Robustness analysis of large power systems with parametric uncertainties

The increasing complexity of power systems imposes a challenge to the analysis and determination of stability margins. Uncertainty modeling and analysis is crucial in this context. This paper examines the use of robust stability theory to assess small signal stability margins of large systems with respect to real parametric uncertainties arising from changes in system operating conditions. Based on a heuristic small signal robust representation of the power system, techniques to reliably estimate small signal stability margins are discussed. The accuracy, efficiency and robustness of the procedure is tested on a 6-area 377-generator model of the Mexican interconnected system. The effects of various operating uncertainties on modal behavior are discussed. Specifically, we investigate and discuss the influence of variations in the power flow of a critical intertie, and the use of TCSC transmission support on the damping of a critical inter-area mode. Comparisons of the stability margins computed using the proposed technique and those obtained from detailed small signal stability studies confirm that robustness analysis provides an accurate estimate of stability limits.