An Alternative for Including Phasor Measurements in State Estimators

With the increasing use of real-time synchronized phasor measurement units, it is necessary to consider applications of these measurements in greater detail. One of the most natural applications of these measurements is in the area of state estimation. A straightforward application of state estimation theory treats phasor measurements of currents and voltages as additional measurements to be appended to traditional measurements now being used in most energy management system (EMS) state estimators. The resulting state estimator is once again nonlinear and requires significant modifications to existing EMS software. This paper proposes an alternative approach, which leaves the traditional state estimation software in place, and discusses a novel method of incorporating the phasor measurements and the results of the traditional state estimator in a postprocessing linear estimator. This paper presents the underlying theory and provides verification through simulations of the two alternative strategies. It is shown that the new technique provides the same results as the nonlinear state estimator and does not require modification of the existing EMS software