Research On PMSM SVM-DTC Speed Control System Based On Active Disturbances Rejection Control

Permanent magnet synchronous motor has been widely used in production, control and other fields because of its advantages of small size, simple structure and high power factor. At present, the direct torque control method is common used in high-performance AC speed control with its advantages of simple control principle and fast response rate. However, the direct torque control has the problem of changeful stator resistance and inconstant switching frequency of the inverter power device. When permanent magnet synchronous motor is set as controlled object, because of the relatively small stator inductance, there will be a large current impact, resulting in the system's flux and torque having large amplitude ripple during the system start-up or load change.Aiming at this condition, using the traditional direct torque speed control system as the basic reference model, the thesis improves the structure of the traditional direct torque speed control system by the method of space vector pulse width modulation and applies the active disturbances rejection control theory to the speed control system. The improvement is aimed at eliminating flux and torque ripple in direct torque speed control system, and optimizing the dynamic performance of the speed control system.The specific research contents are as follows:(1) The rotor structure types and working principles of the permanent magnet synchronous motor are summarized, then derives and concludes its mathematical models of different coordinates.(2) The speed control principles of direct torque control are clarified. Using the permanent magnet synchronous motor as the controlled object, the thesis takes advantage of Matlab/Simulink to build the direct torque speed control system simulation model. The model is simulated and the dynamic performance of the system is analyzed by its results in different working conditions.(3) The thesis researches the principles of space vector pulse width modulation technology and clarifies the sub modules. Taking the advantage of space vector pulse width modulation technology, the direct torque speed control system simulation model is built and the simulation results are compared with the traditional direct torque speed control system.(4) The control principle and relative merits of PID controller are expounded and analyzed. By researching the active disturbances rejection control principle, the structure which is constituted by tracking differentiator, extended state observer and nonlinear state error feedback is explained. In addition, the parameters in the algorithm are analyzed.(5) According to the principle of direct torque control and permanent magnet synchronous motor motion equation, the active disturbances rejection speed controller is designed to replace PI controller in traditional speed control system's speed loop. The direct torque speed control system simulation model based on the active disturbances rejection control is built. By comparing the simulation result with the system referred above, the results are given.