A Dual-Frequency Switchable LCC-S-S and S-S-S Compensated Three-Coil Topology with CC/CV Outputs and ZVS Operation for WPT Applications

Compared with conventional two-coil wireless power transfer (WPT) systems, three-coil WPT systems with an intermediate relay coil offer superior performance in terms of transmission distance and tuning flexibility, making them suitable for a wider range of applications. To address the CC/CV hybrid charging challenge in practical three-coil wireless power transfer (WPT) systems, based on the dual-frequency compensation network (DFCN), this paper proposes a dual-frequency switchable LCC-S-S and S-S-S compensated three-coil topology along with a systematic parameter tuning methodology. Furthermore, the proposed system exhibits zero-phase angle (ZPA) input impedance characteristics at both resonant frequencies, and the ZPA condition remains invariant under coupling coefficient variations. Unlike conventional approaches requiring additional active components, such as relays or AC switches, the proposed compensation topology realizes simple and efficient CC/CV hybrid charging by only switching between two resonant frequencies. An experimental prototype rated at 400 W is constructed to assess the efficacy of the presented framework. The system has a simple structure, is easy to control, and has stable output. The peak DC-DC efficiency reaches 92.15% and 92.75% in both the CC and CV charging modes, respectively.