Novel full-order flux observer structure for speed sensorless induction motors

This paper deals with the flux estimation for sensorless induction motor drives. A new full-order observer structure, which uses the stator and rotor fluxes as state variables in their respective reference frames, is proposed. The stator flux state equation is simulated in the stator reference frame, whereas the rotor flux equation is simulated in the rotor reference frame. This natural combination of reference frames gives well-behaving observer poles in the whole speed region, even without feedback terms. The simple Forward Euler discretization can thus be used. Furthermore, existing adaptation rules can be directly adopted for this structure.