Multiple-Transmitter with Phase-Shift and Dynamic ZVS Angle Controls at Fixed Operating Frequency for Cross-Interference Free Wireless Power Transfer Systems

Resonant inductive coupling wireless power transfer (RIC-WPT) systems with multiple transmitters and multiple receivers often suffer from cross-interference among transmitters as well as among receivers. The cross-interference causes the fluctuation of the output power of the receiver and hard switching of the inverter on the transmitter. To avoid the cross-interference, controlling the amplitude and the phase of each transmitter current is an effective method. Therefore, this paper proposes a multiple-transmitter that can compensate for the cross-interference influence by implementing two controls. First, adopting the phase-shift control on the full-bridge inverter, the current amplitude is controlled to be constant. Second, applying the reactance control, each phase of the current is controlled to be in phase. In addition to the above operations, especially under a high-frequency operation, zero-voltage switching (ZVS) at a fixed operating frequency is essential for improving the power efficiency while not exceeding an allowable narrow bandwidth. Thus, the reactance control also works to ensure ZVS in all load conditions without adjusting the frequency. The RIC-WPT prototype with two transmitters and a single receiver is built to verify that the proposed multiple-transmitter can compensate for the cross-interference influence while achieving ZVS in different load conditions at a fixed operating frequency.