Improved MRAS‐type speed estimator for the sensorless induction motor drive

Abstract

Purpose

This paper aims to obtain an accurate and robust estimation method of the rotor flux and speed for the sensorless induction motor (IM) drive.

Design/methodology/approach

The reduced order observer has been used as an online tuned rotor flux model in the model reference adaptive system (MRAS) concept applied for the IM speed estimation. The output of this observer was used also as a feedback signal required in the direct field‐oriented control (DFOC) structure of the IM.

Findings

It is shown that a new rotor flux and speed estimator are more robust to motor parameter changes in comparison with the classical MRAS estimator and can work stably in the DFOC structure, in the wide speed range, even for relatively high (50 per cent) identification errors of equivalent circuit parameters of the IM.

Research limitations/implications

The investigation looked mainly at the estimation accuracy performance and whole system stability while economic issues will still need to be addressed.

Practical implications

The proposed new improved MRAS speed estimator can be easily realised using modern digital signal processors. The implementation was tested in an experimental set‐up with floating point DSP used as the system controller. The fixed‐point realisation needs to be developed to obtain the practical application in the industrial drive systems.

Originality/value

The application of the reduced order flux observer as a tuned flux model in the MRAS type speed estimator instead of the simple, but very sensitive to motor parameter uncertainties, current flux model, enables much better accuracy and stability of the rotor speed estimation in the complex DFOC structure than in the case of classical MRAS estimator.

Citation

Orlowska‐Kowalska, T. and Dybkowski, M. (2007), "Improved MRAS‐type speed estimator for the sensorless induction motor drive", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 26 No. 4, pp. 1161-1174. https://doi.org/10.1108/03321640710756474