A protection system and a protection method are provided for protecting a
double fed induction generator and a gearbox during a grid fault. The
protection system includes a plurality of controlled impedance devices.
Each of the controlled impedance devices is coupled between a respective
phase of a stator winding of the double fed induction generator and a
respective phase of a grid side converter. The protection system also
includes a controller configured for coupling and decoupling impedance in
one or more of the plurality of controlled impedance devices in response
to changes in at least one of a utility grid voltage and a utility grid
current.