Concentric-Coil Hybrid IPT System With Improved Tolerance to Coupling and Load Variations

Abstract

Hybrid tuning topologies had been proposed with polarized magnetic couplers to improve the alignment tolerance of inductive power transfer (IPT) systems. However, the technologies are mainly applicable to IPT systems with directional coupling and relatively low inductance variations. This article proposes an IPT system with a dual-concentric-coil transmitting (Tx) and single-coil receiving (Rx) coupling configuration with hybrid tuning networks for improving the output voltage characteristics over a wide range of coupling and load variations. The concentric coils allow free rotation while integrated hybrid tuning networks help reduce the output voltage fluctuation under varying horizontal and spatial misalignments. A design procedure is proposed using finite-element method (FEM) and circuit simulations to select tuning parameters accounting for varying self and mutual inductances. Simulation and experimental results show that the self-inductance of the proposed coil can change by 48%, and the coupling coefficient varies between 0.43 and 0.74 under misalignments, leading to over 100% change of the unregulated output voltage if the system is series–series tuned. In contrast, a laboratory prototype of the proposed system demonstrates a stable output voltage within ±9% of fluctuation around 13.25 VDC.