Trandafilov V. Field-oriented control of induction motors invariant to rotor resistance variations

The generalized method of design of sliding mode observers of rotor flux is developed. This method allows designing all existing observers based on equivalent control method and new solutions with improved robustness properties to parametric perturbations. The analytic research of observers' robustness to rotor resistance variations of induction motor is performed based on their generic structure. A comparative robustness analysis of the generic flux sliding mode observers is given. A design method of sliding mode flux observers which are invariant with respect to rotor resistance variations is developed. The observers is globally exponentially stable under accurate rotor resistance information and locally exponentially stable under limited parameter variations as well as allow designing the direct field-oriented control systems of induction motors with invariance properties and therefore improved dynamic performance and energy efficiency. Based on the proposed observer the general theoretical solution of the induction motors with squirrel-cage speed-flux tracking control problem invariance to rotor resistance variations has been solved. The invariance properties with respect to limited variations of rotor resistance are guaranteed in full motor operating range, including zero speed. The advantages of the developed algorithm of vector control in comparison with standard and robust control algorithms confirmed by the results of experimental studies and simulation, which demonstrated stabilization of dynamic and energy performance.