Research On Field Weakening Operation Control Technology Of PMSM

The rotor material of a permanent magnet synchronous motor is a permanent magnet,and the excitation magnetic field cannot be adjusted through the field winding.Problems such as constant magnetic flux also make its field weakening control more complicated.When the motor enters the field weakening control area and the current controller saturates the output voltage,the output torque capability of the motor will be greatly affected,which may cause the permanent magnet to be permanently demagnetized,which will cause the entire control system to lose control.In order to improve the stability of the control system in the full speed range,this paper focuses on the field weakening control technology of permanent magnet synchronous motors.Because the permanent magnet synchronous motor is a strong coupling and nonlinear system,it is difficult for the traditional linear method to make the torque output stable in the full speed range,and the coupling problem is also a problem that must be faced when the control strategy is optimized.Therefore,based on the analysis of the cause of the cross-coupling phenomenon and the saturation nature of the PI regulator,this paper makes a deep research on the decoupling control strategy.The mathematical model of the motor is analyzed and constructed,and the feedback linearization theory is analyzed in detail.A control strategy based on feedback linearization is proposed.Lie differential operation is performed on the output variables to obtain the state feedback of the nonlinear system,and the dynamic characteristics of the original system are converted to linear dynamic characteristics.A current controller based on input and output feedback linearization is designed to realize the input and output linearization control of the motor.The current controller decouples the d and q axis current components and outputs the control voltage.When the motor speed reaches above the base speed,the d and q axis current componentsare redistributed by the current lead angle control technology to achieve a smooth transition between the constant torque region and the field weakening region.Simulation and experimental results show that the designed field weakening control system is simple in structure,robust,and has good dynamic tracking performance.