Comparison of Q- and X-MRAS for Speed Sensor Less Induction Motor Drive On

Abstract

This paper presents a comparative study between a wellknown instantaneous reactive power (Q) based MRAS (QMRAS) and a relatively new X-MRAS used for sensorless speed estimation of induction motor drive from the stability point of view. The instantaneous and steady state values of Q are considered to develop the reference and adaptive models respectively for the former whereas those of a G fictitious quantity X (i.e., vrarro*×ī) are considered in the said models for the later. Non computation of flux in these schemes makes the speed estimation possible over a wide speed range maintaining the drive's stability in all the 4-quadrants. Moreover, Q-/X-MRAS are dependent on rotor resistance variation whereas X-MRAS is also influenced by the stator resistance variation. A small signal stability analysis over a wide range of stator and rotor resistance variations is carried out to ensure the drive's stability for both MRASs. Matlab/Simulink is used to carry out the proposed study and results are being validated in a prototype experimental setup using dSPACE 1104 controller.