A Voltage Stability Contingency Ranking Method Including Unstable Contingencies

In this paper, the fast voltage stability contingency ranking method including unstable contingency cases is proposed. The proposed method provides the following three advantages at once: i) Reduction of the computation time for voltage stability contingencies using the concept of the power flow compensation, ii) Calculation of the voltage stability index for all load buses and assessment of the voltage stability for each N-1 contingency, iii) Estimation of the necessary amount of load shedding ΔPcut on condition that stabilizing the unstable load buses is required. The proposed method makes it possible to arrange contingency cases in descending order according to the severity of voltage stability index and the amount of load shedding, although unstable load buses are included in contingency cases. The performance of the method is validated using simple a 6-node test system and a modified IEEE 30 bus system.