Research On Some Practical Application Issues Of Direct Torque Control Algorithm

This paper studies direct touque control (DTC) algorithm and some issues of direct torque control algorithm encountered during the practical application. Compared with DC motor, AC motor has many advantages, such as reliable operation, low cost, simple structure, easy to manufacture and be able to work in harsh environment and so on. AC motor has been widely used in industrial and agricultural production equipments. In the process of constant development of the AC motor, the speed control methods of AC motor are also in constantly developing. During this period, vector control technology and DTC technology are more prominent methods. DTC algorithm has attracted considerable attention from scholars by virtue of its innovative control idea, simple control structure, excellent dynamic and static performance.On the basis of the previous theoretical research, the thesis analyzes the principle of direct torque control algorithm. First, the mathematical model of the induction motor is established, which is the basis of the study of DTC algorithm. Based on Matlab/Simulink software, we establish the model of direct torque control system of induction motor and simulate it. The simulation results are observed and analyzed to ensure the correctness of the model. According to analyzing and modeling submoduls, we have a deep understanding of the direct torque control algorithm. Then, in allusion to the causes of torque ripple of direct torque control algorithm in the practical application and how to reduce the torque ripple to make research, especially study for the performance of direct torque control system running at low speed, analyze the reasons of impact on the low speed performance and research methods of improving its performance. Finally, considering the performance of the induction motor running at low speed influenced by the conditions, the change of induction motor parameters especially the stator resistance changes with temperature will affect the performance of the direct torque control system. Therefore, in order to suppress the adverse impact on the direct torque control system caused by the changes of the induction motor stator resistance when use DTC algorithm control the induction motor, we choose recursive least squares method to identify the motor stator resistance to improve the performance of DTC system. This thesis introduces the principle of the recursive least square, and uses Matlab/Simulink software to make simulating, then the feasibility of parameters identification is proved. Add the parameters identification algorithm module with recursive least squares into the direct torque control system, and carry out the simulation experiments, contrast the experimental results with the results of traditional direct torque control system, the static and dynamic performance of the direct torque control system with parameters identification is improved, the torque ripple and flux ripple is reduced, the system is running stably.