Misalignment tolerance wireless power transfer system combining inductive and capacitive coupling

Abstract

To resonate with the capacitive power transfer (CPT) system, inductors are usually needed, while additional capacitors are required for the inductive power transfer (IPT) system. To take advantage of the inductance of the IPT system, this study proposes a misalignment tolerance wireless power transfer system that employs the IPT coupler to compensate part of CPT's capacitance for railway applications. In the proposed system, two power transfer paths are formed by the IPT and CPT couplers. Additionally, the system merits a good anti-misalignment ability by carefully designing the parameters of the proposed system. In a well-alignment case, only the CPT coupler is utilised to transfer power. While in misalignment case, the IPT coupler is activated to transfer power to improve the misalignment tolerance. Besides, the transfer capability of the combined system can be improved when the misalignment happens. The system coupler, connection method and output power characteristics are presented in detail. Then, the general design procedure is provided with an example system at 1 kW. Experimental results show that the maximum variation of the output is 5.6% when misalignment is up to 250 mm (50%). While the power variation of the system involving single CPT can be as large as 52%.