CIRED Workshop - Ljubljana, 7-8 June 2018 Paper 0396 Paper No 0396 Page 1 / 4 DC MICROGRIDS FOR ENERGY COMMUNITIES IN THE DEVELOPING WORLD Christina PAPADIMITRIOU Vasilis KLEFTAKIS Nikos HATZIARGYRIOU NTUA – Greece NTUA – Greece NTUA – Greece chpapadi@mail.ntua.gr vkleftakis@power.ece.ntua.gr nh@power.ece.ntua.gr ABSTRACT The main problem of energy supply in the developing counties is that a very large portion of their rural population still does not have access to a secure supply of electricity. DC microgrids seems an attractive solution due to lower capital, operation, engineering and maintenance costs. Many developing countries have shown interest in the development of such systems in order to improve the quality of their inhabitants’ life, together with the development of the local economies (creation of new jobs) through the creation of local energy communities. This paper reviews the conditions under which DC microgrids provide an attractive option for local energy communities in the developing world. It also reviews the best practices of DC local energy communities in developing countries and highlights relevant issues, e.g. regulatory framework, standardization, protection, secure supply etc. that have to be faced, in order to establish DC microgrids in rural areas INTRODUCTION Nowadays, the AC micorgrid concept in the distribution grids is well established. The emerging scenario of a DC microgrid, though, is a concept whose wide application is still under investigation and research. The main technical advantages of the DC microgrids are:  The incorporated Distributed Generations (DGs) can be easier coordinated, as their control is based on DC voltage without the need for synchronization.  The corresponding primary control is notably less complex as there is no need for reactive power flow control. Yet, the DC link can suffer from harmonics.  DC system does not experience high fault currents as the contribution to faults by the converters of the power electronic interfaced load or DGs is limited.  As the DC electronic domestic loads dominate today, unnecessary AC/DC power conversions are avoided as most DGs generate DC outputs. This has a direct effect on system cost and losses. Also, the converters used for the DC microsources interface, are mostly transformer- less reducing further the size and cost of the system.[1] In the latter context, the DC microsources (mostly Renewable Resources) may be grouped together in DC microgrids structures and the multi microgrid system gets connected to the upper distribution LVAC grid. The connection of e DC microgrids to an upper LVDC network opens further interesting prospects. Ref. [2] has carried out a theoretical analysis about efficiency of the LVDC distribution and DC usage in house installations. It is shown that efficiency is not improved, if only the residential installations are replaced by DC-insinuating a hybrid DC microgrid-AC network. Instead the combination of DC power in houses and the LVDC distribution system would be more efficient than the present AC. In Ref. [3] there is a clearer vision of the above statement. It is proven that the hybrid DC MG-AC network may have a lower efficiency (2-3%) than a comparable full AC network, when the load and generation are not well matched. In case that the load and generation profiles are matched, then the hybrid enjoys an efficiency advantage of 2-3% over the AC. The total energy savings, though, of a DC MG e. g in a residential application, is more than 30%, combining both the savings of possible DC-based appliances with the avoided AC-DC conversion within those appliances. In Ref. [4] it is reported that the DC system capital cost is less than the corresponding AC system. This economic difference may not appear as a strong incentive in large applications. However, in smaller applications of developing countries with less capital, this fact may be decisive. It has to be mentioned that the rural sectors of the developing countries, that are less connected to fuel supplies are more likely, also, to be served by DC. PVs into DC microgrids will offer electricity access in the simplest way, even in the remotest places where the interconnection to the main grid is costly. As a result, people of these regions will have the opportunity to light their homes, charge their mobile phones and use other electronic devices in order to stay connected with the rest of the world. This paper is structured as follows. The challenges of the wide application of DC microgrids are reviewed next and some of the best practices of DC local energy communities in developing countries are reviewed. The last section concludes the paper and gives an insight about the future of the DC applications. ISSUES AND CHALLENGES OF DC APPLICATIONS IN RURAL AREAS In spite of all the advantages of DC microgrids and their potential, there are some factors that are slowing down their wide-spread use. One of the main reasons is that until very recently, there has been almost no standardization for LVDC systems. Lately, EMerge Alliance- an open industry association -