A Universal Parameter Design Method of Resonant Coils Under Multiple Boundary Constrains for Wireless Power Transfer Systems

Three-stage charging mode for batteries is usually adopted for fast charging. Under the premise of ensuring fast charging, the reasonable design of resonant network parameters by making full use of power transfer characteristics of the resonant network is essential for the safe, stable, and economic operation of wireless power transfer systems (WPTSs). In this paper, a leap-frequency phase shift control (LFPSC) is adopted to achieve the three-stage charging for batteries. First, the optimal design requirements of resonant network parameters are discussed and presented. Second, a novel universal parameter design method (UPDM) of resonant coils under multiple boundary constrains is derived and summarized. Moreover, a specific case study is presented and its corresponding optimal region of selected self-inductances of resonant coils is calculated. Finally, a 1.5-kW experimental prototype is built to verify the feasibility of the proposed UPDM. The experimental results show that the maximum transfer efficiency of the designed WPTS can achieve 95.2% with the coupling coefficient k = 0.2.