Optimization of the Relay Coil Compensation Capacitor for the Three-Coil Wireless Power Transmission System

The wireless power transmission (WPT) system, which eliminates the limitation of physical connection and improves the convenience of power transmission, has gradually become a research focus in recent years. However, in the current three-coil WPT system, the power repeater is composed of a coupling coil and a compensation capacitor, and its tuning conditions will affect the power transmission ability of the WPT system. However, the exact impact of compensation capacitor is not clear, which leads to the design of power repeaters being based on experience or trial and error methods, making it difficult to achieve the optimization of the WPT system. Therefore, this paper takes transmission power and transmission efficiency as optimization objectives and obtains the optimal relay coil compensation capacitor model of the three-coil WPT system. The result found that the transmission efficiency of the three-coil WPT system after optimizing the compensation capacitor is 3% higher than before, and the anti-migration ability is enhanced. Meanwhile, in view of the dynamic changes in load and mutual inductance that may occur during the use of the three-coil WPT system, a compensation capacitor design and a relay coil compensation capacitor circuit are proposed, respectively, and the parameter setting scheme of the circuit is proposed. The innovative scheme proposed in this paper can effectively improve the transmission efficiency and stability of the three-coil WPT system.