Single-Sided Compensation Network Design Method for Capacitive Power Transfer System Considering Coupling Variation

In capacitive power transfer systems, coupling variation inevitably occurs due to air gap variation and coupler misalignment. This paper presents a single-sided compensation network design method for capacitive power transfer systems considering coupling variation. The proposed method adopts a single-sided compensation network to reduce the volume and weight of the receiver side circuit. The proposed compensation network, within a preselected narrow operational frequency range, effectively transforms the variable load impedance into a single resistive point, resulting in constant output power and zero-phase angle operation under coupling variation. The proposed method employs the impedance matching network design based on a two-port network analysis. The validity of the proposed design method is confirmed with a simulation and a 1.2 kW small air gap capacitive power transfer system prototype. The experimental prototype system achieved a maximum efficiency of 91.2% under no misalignment and a minimum efficiency of 89.9% under a maximum 40% area displacement in coupling conductor plates, with a near-constant output power and zero-phase angle operation.