Voltage sag Assessment Considering Low Voltage Ride-Through Requirement for Wind Turbines Based on SARFI Index

This paper defines a system average root mean square variation frequency (SARFI) index based on the area of vulnerability (AOV) and proposes a systematic method for determining accurate AOVs for fault induced voltage sags. The SARFI index specifies the number of voltage sags experiencing at a given area or in a given system per year more severe than the curve limits. The SARFI index is helpful in establishing efficient planning for mitigation of voltage sags. This paper also assesses voltage sags considering low voltage ride-through (LVRT) requirements for wind turbines. The determination of AOVs is very important for assessing voltage sags performance, since voltage sags can be caused by faults occurring in different parts of a power system. In this paper, the procedure of determining AOVs for balanced faults are considered. The proposed methodology is applied on the IEEE 30-bus test system integrated with eight wind turbines.