Voltage Sag Evaluation in Power Grids Considering the Voltage Support Capabilities of Doubly-Fed Wind Farms During LVRT

Abstract

This paper introduces how doubly-fed wind farms can compensate for reactive power demands of the grid during low voltage ride through (LVRT) events, thereby providing voltage support. This capability significantly influences the assessment of voltage sag. To address this, this paper proposes a method for assessing voltage sags in the power grid that considers the voltage support capabilities of doubly-fed wind farm during LVRT. This method accurately characterizes the voltage support capability during LVRT by establishing a dynamic equivalent model of the wind farm. For each wind farm, the clustering is based on the Crowbar status determination as the primary clustering criterion, while the interconnected voltage at the point of common coupling (PCC), considering the mutual influence among multiple wind farms, is used as a correction factor for iterative clustering. By utilizing collaborative equivalence of multiple wind farms, the final dynamic equivalent model is determined. Subsequently, a comprehensive simulation of various grid fault scenarios is conducted to evaluate the voltage sag. The proposed method's accuracy and effectiveness have been validated through case studies.