A Hybrid Quasi Steady-State Model for Long-Term Stability Analysis of Electric Power Networks: Model Development and Theoretical Basis

The quasi steady-state (QSS) model based on timescale decomposition was developed to reduce the computational burden for long-term stability analysis. However, it was shown that the QSS model may not provide accurate stability assessments for the complete dynamic model in long-term stability analysis. In this paper, a hybrid QSS model, which serves as a remedy to the QSS model, is proposed. The proposed model can provide accurate approximations for the long-term stability model with much less computational time. The hybrid QSS model proves to be capable of consistently providing accurate approximations for the long-term stability model. In addition, numerical algorithms for the hybrid QSS model are elaborated for practical implementation. Numerical examples show that the hybrid QSS model can quickly screen out stable contingencies and accurately capture unstable contingencies for the long-term stability model in cases where the QSS model fails.