PMU Placement to Estimate Power Mismatch for Frequency Stability Assessment

The increased penetration of Inverter-Based Renewable Resources (IBRs) to replace fossil fuel-based Synchronous Generators (SGs) presents significant stability challenges, such as frequency stability. This issue arises primarily from the reduction in system inertia, as Renewable Energy Sources (RESs) provide little to no inherent inertia. Consequently, the Transmission System Operator (TSO) has a shorter time window to implement corrective actions to prevent frequency excursions from exceeding regulatory limits and avoid frequency collapse. These excursions include rapid changes in frequency, such as the Rate of Change of Frequency (RoCoF), and a decline in frequency nadir following a major system disturbance. Estimating the disturbance size immediately after the event is crucial for remedial action, allowing TSO sufficient time to take preventive control actions. This paper proposes an estimation method using the Active Current Frequency Sensitivity Index (ACFSI), which helps identify the most sensitive buses critical for optimal Phasor Measurement Unit (PMU) placement, resulting in accurate disturbance size. The effectiveness and precision of the proposed method are assessed by conducting simulations on the IEEE 39 bus system with various outages.