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Pools of wind farms can provide part of the control reserve required in the German electricity grid.
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Control reserve supplied by renewables
Projektinfo 08/2014
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Stabilising the grid with wind power

In future it is intended that photovoltaic systems and wind farms contribute more to the stability of the electricity grid. They could then replace some of the fossil fuel capacities that until now have had to be used for the sole purpose of balancing out frequency variations. In a study, methods have been developed that can be used for intermittent renewable energies when bidding to supply control reserve as part of regular tendering periods. In addition, the study is also concerned with developing procedures for verifying the provision of the power. In future a pool of wind farms will be able to provide part of the control reserve required in the German electricity grid.

Electricity always needs to be generated in the moment when it is required by loads. The electricity grid requires a balanced ratio between production and consumption at all times. It must reliably maintain a frequency of 50 Hertz in Europe with fluctuations that are as small as possible. In Germany this stability is provided by the four major transmission system operators. They are responsible for balancing out variations between generation and consumption. In order to balance out temporary production surpluses on the one hand and the temporarily higher demand for electricity on the other, the system requires reserves for restoring the nominal grid frequency. This system service is called control reserve and is traded in different qualities and special auctions. With the introduction of direct marketing, the reform of the 2012 German Renewable Energy Sources Act created the legal provisions enabling wind farms to participate in this market.


In collaboration with industry partners, the Fraunhofer Institute for Wind Energy and Energy System Technology IWES has developed methods that in future will enable wind turbines to provide control reserve. The first component is a tender process that enables operators to participate in the auctions. Using probabilistic forecasts that combine a capacity with a probability, several wind farms can calculate their possibilities together as a pool. This primarily involves the minute reserve power that must be provided on a quarterly hour basis and is re-tendered on workdays. It is also known as tertiary reserve. The second component is a method for verifying the provision of control reserves that is suitable for intermittently fed renewable energy. In the later billing it needs to be differentiated between how much control reserve was only offered by the wind farms and how much control reserve was actually activated. Compensation and remuneration for services rendered are already being paid in the market for this purpose. For this verification, the researchers compared two different systems. The first system provides verification using the scheduled generation as a reference value. The second system uses the grid feed-in that would have been possible by the wind farm as a reference for the verification.

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Project management
Fraunhofer IEE

Industrial partners
Amprion GmbH

Industrial partners

Industrial partners
Energiequelle GmbH

Industrial partners
TenneT TSO GmbH


BINE-Projektinfo 08/2014
(PDF, 4 pages, 0.8 MB)


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