Analytical Frequency Security Indicators for Two-Region Interconnected Power Systems

Frequency spatial distribution characteristics of interconnected power systems are highlighted, resulting in significant regional frequency differences and inter-region tie-line power fluctuations, posing a threat to frequency security operation. For two-region interconnected power systems, analytical expressions for regional frequency and inter-regional tie-line power are derived based on the low-order frequency response model. By dividing the fast-varying part and the slow-varying part of the above analytical expressions, analytical frequency security indicators including nadir value, quasi-steady-state value, maximum rate value of regional frequency, and peak value, quasi-steady-state value of inter-regional tie-line power are derived. By dividing the fast-varying part and slow-varying part of the aforementioned analytical expressions, we further derived analytical frequency security indicators, including nadir value, quasi-steady-state value, maximum rate value of regional frequency, and peak value, quasi-steady-state value of inter-area tie-line power. Through case studies based on the IEEE 2-region 4-machine system, the results indicate that the obtained analytical frequency security indicators can accurately describe the frequency dynamics following a major disturbance for two-region interconnected power systems.