Construction and analysis of precise circuit model for SWPT considering parasitic capacitance

Due to seawater's high conductivity and dielectric constant, the traditional pure inductance model used in air cannot accurately describe the coil model in seawater wireless power transfer (SWPT). Therefore, this paper proposes a two-port model for SWPT in seawater, considering the inter-turn capacitance and stray capacitance induced by dielectric properties. The input impedance magnitude of the pure inductance model and the model considering inter-turn and stray capacitance in both air and seawater were analyzed to demonstrate the influence of the dielectric constant on the system's operating frequency. A system model based on the SS topology was established, and the system's resonant frequency was analyzed. Due to the dielectric constant influence, the SWPT system's actual frequency shifts, with higher system frequencies being more significantly affected. Therefore, when designing high-frequency SWPT systems, seawater's high dielectric constant and conductivity must be considered to achieve optimal operating frequency and maximum transmission efficiency. An SWPT prototype was developed, and experimental results confirmed the theoretical analysis.