Analytical Safety Indicators for Frequency Stability Analysis in Two-area Interconnected Power System

With the development of the novel power system under the “carbon peaking and carbon neutrality” goal, the frequency stability problem caused by the “low inertia and low primary frequency response capability” features is highlighted. To accurately describe the security of interconnected system, the frequency response distribution characteristics after disturbance should be considered in the construction of Analytical Safety Indicators (ASI). Aiming at the two-area interconnected power system, based on the two-machine equivalent frequency response model, the Closed-Form Solutions (CFS) of Areal Frequency (AF) and inter-areal tie-line power (ITP) is derived by further simplifying the model. Then, a series of ASI such as the nadir value, quasi-steady-state value, maximum rate value of AF, and the peak value, quasi-steady-state value of ITP are deduced based on the division of fast variation and slow variation terms of CFSs. Results show that the obtained ASI can accurately describe the safety characteristics and the characteristic change trend of two-area interconnected power system.