Voltage-Sag Tolerance of DFIG Wind Turbine With a Series Grid Side Passive-Impedance Network

Due to the increase of the number of wind turbines connected directly to the electric utility grid, new regulator codes have been issued that require low-voltage ride-through capability for wind turbines so that they can remain online and support the electric grid during voltage sags. Conventional ride-through techniques for the doubly fed induction generator (DFIG) architecture result in compromised control of the turbine shaft and grid current during fault events. In this paper, a series passive-impedance network at the stator side of a DFIG wind turbine is presented. It is easy to control, capable of off-line operation for high efficiency, and low cost for manufacturing and maintenance. The balanced and unbalanced fault responses of a DFIG wind turbine with a series grid side passive-impedance network are examined using computer simulations and hardware experiments.