A Key Performance Indicator to Assess the Frequency Stability of Wind Generation Dominated Power System

High penetration of power electronic interfaced generation, like wind power, has an essential impact on the inertia of the interconnected power system. It can pose a significant threat to the frequency stability. This paper introduces the notion of the key performance indicator (KPI) and illustrates its application on large scale power systems, including Fast Frequency Response (FFR) and a high share of wind power, to measure the possible distance to the frequency stability limit. The proposed KPI estimates the change of frequency performance (e,g., ROCOF, NADIR) in the frequency containment period. The effect of FFR is analyzed by introducing a droop based controller for wind power plants. The FFR controller responds to a drop in grid frequency with a temporary increase of the wind active power. The proposed KPI maps a change in key system variables (e.g., system kinetic energy, aggregated generation output) onto the change of frequency performance. A comprehensive analysis using DIgSILENT, Matlab, and Python is performed for GB reduced size system. According to the obtained results, the FFR capability of wind generator leads to improvements of NADIR especially in cases with high penetration levels of wind power. The proposed KPI is a valuable tool for the frequency stability assessment in power system planning studies. It can be determined based on off-line simulations, and it can assist the system operators for frequency stability assessment in intra-day operational planning.