Bidirectional Wireless Power Transfer System with Optimized Coil Geometry

Electric vehicles (EVs) offer the opportunity to use vehicle-to-grid (V2G) technology to utilize the vehicle battery as a grid connected energy storage device and deliver power to the grid and local loads. Recently, wireless power transfer (WPT) in EVs has been studied by numerous researchers due to advantages such as convenience of wireless operation and safety of inductive power transfer. Design challenges for WPT systems in EVs include high charging efficiency, a large air gap, and tolerance for misalignment. By optimizing the coupler coil geometry, the efficiency can be increased over a wide range of parking positions and ground clearances, while at the same time limiting the electrical component stress. With a new control method, the semiconductor stress is minimized and the losses are reduced compared to conventional control methods. A fully functional prototype with V2G capabilities was built, which reaches a DC-DC efficiency of almost 96 %.