Self-Aligning Capability of IPT Pads for High-Power Wireless EV Charging Stations

This paper studies magnetic forces between transmitter (Tx) and receiver (Rx) coils in an Inductive Power Transfer (IPT) system aiming to use those forces to align the coils and, consequently, improve power transfer. The analysis is conducted on a series-series compensated IPT system with planar spiral coils due to its popularity. The proposed method utilizes the bifurcation operation mode of the system and unloaded resonating receiver to maximize attractive force between magnetic couplers. 3D Finite Element Method (FEM) simulations indicate that high-power IPT systems can develop enough attractive force to align Tx and Rx coils even for nominal current. Regardless of the coil shape, e.g., spiral or DD, the attractive forces tend to increase the coupling factor, i.e., to align the coils. Hence, a smart charging station can be devised based on self-aligning capability. Furthermore, this paper proposes a mechanical structure to facilitate the attractive lateral force for the alignment of high power applications, i.e., wireless fast-charging stations. The forces are analyzed, modeled, and simulated for a 100-kW IPT system with an operating frequency of 20 kHz, while the self-aligning capability is experimentally verified on a downscale 11-kW laboratory prototype.