Plane-Omnidirectional Wireless Power Transfer System Based on Vector-Controlled Flux Linkage

The major challenge for wireless power transfer (WPT) is to extend transfer distance and to broaden transfer direction, while a stable power can be transferred with high and constant efficiency. The multi-coil WPT system can transfer power on the plane or space omnidirectionally, but its output power and efficiency are usually difficult to keep stability. For a nonlinear wireless power transfer system based on parity-time (PT) symmetry, when the coupling condition of the system can be satisfied, it can attain a stable power with high and constant efficiency, but it still has a dead-spot problem in the transfer direction. Therefore, this article proposes a design of a plane-omnidirectional WPT system, of which the coupling condition can be maintained across the plane. The transmitter coils are a pair of orthogonal coils which are named transmitter coils 1 and 2. Meanwhile, in the transmitting circuit, the positive direction of transmitter coil 1, which determines the positive direction of current and flux, is controlled by a reversed switch group (RSG) with a logic-check loop (LCL). Moreover, the theoretical analysis shows that the proposed system can reverse the flux direction of transmitter coil 1 while the angle of transfer direction is overly large, then the coupling condition of the system after reversal can still be satisfied. Finally, the experimental results show that when the receiver coil moves around the transmitter coils on the whole plane, the stable output power of 14 W is maintained with an approximately constant transfer efficiency of 87%.