A study on the rotor side control of DFIG-based wind turbine during voltage sags without crowbar system

Abstract

The connection of wind farms to the electrical power system has increased very fast in the last years requiring the ability of the wind turbines to assist network during voltage sags. Most of the modern wind turbines are based on doubly fed induction generator with a back-to-back power converter connecting the rotor windings to the grid. One limitation of doubly fed induction generator is the operation during grid faults. The rotor side converter can be damage by high currents induced by the stator windings. This article investigates the behavior of the wind farm during voltage sags using 2 different control strategies. The results have indicated that the strategy which the reference currents are calculated to compensate the stator flux variation during voltage sags can avoid overcurrents in the rotor windings, in some cases, without the use of a crowbar system.