The precise control and the speed identification of AC motor are the very important issues on AC drive system. In this paper, the speed sensorless direct torque control system of induction motor based on MRAS is constructed on Simulink simulation software. In this system, induction motor is controlled by DTC, stator flux is estimated by u -n model observer that is effective in the full range of speed, motor speed is estimated by MRAS speed identification algorithm. The modified integral rotor flux estimation model is used to solve the problem that the normal model can be affected by the error accumulation and drift of integral calculation in the voltage model of conventional speed I-dentification algorithm. The simulation results show that the MRAS speed identification method can accurately calculate the motor speed, the control system designed has fast dynamic response, small steady-state static error, strong anti -disturbance, and good static/dynamic control performance.%异步电机的精确控制和速度辨识是交流传动系统中重要问题；文中在Simulink软件环境中构建了基于MRAS无速度传感器的异步电机DTC系统；该系统中采用DTC对异步电机进行控制,定子磁链采用在全速范围内有效的u-n模型观测器来估计,电机转速采用MRAS辨识算法来估算；由于速度辨识算法中电压模型的纯积分环节会引起的误差积累和漂移问题,采用改进积分型转子磁链估算模型来解决；仿真结果表明了文中转速辨识方法能准确推算出电机转速,所设计的控制系统动态响应快、稳态静差小、抗负载扰动能力强,具有良好的静、动态控制性能.
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