Research On Fuzzy Direct Torque Control Of Speed ​​Sensorless Induction Motor

The Direct torque control(DTC) was put forward after Vector Control proposed. The Direct torque control is concerned by lots of scholars and develops very rapidly, as its simple structure, fast torque response and so on. But the stator flux error direction and torque error direction are only thought about in Direct torque control. The stator flux error magnitude and torque error magnitude are ignored in this method. As a result, torque ripple is produced under operating conditions.Based on the mathematical model of asynchronous motor and the theory of DTC, the reason of torque ripple is analyzed deeply under operating conditions. In this paper, in order to solve the large torque ripples which exist in induction motors based on conventional direct torque control(DTC),especially at a low speed, fuzzy control theory is applied to DTC system. In the fuzzy model strategy, the structure of the three-input single-output are adopted, the stator flux angle, the stator flux error, and the torque error are as fuzzy variables which are fuzzed into several fuzzy subsets to optimize select of the voltage vector.In Direct torque control, the rotor speed is detected by Speed Sensor. As the device increased, the stability of system is reduced. The speed sensorless is a new focus of AC speed adjustment research. In this paper, the speed of induction motor is estimated by Mras(Model Reference Adaptive System) method. Based on Mras and fuzzy control of speed sensorless induction direct torque control model is constructed in this paper. The stator current and stator voltage of induction motor are used to develop speed sensorless is based on Mras. The new direct torque control system consists of fuzzy control and Mras.The control system is simulated on the platform of Matlab/Simulink. Compared to the conventional direct control system, the results of the simulation prove that the method of the fuzzy DTC controller can effectively improve the low-speed performance of the induction motor, reduce the torque ripple, and have a good dynamic response performance.