An Efficiency Optimization Method for the Multiple-Coil WPT System Against the Pad Misalignment

Wireless power transfer (WPT) is becoming increasingly popular for its convenience, safety, and physical and electric isolation. Pad misalignment in electric vehicle (EV) applications is unavoidable in practical applications, which results in the reduction of output power and transfer efficiency of the system. The traditional anti-misalignment strategy mainly focuses on realizing smooth output power of WPT system while ignoring the transfer efficiency optimization. Nowadays, WPT systems based on multiple coils are usually used for improving the power transfer capability. In this article, an efficiency optimization method for the multiple-coil WPT system against the pad misalignment is proposed. By the proposed control strategy, the smooth output power and high transfer efficiency of the system under misalignment can be realized simultaneously. Finally, a 2-kW laboratory prototype is built to verify the proposed efficiency optimization method against the pad misalignment. When it is fully aligned, the system can achieve 94.2% peak efficiency. The peak efficiency only drops 0.5% with +200-mm misalignment in the x-direction compared with the full alignment by adopting the proposed efficiency optimization method.