A voltage model flux observer design requiring no stator resistance or voltage signal information

Stator flux estimation using the voltage model flux observer requires voltage sensors and is highly sensitive to the stator resistance variation, especially at low speed. This paper designs a new sliding mode voltage model flux observer (SMVMFO). This closed loop SMVMFO is based on the current estimation error and the sliding mode functions are derivative of the stator flux along α and β axes respectively. Therefore, when the sliding mode occurs, the stator flux can be estimated by a mere integration of the sliding mode functions without requiring any voltage signal and the stator resistance information. Thus the proposed observer does not require any voltage signal information, either command or measured one, and is also completely insensitive to the stator resistance variation. The observer stability is verified. Simulation and experimental results for a direct field oriented induction motor drive system are presented to validate the proposed algorithm