Large power systems are highly complex systems that defy predictions with any degree of certainty. In this paper, an analytical framework for the assessment of small signal stability under operating uncertainty is presented.A rigorous analysis framework for the description of uncertainty in operating conditions is suggested. Using structured singular value theory and optimization tools, techniques for robust stability analysis of complex power systems are then derived and a method to quantify the effect of parametric uncertainties on the stability of critical inter-area modes is presented. A computationally-efficient method for modeling parametric uncertainty based on linear fractional transformation (LFT) theory is investigated and tested. With this approach, it becomes possible to estimate the effects of variations in the parameters of major transmission resources on the nominal stability of critical inter-area modes.The use of the analysis methods is demonstrated on two systems: i) a two-machine test system, and ii) a two-area, 11-bus, 4-machine test system.
