异步电机直接转控制仿真研究.pdf

Subject : The simulation research of Direct Torque Control Specialty : Control Theory and Control Engineering Name : Zhang Rui (Signature) Instructor : Gao Yun (Signature) ABSTRACT In the field of AC machines control, Direct Torque Control (DTC) has become a focus which has many advantages such as new control method, simple structure, direct control means and fast torque response. The basic idea of DTC is to control the motor torque directly through the voltage that acts on the stator flux, so as to control and regulate the rotational speed of the motor. This paper described the DTC basic theory of asynchronous motor systematically from mathematical model of asynchronous motor and analyzed the relationship of space voltage vector and stator flux, motor torque. According to different control strategies based on the stator flux, this article intruducs the principle and stucture of the the hexagonal flux trajectory firstly. Based on the simulation software——Matlab/Simulink, the models of the hexagonal flux trajectory DTC are build. The results are obtained through simulation studies that it has low flux switching frequency with large torque ripple especially in the low speed range. In order to improve the performance of the hexagonal flux DTC at low-speed, a circular flux stajectory is analyzed and the simulation model of circular flux trajectory control DTC is build. It can be seen from the simulation result that the torque ripple is smaller with smoth flux path, but the flux switching frequency is much high. Based on the two different control methods with their own control performance at low or high speed range