Modelling of an Induction Motor and Model Reference Adaptive System (MRAS) for Speed Estimation in Xcos

Techniques based on Model Reference Adaptive System (MRAS) are considered as effective approaches for speed estimation due to their commendable performance and direct stability analysis. Different works about the application of MRAS in speed sensorless control of induction motor can be found in literature. However, students usually have problems to understand and implement MRAS algorithm. On the other hand, open source softwares allow students to understand and simulate algorithm, as students can be easily watch, analyze and edit the block diagram. Hence, this paper introduces the block diagram of a 3-phase induction motor and the MRAS algorithm developed in SCILAB/Xcos. SCILAB is an open-source software that include a block diagram simulation interface called Xcos. The MRAS algorithm in this work compares the rotor flux estimated by a reference model and an adjustable model (that depends on the mechanical speed), to get a flux estimation error. A PI regulator adjust the mechanical speed value in the adjustable model to reduce that error. The block diagrams of the dq0 induction model and the MRAS algorithm developed in Xcos and presented in this work allow student to easily understand both algorithms, widely used in motor drives. It is worth to mention that authors did not find any MRAS diagram implemented in Xcos in literature.