Induction Motor Speed ​​sensorless Direct Torque Control System

Direct Torque Control (DTC) of induction motors, which has been developed in the recent decade, is a powerful control method for motor drives. Following the vector control-technique, the quick development of DTC makes itself a new high performance AC driving technique paralleling to the vector control. In this thesis the author makes a study of asynchronous motor model and deals in details with the basic principle of direct torque control. According to the faults of traditional direct torque control and the requirement of an induction motor's control strategy, the author changes the method of regulating stator flux to make its path approximate to a circle as possible as could and put forward a new way to use a three-value torque regulator. Traditional direct torque control uses two value torque regulator which makes zero voltage vector work long and make flux shape bad seriously and makes response time long when the speed of induction motor is very low or drops down quickly. In order to solve this problem the thesis puts forward a new way to use three-value torque regulator, when the motor speed is very low or drops down quickly, the contrary voltage vector is used instead of zero voltage vector and the between the stator flux and rotor flux is reduced quickly so that torque is reduced quickly and response time becomes shorter. Moreover, stator flux can keep round, This is very useful in braking control.Moreover, the thesis puts forward the strategy that fuzzy controller replaces Smith flip-flop. Based on the tolerance of Smith flip-flop is a fuzzy variable, fuzzy controller can replace Smith flip-flop The performance of this system can be improved if the tolerance of flux and torque is graded and voltage vector can be elected by this.The speed estimation without speed sensor is an important trend of modern AC drive. This thesis has probed several primary methods of speed estimation and analyzed emphatically the method of speed estimate based on model reference adaptive system.SIMULINK is a applying tool box of MATLAB and can be used for constituting model, simulation and analyzing. This thesis constitutes DTS simulations with three-value torque conditioner and fuzzy regulator and speed sensorless technology. The simulation results prove that above methods are feasibility.At last the thesis introduces the design method of control system with Intel 80cl96MC. This control method has simple counting and strong function and great developing value.