Observability for PMU-based monitoring of nonlinear power system dynamics

PMUs placed at different buses enable dynamic monitoring of a power system. The question is whether those limited PMU measurements can provide sufficient information. In this research, observability analysis is used to answer this question. Different observability concepts together with their related state monitoring applications are discussed in this paper. Nonlinear dynamic observability based on Lie derivatives is applied to the PMU-based dynamic monitoring of power system. The smallest singular value of the observability matrix serves as an observability index. A 3-bus system is used to illustrate the observability concepts presented in this paper. The concepts of observability are clarified and the nonlinear observability analysis provides a basis for PMU-based on-line wide area monitoring and control to improve the dynamic performance of power systems.