## 5 Simulation Case Analysis
### Symmetrical Case Validation  
To verify the accuracy of the parameter identification results obtained using the proposed algorithm, we conducted experiments under both charging and discharging modes. Symmetrical conditions with high (FP), medium (MP), and small power (SP) levels were tested, where voltage sags to 0%Un and 50%Un and swells to 130%Un were used as the identification experiment group. For the validation of LVRT, a symmetrical FP condition with a voltage sag to 20%Un was selected under both charging and discharging modes. To further evaluate multi-condition adaptability, HVRT validation was performed using symmetrical FP conditions with voltage swell to 125%Un under charging mode and 120%Un under discharging mode. The parameter identification results under symmetrical conditions are listed in Tables 3-7, and their comparison with the measured data are shown in Figures 6-9.  
Figure 6: CH: comparison of simulated and measured results for symmetrical HP voltage sag to 20%Un: (**a**) positive-sequence voltage; (**b**) active power; (**c**) reactive power; (**d**) active current; (**e**) reactive current.  
Figure 7: DH: comparison of simulated and measured results for symmetrical HP voltage sag to 20%Un: (**a**) positive-sequence voltage; (**b**) active power; (**c**) reactive power; (**d**) active current; (**e**) reactive current.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Interval** & \(\mathbf{\Delta U}_{mean}\) & \(\mathbf{\Delta P}_{mean}\) & \(\mathbf{\Delta Q}_{mean}\) & \(\mathbf{\Delta I}_{mean}\) & \(\mathbf{\Delta I}_{Qmean}\) \\ \hline Pre-fault steady-state & 0.25\% & 0.28\% & 0.25\% & 0.31\% & 0.31\% \\ Transient during fault & 0.92\% & 1.64\% & 1.14\% & 1.21\% & 1.24\% \\ Steady-state during fault & 1.51\% & 1.72\% & 2.09\% & 1.91\% & 1.88\% \\ Post-fault transient & 0.96\% & 1.99\% & 1.22\% & 1.56\% & 1.32\% \\ Post-fault steady-state & 0.30\% & 0.32\% & 0.24\% & 0.49\% & 0.42\% \\ \hline \hline \end{tabular}
\end{table}
Table 6: Comparison of steady-state average error in fault identification by the PSO-LM algorithm identification group under symmetrical conditions (CH FP125%Un).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Interval** & \(\mathbf{\Delta U}_{mean}\) & \(\mathbf{\Delta P}_{mean}\) & \(\mathbf{\Delta Q}_{mean}\) & \(\mathbf{\Delta I}_{Pmean}\) & \(\mathbf{\Delta I}_{Qmean}\) \\ \hline Pre-fault steady-state & 0.30\% & 0.21\% & 0.23\% & 0.52\% & 0.39\% \\ Transient during fault & 1.27\% & 1.16\% & 1.32\% & 1.93\% & 1.54\% \\ Steady-state during fault & 1.07\% & 1.83\% & 2.14\% & 3.41\% & 3.97\% \\ Post-fault transient & 1.22\% & 2.01\% & 2.54\% & 2.61\% & 1.74\% \\ Post-fault steady-state & 0.30\% & 0.33\% & 0.32\% & 0.59\% & 0.42\% \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of steady-state average error in fault identification by the PSO-LM algorithm identification group under symmetrical conditions (CH FP20%Un).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Interval** & \(\mathbf{\Delta U}_{mean}\) & \(\mathbf{\Delta P}_{mean}\) & \(\mathbf{\Delta Q}_{mean}\) & \(\mathbf{\Delta I}_{Pmean}\) & \(\mathbf{\Delta I}_{Qmean}\) \\ \hline Pre-fault steady-state & 0.45\% & 0.20\% & 0.53\% & 0.52\% & 0.44\% \\ Transient during fault & 1.17\% & 2.06\% & 1.82\% & 1.93\% & 1.54\% \\ Steady-state during fault & 1.07\% & 2.73\% & 2.04\% & 2.59\% & 1.97\% \\ Post-fault transient & 1.24\% & 3.11\% & 2.75\% & 3.35\% & 2.44\% \\ Post-fault steady-state & 0.31\% & 0.33\% & 0.62\% & 0.59\% & 0.52\% \\ \hline \hline \end{tabular}
\end{table}
Table 5: Comparison of steady-state average error in fault identification by the PSO-LM algorithm identification group under symmetrical conditions (DH FP20%Un).  
Figure 9: DH: comparison of simulated and measured results for symmetrical HP voltage swell to 120%Un: (**a**) positive-sequence voltage; (**b**) active power; (**c**) reactive power; (**d**) active current; (**e**) reactive current.