Super-twisting observer based on PLL technique for sensorless control of induction motors with core loss

In this paper a sensorless control scheme is presented for induction motors with core loss. First, a super-twisting sliding mode observer for stator currents is designed, where, by means of the equivalent control method one can determine the rotor fluxes, second, these fluxes are fed to a PLL stage where the rotor flux velocity is retrieved, then, by easy to follow calculations the rotor mechanical velocity is determined and filtered by a Luenberger observer. In the control part of the induction motor, a twisting controller is designed for the tracking of a desired rotor velocity signal and the tracking of an optimal rotor flux modulus that can minimize the power loss in copper and core. Simulations show that the proposed observer based control scheme performs well, also in the case of time-varying reference velocities.