A constrained bus method for power system state estimation

Static state estimation of electrical power systems often involves a system containing several buses with neither load or generation. These buses are referred to as zero injection buses. The presence of these buses can and should be used to improve the performance of the state estimator. Specifically, the zero injection buses introduce equality constraints that must be satisfied by the state estimation algorithm. The equality constraints can be introduced into the state estimation process by treating the zero injection at the constrained buses as measurements with high weighting factors. Another approach is to use the method of Lagrange multipliers. This dissertation presents a method that incorporates constraints by satisfying the load flow equations at the constrained buses at each iteration in the state estimation algorithm.; The method utilizes solution of the load flow equations at each half of the decoupled state estimator iterative process. Both the magnitude and phase angle of the constrained bus voltages are adjusted at each half of the state estimation iterative process. Several examples are presented to illustrate the use of the constrained bus method to improve observability and bad data detection. In addition, the constrained bus method can treat injections at unobservable buses as pseudomeasurements, thereby making these buses observable.