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) renewable energy (photovoltaic, PV, and wind) and batteries (in particular electric vehicles) operate natively in DC, and the acceleration of renewable energy uptake reinforces this interest, (2) the proportion of energy consumed in DC at home is high (50% in 2018) and growing sharply (80% by 2030) and (3) innovation and falling 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, be a source of simplification and improve the energy efficiency of the electrical system.
Highlights
DC solutions, particularly 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.
Challenges and opportunities for DSOs
- DC grids have several challenges to overcome. Firstly, protection systems and DC circuit breakers need further development.
- There is a general lack of standardisation (especially in terms of voltage levels, other specifications, interoperability, and commissioning procedures), and DC installation costs are currently high due to the required power converters.
- Power converters are still not as efficient as AC transformers and have a lower lifespan.
- For wind or PV plants, storage units or 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. A DC line could allow connecting two areas by controlling the flows between them.
EDSO 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, economic and regulatory aspects of DC networks.
- DSOs should mobilise to play an active role in the development of standards for DC distribution networks.
- To ensure the safety of operations (power protection and control, etc.) experience needs to be gained via pilot projects.
Last update: 28 September 2023