Misalignment-Tolerant Coupling Coils Design for Underwater Wireless Power Transfer Using Particle Swarm Optimization

Underwater charging stations allow Autonomous Underwater Vehicles (AUVs) to recharge batteries, extending missions and reducing surface support. However, efficient wireless power transfer requires overcoming alignment challenges and environmental variations in conductive seawater. This paper employs Particle Swarm Optimization (PSO) to design coupling coils specifically applied for underwater wireless charging station systems. The establishment of underwater charging stations enables Autonomous Underwater Vehicles (AUVs) to recharge batteries underwater, extending mission duration and reducing reliance on surface-based resupply operations. The proposed charging system is designed to address the unique challenges of the underwater environment, such as alignment disruptions and performance degradation caused by seawater conductivity and environmental fluctuations. Given these distinctive underwater conditions, this study explores coupling coil design comprehensively. COMSOL Multiphysics and MATLAB software were integrated to develop an automated coil evaluation platform, effectively assessing coil coupling under varying misalignment conditions. PSO was employed to optimize coil inner diameters, simulating coupling performance across different misalignment scenarios to achieve high misalignment tolerance. The optimized coils were subsequently implemented in a full-bridge series-series resonant converter and compared with control group coils. Results confirmed the PSO-optimized coils enhanced misalignment resistance, exhibiting a variation of coupling coefficient as low as 4.26%, while the control group coils have a variation of 10.34%. In addition, compared to control group coils, PSO-optimized coils achieved an average efficiency of 71% in air and 67% in seawater, outperforming the control group coils at 66% and 60%, respectively. These findings demonstrate the effectiveness of the proposed PSO-based coil design in improving underwater wireless power transfer reliability and efficiency.