Research On The Low Speed Performance Of The Direct Torque Controlled Induction Motor System

The direct torque control technology, developed following vector control technology, is a new high-performance variable frequency speed regulation technology. It has great advantages of rapid dynamic response,imple control and little influence of the change of motor parameters, and can obtain a very nice dynamic performance.In this paper, firstly, the basic principles and structure of direct torque control of asynchronous motor were introduced , simulation model of each module and the whole direct torque control system were constructed, the dynamic and static performance of direct torque control were analyzed, and the defect, a larger low torque ripple, was revealed in the direct torque control system of asynchronous motor.Secondly, the paper analyzed the influence of flux and torque under the change of stator resistance, and then analyzed the role of the duration voltage vector on the effect of torque ripple. On the basis of above analysis, proposed a torque control scheme of the combination of stator resistance identification online and torque predictive control, constituted an improved direct torque control system of asynchronous motor, contracted the model and simulated through Matlab/Simuink. Simulation results demonstrated the feasibility of the improved direct torque control strategy.