Performance of wind driven generators under wind speed variation and grid faults

In this paper the dynamic behavior of a double-output induction generator (DOIG) driven by wind turbine under wind speed variation and during and after grid faults, is investigated. Two damping methods are tested to reduce the high transient values of currents and voltages at different parts of the wind energy conversion system. First, connecting 3-phase capacitors in the rotor circuit did not reduce the high transients due to wind speed variations, but only improved the system power factor. In the second method, 3-phase inductance is connected in series with the stator terminals. This method reduced these transients by 50% and improved the system power factor. The inductance value has to be limited to avoid deteriorating the generation system performance. Fault ride through is investigated after symmetrical and unsymmetrical faults by insertion of inductance at the stator terminals. This method led to suppress the induced over-voltages and, hence, over-currents in the rotor windings and converters.