Direct Torque Control Of Permanent Magnet Synchronous Motor Based On Active Disturbance Rejection Control

With the development of power electronics technology, modern control theory and microprocessor technology, the speed control performance of AC motor is rapidly increasing, and AC motor is gradually replacing DC motor in many areas. As an AC synchronous motor, permanent magnet synchronous motor plays an important role in the field of speed control because of the advantage of simple structure, high power factor and high torque-inertia ratio. With the growing demand for high-precision speed control, the application prospect of permanent magnet synchronous motor has become better and better. At the same time, the requirement of high-performance speed control algorithm is higher and higher.Direct torque control is another high-performance and closed-loop speed control strategy after vector control. By controlling the torque and stator flux linkage, the speed regulation of the motor is realized. Direct torque control emphasizes the direct control of torque, which has the advantages of rapid response and strong robustness. The traditional direct torque control using hysteresis comparator to control the torque, leading to a large torque ripple and the inverter switching frequency is not constant. The direct torque control based on space vector modulation has solve the problem of switching frequency, however, the control performance is often limited by the parameters of PID regulator.To achieve the accurate estimate of stator flux and electromagnetic torque, in this dissertation, based on the structure and characteristics of the motor experimental platform, the observation performance is considered under three conditions:under the condition of different stator voltage source, under the condition of initial flux estimation error and under the condition of stator resistance variation. The observation performance of the stator flux and electromagnetic torque under the three kinds of observation models are verified through theoretical analysis and simulation. Finally, a suitable model is chosen to design the stator flux and torque electromagnetic observer.In order to improve the precision of speed control and reduce the torque ripple, in this dissertation, reference to the idea of active disturbance rejection control, the reference voltage control law is designed based on the mathematical model under magnetic field oriented coordinate, by using the space vector modulation technology to modulate the reference voltage and to drive the inverter to supply power for the motor, a direct torque control scheme based on active disturbance rejection strategy is obtained and the feasibility of the control scheme is verified by simulation.Finally, the speed regulating performance of the control scheme is compared and analyzed through the start-up experiment, the start-up experiment with load and the motor running experiment with a speed changing, and the algorithm complexity is calculated. The feasibility of the speed control scheme is verified by these experiment.