A Fast Discrete-Time State Estimator for Monitoring Power Grids with Inverter-Based Resources

High penetration of inverter-based renewable energy resources (IBRES) introduced faster dynamics to power grids. Modelling and electromagnetic transient (EMT) simulation of these devices became important for their smooth integration. Monitoring of the IBRES dominated power grids holds similar critical importance. Present monitoring tools employ SCADA (Supervisory Control and Data Acquisition) and Phasor Mea-surement Unit (PMU) measurements, but they do not produce measurement samples at sufficient rate to monitor rapid dynam-ics associated with IBRES. Raw “point-on-wave” measurements could capture the fast IBRES responses, and enable the feasibility of monitoring them. Yet, monitoring the power grid at large scale and such a fast rate is a challenging task. Previously proposed transient state estimation approaches establish a theo-retical groundwork for it. However, further enhancements on the computational performance are necessary for the state estimators to keep up with the speed requirements. This paper proposes a method to accelerate state estimation to capture fast dynamics. Discrete-time element modelling based on numerical integration allows a two-step approach for state estimation if the selected time step is sufficiently small. The method introduces significant improvement in computational speed and memory without loss of accuracy. The proposed method is tested on 30-bus and 12589-bus systems, where the results of 30-bus system are verified using Alternative Transients Program (ATP).