Researches On The Related Questions Of The Speed Sensorless Vector Controlled Induction Motor System

Induction motor vector control system as a control program has been successfully applied. The speed sensor-less vector control system not only get rid of the limitation of the speed sensor, but also have many advantages such as, simple structure, excellent performance, low cost and so on. In recent years, the sensor-less vector control system has been one of the hot areas of the AC drive research and development. This paper percents an effective method of parameter identification which based on the sensor-less induction motor vector control system. This method can identify the whole parameters of induction motor before its start working without the locked-rotor experiment and no-load experiment. Moreover, percents a new observer-based source voltage unbalance control method in PWM voltage-source converter which applied in the vector control system. The method extracts the positive sequence and negative sequence from the AC three-phase current which compensate the q-axis current command value. The 2nd harmonics were eliminated and the unbalanced input currents were compensated by this new control method, respectively. Consequently, these techniques are appropriate for higher-power systems with reduced PWM switching frequency and limited current controller bandwidth.