Efficiency Improvement of the Parity-Time-Symmetric Wireless Power Transfer System for Electric Vehicle Charging

Wireless power transfer (WPT) is a promising technology for charging electric vehicles (EVs) due to its intelligence, convenience, and reliability. However, achieving high efficiency and high power with wide misalignment tolerance is still a major challenge in commercializing wireless charging technology in EVs. Here, a novel parity-time-symmetric-based WPT (PT-based WPT) system with multiple decoupled receiving coils is developed to address the above issues. The circuit model of this PT-based WPT system is established. Our theoretical analysis shows that the output power and transfer efficiency of the proposed system also remain constant over a coupling coefficient variation. More importantly, compared to the conventional one-receiving-coil PT-based WPT system, the use of multiple receiving coils can effectively improve the transfer efficiency and reduce the current stress of system. In order to evaluate the proposed WPT system, a 1-kW laboratory prototype is built and tested. Experimental results show that a stable of power transfer is maintained with constant transfer efficiency of 96.1% within a range of 100-200-mm air gap. In particular, the same transfer efficiency is achieved at 100-mm air gap within a horizontal tolerance of 240 mm, while a horizontal tolerance of 100 mm at 200-mm air gap.