Technological change in the power grid

Three things in particular are needed for the stable operation of the electricity grid: A strong transmission grid that can transport power efficiently over long distances, a distribution grid that collects the power of renewable energy plants, or RE plants for short, and brings it regionally to the localities to the consumers. And: both grids, transmission and distribution grid, must be able to react flexibly to fluctuations in generation and load – and maintain stability in the process. The Laboratory of Electrical Energy Supply using Renewable Energies (E5), headed by Professor Jutta Hanson, conducts research in all three of these areas.

For the long-range transmission of electrical power from large solar or wind farms to areas with high consumption, a new technology will establish itself that supports the existing high-voltage three-phase transmission grid (HVDC) in the transport of power: High-voltage direct current transmission, or HVDC, is being used to create corridors with regulated power transmission. In addition to power control, frequency control of HVDC is another feature that can enable stable operation in the future electrical power grid. Innovative frequency control is needed because the elimination of conventional power plants with their mass inertia means that power imbalances in the electrical energy supply grid must be compensated for more quickly or differently than before.

Generation centres far away from the consumers also require possible grid disconnections, the so-called system splits. High-voltage direct current transmission can contribute to the stable continued operation of the asynchronous grid islands that exist after the grid separation by ensuring a regulated power flow between these islands. Thus, HVDC systems are able to prevent large-scale power outages.

The distribution grid is also experiencing major changes: Due to the increasing share of renewable energies and the increased electrification in the transport and heating sector, there are greatly changed load situations. In order to enable the operation of the distribution grids without violating limit values, new concepts for grid operation are needed in addition to targeted expansion measures. Grid-serving operating and control concepts for the generation plants connected to the distribution grid continue to ensure stable and safe operation.

Another challenge for the electrical power grid: RE plants, and here especially plants with solar and wind energy, have a volatile power feed-in. However, there must be a power balance in the electricity grid at any given moment. This requires flexibilities that ultimately help to ensure that the full potential of renewable energies can be exploited.

One possibility to use local power surpluses is the direct coupling of neighbouring distribution grids, which has not been used so far. For this purpose, comparable to HVDC in the transmission grid, power flow regulating equipment, so-called “Unified Power Flow Controllers” (UPFC) can be used.