Sensorless control of inverter-fed induction motor drives

Sensorless control is considered to be a lower cost alternative than the position or speed encoder-based control of induction motors. Two popular sensorless control methods, namely, the model reference adaptive system (MRAS) and the Luenberger observer (LO) methods are compared for speed and torque control characteristics. They are also compared against the well-known vector control principle. For the drive system simulated, the torque and speed obtained from sensorless control are almost identical to those obtained from the vector control method. However, the torque ripple for the sensorless methods is observed to be higher than vector control-based method. The MRAS method introduces higher torque ripple when compared to the Luenberger observer. In addition, speed estimation methods employed in sensorless control are more sensitive to motor parameter variations.