STATOR RESISTANCE TUNING IN A STATOR-FLUX FIELD-ORIENTED DRIVE USING AN INSTANTANEOUS HYBRID FLUX ESTIMATOR

A self-tuning control scheme far stator-flux field-oriented induction machine drives in electric vehicles operating over a wide speed range is discussed in this paper, The stator flux can be determined accurate ly from the terminal voltage when the machine is operating at high spe ed, However, at low speed, the stator resistance must be known to calc ulate the stator flux, The problem of calculating the stator flux accu rately over the entire speed range is addressed, The rotor flux can be found from the machine speed and rotor time constant, The stator flux , at low speed, is then calculated directly from the rotor flux, By al ternating between these two methods of determining the stator Bur, a s elf-tuning operation is achieved, wherein the stator and rotor resista nces are periodically updated, Since both methods of determining the s tator flux are forced to track one another, a smooth transition betwee n flux estimators is obtained, The torque and dull are then controlled in a deadbeat fashion, Good torque control over a wide speed range ca n therefore be obtained, With the proposed scheme, the advantages of d irect torque control are obtained over the entire speed range with the addition of a speed sensor.