## 5 Simulation Results  
In this section, the impact of the different locations and the type of impedance for the FCLs are studied. From the FCL's operation point of view, they should have a very low impedance during normal condition, fast response after fault detection, high impedance value during the fault, and also fast recovery time after fault removal. However, various configurations of the FCLs are slightly different in the characteristics mentioned above. For instance, regarding the configuration of the FCLs, some types of FCLs are superconductive, but then have almost zero impedance in normal operation. Whilst for the other types, there is a small impedance. Meanwhile, the FCLs may have different response and recovery times considering their configurations. However, it should be mentioned that after fault occurrence and during the fault steady state, all FCLs should have a high impedance value and the only difference should be related to the impedance type. Therefore, the type of impedance and its impact on the operation of the DFIG and the FRT enhancement were considered at three different locations, including the stator side, the rotor side, and the terminal side. The DC-link location has the same effect as the rotor side location. So, in order to avoid proliferation, location three was not mentioned. The DFIG was connected to the grid through a three-phase transformer and a transmission line. The parameters of the simulation are presented in Table 2. To have a reasonable comparison, the impedance values for the resistive and inductive type FCLs were the same. Meanwhile, to demonstrate how the FCL's impedance, either as an inductive or a resistive, could affect the RSC controllability, the impedance value was chosen in regards to the FCL impact on the stator side. As discussed, the resistive type FCL in the stator side has a very effective operation because of voltage sag compensation, excess active power consumption, and also increasing the RSC controllability. Therefore, the resistive type FCL in the stator side was selected as a reference to calculate the impedance value. As mentioned, the different locations have different impacts on the FRT improvement of the DFIG. In this section, the rotor and stator currents are shown in Figure 12. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**The DFIG and Transformer**} \\ \hline Rated power & 2 MW \\ Three-phase transformer & 0.69/34.5 kV, 60 Hz, 5 MVA \\ Rated stator voltage & 690 V \\ Rated frequency & 60 Hz \\ Stator leakage inductance & 0.12 p.u. \\ Rotor leakage inductance & 0.12 p.u. \\ Magnetising inductance & 3.45 p.u. \\ Stator to rotor turns ratio & 0.35 \\ Stator resistance & 0.011 p.u. \\ Stator inductance & 0.012 p.u. \\ Nominal wind speed & 13 m/s \\ \hline \multicolumn{2}{c}{**The DC Chopper**} \\ \hline Rated DC-link voltage & 1200 V \\ DC chopper resistor & 0.5 \(\Omega\) \\ DC bus capacitor & 50 mF \\ DC-link activation threshold voltage & 1.1 p.u. \\ \hline \multicolumn{2}{c}{**Transmission Lines**} \\ \hline Length & 30 km \\ Line impedance & 0.01 + j0.1 \(\Omega\)/km \\ Resistance of grid side filter & 0.3 p.u. \\ Reactance of grid side filter & 0.003 p.u. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulated DFIG Specifications. At first, the inductive type FCL was placed at three locations in the DFIG. The results are presented in Figure 12. The value of the inductance was less than the intersection point inductance value of the leakage coefficient curves presented in Figure 5b. Therefore, it can be concluded that the absolute value of the leakage coefficient for the inductive FCL in the rotor side was higher than for the inductive FCL in the stator side. As a result, considering Figure 12 and the discussion in Section 4.1, it is expected that the inductive FCL in the stator side, the rotor side, or the terminal side has almost the same impact on the stator current.