In wireless power transfer, the transfer efficiency decreases with the increase of the transfer distance. To improve the power transfer performance, the operating characteristics of a conformal coplanar four‐coil magnetic resonant coupling wireless power transfer system are investigated and analyzed under four different resonant states. Based on the complete equivalent circuit model, the transmission coefficient and the input impendence are calculated. The performance of the systems operated under four resonant states is studied and compared. Also, the origin of the difference is specifically analyzed. The simulation results indicate that the wireless power transfer system operated under State 1, the state where the compensated serial capacitance makes the coils work at the frequency of the maximum Q‐factor, shows the most excellent transfer characteristic among the four resonant states. The transmission coefficient can be well maintained above 0.8 within the transfer distance of 30 cm. Experiment has been carried out for validation, and the result indicates that more power can be delivered to the load for the system operated under State 1.

中文翻译：

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四线圈磁谐振耦合无线电力在不同谐振状态下的工作特性

在无线电力传输中，传输效率随着传输距离的增加而降低。为了提高功率传输性能，研究并分析了共形共面四线圈磁谐振耦合无线功率传输系统在四种不同谐振状态下的工作特性。基于完全等效电路模型，可以计算出传输系数和输入阻抗。研究并比较了在四个谐振状态下运行的系统的性能。另外，还专门分析了差异的根源。仿真结果表明，无线电力传输系统在状态1下工作，该状态下补偿的串联电容使线圈以最大Q的频率工作。因子显示了四个谐振状态中最出色的传递特性。在30 cm的传输距离内，传输系数可以很好地保持在0.8以上。已进行实验进行验证，结果表明，在状态1下运行的系统可以向负载提供更多的功率。