A Compact Underwater WPT System with Load-Independent Current Output Characteristic under Wide Range of Coupling Coefficient

Wireless power transfer (WPT) technology provides an effective solution to the power supply of autonomous underwater vehicle (AUV). However, the misalignments and rotation often occur between the docking station and AUV, which would result in a fluctuation to system's output characteristics. To maintain constant current output with unreliable communication under seawater environment is a barrier. Aiming at this problem, this article presented an LCC-N WPT system with fewer compensation devices on the receiver side, which is immensely suitable for reducing the weight and volume of the AUV. Meanwhile, based on the switch-controlled capacitance (SCC) technology and frequency modulation at the transmitter side, the mentioned WPT system could stabilize the output current while the coupling coefficient k and load resistance R_L undergo a wide range variation. The determination method of system parameters, including operation frequency, capacitance value of SCC and compensation inductance under various misalignment conditions was detailed derived. Besides, the zero phase angle characteristic could be achieved during the whole process. The experimental results indicate that while the coupling coefficient varies from 0.3 to 0.54, the fluctuation of output current for the proposed WPT system is less than 4.47% and the power transfer efficiency could be maintained above 87%, and the maximum efficiency can reach 92.8%. In addition, the characteristics of load-independent output current during the misalignment process was also verified.