Hierarchical and Distributed State Estimation for Power Systems: The Colombia Case

摘要

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 proposed strategy the estimation areas are able to communicate among them in order to make an initial estimation. Since distributed estimation strategies have less performance than the centralized ones, a higher layer is added to the estimation structure, in order to make a global reconciliation of the initial estimation. The higher layer also improves the robustness of 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 the local estimations can be taken as 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 was used as a testbed. The test uses real data from February 28th 2013.