Moving impedance matching analysis for three-coil wireless power transfer system in mid-range

There is a bottleneck for traditional two-coil wireless power transfer (2C-WPT) system for short transfer distance and low efficiency. In this paper, a novel three-coil WPT(3C-WPT) system based on moving impedance matching window is proposed to increase transfer distance to mid-range. System efficiency is further promoted by optimizing relay coil. Acting as a moving impedance matching window, relay coil improves the flexibility of selecting proper reflection impedance. Once the overall optimization goal is set up, best parameters of the impedance matching can be determined with the given optimization design procedure. Derived conclusions undoubtedly play an instructive role in the design and application of proposed three-coil structure WPT system.