## 2 Proposed MG Architecture  
About the DCMG scheme, multibus architectures, according to the original concept, are able to perform with higher reliability, basically because there is more than one bus in the system to overpass a fail [31]. Each bus gathers at least one DG, one ESS and some loads. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**EVCS Type** & **Power Supply** & **Charger Power** & **Charging Time** \\ \hline \multirow{2}{*}{AC L1 residential} & 120/220 \(V_{AC}\), & \multirow{2}{*}{1.44–1.92 kW} & \multirow{2}{*}{Approx. 17 h} \\  & 12–16 A, single phase & & \\ \hline \multirow{2}{*}{AC L2 commercial} & 208–240 \(V_{AC}\), 15–80 A, & \multirow{2}{*}{3.1–19.2 kW} & \multirow{2}{*}{Approx. 8 h} \\  & single/split phase & & \\ \hline \multirow{2}{*}{DC L3 fast charger} & 30–600 \(V_{DC}\), & \multirow{2}{*}{120–240 kW} & \multirow{2}{*}{Approx. 30 min} \\  & _Max_ 400 A, & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Classification of charge stations based on power levels. The proposed system must be able to satisfy the power demand in the teachers offices building as well as to supply an EVCS or, eventually, it can be able to inject power to mains. Some months ago, a quality energy logger equipment was installed to quantify power consumption. At the same time, a loads characterization study was performed to identify voltage and current requirements at every load inside the building. The highlighted results are: the building peak power consuption is 6 kW; in the other hand, it is necessary to set three DC buses at different voltage level because of the different type of the loads in the building. A primary bus at 380 V to supply electronic loads at every office; another secondary bus at 190 V to power the lighting system of the place (this bus can support the primary bus as an emergency action eventually). From the secondary bus, unidirectional 48 V buses are derivated; every one of them supplies six tandems driver-LED luminary for a specific area lighting. The primary bus and the secondary bus each incorporate an ESS based in batteries. At this point, it can be noticed that the MG has a particular architecture; then, it can be mentioned, according to the aforementioned two criteria, as multibus multivoltage DCMG. The selected DCMG is a flexible architecture able to satisfy the building power demand. In the place, four photovoltaic (PV) arrays are installed as DGs, each at 2.5 kW power rating, eventually 10 kW total power. Then, three buses distribute the power to every load in the building mainly using primary bus (380 V) and secondary bus (190 V). Harvested power at PV arrays is processed through boost converters--three of them linked to the primary bus and one more setting the secondary bus. This kind of structure is able to transfer power from one bus to another at a power level lower than its rated power. In typical multibus architectures, power is transfered between buses with similar level voltage using static switches, but in the DCMG proposed, primary and secondary buses are at different voltage levels. This feature is the main difference with DC typical multibus systems in [32; 33]. This development uses bidirectional power converters to transfer between buses, instead of static switches; then, it is possible to set the secondary bus from the primary bus and vice versa. A couple of PECs with bidirectional feature allows batteries charge/discharge at the ESSs. From secondary bus, 48 V unidirectional buses are derived to supply six tandems driver-LED luminary, four 48 V unidirectional buses are able to supply twenty-four luminaries inside the place. In order to improved DCMG security, all of the eventual power consumers in the system use isolated converters as interface to satisfy current and voltage required by final load. The architecture can be defined as multibus multivoltage; this concept brings flexibility to design a DCMG at any place.