A Dual-Band Coil Array With Novel High-Order Circuit Compensation for Shielding Design in EV Wireless Charging System

For the wireless power transfer (WPT) system in electric vehicle (EV) applications, a serious concern lies in the leakage electromagnetic field (EMF) emission. In order to address this issue, this article presents a dual-band coil array (DB-CA) with novel high-order circuit (HOC) compensation. The most attractive feature of DB-CA is that both the first and third harmonics of leakage EMF can be reduced simultaneously, while the system still resonates at the same frequency. A detailed mathematical model is established to intuitively reveal the relevance between impedance design and shielding performance, as well as the constraints to achieve resonance. In addition, the novel HOC compensation is employed to decouple the shielding design at each harmonic. Both simulated and experimental results verify the effectiveness of DB-CA, and a 1-kW WPT prototype operating at 85 kHz is established. By applying DB-CA, the leakage EMF can be reduced by 3.88 dB at 85 kHz and 1.84 dB at 255 kHz, respectively. Meanwhile, the system resonant frequency still locates at 85 kHz, and the achieved zero-phase angle condition is independent with load condition. It can provide significant guidance to the design of shielding configurations in EV wireless charging system.