# Efficient Wireless Monitoring and Control of a Grid-Connected Photovoltaic System
## 5 Experimental Verification
### Experimental Results for the DC/DC Converter  
An experiment has been carried out for different levels of irradiance. Its value changes from 820 W/m\({}^{2}\) to 500 W/m\({}^{2}\) at t = 7 s, then to 835 W/m\({}^{2}\) at t = 21 s, and to 510 W/m\({}^{2}\) at t = 29 s. Finally, the irradiance takes a value of 838 W/m\({}^{2}\) at 38 s. In this research, the changes have been considered step signals. With these irradiance variations, and consequently the change of the temperature, the operation of the wireless grid-connected PV system is tested. Table 2 summarizes the time intervals and the obtained values of irradiance, temperature, and reference voltage that provide the MPP, and the MPP. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Time** & **Irradiance** & **Temperature** & **V\({}_{\text{PV,ref}}\)** & **PMPP** \\ **(s)** & **(W/m\({}^{2}\))** & **(\({}^{\circ}\)C)** & **(V)** & **(W)** \\ \hline
[0–7] & 820 & 38.1 & 17.5 & 51.1 \\
[7–21] & 500 & 38.3 & 18 & 30.1 \\
[21–29] & 835 & 37.9 & 17.4 & 52.2 \\
[29–38] & 510 & 38.1 & 17.9 & 31.4 \\
[38–55] & 838 & 37.9 & 17.5 & 52.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Values at the maximum power point (MPP). Figure 12: Quality of the signal under the influence of the converter. Figure 13: Measured power consumption of the network node. Figure 14 shows the voltages at the DC/DC converter input and output. Moreover, it presents the reference voltage that must be tracked to reach the MPP. The boost converter output voltage reaches around 54 V when the irradiance is high, whereas the voltage takes a value of about 53 V when the irradiance is low. The input voltage is between 17.4 V and 18 V, depending on the time interval where the signal is located. As it is shown, the voltage signal is properly tracked, obtaining an MPPT tracking efficiency between 99.05% and 99.95%. Figure 15 depicts the inductor current and the DC/DC converter input and output current. The same as the output voltage signals, the values of the current signals increase when the irradiance is high, whereas their values drop when the irradiance is low. Figure 16 presents the parameter estimation of the capacitor and inductor of the boost converter. It shows how the parameters are readjusted by the controller in each change  
Figure 14: DC/DC converter voltage profiles: reference voltage and DC/DC converter input and output voltage. Figure 15: DC/DC converter current profiles: inductor current and DC/DC converter input and output current. to stabilize the system. The system is robust under uncertainty of the parameters and environmental conditions. The power at the DC/DC converter input and output are presented in Figure 17. The input power reaches a value of approximately 52 W for the high irradiance and about 31 W for the interval with the low irradiance. The output power takes slightly lower values than the input power due to the commutation losses in the boost converter. Thus, the efficiency of the boost converter is defined as the relationship between the output power and the input power, achieving a value that ranges from 93% to 98%. Moreover, the MPPT efficiency is also achieved by taking into consideration the values of the input power and the real MPP, reaching an efficiency higher than 99.05%. Figure 18 shows the control signal using adaptive Lyapunov control in the boost converter. The value of the control signal varies when there is a perturbation, i.e., when the irradiance changes. The duty cycle takes a value between 77.9% and 78.6% when the  
Figure 16: Evolution of the adaptive parameters. Figure 17: DC/DC converter power evolution. irradiance is high, and it decreases to between 76% and 76.5%, approximately, when the irradiance drops. The results conclude that the operation of the wireless grid-connected PV system is robust when there are sudden variations in the environmental conditions. The reference voltage is tracked and the maximum power is reached in all the conditions.