Impact of DFIG-Based Wind Farm on Outgoing Transmission Line Protection

Abstract

The conventional wind farm outgoing line protections have not taken the wind farm fault features into consideration, as a result, the protections may mal-operate because of integration of large-scale wind generation. This paper analyzes fault features of doubly-fed induction generator based wind farm which possesses Low Voltage Ride Through ability, discovering that the main frequency composition of short circuit current at the wind farm side is no longer power frequency because of the wind speed variation. However, the wind farm side bus voltage remains power frequency, leading to mal-operations of protections which apply power frequency filter algorithm. Moreover, the weak power feature makes the positive and negative sequence impedance much greater than zero sequence impedance. Thus, during grounded faults, the three phase fault current amplitude is almost the same, leading to the failure of phase selection element applying sequence current or phase current criterion. Finally, within an actual wind farm model on PSCAD/EMTDC, simulation results show that the sensitivity of current differential protection is greatly reduced, and the action performance of direction element, distance element, phase selection element is severely affected.