**5. Conclusions**

This work proposes an energy managemen<sup>t</sup> strategy applied to a stand-alone DC microgrid formed by a PVS, a battery, a not-critical DC load, and a capacitor as a backup storage element. Such EMS manages the connection and disconnection of the battery and the load, as well as the generation of the photovoltaic system and the ESD charge/discharge process, in order to guarantee the power balance and the operation of the system within allowable technical limits, thus increasing the lifetime of the devices that form the MG. The validation of the proposed EMS demonstrated that, by implementing a backup energy storage element (in this case a capacitor) and PVS generation control, load disconnections and inappropriate use of the main storage device can be reduced. Furthermore, using the auxiliary capacitor, the charge and discharge sub-cycles produced by the PDT control strategy can be eliminated. Those advantages extend the battery lifetime and reduce the costs associated with the maintenance and disconnection of the microgrid. In addition, the installation of SPVSs

with the proposed EMS, into education buildings, allow to reduce the energy purchasing from the utility grid, the dependency of fossil fuels to reduce the environmental impact, and also reduce the operational complexity of the system in comparison with systems based on other renewable resources, e.g., wind generation, small scale hydroelectric, among others. The main limitation of the proposed solution is the total load disconnection; hence as future work, the fragmentation of the load or the integration of multiple critical and non-critical loads into the microgrid will be considered. Those considerations allow the implementation of more complex load shedding strategies, multiple generation and storage systems integration to improve the energy storage capacity of the MGs. Moreover, microgrids could be connected to electrical grid where possible, thus enabling a cheaper energy dispatch that enhances the financial impact of the microgrid and improves the quality of the service provided to final users.

**Author Contributions:** Conceptualization, L.F.G.-N., C.A.R.-P., D.G.-M., G.A. and Q.H.-E.; methodology, L.F.G.-N., C.A.R.-P., D.G.-M., G.A. and Q.H.-E.; formal analysis, L.F.G.-N., C.A.R.-P., D.G.-M., G.A. and Q.H.-E.; investigation, L.F.G.-N., C.A.R.-P., D.G.-M., G.A. and Q.H.-E.; resources, L.F.G.-N., C.A.R.-P., D.G.-M., G.A. and Q.H.-E.; writing—original draft preparation, L.F.G.-N., C.A.R.-P., D.G.-M., G.A. and Q.H.-E. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Instituto Tecnológico Metropolitano, Universidad Nacional de Colombia, and Colciencias under the project "Estrategia de transformación del sector energético Colombiano en el horizonte de 2030—Energética 2030"—"Generación distribuida de energía eléctrica en Colombia a partir de energía solar y eólica" (Code: 58838, Hermes: 38945).

**Acknowledgments:** Authors want to acknowledge to the research groups "Materiales avanzados y energía" from Instituto Tecnologico Metropolitano, "Mecánica Eléctrica" from Universidad Veracruzana and "GAUNAL" from the Universidad Nacional de Colombia.

**Conflicts of Interest:** The authors declare no conflict of interest.
