Abstract
Direct current (DC) microgrids (MG) constitute a research field that has gained great attention over the past few years, challenging the well-established dominance of their alternating current (AC) counterparts in Low Voltage (LV) (up to 1.5 kV) as well as Medium Voltage (MV) applications (up to 50 kV). The main reasons behind this change are: (i) the ascending amalgamation of Renewable Energy Sources (RES) and Battery Energy Storage Systems (BESS), which predominantly supply DC power to the energy mix that meets electrical power demand and (ii) the ascending use of electronic loads and other DC-powered devices by the end-users. In this sense, DC distribution provides a more efficient interface between the majority of Distributed Energy Resources (DER) and part of the total load of a MG. The early adopters of DC MGs include mostly buildings with high RES production, ships, data centers, electric vehicle (EV) charging stations and traction systems. However, the lack of expertise and the insufficient standards’ framework inhibit their wider spread. This review paper presents the state of the art of LV and MV DC MGs in terms of advantages/disadvantages over their AC counterparts, their interface with the AC main grid, topologies, control, applications, ancillary services and standardization issues. Overall, the aim of this review is to highlight the possibilities provided by DC MG architectures as well as the necessity for a solid/inclusive regulatory framework, which is their main weakness.
Highlights
In electrical microgrids (MG), as in all sectors of modern technology and applications, the need for sustainability in terms of reducing the energy footprint is considered to be a major priority
The purpose of this review is to provide an overall framework of the Direct current (DC) MG capabilities, addressing all their main aspects and highlighting their importance in future grids and power distribution applications
Special attention is paid to the Dual Active Bridge (DAB), the minimization of the core’s volume, losses and cost, and the optimal incorporation of the three-stage Solid State Transformer (SST) in modern applications [30,31]
Summary
In electrical microgrids (MG), as in all sectors of modern technology and applications, the need for sustainability in terms of reducing the energy footprint is considered to be a major priority. According to the European Union (EU) targets of 2020, the greenhouse gas emissions need to be reduced by at least 55% by 2030, compared to 1990 levels [1] In order for such goals to be achieved, the reduction in fossil fuel-based energy production is required. In order for the production to meet the demand curve, the utilization of Energy Storage Systems (ESS) is considered to be an effective solution. For sustainability-related reasons, the combination of distributed RES (especially PV systems and WGs) with BESS has created a new field of Energies 2021, 14, 5595 has created a new field of research and development, promoting the decarbonization, autonomy and cost efficiency of MGs [6]. The purpose of this review is to provide an overall framework of the DC MG capabilities, addressing all their main aspects and highlighting their importance in future grids and power distribution applications
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