State Reconstruction from Synchronized Phasor Measurements

The traditional state estimator relies on measurements affected by time skew and, while the whole system can be made observable, it cannot track the post-disturbance dynamics. Synchronized phasor measurements, on the other hand, can track those dynamics but, in a foreseeable future, they will be available in scarce configurations that do not allow estimating the whole system state. State reconstruction precisely aims at using the available phasor measurements to track the evolution of the power system - at least in a region of interest - in between two runs of a traditional state estimator. It minimizes under constraints a weighted least square objective involving both the phasor measurements and bus power pseudo-measurements relative to a reference state. The placement of phasor measurement units at the generator buses is recommended for accuracy. Tests are reported with phasor measurements obtained from time simulation of post-disturbance system evolution. The results deal with the effect on accuracy of the relative weights assigned to phasor and pseudo-measurements, the benefit of taking the reference bus powers from the last reconstructed instead of the pre-disturbance state, and the rate of the state reconstructions.