Research On The Speed-sensorless Vector Control System Based On MRAS

The induction motor speed controlling is a complex subject, it includes the knowledge of many other subjects, such as the electric and electronic technology, the control engineering, the computer and the induction motor etc. The realization of the good performance induction control system is a hard work. Vector control is one of the advanced theories, which is based on motor unification principle, energy conversion and vector coordinate transformation theory. It has many advantages such as novelty, practicability and advancement. Speed-sensorless vector control VVVF system of induction motor is a high performance speed-control system and has been used in a lot of situations of high precision and high performance. Speed-sensorless vector control system of induction motor is not only an important aspect but also a hotspot of investigation in modern AC drive. The key problem is that how we can get the speed of induction motor accurately, now there are many methods to estimate the speed of induction motor.This thesis made a study on the speed-sensorless vector control system. and built up a speed-sensorless vector control system based on model reference adaptive system (MRAS). According to the reduced order model of induction motor, a model reference adaptive speed estimation algorithm was obtained from the equations of induction motor stator voltages and currents. An improved model MRAS speed estimation model was built with variable parameters. The detailed simulation researches were tested on the speed-sensorless vector control system of induction motor using the software MatLab/Simulink. The simulation results show that this improved MRAS speed estimation model has satisfied estimation precision and dynamic performance. Some simulation models can be used in other VVVF control strategy system also. This thesis also makes an introduction of the speed-sensorless vector control system based on DSP, the hardware circuit and the software process.