Symmetrical Components-Based Control Technique of Doubly Fed Induction Generators under Unbalanced Voltages for Reduction of Torque and Reactive Power Pulsations

This paper presents a control technique to reduce the effect of unbalanced voltages in the doubly fed induction generator (DFIG) in wind energy conversion systems. The unbalanced voltages cause negative effects to the DFIG such as torque pulsation and increased stator current. Based on the symmetrical component theory, the negative sequence of the stator voltage can be extracted from the three-phase stator voltage and fed to compensate the rotor voltage to reduce the unbalanced effect. The magnitude of the compensating negative sequence is calculated from the negative sequence of the stator voltage and rotor speed. The proposed method shows a promising result for reduction of torque and reactive power pulsations.