Hybrid DC and AC power distribution network as an alternative solution for isolated microgrids

This work proposes a topology of isolated microgrids with hybrid network (part in DC and part in AC) of electric power distribution. The topology consists of using a main DC power distribution system and subsystems with AC distribution. DC/AC converters are strategically distributed along the main DC network, forming AC subsystems, in order to serve a certain number of consumers with AC loads. Although there are loads that can be fed in DC, this is not a reality for household loads in several countries, which are basically AC powered. Thus, the interest of this work was to evaluate the possible advantages of this topology as compared to the conventional AC microgrids with low voltage distribution network. In this context, the main aspect studied was to increase the extension of the distribution network without the need to use electric transformers or conductors with larger cross sections. Intrinsically, the efficiency of the energy distribution was evaluated with respect to the energy losses, and the variation of the implantation and operation costs. An isolated microgrid with a purely AC distribution network was used as reference: the microgrid with solar-wind generation of Lençóis Island is located in northeastern Brazil.