On-line Static Security Assessment Method Using A Hybrid Steady-state Model

Online static security assessment(online SSA)has been performed based on power flow model.This practice has been satisfactory when loading conditions are not sufficiently high.As loading condition and penetrations of renewable energies increase,power flow model may not be accurate for online SSA.The gaps of power flow solution under contingency compared with the steady states of power system time-domain stability model are numerically analysed in different scenarios.It is numerically shown that the steady-state solutions of the power flow model and the stability model can be very different;raising serious concerns on the accuracy of using the power flow model for online static security assessment.Counter examples are given to show that point.Physical explanations for the gaps between the steady states of power flow model and time-domain stability model are given out.A novel online SSA scheme using a hybrid steady-state model is suggested adapting to modern power system.Numerical examples are given to show that the suggested scheme is pressingly needed and can resolve the issue as well as maintain the accuracy of online SSA.