Analysis of the DFIG during voltage dips

The doubly-fed induction generator (DFIG) is normally controlled with stator-flux orientation. Stator-voltage orientation and other methods like Direct Power Control can also be adopted. It is a poorly damped system with a natural frequency near the grid frequency. This leads to natural oscillations on the flux and torque and, for stator-flux orientation, in some cases, to instability. When voltage dips occur, the stator flux oscillates at the mains frequency leading to perturbations on the rotor currents. This paper presents a comprehensive study of the DFIG behavior during voltage dips. Analytical, simulation and experimental results are shown.