Sensorless Indirect Control of Induction Motor Fed by a Multi-level Inverter with Consideration of Variation in Rotor and Stator resistances

Abstract

This paper, present a work on indirect field oriented control of an asynchronous machine fed by a multi-level inverter with using adjustment mechanisms for estimating the rotation speed, the stator resistance and the rotor resistance. In the absence of the speed sensor, we use a MRAS (Model reference adaptive system) observer to estimate the mechanical speed. In the MRAS method, the magnetizing current of the adaptive model is compared with that of the reference model. The rotor speed, the stator and rotor resistances are estimated from the magnetizing currents difference of the two models using adequate adaptive mechanism. The choice of this Observer is due to its simplicity, less computation time and good stability. For the choice of multi-level converter, we use five-level cascaded H-bridge inverters to feed the induction motor. This multi-level converter allows to obtain a greater number of output voltage levels with a very acceptable harmonic spectrum. The present approach (IFOC, MCHI and MRAS) helps to achieve a good dynamic response at low speed with reduction of total harmonic distortion. Simulation results show the effectiveness of the proposed method with consideration of variation in thermal parameters.