Research Of Direct Torque Control System Of Induction Motor

Direct torque control (DTC) system of induction motors has got wide attention with advantages such as new thoughts, simple control scheme and excellent performance. However, because of induction motor is a high-order, nonlinear and strong coupling of complex systems of many variables, and by the parameters perturbation, as well as the impact of outside interference, making the design of controller into a complex issue. To achieve high dynamic performance of drive system, a nonlinear active disturbance rejection controller (ADRC) used in direct torque control system of induction motors is introduced in this paper.Firstly, the basic math model of an asynchronous machine and of a PWM inverter is introduced, then the principle of direct torque control system of induction motors is analyzed, the round track of flux of direct torque control system is developed in MATLAB/Simulink software. Simulation results show that, a group of PI parameters can be made only for a certain range of speed of implementation of better regulation, for the speed control other range of poor performance.The defects of traditional PID control methods are discussed, tracking differential(TD), extended state observer(ESO), nonlinear state error feedback(NLSEF) and the basic principle of active disturbance rejection controller are introduced, the standard structure of active disturbance rejection controller is given, the simulation model of active disturbance rejection controller is developed. The basic principles of active disturbance rejection controller to solve multi-variable system coupling is expounded, the simulatio,n shows that active disturbance rejection controller is not dependent on controlled object model, and can achieve a good decoupling with the mutual interference. Active disturbance rejection controller has good robustness and anti-disturbances.The direct torque control system of induction motors based on active disturbance rejection controller is focus studied, and the structure of this system is given, the design proposal of the speed of active disturbance rejection controller of induction motor is analyzed, one-order active disturbance rejection controller is used to the direct torque control system of induction motors, and s-function are edited to achieve active disturbance rejection controller algorithm. Some methods of controller's parameter setting are generalized, and the simulation model of direct torque control system of induction motors based on active disturbance rejection controller is created.Simulation results show that, compared with the PI controller of which parameters are optimized, direct torque control system of induction motors based on active disturbance rejection controller has a better performance in increasing-load, outside disturbances,and parameter perturbations and so on. It has powerful robustness and anti-disturbances capability.We hope through the study of the active disturbance rejection controller in direct torque control system of induction motors to expand the applications of the active disturbance rejection controller and to provide a new thinking to direct torque control strategy.