The secondary control reserve (SRL) is an important component of the control reserve in the power grid, which helps to compensate for medium-term imbalances between power generation and consumption and to maintain grid stability. In contrast to the primary control reserve, which reacts within seconds to sudden changes, the secondary reserve acts more slowly, but over a longer period, and is therefore a second line of defense for maintaining grid stability.
Functioning of Secondary Control Reserve
The secondary control power reacts more slowly than the primary reserve, but faster than the tertiary reserve, to fluctuations in the power grid. It is required to compensate for medium-term imbalances between power generation and consumption and to stabilize the grid frequency. Typical use cases for secondary control power include sudden load changes or failures of power generation plants. It plays a central role within the control area in which the stability and security of the power grid must be guaranteed.
Actors and provision of secondary reserve
The secondary reserve is provided by various actors, including easily controllable and fully automatically switchable power plants as well as Virtual Power Plants. Typical plants that can provide secondary reserve include:
- Pumped-storage power plants are able to switch quickly between pumping and turbine operation and thus react flexibly to fluctuations in the power grid. These plants can also be used for the minute reserve if short-term adjustments are necessary.
- Gas turbines can be started up or shut down within a few minutes and are therefore well suited for the provision of secondary control reserve and as part of the control energy required for grid stability.
- Virtual power plants are combinations of various decentralized energy generation and storage plants that are controlled via a central control unit. They can provide secondary control power from a variety of sources, including biogas plants, hydropower plants and electricity storage.
In the event of grid fluctuations lasting longer than 15 minutes, the secondary reserve is replaced by the longer-term tertiary reserve, which is used in such cases to stabilize the grid frequency.
Auction and activation of secondary control reserve
Auction
The provision and remuneration of secondary control reserve takes place via auctions and activations by the transmission system operators (TSOs). Providers of secondary control reserve can register their capacities on the corresponding platforms and participate in the auctions to offer their control energy.
Activation
In the event of a need on the part of the grid operators, the plants for the provision of secondary control reserve are activated and remunerated accordingly. This activation usually takes place in accordance with the requirements of the respective control area.
Capacity price and energy price
The capacity price and the energy price are important parameters in the remuneration of secondary control reserve. The capacity price is paid for keeping the secondary control reserve available, while the energy price is calculated for services actually provided. The exact conditions are determined within the framework of the auctions and can vary depending on the market situation. In this context, the distinction between secondary control reserve and other forms of control energy, such as primary control reserve and minute reserve, is important.
Difference to primary and tertiary reserve
The SRL complements the primary and tertiary reserves to keep the power grid stable and ensure grid quality.
- Primary control reserve (PRL) reacts within a few seconds to sudden failures of power generation plants or loads and serves to stabilize the grid frequency in the short term.
- Tertiary reserve is used in the event of longer-term grid fluctuations and serves to stabilize the grid frequency in the longer term.
Summary
The secondary control reserve (SRL) plays a decisive role in maintaining grid stability and ensuring a reliable power supply. By using various technologies and business models, the challenges associated with the provision of secondary control reserve can be successfully overcome. The integration of secondary control into the overall system of control energy is of central importance in order to ensure a reliable energy supply within the control area.
Note: Please note that the Wiki entry secondary control reserve (SRL) is for information purposes only and does not replace legal advice. be.storaged GmbH assumes no guarantee for the completeness, accuracy and timeliness of the information in this entry.
