A Generalized Method of Controlled Voltage Source-Fed Induction Motor Vector Control Using the Observer Theory.

Abstract

A Vector control of an induction motor is widely used for industrial applications. An on-line parameter identification and the speed sensor-less control are studied actively. The representative method for these problems is an application of the adaptive full order observer. The rotor flux for the vector control is estimated by a full order observer and machine parameters or the rotor speed are determined by an adaptive algorithm. In this paper, a new vector control scheme with parameter identifications is proposed. This method is based on the adaptive full order observer. However, the observed currents which are estimated usually in the voltage model are considered as the commanded currents and the voltage model is used for the current controller instead of the conventional one. As the result, the proposed system is simplified than the conventional adaptive full order observer system. As the proposed system is composed of the induction motor model in a synchronously rotating reference frame, well-known slip frequency control block is contained. An arrangement of the poles which are obtained from the torque transfer function is discussed. A linear model is derived taking into account the effects of the change of the stator and rotor resistances. The trajectories of poles and zeros of the torque transfer function are computed and discussed for various system parameters. An identification of stator and rotor resistances is confirmed by the simulation using a nonlinear system model. The proposed idea is applied to the speed sensor-less system and this system has a similar configuration to the conventional systems under some assumptions.