A Misalignment-Tolerant Coil Array for High Output Stability and Low Magnetic Field Exposure in EV Wireless Charging System

Abstract

Wireless charging liberates complex manual operations but typically suffers from an inherent sensitivity to the arbitrary offset for parked electric vehicle (EV). To address this issue, this article presents a misalignment- tolerant coil array (MT-CA) as a repeater, which consists of three identical coils but with distinct compensation. Specifically, MT-CA can suppress the output fluctuation and high leakage magnetic field due to offset. By applying the concept of current ratio (CR), a detailed mathematical model is derived to intuitively reveal the compensation strategy for MT-CA under misalignment. It suggests that anti-misalignment performance of MT-CA can be achieved by only solving a quadratic programming (QP) problem containing two equality constraints. The effectiveness of MT-CA is evaluated in a 1-kW prototype under three typical misaligned cases. The results state that the output current fluctuation among these cases is only 5.82% with a peak efficiency of 93.79%. Besides, decline of leakage magnetic field can reach up to 8.85 dB while meeting safety limit. The proposal of MT-CA can serve as guidelines to improve the misalignment tolerance of EV wireless charging system.