## 3 Simulation Studies  
In this study, the simulation model of the PMSG-based WECS is as shown in Figure 8. The PUC MLI is able to generate five or seven voltage levels at the output. As can be seen, the output of the DC-DC converter \((V_{DC})\) is used to feed the PUC MLI as \((V_{IN})\). Obviously, by using only a single DC source, five or seven levels can be produced to feed the load. The design parameters of the proposed PMSG-based WECS are tabulated in Table 4.  
Figure 8: The simulation model of the PMSG-based WECS. Figure 7: (**a**) PUC15 or PUC9 MLI topology, (**b**) PUC31 MLI topology [55; 56]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**MLI Type** & **DC Source** & **Capacitor** & \begin{tabular}{c} **Clamped** \\ **Diode** \\ \end{tabular} & **Active Switch** & \
\begin{tabular}{c} **Total** \\ **Components** \\ \end{tabular} &
\begin{tabular}{c} **Control** \\ **Complexity** \\ \end{tabular} \\ \hline CHB & 2 & 0 & 0 & 8 & 10 & Low \\ NPC & 1 & 4 & 6 & 8 & 19 & Very High \\ FC & 1 & 3 & 0 & 8 & 12 & Very High \\ PUC5 MLI & 1 & 1 & 0 & 6 & 8 & Low \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of single-phase MLIs in terms of component numbers. The PMSG is provided to generate voltages at different speeds. As a result of the change in the speed of the wind, the voltage output of the PMSG ranges from about 170 V to 240 V depending on this speed. The wind speed and the three-phase voltage form at the PMSG output are demonstrated in Figures 9 and 10, respectively. \begin{table}
\begin{tabular}{l c} \hline \hline \multicolumn{1}{c}{**PMSG**} \\ \hline Stator phase resistance (ohm) & 14 \\ Inductance (d,q) (mH) & 0.8 \\ Rated power (kW) & 1.5 \\ Flux linkage (V.s) & 0.175 \\ Number of poles & 20 \\ Inertia (J) & 0.089 \\ \hline \multicolumn{3}{c}{Rectifier} \\ \hline Number of diodes & 6 \\ Diode reverse current (A) & 30 \\ Diode reverse voltage (A) & 600 \\ Max. output voltage (V) & 240 \\ \hline \multicolumn{3}{c}{DC–DC Boost Converter} \\ \hline Inductor (mH) & 0.3 \\ Capacitor (uF) & 690 \\ Resistor (ohm) & 50 \\ Switching frequency (kHz) & 20 \\ Diode reverse current (A) & 30 \\ Diode reverse voltage (A) & 600 \\ Max. input voltage (V) & 240 \\ Max. output voltage (V) & 315 \\ \hline \multicolumn{3}{c}{PUC7 MLI} \\ \hline Semiconductor switch & IXFH50N60P3 \\ Number of switches & 6 \\ Switch reverse current (A) & 50 \\ Switch reverse voltage (A) & 600 \\ Switching frequency (Hz) & 10 k \\ Load resistor (ohm) & 25 \\ Load Inductor (H) & 0.1 \\ Input voltage (V) & 315 \\ Max. output voltage (Vrms) & 220 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Design parameters of PMSG-based WECS. Figure 9: Wind speed. The conversion of the AC voltage at the output of the three-phase PMSG into DC voltage is carried out by an uncontrolled full rectifier with six diodes. The shape of the voltage at the rectifier output is indicated in Figure 11. The voltage values at the rectifier output adjust accordingly as the output voltage of the PMSG varies. The AC voltage produced as a result of the changing wind speed of the PMSG is rectified with a diode rectifier. This obtained DC voltage is connected to the input of the DC-DC boost converter. As the wind speed changes, the input voltage of the boost converter also changes. In this study, the main purpose of the DC-DC converter is to keep the output voltage constant even though the input voltage is variable. A PI controller is used to obtain a constant output voltage. The switching trigger of the DC-DC boost converter is generated from the PWM generator block, as shown in Figure 12. The PWM generator's switching frequency is selected as 20 kHz. Figure 13 shows the input and output voltages of the DC-DC boost converter. It was previously mentioned that the circuit topology in Figure 5a can be designed as an MLI with five or seven levels depending on the capacitor voltage. In this section, the results of the simulation studies for five and seven levels are given in Case 1 and Case 2, respectively.