Malfunction operation of LVRT capability of Wind Turbines under islanding conditions

Abstract

The Low Voltage Ride Through (LVRT) capability of Wind Turbines (WTs) determines the connectivity of WT to the grid based on both voltage sag magnitude and duration locally measured at Point of Common Coupling (PCC), in order to protect the WT against overloading out of its tolerable apparent power. If the WT is still inside its safe and secure operating condition and there is still some standby capacity available in it to support the grid, the WT should remain connected to the power system regardless of voltage sag magnitude and duration until the WT apparent power exceeds its nominal value. In case of islanding, which often is accompanied with a low voltage drop, the WT may be improperly disconnected while operates with less than half of its nominal apparent power. This situation necessitates investigation or perhaps a revision of LVRT grid code to be efficient for all possible incidents, not only short circuit faults, but also cascading events and islanding.