A Dual-Frequency 3-D WPT System With Directional Power Transfer Capability at Two Separately Regulated Outputs

This article proposed a dual-frequency 3-D wireless power transfer (WPT) system that can simultaneously drive two separate loads with independent voltage regulation. This dual-frequency 3-D system forms two directional magnetic fields rather than one spatial rotating field due to the dual-frequency excitations. The extended frequency channel enables the system to directly transfer power to the receiver tuned at the corresponding frequency with low magnetic field leakage. The two legs of the H-bridge inverters are driven at two different switching frequencies and duty cycles to output a transmitter current consisting of two frequency components. A dual-frequency resonant network is designed to retain the currents at the required frequency by filtering out other harmonics. By adjusting the duty cycle and phase of the corresponding bridge legs, individual current control of each frequency channel is realized without cross-interference, which provides the basis for the magnetic field orientation of either of the two loads. A proof-of-concept prototype with two receivers has been built with the rated output voltage of 12 V at 80 kHz, and 24 V at 200 kHz. It is demonstrated that this dual-frequency 3-D system can transfer about 40 and 36 W of power to the two loads at different positions, with an overall system efficiency of about 72%.