A new method of speed-sensorless control of induction motor at very low speed

This paper presents a new sensorless vector control method for induction motor drive at very low speed based on signal injection. In the proposed method, a low frequency signal is injected to stator currents and the corresponding angle error is detected to estimate the rotor position and speed. This method is independent of load variation, structures and the non-ideal features of the induction motor, only the fundamental model of the motor is needed. Furthermore, it is robust to the motor parameter changes. Various simulations and experiments have been carried out to prove the good performance of the proposed method on speed sensorless control of IM at very low speed.