Research On Frequency Tracking Of Magnetically Coupled Resonant Wireless Power Transmission System

Wireless Power Transfer(WPT)technology refers to a technology that uses soft media in space to implement power transmission without using any physical connection.This technology has the advantages of safety,reliability,convenience and is widely used in electric vehicles,medical equipment,special environmental operations.And Magnetically Coupled Resonant Wireless Power Transfer(MCR-WPT)has become the most promising wireless power transmission method at present with the advantages of high efficiency,long-distance transmission and large transmission energy.Frequency is important for system stability and transmission.The frequency is affected by external obstacles(magnetically permeable objects)during the wireless transmission.In addition,changes in the circuit parameters of the transmitter and receiver system aging and temperature will cause the system operating frequency to be inconsistent with the resonant frequency.As a result,detuning results in reduced transmission performance.In order to make operating frequency consistent with the natural frequency,to ensure that the wireless power transmission system does not cause transmission performance degradation due to detuning,frequency tracking of the wireless t system should be performed.This paper models the coupling mode theory and equivalent circuit theory,analyzes the specific factors that affect the energy transfer of the system,and proposes two different frequency tracking control methods.One is to use a phase-locked loop to track the frequency,while introducing a Differential Evolution algorithm(DE)to optimize control adjustment.The second is based on the LCC self-tuning method to ensure that the emitted frequency changes near the natural frequency of the system to achieve the purpose of frequency tracking.Furthermore,the frequency tracking control strategy based on DSP phase-locked loop(PLL)is further studied,and the frequency tracking control method with the same frequency and frequency phase correction is designed and a digital phase-locked formula is obtained to constrain the frequency.Further,the transmission links and control loops of the wireless system are designed.Combining MATLAB simulation and wireless energy frequency tracking theory,the system experimental platform is overlapped,experimental verification of the proposed frequency tracking method under variable load,variable distance and variable coupling coefficient and the comparison and analysis of frequency tracking before and after frequency tracking of the wireless energy transmission system are performed.In addition,change the transmitting frequency to simulate the detune condition and observe the frequency tracking of the system.In order to prove the superiority of this tracking method compared with other control tracking methods,a comparative control experiment was set up.The results show that when the performance is degraded due to detuning,the frequency tracking system can effectively track the frequency and make the system reach the resonance state,which proves the correctness of the control method.And,the method based on DSP’s frequency before frequency phase has the characteristics of faster response speed,better tracking effect,and better performance than other methods,which proves that this method can improve the performance of wireless transmission systems.