Research And Design Of Four-coil Wireless Power Transfer System Based On Electromagnetic Resonance

As a landmark of high and new technology, the technology of electromagnetic resonant wireless power transfer can realize electrical isolation between the power and electric equipments. What’s more, it can be extended to many fields and achieve generalization. Compared with the traditional way of power transfer, it is more secure, more reliable and more flexible. Therefore, this technology satisfies the needs of convenience, flexibility and security in the production and use.The most important performance indexes of the wireless power transfer system include transmission distance, load power and efficiency, etc. The resonance parameters and operating parameters can affect the performances of the system, so it is important to find out the optimal parameters of the system. The parameters of the system are classified into two parts: the resonance parameters and the operating parameters. The effects of the two kinds of parameters on the system are studied respectively.First, according to the characteristics of the electromagnetic resonance transfer, this paper proposes the method of partitioning the resonance parameter space and comparing them, then study the influence of the resonance parameters on the two-coil system. It points out that the system has the optimal power stability region and efficiency stability region when the resonance parameters of the system are symmetrical. The ratio of inductance and capacitance to the efficiency stability region are also analyzed. Secondly, this paper builds a four-coil electromagnetic resonance power transfer system based on the optimal resonance parameters, and establishes the load power model and efficiency model. Then, the best working frequency of the system are analyzed and the phenomenon of efficiency frequency splitting in four-coil system is studied. The paper studies the influence of the adjacent coupling coefficient to the efficiency, and points out the optimum coupling coefficients between four resonant coils. In addition, in order to improve the output of the power supply, the impedance matching technology of the four-coil system is studied. It points out the expression of the parameters of the pour L impedance matching network.According to the study results of the resonant parameters and operating parameters, the four resonant coils were made with litz wire, and a double-coil that contains the power coil and transmitter coil was designed. The best distance of the receive coil and load coil was found. What’s more, the paper designed a class D power amplifier, and completed the driver module using the structure of H bridge, then the whole system was realized. Last, the load power and efficiency were tested under different resonant parameters and operating parameters. The consistency of the experimental results and the theoretical analysis proves the correctness of the model and study conclusion. Under the optimal parameters, the system’s maximum transmission distance is 40 cm, the maximum load power is 13 W, and the system efficiency is up to 80%.