Dynamic Wireless Power Transfer for Stable Efficiency in a Dual-Receiver System With Cross-Coupling

Supplying power for multi-load devices via magnetic resonance wireless power transfer (MR-WPT) has attracted extensive attention, but it also presents more challenging analysis for the system configuration. This study provides an optimization analysis of coil position considering the cross-coupling effect, thereby improving the performance of a dual-receiver MR-WPT system with dynamic transmitting coil (Tx-coil) position. First, the expression of the overall power transfer efficiency (PTE) and the optimal load are derived using equivalent circuit model (ECM), and a comparative discussion of the system characteristics with and without cross-coupling is carried out. It shows that the PTE reaches the peak at the resonant frequency of each receiver (Rx) rather than at that of the transmitter, and the PTE decreases and optimal load increases after considering cross coupling at a short transfer distance. Then the relationship between the coil position and PTE under cross-coupling is discussed, it proves the existence of an optimal transfer distance to achieve the maximum PTE for the symmetric Rxs system, and the dynamic Tx system has an optimal movement range of Tx-coil at the optimal load, so that the system can obtain stable and efficient power transfer when the Tx-coil moves within this range. Finally, the theoretical results are verified through experiments in the lab. Under the optimal operation, an overall efficiency above 75% can be achieved for a system when the Tx-coil moves within this range that the gap of receivers at 100mm.