Stable MRAS-based sensorless scheme design strategy for high power traction drives

A model reference adaptive system (MRAS) based observer is the dominant speed estimation scheme for sensorless induction motor drives. The main drawback of fundamental model based estimation techniques is instability in the low speed region under regenerating conditions. Furthermore, accuracy and estimation stability is especially influenced by stator resistance thermal variation in this region. The main novelty of the proposed sensorless control scheme lies in its flexibility for ease of use in both stator flux and conventional rotor flux control drives. Both degrees of freedom of stator currents errors are used for speed and stator resistance estimation in parallel whilst the speed estimation adaptive function is reconfigured for assuring stability in the whole speed region. Overall stability is analyzed by linear adaptive control theory methods such as closed-loop system Bode and poles placement.