A 1-kW and 100-cm Distance Magnetically Coupled Resonant WPT System Achieving 80% Efficiency

For the magnetically coupled resonant wireless power transfer (MCR WPT) applications with high-power level and medium-range distance, the low coupling coefficient brings severe challenges to the system efficiency and reliability, as the coil loss and the voltage/current stress on compensation components are both considerable; meanwhile, the high operating frequency that contributes to improve the power density will result in high switching loss and related electromagnetic interference. In this article, a parameter design methodology for high-power and medium-range-distance MCR WPT applications was proposed to achieve high system efficiency. The accurate time-domain system model was built to obtain the relationship among voltage/current stresses on the compensation components, zero-voltage-switching (ZVS) conditions of power switches and system parameters. The key parameters, including the switching frequency, the coil self-inductance, and the compensation inductance, are designed to realize wide-range ZVS and reduce voltage/current stresses. Double-layer coil configuration was adopted instead of the traditional single-layer coil to reduce coil losses, and the series compensation capacitors in TX and RX coils were split to achieve current sharing between double-layer coils. Meanwhile, the LCCL-TT compensation network was used to achieve the optimal load and maximize the system efficiency. Finally, a 1-kW MCR WPT prototype within 100-cm transmission distance was implemented in the laboratory for experiments, and the system efficiency under the rated condition is 80.62%.