Abstract
Recently with the development of power electronic techniques,computer control techniques and automatic control techniques,many kinds of inducdion motor control techniques are improved greatly.Among them the Direct Torque Control(DTC) technique attracts more and more attention after vector control theory because of its robust characteristics,simple realization and excellent dynamic response.Direct Torque Control takes the parameter of torque as its control control object,and it based on stator coordinate.As a result,DTC system is a fected by fewer parameter of the motor and has less complex structure and fewer calculations.Since it was brought forward,Direct Torque Control has been taken serious attention by domestic and foreign scholars. The speed sensorless method is a heated-spot in the field of AC drive nowadays. Mechanical speed sensor not only increases the cost, but also has the disadvantage of inconvenient fixing and maintenance. The speed sensorless method, that is, application to software instead of mechanical speed sensor, has good prospects.
This paper builds a mathematic model for asynchronous motor and tells the basic principle of direct torque control. This paper studies emphatically speed sensorless techniques , the mathematic models of speed identification schemes based on rotor flux linkage force is simulation and is applied in DTC system.
The paper uses Matlab/Simulink to simulate DTC system and constructs different simulation models in various speed range and simulates.The simulation results are shown and it suggests that the model is right and the control system has satisfactory identification precision,excellent dynamic and static performances and high control effect. In order to simplify the structure of alternating current speed adjusting of system,reduce the cost,and improve the system performance,the speed estimation withoutspeed sensor is an important trend of modern AC drive.
Key Words: Asynchronous Motor; Direct Torque Control; Speed Sensorless; Simulation
