Design and Analysis of Optimal Current Vector for HTS-Based Multi-Input Wireless Power Transfer Systems

This paper presents a newly-designed optimal current algorithm for high-temperature superconductor (HTS)-based multi-input wireless power transfer (WPT) systems. In this way, both high controllability and lower AC losses can be achieved in the proposed systems, and they are especially superior for long-range and long-time operations. Simplified AC loss modeling for HTS windings is developed for the designed transmitter coils. The accordant optimal current vector is derived and analyzed in order to achieve the highest output power and the lowest primary AC losses. With the proper current control of multiple transmitters and the use of a designed HTS coupler, the system controllability can be greatly improved compared with conventional WPT systems. Based on the information on the impedance characteristics on the primary side, the magnetic field generated by different transmitters can be maximized at the target position. Thus, the maximum output power tracking can be realized with a relatively long transmission distance and a low coupling coefficient. Both active and passive solutions are designed and presented to deal with the cross-coupling issue in multi-input WPT systems. For numerical validation, a practical prototype of the HTS couplers is fabricated. An experimental platform is established with a liquid nitrogen cooling system. The test results further validate the feasibility and the high controllability of the proposed system.