Capacitive Power Transfer for EV Chargers Coupler

Abstract

Different from previous chapters of inductive power transfer (IPT), this chapter introduces capacitive power transfer (CPT) for static wireless electric vehicle (EV) chargers. A four‐plate compact capacitive coupler and its circuit model for a large airgap distance CPT is proposed. The four plates are arranged vertically, instead of horizontally, to save space in EV charging applications. The two plates that are on the same side are placed close to each other to maintain a large coupling capacitance and are of different sizes to maintain the coupling between the primary and secondary sides. The circuit model of the coupler is presented, considering all six coupling capacitors. The LCL compensation topology is used to resonate with the coupler and provide high voltage on the plate to transfer high power. The circuit model of the coupler is simplified to design the parameters of the compensation circuit. Finite element analysis (FEM) is employed to simulate the coupling capacitance and design the dimensions of the coupler. The circuit performance is simulated in LTspice to design the specific parameter values. A prototype of a CPT system was designed and constructed with the proposed vertical plate structure. The prototype achieved an efficiency of 85.9% at 1.88 kW output power with a 150mm air gap distance.This chapter is based on the recently published paper by Chris Mi (H. Zhang, F. Lu, H. Hofmann, W. Liu, and C. Mi, “A 4‐plate compact capacitive coupler and LCL compensation topology for capacitive power transfer in electric vehicle charging applications,” IEEE Trans. on Power Electronics , vol. 31, no. 12, pp. 8541–8551, December 2016). Those who want to investigate further can read another CPT paper by him (F. Lu, H. Zhang, H. Hofmann, and C. Mi, “An inductive and capacitive combined wireless power transfer system with LC‐compensated topology for electric vehicle charging application,” IEEE Trans. on Power Electronics , vol. 31, no. 12, pp. 8471–8482, December 2016).