Research On The Speed-sensorless Vector Control System For Induction Motor

Induction motor is a non-linear, multivariable, high-order and close coupling system. It's torque couldn't be controlled easily as the DC motor. The problem of traditional induction motor drive can be solved by vector control, while the sensor is eliminated in sensorless vector control system and this makes the relative inductor motor drive easier, more economical and more reliable. For this reason, the sensorless vector control is becoming the attractive researching project.Firstly, the basic theories of vector control is introduced. The dynamic mathematical model of inductor motor under static reference frame is given. Then through coordinate transforming, the mathematical model of inductor motor based on the synchronous reference frame is deduced. The rotor flux linkage control and torque control based on the rotor field orientation are separately achieved.Secondly, a new scheme of speed-sensorless vector control is introduced, The proposed scheme is based on the current estimation without the flux and speed estimation, in which the controlled stator voltage is applied to the induction motor so that the difference between stator current of the mathematical model and motor may be forced to decay to zero, the performance of the proposed scheme is verified through simulation. Then a method for states estimation based on extended kalman filter(E K F) is introduced, and the emulational model of sysrem is founded with Matlab.Experiment is done based on the DSP design system for digital motor control. The extended kalman filter algorithm is carried out to estimate the rotor speed and fluxes, and space vector pulse width modulation algorithm. The satisfied experimental results prove that extended kalman filter algorithm can real time estimate rotor speed and flux accurately, and based on which the speed sensorless drive system shows good static and dynamic performance.