Efficiency analysis and optimization of a three-coil wireless power transfer system based on an active rectifier using optimal current ratio control

The efficiency analysis and optimization methods for achieving optimal efficiency in two-coil wireless power transfer (WPT) systems have been considerably discussed. Recently, that the efficiency of three-coil WPT can be higher than its two-coil WPT counterpart with an extended transmission distance has been verified. Nevertheless, the research on the efficiency analysis and optimization of the three-coil WPT system still needs to be examined. Therefore, this paper systematically investigates the efficiency characteristics of the three-coil WPT system. Especially, an optimal current ratio control strategy is developed with an active rectifier to achieve efficiency optimization and keep the output voltage constant. Consequently, overall efficiency can be improved using the optimal current ratio compared with traditional three-coil WPT systems. A scaled-down experimental prototype is established to validate the effectiveness of the proposed coupling structure and the feasibility of the proposed control approach. Overall, a three-coil WPT system with an active rectifier is proposed, which utilizes the optimal current ratio control strategy. Experimental results successfully validate that the proposed methods can substantially improve the efficiency of three-coil WPT.