Speed-sensorless control for induction motor based on back-EMF integration

Rotor field oriented vector control system has been widely used in high-performance industrial applications. Because vector control needs the speed closed-loop, in many cases, people use installed coaxial speed sensor to achieve speed measurement. But the precise speed sensor not only increases the cost of the system and reduces the reliability of the system, but also add difficulties to the installation and maintenance. Besides, the speed sensor is not able to be installed in some harsh environment. Therefore, the research on speed-sensorless vector control technology is greatly valuable. For speed-sensorless system, since one can only measure terminal voltage and current of the motor, thus rotor speed and rotor flux can only be obtained by calculating the voltage and current. This paper achieves speed-sensorless vector control through real-time estimation for the motor speed based on the motor back- electromotive force (EMF) integration algorithms.