Encoderless Model Predictive Direct Torque Control of Induction Motor Drive based on MRAS

Abstract

This paper presents a modified MRAS (MMRAS) based encoderless model predictive direct torque control (MPDTC) of an induction motor (1M) drive. MPDTC of 1M drive is based on the future predictions of controlled variables and these predictions depends on the rotor speed. To estimate this rotor speed a new MMRAS is used. The presence of the pure integrator in the reference model of conventional MRAS deteriorates its performance during low speed operations, where as MMRAS uses forward Euler based discretized rotor flux estimation from the MPDTC algorithm as the reference model. Further, a suitable weighting factor is selected for stator flux in the cost function of the MPDTC algorithm to limit the flux ripple during low speed operation. The simulations of the proposed algorithm are implemented using MA TLAB/Simulink for a wide range of speeds including the low speed operation. The results show that, it offers satisfactory operating conditions during low speed operations.