Hierarchical State Estimation Applied to Wide-Area Power Systems

This paper discusses the application of the hierarchical state estimation technique to wide-area monitoring. A wide-area network comprised of a large number of interconnections between various utilities requires monitoring of the entire system. Hierarchical state estimation can be modified to consolidate the state outputs from the existing state estimators of the individual entities in a wide area. This type of estimation is faster than an integrated state estimate of a wide area. However, problems such as delay of state output arrival, loss of state output of an area, overlap of areas and asynchronism of state estimate cycle occur. These problems are addressed in this research through the modification of the traditional hierarchical state estimation. Specifically, synchronized phasors are used in the hierarchical state estimation structure to improve the performance of the overall state estimation. The state estimator is run on the IEEE 118 bus system with phasor measurements in a selected number of buses. The results of the use of phasor measurements in various levels of the hierarchical state estimation are presented here.