Underwater wireless power transfer system with a curly coil structure for AUVs

An underwater wireless power transfer system with a curly coil structure is proposed to adapt to the cylindrical symmetric hull of the autonomous underwater vehicles (AUVs). The unipolar and bipolar curly coils are optimised to minimise the weight of the receiver with the same output power. It is revealed that the bipolar curly coil structure has a heavier receiver than the unipolar curly coil structure. However, the electromagnetic field radiation in the AUV of the bipolar curly coil structure is much smaller than that of the unipolar curly coil structure, which means that the bipolar curly coil structure has a smaller influence on the electronics components in the AUV. Therefore, the bipolar curly coil is adopted for the prototype. The series −series (SS) and double-sided inductor−capacitor−capacitor (LCC−LCC) compensation topologies for the bipolar curly coil structure are also investigated. A prototype was built and the experimental results showed that distorted coil currents are generated in the SS compensation topology, while the LCC−LCC compensation has a nearly sinusoidal coil current. The efficiencies of the SS and LCC−LCC compensation topologies are approximately the same, at ∼95%, which indicates that the proposed curly coil structure is applicable.