Research On Transfer Performance And Control Strategy Of Magnetic Resonance Coupling Wireless Power Transfer System

Wireless Power Transfer is a kind of transmission and distribution technology which utilizes electromagnetic field or wave space distribution to transfer electric energy from the power supply to the load without wire contact.WPT is the innovation of traditional power transmission and supply method,with the advantages of safety,reliability,wideness,flexibility and so on.It is expected to replace wire transmission as the main power dispatching method in some scenarios.Magnetic resonance coupling,which takes into account the balance of transmission distance and efficiency,has become a research hotspot in the field of WPT in recent years.However,the system performance of the magnetic resonance coupling is very sensitive to the change of coupling parameters,the transfer efficiency is greatly affected by the dynamic change of the coil relative position.Although the resonance compensation can improve the transmission performance under certain conditions,it makes the stability of system worse.Aiming at the above problems,the following contents are studied in this thesis :1.The simulation analysis of the coupled mode model and equivalent circuit model is established and carried out.From the point of coupling mode,it is concluded that the transfer efficiency is determined by the coupling coefficient and the quality factor,and the resonance compensation is to compensate for the low coupling coefficient by raising the quality factor.From the point of circuit parameters,the main factors affecting the transfer efficiency include the primary input voltage,working frequency,mutual inductance,AC internal resistance and load impedance.2.The finite element model of the magnetic coupling mechanism is designed and optimized,and the optimization of magnetic field distribution is verified by static field simulation.The coupling characteristics of coil inductance,coupling coefficient,AC impedance,loss and efficiency with coil relative position and exciting frequency are analyzed by transient field simulation.The frequency splitting phenomenon and its effect on the transfer efficiency are described through the analysis of the high frequency network analysis.3.The steady state power control strategy.According to the equivalent circuit model and the magnetic coupling mechanism,the magnetic resonance system with LCL resonance compensation is built,and the steady-state power control method based on phase-shift control and frequency locking is proposed.The feasibility of the proposed power synchronization control based on phase-shifting control is proved by system simulation.4.The experimental prototype of the WPT system with the maximum transfer power of 100 W and the maximum transfer distance of 30 cm is designed.The transmission performance of the experimental prototype under the change of the coil relative position and the effect of control strategy under the condition of the magnetic field steady state are tested.The effectiveness of the coupling mechanism design,finite element analysis and control strategy is verified by experimental test.The proposed steady-state power control strategy based on phase-shift control and automatic frequency locking can realize the steady-state control of LCL magnetic resonance wireless power transfer system.Under steady-state conditions,the proposed controller can control the power magnitude and direction,and has good robustness and effectiveness,and can avoid frequency flitting by automatic frequency locking.The research results are valuable for the theoretical understanding,simulation modeling,controller design and experimental platform building of WPT system.