPT) system that can be extended by a modularized approach with multiple electric field couplers. A dual-input dual-output (DIDO) system with four pairs of coupling plates is studied in detail, and it is found that the complicated cross coupling between the plates is a major barrier affecting the resonance and power transfer performance of the system. In this article, the effect of mutual capacitances on the system resonance is analyzed based on a general mutual coupling model of a multiple-input multiple-output electric field coupler. A decoupling circuit based on shared inductances and the corresponding compensation network are proposed and designed. The example system with a DIDO coupler is regarded as an extension by doubling the single-input single-output (SISO) couplers via appropriate double-sided compensation. A 1.5-kW CPT system with a DIDO coupler is built by paralleling two systems with SISO couplers, and the experimental results show that the output power doubles that of the system with the SISO coupler, so the effectiveness of the modular design approach is validated.