High Efficiency Three-Coil Wireless Power Transfer for EV Battery Charging Through Negative-Polarity Partial Power Conversion

As electric vehicles (EVs) become increasingly prevalent, the need for efficient wireless charging solutions grows more pressing. Herein, an innovative wireless charging system is proposed for EVs that achieves high efficiency through a negative-polarity partial power conversion (NP-PPC) approach. While conventional PPC methods are constrained by series-connected relationships, our proposed NP-PPC approach inverts the voltage polarity of the dc/dc regulation converter that enables a redesign of power flow paths. This breakthrough allows a significantly larger portion of power to be unregulated, thus substantially improving the overall system efficiency. Moreover, the system implements a novel three-coil loosely-coupled transformer structure that creates two noninterfering power paths that can eliminate the complexity of conventional coil designs. On this basis, a synchronous checking and mode-switching control strategy achieves both constant current and constant voltage charging without wireless communication. Finally, experimental results from a 1200 W prototype demonstrate the system's effectiveness, achieving a peak efficiency of 94.156%.