How do you prevent a power line from overloading?

More and more often, grid operators have to contend with the fact that the forecast feed-in power from renewable energy sources is exceeded on particularly sunny or windy days. The additional generation of power can pose a risk to the specific sections of the grid. The redispatch procedure is used to counteract this danger before it happens.

Redispatching helps avoid line sections in the electricity grid overloading by regulating the feed-in power of power plants. A special feature of the redispatch procedure is the use of pairs of power plants. A power plant downstream from the bottleneck reduces its feed-in power, while the power plant upstream from it increases its output. This shifts the feed-in power without changing the total amount of electricity fed into the grid. This creates a balancing load flow to prevent the bottleneck.

Redispatch measures are required more frequently as more and more electricity is being generated by renewable energy sources. Wind power and solar plants in particular are subject to fluctuations that are dependent on the weather, which is why sufficient reactive power must be available to compensate for voltage fluctuations. Power plant operators are legally obliged to participate in redispatch measures and also receive remuneration for doing so.

The redispatch procedure is not limited to a specific control area, but can be carried out within a control area or in the entire grid. In summary, it is a central instrument for ensuring grid quality and enables the secure integration and efficient use of renewable energy sources in the existing electricity grid.

What changes did Redispatch 2.0 bring?

Redispatch 2.0, which came into effect on 1 October 2021, brought some significant changes. For example, plant operators receive financial compensation for redispatching, which is borne by the distribution system operator (DSO) instead of the respective balancing group as before. This also means that the DSO has additional efforts such as data exchange, processes and bookings.

The 2.0 version of redispatching also takes into account plants that supply less than ten megawatts (MW) of net capacity. In the original redispatch, only plants with a generation capacity of more than 10 MW were considered. The threshold has now been lowered to ≥100 kilowatts (KW), and remote-controlled systems with <100 KW are also eligible as a lower priority. The shutdown order considers renewable energy sources, high-efficiency combined heat and power plants and remotely controllable small-scale plants in subordinate order. As a result, significantly more plants are now affected by the redispatch measures than previously.

There are also some concerns about the cost–benefit ratio in the area of photovoltaic systems. Older plants in particular cannot contribute fully to system security and entail a high effort in advance in order to be integrated into Redispatch 2.0. The reason for this is that older systems need to be set up for remote control first, with modifications and adaptations of the systems being required.

Another problem associated with Redispatch 2.0 can be found among the direct sellers. A gradual introduction was not carried out even though the short introduction time of the legally anchored Redispatch 2.0 was criticised by market partners. The transitional solution has led to immense additional work on the part of direct sellers, which is worsened by the lack of clear formats and deadlines for market communications and invoicing. The discrepancy between remuneration and financial compensation leads to losses. There is also a lack of transparent communication between DSOs, which means that implementation of Redispatch 2.0 is non-transparent and leads to delays.

Although the current implementation of Redispatch 2.0 has not been without criticism, it is important to emphasise that this mechanism makes an essential contribution to ensuring system security. The difficulties described could be successfully overcome through targeted adjustments to the processes involved.

Why do we need a Redispatch 3.0?

Redispatch 2.0 has already brought meaningful changes, but there is still a need to regulate renewable energy sources and consumers. This is due to a variety of reasons:

  • 1. Lack of power plant capacity – southern Germany lacks a flexible power plant capacity of approx. 7.7 gigawatts due to the decommissioning of the nuclear and coal-fired power plants in Baden-Württemberg and Bavaria. This lack of power plant capacity could be solved by electricity from wind power in the north.
  • 2. Lack of network capacity – the planned electricity ‘motorways’ from north to south have not yet been completed and continue to be delayed. Therefore, the logical consequence is to use existing and future technologies and not to wait for grid expansion.
  • 3. New players in the field – the number of producers and consumers of less than 100 kW of nominal power is increasing significantly due to the electrification of the heat and transport sectors. The sales figures for heat pumps increased by 53 per cent in 2022 compared to the previous year, thanks to the energy crisis, in particular. We also observe strong growth in electric cars and home battery storage. These three technologies increase the demand for electricity and at the same time open up new opportunities.

This is where Redispatch 3.0 comes in. It can leverage the potential flexibility of these small plants and micro-plants to stabilise the electricity grid. In this context, the cost-based regulation of Redispatch 2.0 is not to be changed or even abolished, but a supplementary construct is to be created. A market is to be created through Redispatch 3.0 – one in which electric cars, home battery storage and heat pumps can participate. Owners who decide to connect their system to the market can hope for additional revenues. These systems can adjust their load behaviour depending on the market price, enabling, for example, an electric car to only charge during certain hours or a heat pump to shift its load profile to certain hours. A concrete implementation of the market design for Redispatch 3.0 does not yet exist, but the transmission system operators (TSOs) are developing possible concepts in initial research projects and field trials. One potential implementation would be to allow system owners to offer both a demand rate and a kilowatt hour rate. The demand rate is only used for the provision of flexibility and compensates the owner for the provision of a certain capacity. If the operating reserve is required and the flexibility is actually utilised, the delivered energy quantity is remunerated by means of the kilowatt hour rate. This division is based on the supplemental reserve market and is a tried-and-tested market design.

What are the challenges in the future?

The challenges for a successful implementation of Redispatch 3.0 range from the creation of legal frameworks to user-friendliness and the technical connection of the plants. The Clean Energy Package, which has been adopted by the EU, already includes the idea that the flexibility of decentralised micro-plants should be used to ensure grid stability. However, Germany has not yet implemented the law in national law, meaning that there is no definition of any rules for consumers currently, for example. Furthermore, an electric car driver will not participate in such a market if the effort is too high, because the additional revenue must justify the effort. In this context, it is also necessary that the legislator formulates administrative hurdles and tax law in a streamlined manner so that private individuals are not deterred.

Finally, implementation will only succeed if all systems have a BSI-compliant smart meter gateway for communications. Furthermore, real-time data exchange and data processing must be guaranteed. This is where Gaia-X comes in. Gaia-X is an initiative with the aim of developing a European cloud and data infrastructure. Its aim is to enable a trusted, independent and secure data infrastructure in Europe so that companies in the energy industry, among others, can store, process and share their data securely. Through this secure and interoperable data infrastructure, Gaia-X can indirectly contribute to the integration of renewable energy sources and in turn stabilise the power grid and reduce the need for redispatch measures. In addition, Gaia-X can help improve the efficiency of the power grid by facilitating the implementation of real-time monitoring and control systems.

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Picture Timo Hartmann

Author Timo Hartmann

Timo Hartmann is a student of business informatics at the TU Braunschweig. As a student employee at adesso he is working in the Line of Business Utilities. Within the research project VideKIS he focuses on the development of virtual power plants and especially on strategies for the implementation of processes in the context of market communication.

Picture Simon Bächle

Author Simon Bächle

Simon Bächle is writing his master's thesis in the VideKIS research project. He is investigating the economic operation of virtual power plants with the help of a mathematical optimization model. He is also working intensively on the application of data science in the energy industry.

Picture Ellen Szczepaniak

Author Ellen Szczepaniak

Ellen Szczepaniak is an experienced project manager specialising in consulting for companies in the energy industry. In her projects, she has gained experience both as a requirements engineer and scrum master in an agile environment and as an interaction room coach and management consultant in traditional projects. She is characterised in particular by her structured and analytical approach as well as her expertise in the context of the energy industry and electromobility.

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