Simulation Of Induction Motor DTC System Using The New Anti-windup Controller

Induction motor has many advantages. It’s cheap, and the structure is simple.Induction motor is easy to manufacture and maintain. But the induction motor’s obviousshortcoming is that the speed control performance is poor and complex. Thereforeinduction motor needs an advanced control technique for effective control performance.Direct torque control technology is direct, control variable is clear, dynamic and staticperformance is superior. DTC is out the complex coordinate transformation, reduces thedependence on motor parameter. And it has good robustness. Direct torque controltechnique because of its simple and effective control strategy to make it very suitablefor the induction motor system.The work of this paper is mainly in the following aspects:(1) First on the analysis of mathematical model of induction motor and basicprinciple of DTC. The DTC system is made for the modular processing. We designedthe induction motor module, inverter module, flux linkage and torque estimationmodule, the switch table module and speed estimation module by using the Simulink ofMATLAB simulation software. The five modules together set up the simulation schemeof induction motor DTC system. The simulation results reach the expected effect. Thesimulation system is feasible and effective. From the simulation results we find twoproblems. One is the existence of integral saturation phenomenon. The second is the bigpeak of starting current.(2) PI controller has nonlinear integral saturation phenomenon which will affectcontrol performance of the system. Even make the system unstable. So in this paper weadopt a new kind of Anti-Windup controller, which is on the basis of the PI controller.This controller is improved on the basis of the PI controller. It improves theperformance of the PI controller and retain the advantages of PI controller, such assimple and easy to implement.First this paper gives the new Anti-Windup PI controller’s structure andmathematical model, and then analyzed its working principle. Later on this paper makesthe stability analysis of the new Anti-Windup PI controller in theory, and gives theconditions of the new Anti-Windup PI controller. Then this paper establishes the simulation model of the new Anti-Windup PI controller with MATLAB/Simulinksoftware. As comparison and reference this paper introduces the tracking-backcalculation controller which is commonly used in engineering. The result shows that thenew Anti-Windup PI controller is better than the PI controller and the tracking-backcalculation controller.(3)The current peak of induction motor direct torque control system is very big atboot time. Sometimes it is far beyond the maximum allowable current. This will causefrequent protection action. Even damage the system. This article considers the statorflux linkage, rotational speed, torque and current of startup, and then researches thesimulation results of the DTC system using MATLAB/Simulink. Then this articleexpounds their influence on system startup current pulse. According to the result ofsimulation, the current-limiting starting method is simple and practical. It caneffectively inhibit the starting current peak and does not affect the other performance ofthe motor.