*Article* **Double-Coil Dynamic Shielding Technology for Wireless Power Transmission in Electric Vehicles**

**Yuan Li , Shumei Zhang and Ze Cheng \***

School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China; leeyuan@tju.edu.cn (Y.L.); shumeizhang@tju.edu.cn (S.Z.)

**\*** Correspondence: chengze@tju.edu.cn; Tel.: +86-139-0201-8892

**Abstract:** During wireless charging, the transmission distance of electric vehicles varies, resulting in different levels of electromagnetic field leakage. An improved active shielding technology, the double-coil dynamic shielding technology, is proposed in this paper for wireless power transfer (WPT) systems with different transmission distances. Modeling, simulation, and experiments are performed for the WPT system with a double-coil dynamic shielding scheme and compared with other cases. The results show that the proposed double-coil dynamic shielding scheme is able to shield approximately 70% of the electromagnetic field leakage for WPT systems at different transmission distances. In addition, it essentially causes no degradation in transmission efficiency (only 3.1%). The effectiveness and feasibility of the proposed scheme are verified.

**Keywords:** electromagnetic field; wireless power transfer; shielding
