Variational approach in modal analysis

Modal analysis is a rigorous technique to handle steady-state voltage stability for large-scale power systems. In this method, participation factors are computed to identify critical buses, branches and generators in the system. This paper adopts a unified variational approach to calculate eigenvalue perturbation of power flow Jacobian matrix with respect to system parameters such as network elements or reactive loads. The results lead to the definition of a family of participation factors which are more symmetric, meaningful, and easier to compute than before. These participation factors are proved valuable and effective in the analysis of large-scale power systems, which is demonstrated in a sample study on South China power grid.