A New Formulation of Dynamic-Phasor-Based State Estimation With Inclusion of an Equality Constraint

Power system dynamic state estimation (DSE) is a powerful method for monitoring the state evolution over time, hence enabling the adoption of advanced protection and control applications. In this work, we enhance our previous work on dynamic-phasor-based dynamic state estimation (DP-DSE) approach for estimating network states by reformulating the state-transition model to incorporate an equality constraint based on zero-current injection nodes. Inclusion of such an equality constraint not only adds additional system information into state-transition model, but also the resulting DP-DSE formulation has a reduced state-vector size in comparison to the previous formulation, implying a gain in the speed of the estimator. Since uncertainty in the control input can affect the accuracy of the estimator, in this work, the Kalman filter technique is modified slightly to incorporate input error covariance. This new DP-DSE formulation is validated on the modified WSCC-9 bus grid for different dynamic operating scenarios. To assess applicability of DP-DSE on different grid structures, the estimator is also validated on modified IEEE-39 grid and modified CIGRE-MV grid. In addition, the DP-DSE is compared against its time-domain (TD) and static-phasor (SP) domain counterparts to demonstrate advantages of the former.