Field Weakening Control And Efficiency Optimization Of Induction Motor

The popularity of electric vehicles has changed the way people travel and the electric motor plays an important role as its driving device.The induction motor is used as one of the driving devices of electric vehicles due to its performance advantages.In this paper,the induction motor and its vector control system are taken as the research object,and the efficiency of the motor is taken as the optimization goal.The field weakening control algorithm is designed to optimize the efficiency of the induction motor while ensuring the torque output capability.The method of parameter identification of rotor resistance and mutual inductance improves the accuracy of efficiency optimization and vector control,and the robustness of the system.First,this paper introduces the mathematical model and vector control system of induction motor,including voltage equations,flux linkage equations,torque equation of induction motors in different coordinate systems,Clark and Park transformations in vector control system,and flux linkage observation methods,as well as voltage space vector modulation technology.Matlab/Simulink software is used to build the control system,which lays the foundation for the design.Next,on the basis of induction motor and vector control system,this paper considers the voltage and current limit conditions,introduces the optimization of torque,Loss Model Control(LMC)and Maximum Torque per Ampere Control(MTPA),and designed the d-q axis current distribution method.The designed control method can calculate the reference value of the flux current according to the different reference value of electromagnetic torque,and limit the torque current to achieve the purpose of current distribution.This method can integrate the two efficiency optimization methods separately,so the simulation verification and comparative analysis of the optimization results of the two are carried out.Finally,because the accuracy of the efficiency optimization method of MTPA and LMC depends on the parameters of the motor,the calculation of the electromagnetic torque and flux in the system also involves the parameters of the motor.At the same time,the parameters of the motor will be affected by environmental factors and the operating point of the motor.So,identification of related parameters can improve efficiency optimization accuracy and system controlling accuracy and robustness.This paper analyzes and designs the identification method of rotor resistance and mutual inductance,and uses a parameter identification method based on Model Reference Adaptive System(MARS).The method converts the AC current into the DC amplitude and phase angle,and the PI controller is used to identify the parameters.