  The concept of direct current distribution minigrids has been gaining ground
in academia and industry regarding the development of distribution grid
applications with high penetration of distributed energy sources and storage
systems. The adoption of a direct current distribution system facilitates the
integration of sources such as photovoltaic and wind generation and storage
systems such as batteries, as these technologies in general operate
intrinsically in direct current. This work presents the development of a direct
current distribution nanogrid (DCDN) installed in the laboratory of the Grupo
de Estudos e Desenvolvimento de Alternativas Energeticas (GEDAE), of the
Universidade Federal do Para. The developed grid is composed of three
photovoltaic generation and storage systems in battery banks and three load
banks, distributed over the 200 m grid in a ring topology, with a 24 Vdc bus.
Two simulation methodologies were developed and can reproduce the nanogrid
operational behavior under static and dynamic conditions, allowing the
evaluation of the grid performance over a day of operation. Tests are also
presented with measurements at strategic points of the grid to evaluate the
system behavior under specific operating conditions, being normal or under
contingency. The results attest the nanogrid ability to reliably supply the
loads, as long as it respects the limitations of the implemented power
generation and storage capacities. In addition, it was found that the
characteristics related to the topology of the commercial charge controller
that is used to form the DC distribution nanogrid benefits the power quality
for the developed grid size and topology.
