## 8 Simulation Results
### Scenario 1  
In Scenario 1, PV plants account for 20% of the total generation of the grid, while synchronous generators provide 80%. The PV plants contribute 1228.16 MW, while synchronous generation produces 4896.4 MW (see Table 1).  
Initially, the simulation is executed with the FFT detection function disabled to observe the system's natural oscillatory response without POD-P controllers. The aggregation of PV plants reduces the damping ratio of the electromechanical mode to 3.19%, below the 5% stability threshold [51], increasing the system's susceptibility to disturbances. Figure 4a displays the frequency of all grid terminals. The oscillations observed at 5 s and 80 s correspond to the terminal and the line short-circuit (followed by its switching) events, respectively. As the system is initially unstable, these disturbances lead to inter-area oscillations that propagate over time. Figure 4b focuses on the frequency of the PV plant terminals and the synchronous generator speeds.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Scenario**} & \multicolumn{2}{c}{**PV Active Power**} & \multicolumn{2}{c}{**Synchronous Machine Active Power**} & \multicolumn{1}{c}{**Total Generation**} \\  & **P\_PV [p.u.]** & **P\_PV [MW]** & **P\_synch [p.u.]** & **P\_synch [MW]** & **[MW]** \\ \hline
1 & 0.2 & 1228.16 & 0.8 & 4896.4 & 6158.54 \\
2 & 0.5 & 3070.4 & 0.5 & 3057.5 & 6127.9 \\
3 & 0.8 & 4912.64 & 0.2 & 1245.9 & 6124.56 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Simulated scenarios.  
When the FFT detection function is enabled, the system identifies and damps oscillations via the POD-P controller, which modulates the PPC active power setpoint. The activation of the POD-P controller, with appropriately tuned parameters, increases the damping ratio of the electromechanical mode to 11.86%, exceeding the stability threshold of 5%. Consequently, the system exhibits enhanced stability under disturbances, effectively mitigating oscillations. Figure 5a highlights the frequency response across all terminals with the POD-P controller activated, demonstrating the effective damping of inter-area oscillations. Figure 5b provides a focused view of the frequency at the PV plant terminals and the synchronous generator speeds, confirming that the system achieves stability.  
For clarity, Figure 6 shows the FFT-triggered activation signal Enable_POD of the POD-P controllers and the corresponding adjustments to the PPC active power setpoint. Pout for each controller. Upon activation, the POD-P controllers dynamically modify the active power setpoint to mitigate oscillatory behavior. Once the inter-area oscillations are  
Figure 4: Scenario 1. System response without the POD-P controller activated following the terminal short-circuit event (t = 5 s) and the line short-circuit event (t = 80 s): (**a**) frequency at all grid terminals [p.u.]; (**b**) frequency at PV terminals [p.u.] and speed of synchronous generators [p.u.].  
Figure 5: Scenario 1. System response with the POD-P controller activated following the terminal short-circuit event (t = 5 s) and the line short-circuit event (t = 80 s): (**a**) frequency at all grid terminals [p.u.]; (**b**) frequency at PV terminals [p.u.] and speed of synchronous generators [p.u.].  
sufficiently dampened, the POD-P controllers deactivate, restoring the PPC active power setpoints to their pre-disturbance values. The same process is repeated for the second event.