Abstract
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%.
Highlights
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)
The theoretical analysis is shown that the proposed system can reverse the flux direction of transmitter coil 1 while the angle of transfer direction is overly large, the coupling condition of the system after reversal can still be satisfied
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%
Summary
The stable output power with the high and constant efficiency for multi-coils system poses a great challenge to the robustness of wireless power transfer (WPT). The oscillation frequency of the system is decided by a resonant network of the primary and secondary circuits It can realize high-power and high-efficiency transfer in short-range and mid-range distances. This article differs and extends from those of [1][2] in many respects as follows: 1) The system implementation, including the reserved method realized by the reversed switch group (RSG) and the logic-check link (LCL), and the transmitter coil 1 of which flux linkage is vector-controlled; 2) The analytical method by which the detailed form of the normal and reversed states is derived from the accurate circuit model; 3) A practical WPT application with high transfer efficiency on the whole plane omnidirectionally.
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