The popularity of renewable energy systems has contributed significantly in the last years to the utility of low voltage direct current microgrids. However, these systems come with new challenges. This survey focuses on introducing a state-of-the-art low voltage direct current distribution system and sheds light on the challenges that must be faced in order to complete energy transition. This literature review was systematically carried out using the two largest scientific databases (SCOPUS and WOS) where the query (low voltage direct current microgrid) resulted in 198 articles. The purpose of this paper is not to reiterate the comparison of direct current with alternating current systems, which has already been discussed extensively. Instead, the objective of this survey is to assess the feasibility of the low voltage direct current distribution system and its impact on social development. To this end, this work provides valuable information for renewable energy planners, giving some insights or solutions to bridge the gap between the current energy network and the future DC energy microgrids. In particular, this article focuses on parameters such as grid topologies, distribution and voltage standardization efforts. The three major findings are: (i) the off-grid solutions enhance the efficiency rate in energy facilities (from 15% to 30%), and the vast majority of them are supported with energy storage systems to increase their reliability. However, in economic terms the most suitable systems still are the grid-connected solutions. Another finding is that (ii) the bus configurations are most used as well as the best in terms of their effectiveness to distribute low voltage and direct current energy within the microgrid. Lastly, (iii) the voltage value standardization around 48 V and 380 V, and even though there seems to be a clear convergence between them, the lack of agreement is delaying the massive implementation of these solutions worldwide. Finally, a novel assessment of social impacts and reflections on low voltage direct current microgrids is also included. 

Is it feasible a massive deployment of low voltage direct current microgrids renewable-based? A technical and social sight

DC-DC power conversion, ranging from volt-fraction to ten of kVs, and mWs-MWs, is found in various applications, the latter making a human’s life comfortable. DC motor drives [1], telecommunications [2], satellite [3], fuel cell electric vehicles [4], are among many other such applications. The literature reports a large number of topology, and design variants of a DC-DC converter (DDC) as in [5]– [17] and references within, to achieve an improvement in the efficiency [18] of the DC-DC power conversion. The advent of novel configurations enables the DDC to make a shift from conventional single-input-single-output (SISO) based two-port DDC configuration to the multi-input-multi-output (MIMO) based multiport designs. This article highlights the need of this structure shift by detailing the SISO, multi-input-single-output (MISO), single-input-multi-output (SIMO), and the MIMO DDC structures. Afterward, this brief discusses time-domain simulations of each of these structures to confirm the aforesaid structure shift.

DC-DC Converter and Its Multiport Interface

The recent advancements in renewable energy technologies is empowering residential consumers to meet their energy requirements from locally installed renewable energy devices and energy storage devices. In this context, the adjacent microgrids can interact and share these resources using a stable strategy through which economic, environmental and operational advantage can be gained. In this paper a three-level hierarchical control is introduced into residential houses to effectively share the power between houses coming under the community microgrid in such a way that users will get power at an optimized price. The hierarchical control algorithm is developed for primary control (Local control center), secondary control (Microgrid control center) and tertiary control (Upstream control). This paper shows that implementing hierarchical control for the residential distributed generation paves way for the power-sharing across different community grids thereby upgrading the existing AC smart grid operation.

Hierarchical Control of Community Grid for Residential Houses

One of the major challenge in the power generation is heavily depends of thermal power plant based on coal, at the same time for construction of coal based thermal plant there is restriction from environment aspects, so it is necessary to promote renewable energy like solar and wind energy generation. In case of installing the hybrid energy system, the main causes behind requirement of this installation is the intermittency of various energy resources and unbalanced quantity of sources of energies. The performances of solar PV and wind turbine connected hybrid generating systems are much better in conditions where the sunbeam and wind shifts their rate of availability based on the seasonal changes. A hybrid arrangement of combining the power harnessed from both the wind and the sun and stored in a battery can be a much more reliable and reliable and realistic power source. But, still the load can be powered through the energy stored in the batteries even when there is absence of solar or wind. Hybrid system is usually built for design of system with lowest possible cost and also with maximum reliability. The high cost of solar PV cell makes it less competent for larger capacity designs.

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Modelling, Simulation and Analysis of DC & AC Outputs using Hybrid PV and Wind Power System for Remote and Hilly Areas

With the increasing use of power electronics in all types of appliances, and with the increasing penetration of solar PV, distribution of power in the DC form is becoming attractive This paper brings together various concerns that have been expressed in DC distribution at low voltages for consumption in domestic and other building needs The paper presents various arguments and attempts to arrive at a solution from various points of view A suitable voltage level of 48 V, and a suitable distribution scheme are presented along with some field experiences of installation of such systems

Rajesh Kunnath

Papers

Low voltage DC distribution - are we ready yet?