## 5 Simulation Verification
### Effects of ESS Controller Parameters on System Dynamics  
Figure 8 shows the simulation results of the grid frequency and the electromagnetic power of the equivalent SG when the parameters of the D and P controllers in the ESS change, respectively. The simulation results show that the P controller mainly affects the damping ability of the power system. The larger the P controller parameter, the stronger the damping ability of the power system, the faster the oscillation attenuation, the shorter the time required for the power grid to return to its stable state, and the more conducive it is to the stability of the power system. The D controller mainly affects the system inertia. The larger the D controller parameter, the stronger the system inertia, the smaller the maximum oscillation amplitude, and the longer the oscillation period. Increasing power grid stability is the general change trend, which is more conducive to power grid stability. It should be noted that when the D controller parameter is increased to a certain extent, the oscillation time will be longer, and it is possible to trigger the power system separation device. Furthermore, an excessive D controller parameter leads to the system poles close to the right half plane of the eigenvalue complex plane, which is not conducive to the small signal stability of the power system. The simulation results in Figure 8a,c confirm this feature. When the D controller parameter increases to a certain value, the electromagnetic power will oscillate at a subsynchronous frequency.  
The change of ESS controller parameters can indirectly change the inertia effect and damping ability of the power system, so that the electromechanical oscillation can be effectively suppressed. However, since the controller parameters remain constant throughout the whole oscillation process, the inertia and damping provided by the ESS cannot be flexibly adjusted according to the operation status of the power system, the performance of oscillation suppression is always limited, and the dynamic performance of the power system cannot be further improved. As shown in Figures 8a and 8c, with the increase of K\({}_{\text{d}}\), the system inertia increases and the oscillation amplitude decreases significantly, while the time for the system to return to its steady-state point becomes much longer. In the process of the system moving towards the steady-state point, this process is expected to occur at the fastest possible speed, however, due to the fixed inertia parameter, the recovery process to the steady-state point cannot be effectively accelerated. As shown in Figure 8b,d, as the \(K_{\text{p}}\) increases, the damping ability of the power system increases, the oscillation peak decreases, and the attenuation  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameters** & **Values** & **Parameters** & **Values** \\ \hline Utility voltage U & 10.5 kV/50 Hz & ESS DC-side voltage V\({}_{\text{dc}}\) & 800 V \\ Line impedance Z & 0.02 + 9.5 \(\Omega\) & ESS location k & 1 \\ Frequency deviation threshold K & 0.5 Hz & ROCOF threshold m & 0.1 Hz/ms \\ \hline \hline \end{tabular}
\end{table}
Table 1: System parameters.  
speed increases, while the oscillation period is hardly affected. Therefore, fixed inertia and damping cannot achieve the desired oscillation suppression. It is necessary to flexibly adjust the inertia and damping effects according to the specific stage of the oscillation process.