Modeling and Optimization of The Four-Coil Wireless Power Transfer System

The four-coil type Wireless power transfer (WPT) system, which is based on magnetic resonance coupling, can be widely used in the mid-range WPT applications. As a power converter, the analytic model, which consist of efficiency and output power calculation, is the most important theoretical basis for the optimization of WPT system.In this paper, a analytic model of the four-coil type system is built and verified. It overcome the drawbacks of present models, which are too complex to used in general design of WPT system. With the formulas of the model proposed, the efficiency optimization can be achieved easily through coupling coefficient and load resistance selection at particular parameters condition. A WPT prototype based on FEM simulation is built for verifying the model proposed. The transfer efficiency, output power and load feature are matched well between the calculation and PSPICE simulation. The model proposed is proved to have high accuracy. In the prototype, the peak transfer efficiency reaches 95.33% at rated parameters. Meanwhile, the transfer efficiency is improved significantly with the optimized RL when the transfer distance variates.