Load detection method for multiple-receiver wireless power transfer systems

The influence of the changes in load quantity on a multiple-receiver wireless power transfer (WPT) system should be minimised, so that the stability of received power for each load can be guaranteed. Here, a multiple-receiver WPT system with an series-series topology is compared with that with an inductance-capacitance-inductance-parallel (LCL-P) topology, and a WPT system with an LCL-P topology is selected to maintain the stability of load power. Then, the concept of effective working area is proposed. If the receivers are placed within the effective working area, the mutual inductances between receivers and transmitter are almost the same. Additionally, to realise the load detection method, which is convenient for system control purposes, reflection impedance theory is applied to detect the quantity of loads. Finally, the proposed circuit topology and detection method are practically verified in an experimental prototype.