The continuous displacement of conventional synchronous generation by non-synchronous technologies (NSG) significantly reduces power system inertia (?). Concurrently, modern power electronics-dominated loads increasingly decouple demand consumption from grid frequency deviations, leading to a critical degradation of the system damping coefficient (D). This paper presents a comprehensive sensitivity analysis investigating the coupled effects of inertia reduction, damping degradation, and varying disturbance magnitudes (∆P) on aggregate primary frequency dynamics, using the 28 April 2025 Iberian Peninsula disturbance as a real-world validation baseline.

A mathematical aggregate frequency framework is developed to characterize the initial Rate of Change of Frequency (RoCoF), frequency nadir, and time-to-threshold operational windows. Through a parametric evaluation implemented in MATLAB, the system performance is tested under three operational inertia levels (? = 6 s, ? = 4 s, ? = 2 s) subjected to load-shedding severities ranging from ∆P = -0.10 to -0.20 pu Crucially, the study evaluates the transition from a traditional high-damping paradigm (D = 0.05 pu/Hz) to an extreme, electronics-dominated low-damping scenario (D = 0.01 pu/Hz).

Numerical results reveal that while initial RoCoF is governed exclusively by mass inertia at t = 0+, triggering extreme initial gradients, the subsequent decay is highly sensitive to the damping-to-disturbance ratio (∆P/ D). Under the modern D = 0.01 pu/Hz paradigm, the system lacks sufficient self-regulation to arrest frequency excursions natively. Within the evaluated 10-second simulation window, the trajectories experience severe, unmitigated decay, driving the frequency down to catastrophic levels (e.g., 41.74 Hz for ? = 2 s) that imply full grid collapse. Furthermore, critical operational time-windows before triggering automated defense mechanisms compress dramatically; the times required to cross the FFR activation threshold (49.0 Hz) and the under-frequency load shedding baseline (48.8 Hz) drop to less than 0.7 seconds under low-inertia conditions. This severe compression leaves conventional governor responses obsolete and establishes the boundaries for mandatory fast active power injections from wind facilities.

The findings map the boundary conditions where passive grid resilience fails entirely. The paper concludes by defining the precise requirements for emergency fast active power injections (FAF) and grid-forming capabilities necessary to counteract the combined degradation of inertia and damping in future net-zero power grids.