## 5 Simulation Verification  
In this paper, Matlab/Simulink simulation software is used to verify the influence of the proposed control strategy on the low-frequency oscillation characteristics of the system, and the infinite system model shown in the figure is constructed and the simulation is performed, and the system parameters are shown in Table 1.  
In the model, the active power of each power generation unit is shown in the table, the structural parameters of the doubly-fed fan are shown in Table 2, the parameters of the energy storage converter are shown in Table 3, and the loads are 49 MW, 6 MW, 24 MW and 12 MW, respectively. In addition, the doubly-fed fan adopts additional POD combined with maximum power tracking control, and the energy storage part adopts additional POD combined with sag control and maximum power output control. Taking a 2 MW energy storage converter as an example, the main parameters are shown in Table 3.  
In the negative damping state, the system amplified oscillation caused by low-frequency oscillations is shown in Figure 11: \begin{table}
\begin{tabular}{l l} \hline \hline
**Power Generation Unit** & **Rated Active Power** \\ \hline Power plant 1 & 30 MW \\ Power plant 2 & 50 MW \\ DFIGs & 40 MW \\ Battery energy storage & 20 MW \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Active power of each power generation unit in the simulation model. Figure 10: Optimal Solution Sorting Method Based on Pareto Dominance Relationship. After the wind storage system is connected to the grid, based on the analysis of the power system characteristics of the wind storage system, the change of low-frequency characteristic values before and after the grid connection is shown in Figure 12. It can be seen that the wind storage grid connection system is connected to the grid to reduce the \begin{table}
\begin{tabular}{l c} \hline \hline
**Parameter** & **Value** \\ \hline Rated voltage/V & 690 \\ Rated power/MW & 2 \\ Blade radiusRr/m & 34 \\ Stator resistance (pu) & 0.03288 \\ Rotor resistance (pu) & 0.0449 \\ Excitation inductance/Lm & 6.5527 \\ Stator leakage feeling (pu) & 0.44241 \\ Rotor leakage (pu) & 0.44955 \\ Rotor moment of inertia (Hr/s) & 0.7 \\ Fan moment of inertia (Ht/s) & 3 \\ Damping factor (pu) & 2.4 \\ DC capacitors/F & 0.02 \\ DC voltage/V & 1200 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Structural parameters of doubly-fed fans. Figure 11: Power Angle Variation When Out of Synchronization. damping ratio of some modes, and a new oscillation mode is introduced. Table 4 shows the influence of LFO under weak damping before and after wind storage is connected to the grid. The focus is on oscillation suppression at the minimum damping ratio (0.03). In order to display the image clearly, only the characteristic roots of the second quadrant of the complex plane are shown, and the conjugate characteristic roots that are symmetrical about the real axis in the third quadrant are omitted. Low-frequency oscillations mostly occur in large-area and cross-area power grids with weak connections. This type of instability is mainly caused by weak damping and negative damping. The strength of system damping can be judged by the damping ratio of several dominant oscillation modes. It is generally believed that when the damping ratio is greater than or equal to 0.1, the system damping is strong; when the damping ratio is less than 0.03, it indicates that the system damping is weak; when the damping ratio is less than or equal to zero, it indicates that the system damping becomes negative, and constant amplitude oscillation will occur. Therefore, only the characteristic roots below the damping ratio of 0.03 are considered, that is, the bolded part in the above figure. The initial parameters of the POD are set \(K_{\rm POD}\) to 10, \(T_{\rm D}\) to 0.2, \(T_{\rm h}\) to 3, \(T_{\rm d1}\) to 0.5, \(T_{\rm d2}\) to 0.1, \(T_{\rm d3}\) to 0.05, and \(T_{\rm d4}\) to 0.07.