## 5 Methodology Validation
### Scenario 2: Solar Photovoltaic and Battery Storage System  
This scenario consists of a MG with the capacity to supply the critical loads during a contingency. When a contingency occurs, the main grid is off, in this case the MG should be in off-grid operation mode. For this reason, it needs a back-up: batteries. The batteries generate a reference to the PV MG to operate in islanded mode. The capacity installed of the MG was determined contemplating the energy consumption for the critical load in one day. Additionally, the average solar radiation in one year in Mayaguez was considered. Calculations were done with the average solar radiation in Puerto Rico daily per year, the number of hours used was five. The configuration of the arrays to the parking lot of Biology and white area are considered same to scenario number one. However, the space available in the university is distributed in different sectors, such as Table 2 indicates. For example, the library parking and library roof (LR) are close, the total space between both is 14,349 m\({}^{2}\). Considering the space necessary for the panel, this space has a possible total installed capacity of 1.83 MW. Both spaces have a possible installation 1.4 MW with two PV arrays of 700 kW. Table 6 presents summary of the design. Figure 15: Voltage profiles in the substation, average solar radiation. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Energy [MWh]** & \\ \hline UPRM SS & PV Generation & \% Contribution \\ \hline
135.89 & 5.864 & 4\% \\ \hline UPRM CL & PV Generation & \% Contribution \\ \hline
15.05 & 5.864 & 39\% \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Contribution of Energy to UPRM. The scenario with PV and Batteries storage was proved in the simulation, the variables considered were annual solar radiation per day at Mayagiez, 3 MW of installed capacity for the PV MG, battery backup with the capacity (3.94 MW) of providing the energy necessary to supply load demand when the grid and PV MG are off, as well as provide support when the solar radiation is not enough to provide the load demand. To test the MG in islanding mode, the simulation was run with the disconnection of the main grid. Initially, the total demand of the university is supplied, however, when the main grid is disconnected, the MG is in charge of supplying the demand required for the critical loads. It is important to mention that for the simulation the state of charge of the battery is between 20 and 80%. If the energy produced for the PV MG exceeds the energy demand for the load, this energy is used to charge the batteries. In addition, if the SOC of the battery is more than 99%, and the PV MG exceeds the energy demand to maintain a power balance, the PV MG is disconnected. For the simulation, 30 days of solar radiation were used. The duration of the simulation could allow to analyze the behavior of the system during its timescale, however, the results are shown only the first three days, for a better visualization. The behavior of the power supply for the main grid, as well as the power produced for the PV MG, and the power supply for the battery are shown in Figure 16. In addition, the power demand for the critical load, the state of charge of the battery, and voltage in the point of interconnection are shown in Figure 17. The curves demonstrate that the power required for the critical loads is supplied for the PV MG during the day, and the battery supplies the load when the day is over. The initial SOC of the battery is 100% when the grid is disconnected and the PV system is generating an excess of energy, so the battery system cannot store this excess energy. For this reason, curtailments to the PV system are applied, with the objective to conserve the energy balance. This only happens at the beginning of the simulation. When a MG operates in islanding mode, it is necessary to know the days of austerity that it could provide. The days of austerity are defined as the days that the MG could be operated in islanding without load interruptions.