State-feedback linearization using a robust differentiator combined with SOSM super-twisting for controlling the induction motor velocity

In this paper, the authors propose a robust controller by applying state-feedback linearization technique combined with the super-twisting algorithm as control law, which is applied to control the velocity of the squirrel-cage induction motor under unknown load conditions directly coupled to an induction generator, which delivers the generated energy toward the utility grid. The controlled output variables of the system are the angular rotor velocity and the square modulus of rotor flux linkages. We estimate the time derivative of the tracking error variable through a robust differentiator to define the sliding surface for control purposes. Consequently, the load torque estimation via an observer is not necessary. By using a robust differentiator in the controller design, the resulting control law does not depend on the system parameters, which are usually difficult to obtain, which constitutes one of the main contributions of this paper. Finally, real-time experiments are carried out in a laboratory prototype to validate the robust operation of the proposed velocity controller.