An LCC-LCC Compensated WPT System With Switch-Controlled Capacitor for Improving Efficiency at Wide Output Voltages

In this article, a triple-phase-shift (TPS) control strategy combining a switch-controlled capacitor (SCC) is proposed for LCC-LCC compensated wireless power transfer (WPT) system to improve the overall efficiency at wide output voltages. The basic mathematical model of the system is first established, and the conditions for zero-voltage switching (ZVS) and load matching are described under TPS. Then, the mechanism of TPS reducing system efficiency at wide output voltages is revealed based on the established model. An SCC is employed to adjust the compensation capacitance to achieve a minimum circulating reactive power on both sides and reduce the rectifier input current. Finally, the impact of the compensation capacitance variations on the current, output power, and impedance are analyzed, based on which the optimal value of adjustable capacitance for maximum efficiency is derived by further considering the established time domainmodel. A comparative experiment is performed with traditional TPS and the proposed control technique, which shows that the system with the proposed control technique achieves a higher efficiency over the TPS within the entire power range.