ROBUST STATE ESTIMATION OF ELECTRIC-POWER SYSTEMS

The exact fit points of the Least Median of Squares (LMS) and the Leas t Trimmed Squares (LTS) estimators in electric power systems are inves tigated. The expression of the maximum possible exact fit point delta( max) is derived, and the corresponding quantile index nu of the order ed squared residual is determined. It is found that delta(max) as wel l as nu hinge on the surplus of the network, defined as one less than the smallest number of measurements whose deletion from the data set d ecreases the rank of the Jacobian matrix. Based on the surplus concept , a system decomposition scheme is developed; it significantly increas es the number of outliers that can be handled by the LMS and the LTS e stimators. In addition, it dramatically reduces the computing time of these estimators, opening the door to their application in a real-time environment, even for large-scale systems.