Analytical structures for eigensystem study of power flow oscillations in large power systems

The authors argue that since eigensystem analysis of large-order power systems is based on numerical methods, each engineering case study is uniquely discrete and lacks the analytical continuity to link it to other case studies so that universally applicable conclusions can be drawn. They provide some analytical structures to validate some of the engineering intuitions which have been formed from extensive inspection of numerical eigenvalues and eigenvectors. A correlation is found between the frequency of oscillation and the mode shape of power system load flow. It is concluded that there is an analytical basis for associating the low-oscillating-frequency modes with light or unstable damping