A simple and robust adaptive controller for detuning correction in field-oriented induction machines

A novel adaptive controller for correcting the rotor time constant estimate used in the slip frequency calculator of indirect field-oriented controllers (IFOCs) is presented. The controller possesses near digital deadbeat performance and simultaneously maintains its correctness down to zero speed. The robust controller dynamics are based on an operating-point form of digital deadbeat control. The correctness down to zero rotor speed is based on the determination of the rotor flux from an accurate air-gap flux estimate obtained from the third harmonic stator phase voltage component introduced by the saturation of the machine stator teeth. The proposed controller is implemented using a digital signal processor, and the experimental results demonstrate its excellent performance for a wide range of rotor speeds, including locked rotor conditions