While direct current transmission lines are already established in the high and extra-high voltage range (HVDC), areas of application in the field of low and medium voltage direct current systems (LVDC, MVDC) are currently developing rapidly, as new fields of application for direct current systems are emerging in the course of the energy transition in the connection of photovoltaics and wind power to public grids, at the interfaces to electromobility and to storage systems. DC technology also plays a key role in the energy transition in the area of industrial power supplies, as it offers greater flexibility, energy efficiency gains and material savings compared to traditional AC supplies.
However, there are also numerous technological questions that require a very specific research and testing infrastructure to answer them.
- New, efficient topologies for DC-DC and DC-AC conversion
- Innovative DC protection concepts, e.g. based on current limiting or semiconductor-based switch-off of short-circuit currents
- Design of application-specific protective devices and fuses
- Earthing systems and corrosion with DC earth currents
- Insulation materials and insulation systems and their monitoring
- Interoperable, future-proof automation technology for DC grids
The DC Hub Austria exploratory project between the IHS and the AIT is investigating the feasibility of a research and demonstration facility for a medium-voltage direct current distribution system at the AIT site in Seibersdorf. This plant is intended to promote technology development in the field of medium-voltage direct current systems through research infrastructure. The plant is intended to act as a catalyst for new developments and provide infrastructure that small and medium-sized industrial companies are unable to build. The feasibility, advantages and limits of MVDC systems must be demonstrated and researched in practice. Despite dynamic market development in the field of direct current technology, the boundary conditions for a research and demonstration plant for an MVDC at a specific location are complex. On the one hand, it is necessary to define an adequate and advantageous long-term research infrastructure in a dynamic environment; on the other hand, a sustainable operator model must be developed, which should include research topics as well as the productive use of the infrastructure for energy transport.
While there are already a number of industrial and scientifically operated demonstrators in the field of LVDC (e.g. sites of the German DC industry project, DC laboratory at EPFL, several DC supply systems for industrial sites/production facilities that already exist or are currently under construction, high degree of maturity in the field of LVDC on-board electric mobility systems), there are only a few MVDC demonstrators. In order to achieve the necessary increase in transmission capacity for renewable energy, an existing AC connection in the UK, for example, was converted to MVDC. As this is a transmission system that has been in operation for a long time and consists of various cable types (oil/paper-insulated cables, earth cables and XLPE cables) and an overhead line, the nominal DC voltage was set at ±27 kV (peak value of the 33 kV AC voltage). MVDC systems are also being built in the densely populated Asian centres, such as in South Korea, where a new MVDC substation is currently being constructed.
The project aims to realise a DC Hub Austria for the first time as a platform for integrating and testing innovative medium-voltage DC solutions. It would currently be the first system with a connection to wind, photovoltaic, electrolysis and fast-charging systems with a significant output and would also be available as an open platform for scientific and industrial users. The aim is to achieve a targeted increase in the technology readiness level of MVDC for various areas of application in the public and non-public energy supply sector. The plan is to realise the DC Hub Austria in an R&D project following the exploratory study. The aim is to fulfil the requirements of industry in the coming years. One example of this is the choice of operating voltage for the DC Hub (±10 kV to ±50 kV). As the voltage increases, so does the special status of the DC hub, but also the costs and the basis from which possible components can be selected.
