Integral Sliding-Mode Method Based on Back-EMF for Restarting Speed Sensorless Controlled Induction Motor at Free Running Status

Restarting at free running status is essential for the speed sensorless control of Induction motor. Exact estimation of the initial speed makes the procedure of restarting smooth without current impact or voltage impact. An integral sliding-mode (ISM) restart method based on back electromotive force (EMF) is proposed in this paper. The nonlinear model of the rotor back-EMF which is used to estimate ωs ignores the variation of the stator current, which causes the modeling inaccuracies. The ISM method can reduce the effect of modeling inaccuracies. Moreover, the ISM method improves the robustness of the motor parameters and noise. The design and implementation of the proposed method are illustrated in detail. The validity of the proposed method is verified by simulation and experimentation.