Secondary-Side Power Control Method for Double-side LCC Compensation Topology in Wireless EV Charger Application

Wireless electric vehicle (EV) charger has become increasingly popular because of its improved convenience and safety and its advantage of smaller green-house gas (GHG) emissions. The power control method of the wireless power transfer (WPT) system has great impact on the performance of the charger. In order to simplify the power electronics converters and improve the reliability of the system closed-loop control, a novel secondary-side power control method by adding a pair of bidirectional switches is presented for the wireless EV charger. The proposed control method, which is applied on a double-side LCC compensated wireless power transfer system, is analyzed based on the fundamental harmonic approximation (FHA) approach. The relationship between the controlled duty cycle of the secondary switches and the output power is derived and discussed. The total harmonic distortion (THD) of the input current is also calculated to estimate the influence of the duty cycle on the primary side. A prototype of the WPT system with the proposed control method has been built and tested, and the confirmatory experiment is also presented to validate the theoretical analysis.