Research On Automatic Tuning Technology Of Resonant Wireless Charging System

Wireless charging technology overcomes the shackles of traditional cable transmission of electric energy,and can complete the transmission of electric energy without wires,and has been widely used in many fields.Magnetic coupling resonance wireless power transmission technology has the advantages of greater transmission power,higher transmission efficiency,and moderate transmission distance.It is a research hotspot in the fields of electric vehicles and unmanned aerial vehicles.However,the following problems will occur during actual operation:(1)When the transmission distance is large,the coupling coefficient of the system will decrease and the transmission efficiency will decrease.(2)Due to the change of load and the change of mutual inductance between coils,the natural resonance frequency of the system changes,which makes the system in a state of detuning,resulting in a decrease in the power transmission performance of the system.In order to increase the transmission distance of the power transmission system,two resonant coils with a high quality factor and mutual coupling are added between the transmitter coil and the receiver coil.The resonant coil generates a higher-strength magnetic field in the transmission space,thereby achieving greater energy efficiency.Efficient transmission at long distances.Using the theory of mutual inductance coupling,the calculation methods of the primary side compensation capacitance of four different topological structures are derived.The power transmission model of the PSSS four-coil coupling mechanism is established,and the influence of the change of load and mutual inductance on the system transmission power and transmission efficiency is analyzed.According to the primary compensation capacitance,the relationship between the resonance frequency of the four-coil coupling mechanism and the mutual inductance and load of the system is obtained.The four-coil coupling mechanism is equivalent to a two-coil model,and the power transmission characteristics of the system are analyzed from the aspects of quality factor and coupling coefficient.Aiming at the problem of system detuning caused by changes in load and mutual inductance,this paper proposes a hybrid tuning method that combines the compensation capacitance matrix and the phase-controlled inductance.This method firstly adjusts the resonance parameters through the capacitor matrix,and then combines the phase-controlled inductance tuning branch to fine-tune the system to compensate the impedance of the primary resonant circuit,so that the natural resonance frequency of the primary coil is always the same as the rated operating frequency of the system.Keep consistent,make the system work in the constant frequency mode,overcome the frequency bifurcation and frequency drift caused by the floating frequency control.According to the principle of resonance,the value range of matrix capacitance and phase-controlled inductance is analyzed.Build a simulation model on MATLAB/Simulink.Under the condition of load type change and load change,the effects of the compensation capacitance matrix,the independent tuning of the phase-controlled inductance and the hybrid tuning are compared.The simulation analysis shows that the resonance frequency fluctuation of the hybrid tuning control is less than 4%.