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Sensorless Control Methods For Variable Speed Drives With Induction Motor Used In Traction Application


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D O Kisck, H-J Ryoo, D-Y Park, Y-J Kim & S Bucurenciu


In this paper there are proposed several methods for sensorless control of the rotor field oriented induction motor, such as: speed estimators, rotor slots ripple speed estimators, Model Reference Adaptive Systems, Luenberger speed observer. It is described the mathematical model for the rotor field oriented system with induction motor, which uses the estimated speed and rotor flux, based on a Model Reference Adaptive System or Luenberger speed observer, as well as the real-time approach. The estimated speed is used for the speed feedback control. The stability and the convergence of these estimators are improved on the basis of hyperstability theory for the non-linear systems. The proposed MRAS speed estimator or Luenberger estimator can be applied for traction application because the integration of sensed variables was avoided, increasing in this way the system stability. Rotor flux integration in the reference model is avoided, using the counter-EMF vector. Because of this, the system can operate at very low speed and high speed also, even if the rotor resistance is quite wrong or in overload operation. The real-time controller and estimator are implemented with a dual TMS320C44 floating-point digital signal processor. The validity of the proposed method was verified by simulation, the sensorless control being also tested on the propulsion system simulator used for the development of Korean High-speed Railway Train. The simulation and experimental tests are performed also, to compare different sensorless methods.