Addressing Nonlinear Observability Issues in Power Systems

In recent years the power system industry has witnessed an increase of automation techniques in system operation. This development is especially evident with smaller systems, such as naval shipboard power systems. Traditionally, a nonlinear algebraic model of the power system is used to determine the system observability. In particular, the sensitivity of the system measurements (real and reactive power for example) to the change in the system states (bus voltages and angles) is used as a measure of observability, derived from the power system stateestimation problem. It ignores, however, the non-linear dynamics of the system related to generator performance, non-linear components, etc. The proposed observability formulation accounts for these nonlinearities providing a more comprehensive observability determination with the ability to track the trajectories of the dynamic variables over time and is derived from a DAE model of the power system. An example 3-bus power system is presented to illustrate the proposed method.