Magnetic saturation in rotor‐flux‐oriented induction motor drives: operating regimes, consequences and open‐loop compensation

Abstract

Parameter variation effects infield‐oriented induction machines can cause significant performance deterioration. Magnetic saturation of the main flux path is one of the sources of parameter variations, caused by non‐linear nature of the magnetizing curve. The paper at first discusses operating regimes of a rotor‐flux‐oriented machine which lead to operation with variable main flux in the machine. These are shown to be operation with variable stator d‐axis current command during forced excitation and in field‐weakening region, and operation with variable q‐axis current command during rapid speed changes when cross‐saturation effect causes variable main flux operation. Actual effects of variable saturation level on performance of the drive are assessed by simulation. Modified rotor flux estimation schemes are then derived, which enable instantaneous open‐loop adaptation to actual saturation degree in the machine. The proposed adaptive rotor‐flux estimators are verified by simulation and some experimental results are included as well. As the saturated induction machine representation is based on the current state‐space model, while the modified rotor‐flux estimator relies on the flux state‐space model, the performed simulation study shows that current state‐space model and flux state‐space model, although considerably different in their appearance, account for the main flux saturation in basically the same way.

Robustness Analysis on Sliding Mode Control of Induction Motor

“…Thus, the indirect field orientation control received much attention in order to maintain satisfactory performances in presences of the internal disturbances. For this need, are developed the solutions relates to the on-line identification of the rotor timeconstant or of the machine model in field orientation state [2,3] and other works take account of the saturation of the machine [4]. Another approach consists in exploiting the non-linear controls, which essentially incorporate properties of robustness.…”