Optimization on Three-Coil Long-Range and Dimension-Asymmetric Wireless Power Transfer System

With the rapid development and extensive application requirements of wireless power transfer (WPT) technology, the common symmetrical WPT system is growing more mature, but it may still struggle to meet the vast demands. When the WPT system has a long transmission distance and the dimensions of transmitter and receiver coil are asymmetric, the current in the transmitter coil of traditional two-coil symmetrical structure may be excessive. The addition of a relay coil between the transmitter and the receiver coil can effectively reduce the current of transmitter coil, thereby improving system efficiency and reducing electromagnetic field (EMF) leakage. In this article, the parameters of relay coil are optimized by theoretical calculation and multiobjective genetic algorithm. The results show that the optimized three-coil system can reduce the current of transmitter coil by 73.1%, improve the efficiency by 10.7%, and suppress the EMF leakage by 12 dB simultaneously. Finally, the effectiveness of the proposed system is verified by experiments.