Design and Implementation of High-Misalignment Tolerance WPT System for Underwater Vehicles Based on a Variable Inductor

Wireless charging for autonomous underwater vehicles has been widely explored recently by the merit of safety and convenience. However, due to the misalignment between charging coils in the horizontal and vertical directions, the system may not maintain constant current or constant voltage output. Therefore, this article proposes a mistuned inductive power transfer (IPT) system structure and corresponding design methods to improve misalignment tolerance. The proposed IPT system adopts series–series compensation and includes a variable inductor (VI) on the secondary side. A general design method based on the established mathematical model is proposed. The worst scenarios (i.e., the maximum value of misalignment) are used for the optimization of the system parameters. The control strategy for VI without any communication link to the primary side is established. Finally, a 1-kW IPT system for tolerance of k of 0.15–0.5 and output voltage of 74–150 V variation is set up. The experimental results show that the horizontal and vertical direction misalignment ranges reach ±47% and +140%, respectively, and the maximum system efficiency exceeds 96% for full power output. The proposed system improves the freedom and stability of charging in the harsh underwater environment.