Nodal Inertia Assessment for Renewable Energy Power Systems Based on Vector Fitting Method

• • The PSO-VF method reduces frequency fitting mean square error by up to 42% compared to conventional VF with fixed initial poles, as validated on the IEEE-39 system; this directly enhances the reliability of inertia estimates for dispatch decisions, where a 10% error in inertia could mislead reserve allocation by hundreds of MW. • • Nodal inertia assessment accuracy exceeds 95% under multiple operating conditions, including wind penetration levels from 20% to 60%; this threshold is critical for grid operators to maintain frequency nadir above 49.5 Hz after a 0.1 pu disturbance, avoiding under-frequency load shedding. • • The method eliminates dependence on disturbance data and high-quality PMU measurements, achieving robust performance even with 5% noise in power and frequency signals; this reduces infrastructure costs by avoiding additional phasor measurement units, estimated at $50k per node. • • Computational time for optimizing initial poles via PSO converges within 50 iterations, enabling near-real-time assessment with a time window of 2 seconds; this supports online monitoring at 1 Hz update rates, essential for adaptive virtual inertia control in inverter-dominated grids.