Implementation Of Control Strategy For Speed-sensorless Induction Motor System

Induction motors based on variable frequency speed adjustment system arewidely applied in industrial fields and daily life. According to vector control technique,AC (Alternating Current) speed control system could be compared with DC (DirectCurrent) speed control system in the facets of speed control and torque control. But,stability and working environments will limit system performance with the speedsensor. Speed-sensorless vector control system is one of the most popular items of ACvariable frequency speed adjustment technologies.Based on the deep research on the AC induction motor's mathematic model, theessential principles of variable frequency speed adjustment system including controland structure principles are proposed.Speed-sensorless vector control system of AC induction motor based on MRAS(Model Reference Adaptive System) mechanism is presented in this paper. Theproposed system includes a rotor flux estimator and a speed estimator. By means offlux observing, the flux calculation's integration problems of the voltage model, suchas the initial value and the drift of a pure integrator, are avoided. A further advantageis the stability of low-speed operation and control accuracy is obtained. All themathematic models are based on the rotating reference frame.A simulation research is done for the speed-sensorless vector control system ofAC induction motor under MATLAB/SIMULINK. The theory presented in this paperis confirmed by means of the computer simulation. Simulation results show the goodperformance of the system in torque, speed and robustness.Grounded on the work above, a real system includes TI's DSP TMS320LF2407Aas central control unit is developed, and the theory analysis mentioned above is testedby experiments. Finally, the communication network system based on Controller AreaNetwork (CAN) bus is designed.The variable frequency speed adjustment system using TMS320LF2407A havemany advantages, such as simpleness of hardware, stability and good real-timeperformance. The AC induction motor can run in the status of const torque under ratedfrequency and of const power above rated frequency. Having much superiority, thesystem can be widely used in modern industry.