Research on Resonant Frequency Characteristics of Wireless Power Transfer in Seawater Medium

Wireless power transfer (WPT), as a non-contact power transfer technology, is expected to solve the power supply difficulties faced by ocean power equipment due to the environment's complexity. However, when the magnetically coupled WPT system operates in seawater, eddy current losses (ECL) affected by the resonant frequency are generated, which in turn causes the resonant frequency characteristics of the system to be altered compared to those in air. The resonant frequency characteristics of WPT have been thoroughly researched, and expressions for the relationship between resonant frequency and efficiency have been derived by utilizing the mutual inductance circuit model with equivalent ECL resistance. The influences of resonant frequency variation on transmission efficiency and distance are comparatively analyzed for the system in seawater and in air, respectively, with the differences between the two situations further illustrated. Research has discovered that there is an optimal resonance frequency for WPT. The factors influencing the optimal resonance frequency were analyzed, and it was concluded that the contact area between the coil and seawater was the key factor affecting it. An experimental system for WPT in seawater media was constructed, and theoretical and simulation conclusions were validated through experiments.