## 5 Simulation and Verification of SDC Inhibition Effect  
### Simulation and Verification of the Suppression Effect of SDCs Added to the Control System  
The SDC are installed in the abc axis control structure at the output of the GSC and RSC and are enabled simultaneously. In order to verify that the proposed optimization method can effectively suppress SSOs under all operating conditions, the time domain simulation was carried out with parameters such as the gain and phase-shift time constant in SDC as variables. Table 2 lists the parameters of the DFIG. The rated power and voltage of the stator were selected as the reference values. I\({}_{\text{aa}}\) is the phase A current of the bus on the grid side The following operating conditions are taken as an example for simulation experiments. The wind  
Figure 4: Algorithm implementation step diagram. speed was set to 6 m/s, the capacity of each DFIG was 1.5 MW, and the number of wind turbines was 100, and they were connected to the infinite power grid through the series compensation capacitor of 445F. As shown in Figure 5, the proposed method was tested with the RTLAB platform. In Simulink, a model for the grid-connected system of a DFIG with series compensation was built. The process involved several steps: firstly, dividing the system into subsystems; secondly, adding the OpComm module; thirdly, maximizing parallel execution and configuring priority/state variables; fourthly, setting real-time parameters; and finally, running the model offline. The SDC gains Kg and Kr installed in both the GSC and RSC, as well as the phase shift time constants Tg and Tr, were calculated from the GA. The current waveform without SDC under the same operating conditions was compared, and the amplitude suppression rate \(\beta\) was calculated according to Equation (9); results are shown in Table 3. Figures 6 and 7 show the comparison of the current La\({}_{\text{aa}}\) output waveform of phase A before and after adding the SDC; the red line in the figure is the Ia\({}_{\text{aa}}\) output waveform before adding the SDC, and the blue line is the Ia\({}_{\text{aa}}\) output waveform after the SDC is added. \begin{table}
\begin{tabular}{c c c c} \hline
**Parameter** & **Value** & **Parameter** & **Value** \\ \hline Rated power & 1.5 MW & Rotor resistance & 0.01827 p.u. \\ \hline Rated frequency & 50 Hz & Rotor self-sensing & 0.2222 p.u. \\ \hline Stator rated voltage & 0.690 kV & Excitation inductance & 15.71 p.u. \\ \hline Rotor rated voltage & 1.975 kV & Stator resistance & 0.01638 p.u. \\ \hline Constant of inertia & 0.0685 s & Stator self-sensing & 0.2552 p.u. \\ \hline GSC scale factor & 0.83 & GSC points factor & 5 \\ \hline RSC scale factor & 0.6 & RSC points factor & 8 \\ \hline \end{tabular}
\end{table} 
Table 2: DFIG parameters. Figure 5: Testing with RTLAB platform. After many experiments and analyses of the experimental results, the following conclusions were obtained:  
* Comparing Figures 6 and 7, the optimization effect of adding SDC on both the grid side and rotor side is obviously better than adding SDC to the single-side controller only. * To achieve optimization under this working condition, the value range of the SDC gain \(\mathrm{K_{g}}\) in the GSC is \([-10,\,-64]\), the value range of the SDC gain \(\mathrm{K_{r}}\) in the RSC is \([-30,\,-120]\), and the value range of the phase-shift time constant T in the two control systems is \([0.2,\,0.99]\). * The gain K is related to the phase-shift time constant T, and the parameters should be synchronously increased or decreased. When the absolute value of K is extremely large and that of T is extremely small, the system becomes unstable, as shown in Figure 8a. When the absolute value of K is too small and that of T is too large, the inhibition effect is extremely insignificant, as shown in Figure 8b. * When the absolute values of K and T were increased, the inhibition effect was better.