Research On Power Converter Of Wireless Power Transmission Via Magnetic Resonance Coupling

The transmission efficiency of wireless power transmission systems via magnetic resonance coupling is higher than electromagnetic radiation type wireless power transmission systems, while the transmission distance of wireless power transmission systems via magnetic resonance coupling is larger than inductive contactless power transmission systems, therefore, it has great application value in the medium distance case. The transmission characteristics of wireless power transmission system are the basis of research on wireless power transmission, high frequency inverter is an important part for wireless power transmission systems via magnetic resonance coupling, and the resonance frequency detuning brought by load fluctuation has bad influence on wireless power transmission. In this paper, we mainly researched on the above problems.Firstly, we researched on the characteristics of wireless power transmission systems via magnetic resonance coupling (RWPT). According to the resonance in circuit theory as well as the mutual inductance between the transmitting and receiving coil, we established an equivalent circuit model for wireless power transmission system via magnetic resonance coupling.According to this model, theoretical analysis and simulation research demonstrated the follow conclusions:when the frequency of the AC power supply is equal to the natural resonant frequency of the transmitter and receiver, the average power of the load maximizes, when this condition is not satisfied, the average power of load decreases, and the power transmission efficiency always keeps at a high level as the frequency of the AC power supply varies from low to high; as the transmission distance increases, the power transmission efficiencydecreases, while the average power of the load increases first, and then decreases; with the increase of load, the power transmission efficiencydecreases, but the average power of the load increases first, and then decreases. Through the simulation of different topologies of wireless power transmission, we drew the conclusion of how to select topology under different conditions.Then, we studied the issue of the frequency tracking control of wireless power transmission to solve the adverse effects caused by the resonant frequency detuning. Theoretical analysis demonstrated that directly tracking the frequency of transmitter current is effective when using SS or SP topology in wireless power transmission system via magnetic resonance coupling, however, we can’t directly track the frequency of receiver current if not conditioned it at all. Simulation result demonstrated that the circuit finally worked at the natural resonant frequency even if the start frequency wasn’t equal to the natural resonant frequency when directly tracking the frequency of transmitter current, however, the circuit worked at a frequency which was away from the natural resonant frequency when directly tracking the frequency of receiver current. The result of RWPT with directly tracking the frequency of transmitter current is better than RWPT without frequency tracking under different transmission distance.Finally, based on the above theoretical analysis and simulation research, we implemented the high frequency inverter and basic wireless power transmission system with DSP&FPGA as a controller. We experimentally verified the wireless power transmission system of directly tracking the frequency of transmitter current.