Research On Parameter Identification Method Of Wireless Power Supply System Based On Pulse Density Modulation

As a substitute for traditional fuel-powered vehicles,electric vehicles are favored by people because of their advantages in effectively reducing greenhouse gas emissions.Wireless power supply technology provides a new solution for solving short circuit,leakage and other potential safety problems in the traditional plug-in charging mode of electric vehicles.However,during the wireless charging process of electric vehicles,the changes of mutual inductance and equivalent load of the system caused by various factors will change the reflected impedance from the receiving end,lead to the resonance frequency drift of the transmitting end circuit,affect the working state of the system,cause energy waste,and even lead to safety accidents.Based on this,this paper proposes a parameter identification method of wireless power supply system based on pulse density modulation.By collecting the voltage and current information of the transmitter side,the mutual inductance and output voltage of the system can be identified,and the working state and battery charging state of the system can be judged according to the identification results,thus ensuring the charging safety of electric vehicles.The main contents of the thesis are given as follows:Firstly,a parameter identification method of wireless power supply system based on pulse density modulation is proposed.Firstly,the principle of power regulation of pulse density modulation is expounded.Taking the wireless power supply system with S-S compensation topology as an example,the output characteristics of the system are analyzed.Based on the wireless power supply system,the mathematical model of this parameter identification method is deduced and analyzed.At the same time,in order to reduce the influence of measurement errors and other factors on the identification accuracy,the least square method is introduced to determine the parameter identification results.Secondly,the selection strategy of interharmonics is put forward.The frequency spectrum of inverter output pulse is analyzed,and the relationship between inverter output pulse sequence and the content of interharmonics is expounded.Subsequently,it is proved that changing the output pulse sequence of the inverter will basically not affect the output of the system under the condition of constant duty cycle.Then,under the condition of fixed duty cycle,by comparing and analyzing the spectrum analysis results of various inverter output pulses,the selection strategy of inverter output pulse sequence and interharmonics is put forward.Based on this selection strategy,the output pulse sequence of inverter and the interharmonics applied to the mutual inductance and output voltage identification are specially selected.Finally,in order to verify the effectiveness of the proposed parameter identification method,a simulation model is built with the help of MATLAB/Simulink simulation platform,at the same time,the experimental platform is set up,the simulation and experimental verification are carried out when the mutual inductance and load of the wireless power supply system change.The simulation and experimental results show that when the load and mutual inductance change,the identification result is close to the actual value,the identification accuracy is greater than 95%,and the energy transmission efficiency of wireless power supply system is about 90%.