A μ-analysis approach to power system stability robustness evaluation

A general approach based on structured singular value (SSV) theory is proposed for the analysis of robust stability of large power systems with parameter variations. SSV theory is utilized to find a structured-based parametric uncertainty description of the system that explicitly address and treat the effect of multiple, interrelated uncertain parameters on system dynamic behavior. Techniques to handle parametric uncertainties are given and methods to generate linear fractional transformation based uncertainty descriptions for the model and its associated uncertainty are discussed. Attention is focused on the study of uncertainties in the nominal system representation arising from two different sources, namely variations in the system operating conditions and uncertainties in the structure of the power system. The performance robustness of the proposed method is verified through simulation studies on a 6-area, 377-machine practical system. In particular, the developed technique is used to estimate the combined effect of variations in the level of power transfer across a critical system interconnection, and variations in the interconnecting tie-line reactance on the stability of critical inter-area modes. Several case studies are presented in which both conventional eigenanalysis techniques and SSV-theory are used to determine robust stability margins.