A robust nonlinear observer for states and parameters estimation and on-line adaptation of rotor time constant in sensorless induction motor drives

This paper presents a robust non linear observer for variables and parameters estimation in sensorless Indirect Field Oriented Control (IFOC) of induction motors (IM). Based on the reduced order of the IM model, the rotor fluxes and time constant are estimated with the High Gain Observer (HGO) using only the stator currents and voltages. This reduced order model offers many advantages for real time identification and fault diagnosis of the IM. The major contributions of this work are: first, avoid the use of fluxes and speed sensors which increases the installation cost and degrades the mechanical robustness. Second, by reducing the order of the IM model, the implementation of the proposed observer doesn’t require a very effective Digital Signal Processor (DSP). Finally, we show that the proposed control scheme is not sensitive to disturbances and parametric errors and it is robust against load variations and measurement noises. Simulation results are provided to prove the effectiveness of the proposed method.