Improving performance of dynamic state estimators under unknown load changes

This paper investigates the use of dynamic state estimation for monitoring the transmission grid not only during pseudo steady-state but also during and following disturbances. The paper mainly considers line switching events but the developed estimator can be used under any other type of system disturbance. Unlike previous studies reported in the literature, this work takes into account changes in bus loads which are assumed to be monitored at longer intervals. Assumed variance of the system state is strategically varied to minimize the impact of this approximation on the dynamic state estimation. The well-known and documented Unscented Kalman Filter (UKF) is chosen in formulating the dynamic state estimator, due to its advantages over the commonly used Extended Kalman Filter (EKF). Simulation results will be shown to illustrate the proposed approach to handle slow load changes as well as dynamic estimation of state trajectory during line switching transients.