Abstract

State estimation is a procedure which determines unavailable information of a given system from known measurements. Such procedure is based on a mathematical model of the system and consists on a comparison of the available information with the theoretical results. This comparison provides the values of the unknown variables and/or parameters of the system.In this work it is proposed a mixed estimation strategy combining a hierarchical and a distributed structure. In the proposedstrategythe estimation areas are able to communicate among them in order to make aninitialestimation. Since distributed estimation strategies have less performance than the centralized ones,a higher layer is addedto the estimationstructure,in order to make a global reconciliation of the initial estimation. The higher layer also improves the robustnessof the proposed state estimator while reduces the computational burden of the global reconciliation process. The robustness is improved because the initial joint estimation is able to isolate the areas with an anomalous behavior. Furthermore, if there is a communication failure between any estimation area and the upper layer, the local estimations are available and can be used to make any decision related with the system operation. The computational burden of the global reconciliation process is decreased because it is used only for checking the quality of the estimations (particularly the estimation of the common variables to two different estimation areas). This reduces the complexity of the reconciliation process, since thelocal estimations can be takenas measurements from a phasor measurement unit. In order to test the performance of the proposed estimation scheme, the Colombian power system at 500 KV level wasused as a testbed. The test uses real data from February 28th 2013.