A Robust AUVs Wireless Power Transfer System Based on Seawater Cross-coupling Capacitance Model

Autonomous underwater vehicles (AUVs) serve as crucial equipment for marine exploration and operations. However, the output power and efficiency of the underwater wireless power transfer (WPT) system are affected by underwater unique electrical parameters, and ocean current disturbances can easily trigger coil angular deflection, thereby influencing the system output characteristics. To address this critical challenge, this paper establishes an equivalent circuit model for seawater environments by considering the cross-coupling parasitic capacitance. By incorporating the parity-time (PT) symmetry principle and a DD coupling coil structure, a novel AUVs underwater wireless power transfer system is proposed. Within the strong coupling PT symmetric operating region, the output power and transfer efficiency of the proposed topology become independent of the coupling coefficient k . Consequently, alignment insensitive constant power transfer is achieved without wireless communication modules. The theoretical derivations of the system are detailed through equivalent impedance simplification. Furthermore, the transmission characteristics in air and seawater media are compared, and an experimental prototype is built to conduct multidimensional misalignment tests. Experimental results indicate that the transferred power and efficiency of the system remain remarkably stable under an axial misalignment of ± 80 mm and various angular deflections. The DC-DC power transfer efficiency in seawater environments is stabilized at approximately 90%, demonstrating that the proposed system exhibits exceptional tolerance against both axial and rotational misalignments.