The impacts of distributed doubly-fed induction generators on smart distribution Grid protection

Doubly-fed induction generators (DFIG) used an AC-DC-AC power converter to excite the machine and connected crowbar protection in its rotor side, which makes fault characteristic differ from the synchronic generator´s. That may bring problems to traditional current protection in distribution grid. Also, DFIG as a distributed generator (DG) had capability of Fault Ride-Through (FRT), but the tripping principles of the protection installed at point of common coupling (PCC) may disconnect DG when a fault occurred in the Grid. Based on the short circuit current analysis concerned its magnitude and decay time, a compounded current-voltage protection at the PCC is proposed. That scheme could overcome “negative” impact on protection caused by fault current characteristic of DFIG and ensure the DFIG operate under FRT when a fault happens in distribution network..