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1. MVDC and LVDC networks

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Although the transmission and distribution of electricity are almost exclusively carried out in alternating current (AC), certain trends call for a reconsideration of the interest in direct current (DC):

  1. The uptake of renewable energy (photovoltaic and wind) and batteries (in particular electric vehicles), which natively operate in DC, is accelerating.
  2. The proportion of energy consumed in DC at home is high (50% in 2018) and growing sharply (80% projected by 2030).
  3. Innovation and fast-decreasing costs in power electronics are making the use of DC increasingly economical.

The use of direct current could allow limiting conversions on the distribution network, representing a source of simplification and improving the energy efficiency of the electrical system.

Highlights

DC solutions, in particular for the distribution network, are raising great interest, with numerous demonstrators worldwide and, as it appears, a proactive industrial policy in China. Standardisation of DC networks is of critical importance, even more so for low voltage DC (LVDC) to enable the development of appliances. The International Electrotechnical Commission (IEC), and the Institute of Electrical and Electronics Engineers (IEEE) have all started standardisation work on medium voltage (MV) and LVDC networks.

Opportunities for DSOs

DC grids are a solution of interest for some relevant use cases. 

  • For wind or photovoltaic (PV) plants, storage units and charging stations, a DC connection could be a relevant solution from a technical-economic point of view.
  • Microgrids: MVDC or LVDC or hybrid microgrids could be developed.
  • Control of power flows: DC lines could allow connecting two areas by controlling the flows between them.

Challenges for DSOs

DC grids have several challenges to overcome:

  • Technical aspects, in the absence of global standards and within an incomplete international regulatory framework, including:
    • Definition of voltage levels; conversion topologies and electrical architectures; connection, operation, and protection.
    • Availability and sustainability of suitable hardware offerings, and equipment interoperability; metering and communication chain.
    • Concept of power quality, definition of a point of delivery (POD) in DC.
  • Non-technical aspects, within a regulatory, normative, contractual, and insurance framework built for AC systems:
    • Energy Code, quality decree, and technical decree.
    • European standard EN50160 (characteristics of voltage supplied by the DSO).
    • Suppliers’ general terms and conditions.
    • Commissioning and insurance guarantees for installations.
  • Issues related to network economics and planning:
    • Need for clear identification of use cases where DC could be part of the reference solution catalogue, based on robust comparative cost-benefit analyses.
    • Integration of DC solutions into the existing AC network and consideration of long-term impacts. Equipment robustness. Scalability.

E.DSO Considerations

  • DSOs should carry out the analyses and implement the demonstrators necessary to identify the relevant use cases of DC links.
  • DSOs should master the technical and economic aspects of DC networks and the related regulatory aspects.
  • DSOs should mobilise to play an active role in the development of standards for DC distribution networks.
  • Experience needs to be gained via pilot projects to ensure the safety of operations (power protection and control, etc.).

Potential use cases

  • AC/DC network hybridisation for greater energy efficiency.
  • High-power and/or long-length connections.
  • Controlling power flows between electric zones.
  • Connection of linear transport operators.
  • Solutions for recharging all types of electric mobility.
  • Networks for specific applications (e.g. data centres).
  • Hybrid AC/DC indoor distribution.
  • Connections for wind or PV plants, storage units or charging stations.
  • Microgrids.
  • Control of power flows.

Ongoing projects

  • ORES (Belgium) conducted a study on DC connections with the Laborelec research centre. Broadly speaking, the study shows that a DC connection for wind generation units is technically feasible but does not yet offer a sufficient cost-benefit ratio for the use case to be exploited. At lower voltage levels, the problem was a too great difference in standards between the various devices to be able to create an effective DC network (many DC-to-DC converters were needed).
  • The ASTRA-CC project was developed by i-DE (Spain) to explore the conditions for the creation of DC networks with an operation equivalent to the LV and MV AC networks. The project is currently investigating new DC secondary substation designs, converters and public DC network architectures that reduce barriers for the connection of direct current loads to the MV grid, such as renewable generation and storage systems. ASTRA-CC aims to further assess the feasibility of deploying DC public networks as a complement to the AC networks for specific applications.
  • Enedis (France) is considering implementing a project (“DC Douai”) with a field demonstrator. This would involve a LVDC line to which one PV production and two EV charging stations would be connected.
  • Enedis is also working through academic partnerships on different aspects of the DC networks and has been financing several PhD and postdoctoral works:
    • “Hybrid AC/DC distribution network architectures: Analysis of power quality and protection aspects” (PhD, ESTIA 2020-2023).
    • “Optimisation of the architecture of a hybrid AC/DC MV/LV distribution substation: Design and sizing” (PhD, Centrale Supelec 2020-2023).
    • “DC network protection” (Post-doc, INPG 2024-2025).
    • “Stability of multi-source DC power networks” (PhD, Centrale Supelec 2025-2028).

Last update: 26 June 2025