Fundamental Study of Underwater Multi-Stage Contactless Power Transmission by Applying Periodic Structure Theory

Underwater contactless power supply technology has important applications in underwater vehicles, sensors, offshore drilling operations, and scientific drilling. However, some obvious crucial problems confront multi-stage contactless power transfer, in particular exponential power transfer decay and the influence of surrounding seawater or a low-electrical-conductivity metal such as steel and stainless steel. This study fundamentally investigates multi-stage contactless power transfer in seawater and steel surrounding environments. It first examines single contactless power transfers consisting of typical coil resonators. However, coil resonator technology for multi-stage contactless power transfer poses an additional crucial problem: coil resonators are extremely sensitive to the accuracy of impedance at a power supply surface. This study therefore proposes a multistage contactless power transfer applying periodic structure theory, and presents the results of simulations and simple experiments as validation of the proposed approach.