## 5 Design Procedure and Application Example  
The PV system is designed depending on the operation conditions required by the PV panel and grid-connected inverter (or micro/nanogrid). For this application example, a BP585 PV panel is selected to be interfaced with a \(v_{b}=48\) V DC-link, which is common for low-voltage nanogrids and some commercial inverters (e.g., ATO-GTI-300 inverter), but any other panel and bus voltage can be considered depending on the application. The datasheet parameters of the BP585 PV panel are reported in Table 1[33]. The first step to design the PV system is to define the desired current and voltage ripples. Taking into account that the P&O algorithm could provide a precision higher than 99%, as demonstrated in the works reported in [27; 28], the PV voltage ripple must be lower than 1% of the optimal operation voltage, which in Table 1 is \(V_{mpp}=18\) V. Therefore, this example considers the desired peak-to-peak ripple of the PV voltage equal to 0.1% of \(V_{mpp}\), i.e., \(\delta v_{pv}\leq 9\) mV. The main advantage of the NEC boost converter, in comparison with the classical boost converter, is the capability to provide a continuous current to the output DC bus. This is possible since the current provided by the NEC boost converter is \(i_{2}\), which is continuous when the ripple \(\delta i_{2}\) (24) of that current is smaller than the average value \(\langle i_{2}\rangle\). Therefore, \(L_{2}\) will be designed to provide a continuous current for at least 75% of the irradiance space: Figure 12 shows the electrical characteristics of the PV panel for the maximum irradiance possible (1000 W/m\({}^{2}\)), and for the 75% (750 W/m\({}^{2}\)), 50% (500 W/m\({}^{2}\)), and 25% (250 W/m\({}^{2}\)) of such an irradiance space. Thus, \(L_{2}\) must be designed to provide \(\delta i_{2}\leq\langle i_{2}\rangle\) for irradiances \(S\geq 250\) W/m\({}^{2}\) (green zone of Figure 12). For irradiances \(S<250\) W/m\({}^{2}\), the \(L_{2}\) current will be discontinuous (red zone of Figure 12), but the power provided to the DC-link will be low; thus, the high-frequency current components will also have a low \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Maximum Power (\(P_{mpp}\)) & 85.0 W \\ Voltage at \(P_{mpp}\) (\(V_{mpp}\)) & 18.0 V \\ Current at \(P_{mpp}\) (\(I_{mpp}\)) & 4.72 A \\ Short-circuit current (\(I_{sc}\)) & 5.0 A \\ Open-circuit voltage (\(V_{oc}\)) & 22.1 V \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Datasheet parameters of the BP585 PV panel [33]. Figure 11: Implementation of the complete control structure. impact on the DC-link. Finally, \(L_{2}\) could be designed to impose a continuous current for a larger irradiance space depending on the requirements of the second stage. The MPP conditions of the PV panel under an irradiance of 250 W/m\({}^{2}\) are \(I_{mpp@250}=1.15\) A and \(V_{mpp@250}=16.5\) V, which produce a duty cycle \(d=0.656\) for the NEC boost converter (22); those values assume a temperature of 25 \({}^{\circ}\)C (i.e., the STC temperature considered in the datasheet). For different temperature conditions, the MPP current and voltage can be extracted from experimental measurements or estimated using a model parameterized at the desired temperature. Then, using expressions (18) and (21) it is calculated the average value of \(i_{2}\) as \(\langle i_{2}\rangle=I_{mpp@250}/(1+d/(1-d))=0.39\) A. Therefore, the current ripple on \(L_{2}\) must be \(\delta i_{2}\leq 0.39\) A when \(S=250\) W/m\({}^{2}\). The electrical scheme of Figure 3 shows that the ripple of the PV current is shared between \(i_{1}\) and \(i_{2}\) currents; hence, \(L_{1}=L_{2}\) is selected to ensure a balanced sharing of the current ripple, which is confirmed by expressions (23) and (24). On the other hand, the voltage of the internal capacitor \(C_{cb}\) affects the derivative of both \(i_{1}\) and \(i_{2}\), as reported in (9) and (10); hence, \(C_{cb}\) must be designed to have a small voltage ripple \(\delta v_{cb}\).