The Research On Direct Torque Control System For Speed Sensorless Asynchronous Motor

With the rapid development of power electronics technology, computer technology and the automatic control technology, various types of motor control technologies have continued to develop. Direct Torque Control Technology (DTC) as a new type of modern AC variable speed control technology after the appearance of the vector control, the idea is taking the AC inverter and as a whole, using space vector analysis method, removed the complex calculation from the vector transform. The control system is simple, robust, good for the static and dynamic performance, easy to achieve the advantages of digital, so it has been paid more and more attention.In this paper, a detailed study of the induction motor mathematical model based on the traditional direct torque control as well as the shortcomings of the motor speed performance requirements, changes the way to adjust the stator flux so that the track of the stator flux looks like a round. In order to verify the design of direct torque control of asynchronous motor feasibility and effect, the author use MATLAB / SIMULINK simulation tool for the completion of hexagonal stator flux and a circular path of stator flux track both direct torque control System Simulation. Analysis and Compare the final results, combined with direct torque control algorithms, analysis the direct impact on the performance if the induction motor torque parameters changed.Speed sensorless is an important research direction, the adaptive observer is the most commonly used method in speed sensorless technology. Speed sensor control system for detecting the use of stator voltage, current, and so easy to carry out physical measurements of the speed estimates to replace the speed sensors to enhance control system reliability and lower its cost. Speed sensorless control of the induction motor to the stator resistance changes is very sensitive, especially in low-speed range. This paper proposes a novel method, based on back-EMF model reference adaptive speed and stator resistance estimator combination, which can be both used at the same time. Lots of simulations are done under MATLAB / SIMULINK. Simulation results prove that the method of MRAS is accurate.