A Hybrid State Estimation Strategy with Optimal Use of Pseudo-Measurements

Despite the rapidly increasing number of PMUs in power grids, it is still not possible to obtain observability in large power systems solely using PMUs. Therefore, use of hybrid state estimators became a necessity to utilize PMUs in power system state estimation. The main challenge in the hybrid state estimation is the mismatch between the refresh rates of the SCADA and PMU measurements. This results in power system unobservability between the instants SCADA measurements are refreshed, even if PMU measurements are received. In this paper, a hybrid state estimator, which employs pseudo-injection measurements during this unobservable duration, is proposed. The pseudo-injection measurements are generated using historical data, and updated during the estimation process using Kalman filter. In order to minimize the biasing effect of those pseudo-measurements, their number is kept at minimum while guaranteeing that the possible most accurate ones are employed.