## 4 Experimental Studies  
The proposed PUC MLI has been designed and validated experimentally as well as through simulation studies. The experimental realization is performed for both seven and five levels. Figure 22 shows the experimental setup of the proposed PMSG-based WECS. The electrical parameters of the experimental setup are tabulated in Table 5.  
Figure 19: Input voltage and capacitor voltage of PUC5 MLI: (**a**) actual input voltage, (**b**) one half of input voltage.  
Figure 20: Load voltage of PUC5 MLI.  
A 1.1 kW asynchronous motor is used in the laboratory environment to model the changing wind speed. The rotor of the PMSG and the rotor of the asynchronous motor are coupled to each other. The speed of the asynchronous motor is changed using a motor driver. Thus, different values of voltage are generated at the output of the PMSG. Figure 23 demonstrates the coupling of a three-phase asynchronous motor and PMSG. As shown in Figure 24, different voltage values ranging from approximately 25 V to 35 V are generated at the output of the PMSG. The three-phase AC voltage generated at the output of the PMSG is converted into DC voltage using a diode rectifier.  
Figure 23: Wind turbine emulator and PMSG.  
Figure 22: The experimental setup: (1) L-load, (2) R-load, (3) PUC MLI topology, (4) auxiliary capacitor, (5) TMS320F2837 xD microcontrollers, (6) DC–DC boost converter, (7) gate drivers, (8) asynchronous motor, (9) motor driver, (10) PMSG, (11) diode rectifier, (12) current sensor, (13) voltage sensor, (14) power unit, (15) current probe, (16) host PC, and (17) oscilloscope.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline PMSG rated power (W) & 700 \\ Asynchronous motor rated power (W) & 1100 \\ Motor driver rated power (W) & 1500 \\ Diode rectifier reverse current (A) & 5 \\ Diode rectifier reverse voltage (A) & 100 \\ DC–DC boost converter rated power (W) & 600 \\ PUC MLI input voltage (V) & 45 \\ PUC MLI output frequency (Hz) & 50 \\ Auxiliary capacitor (uF) & 2200 \\ Switching frequency (kHz) & 4 \\ Voltage sensor, LEM LV 25-P (max V) & 500 \\ Current sensor, LEM LA 55-P (max A) & 50 \\ Load resistance (\(\Omega\)) & 30 \\ Load inductance, L\({}_{1}\), L\({}_{2}\) (mH) & 69, 100 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Electrical parameters of the experimental setup for PUC MLI.  
The state of the selected PMSG operating without a load is expressed as the situation where no load is connected to its output. The result of the test carried out to determine the relationship between the speed and the output voltage of the generator at no load is given in Figure 25.  
The voltage at the output of the diode rectifier varies as the wind speed changes. The input voltage of the PUC MLI must be a constant DC voltage. To obtain this voltage, a DC-DC boost converter is used. Figure 26 shows the output voltage of the DC-DC boost converter corresponding to the change in the voltage of the diode rectifier. The voltage at the output of the diode rectifier varies between approximately 25 V and 35 V, while the output voltage of the DC-DC boost converter is set to 45 V.  
While designing the PUC MLI, six IRFZ44N power MOSFETs are included, and a TLP250 MOSFET gate driver output optocoupler integrator is used to drive these MOSFETs in the circuit. In addition, the voltage of the auxiliary capacitor is realized with closed  
Figure 24: The output voltage of the PMGS and rectifier voltage.  
Figure 25: Speed–voltage relationship.  
loop PI control. The PUC MLI's input, output, and auxiliary capacitor voltage values and output current values are given to the closed loop control system using sensors. The TMS320F2837 xD microcontroller is used to perform the control of the circuit and its switching.