DIRECT TORQUE CONTROL OF ROTOR-TIED DFIG WITHOUT ROTOR POSITION SENSOR

Rajeshkumar M. Prasad and Mahmadasraf A. Mulla

Keywords

Direct torque control (DTC), position-sensorless control, rotor-tieddoubly fed induction generator, wind energy conversion system (WECS)

Abstract

This paper illustrates the direct torque control (DTC) scheme for rotor-tied doubly fed induction generator (DFIG). Furthermore, a novel rotor position computation algorithm (RPCA) is developed to compute the rotor position for rotor-tied DFIG. Accuracy of computation at starting and around synchronous speed helps in application like wind energy conversion system (WECS), which necessitates the constant frequency operation against variable wind speed. The rotor is connected to the grid via brushes. Hence, the direction of rotation for the rotor is set opposite to the direction of rotating flux created by grid frequency. This helps in achieving the slip frequency in the stator. The proposed scheme is validated using simulation results of 250 kW rotor-tied DFIG-based WECS, under different wind speed conditions.

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