A CLLC-compensated high power and large air-gap capacitive power transfer system for electric vehicle charging applications

This paper proposes a CLLC-compensated capacitive power transfer system for electric vehicle charging applications. Four metal plates are utilized to form two capacitors to transfer power through an air-gap distance of 150 mm. The CLLC compensation circuit topology is used on both the primary and secondary sides to resonate with the power transmitting capacitors. The resonance provides high voltage on the plates to increase the system power level. A comparison to the previously proposed LCLC circuit topology is also presented, which shows that the resonance inductance can be reduced. The circuit model of the coupling plates is provided and the capacitance variation with differing misalignments and air-gap distances is also analyzed. A 2.9kW input power CPT system with a CLLC compensation circuit is designed and implemented. The experimental prototype operates at 1MHz, and its dc to dc efficiency is 89.3% at 2.57 kW output power and a 150 mm air gap distance, which validates the effectiveness of the proposed CLLC compensation circuit. In the future, the system will be optimized to increase its efficiency.