Research On Speed Sensorless Vector Control System Based On MRAS

In an asynchronous motor vector control system, one of its key links is to acquire the amplitude and phase of rotor flux accurately. Initially, the rotor flux observation method is installing hall element or magnetic sensitive element in the motor stator, or buried detective coil in the slot of the motor for air-gap flux, then calculated it. But this method will affect robustness of the system, and is also to required of good design. Now the common flux observation method is establishing the model of rotor flux by voltage, current, speed of the system. Through these parameters, we can calculate the amplitude phase of the rotor flux.According to the rotor flux orientation, an asynchronous motor vector control system is designed. Because of the need to obtain information of rotor flux from vector control system, this article lists the two common flux observation models:current model based on DQ coordinate and voltage model based on DQ coordinate,then put forward current model based on MT coordinate. The simulation results of the three flux observation models show that the calculated amplitude of the current model based on MT coordinate is more identical with the actual one than the other models.Because of the need to closed-loop control the motor speed, it is a difficult point to obtain the speed of motor accurately in motor control. Traditional method to detect motor speed is to install speed sensor on motor shaft, but this method not only increases the additional cost, but also decrease the accuracy of speed sensor. In order to make the designed system perfectly, this paper use MRAS method to establish speed calculated model based on vector control system. The simulation reveals that the model can estimate the rotor speed accurately, and the speed has good resistance to load disturbance.