Design of the coupling coils with misalignment tolerance for underwater charging applications

This paper focuses on the research and the design of coupling coils of an underwater wireless charging station system. The system must adapt to the underwater environment and address alignment issues caused by seawater as the medium. A detailed investigation of coil coupling design is conducted, considering the unique underwater dynamic environment. An automated coil evaluation platform is established by integrating COMSOL Multiphysics® and Matlab software. The Exhaustive Search Method is used to optimize the coil inner radius design to achieve high misalignment tolerance. Finally, the optimized coils are applied in a H-bridge series-series resonant converter and compared to a control group of coils. The optimized coils show superior misalignment tolerance, with minimal coupling coefficient variation (i.e. 0.013) and an average coupling level of 0.232. In contrast, the control group exhibits a higher coupling coefficient variation (i.e. 0.026) and an average coupling level of 0.18 under the same conditions.