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An advanced solution for low-cost implementation of the sensorless vector control of an induction motor is presented in this paper. The proposed system is based on a new set of variables for the induction motor model. The system works using vectors coordinates in a stationary α-β frame of references. A phase-locked loop was used to control the angle between the flux vector and the stator current vector. The induction motor model variables and the rotor velocity are calculated from simple equations based on the steady state relationships for the active and reactive powers. A current controller for the current-regulated pulsewidth-modulation inverter based on the simplified load model is presented. The proposed current controller is based on the back-electromotive-force calculation. The developed sensorless system was investigated both in simulations and experiments. The overall system was implemented using a simple and cheap fixed-point microcontroller.
Date of Publication: Nov.-Dec. 2003