Manual Frequency Restoration Reserve (mFRR)

Manual Frequency Restoration Reserve (mFRR)

Manual Frequency Restoration Reserve, also called mFRR, is a process for restoring the frequency and power balance in the power grid. It is activated manually or semi-automatically by grid operators in response to a disturbance on the grid, such as a sudden loss of generation or an increase in demand.

Manual Frequency Restoration Reserve (mFRR) ilustrace

mFRR is a type of ancillary service, it works as a tertiary reserve. It is used when there are longer-lasting irregularities in the power system that cannot be fixed alone by the other balancing services - primary and secondary reserve (FCR or aFRR).

When Is mFRR Activated?

In an electrical power system, the balance between generation and demand needs to be constantly maintained to ensure stability and reliability of the system and prevent blackouts. 

Variations in electricity supply or demand and unexpected disruptions, such as the sudden loss of a power plant or transmission line can lead to frequency deviations. Frequency is a crucial parameter in power systems. Maintaining it within a specified range is essential for the proper functioning of electrical equipment and the stability of the entire grid.

When the frequency deviates from its nominal value (usually around 50 or 60 Hz, depending on the region), it indicates an imbalance between generation and demand. To restore the frequency to its desired level, power system operators utilize frequency restoration reserves. These reserves consist of different types of reserves - FCR, aFRR and mFRR.

How Does It Work?

mFRR is specifically designed to address short-term frequency deviations. It involves the rapid activation of reserve power sources, such as hydroelectric plants, energy storage systems or any kind of conventional power plants. These resources have to be capable of quickly increasing or decreasing their output. The activation will inject additional power into the system and help restore the frequency back to its nominal value.

Once the frequency has been restored, the mFRR resources are deactivated and returned to their normal operating state.

According to the European Network of Transmission System Operators in Europe (ENTSO-E), mFRR has to be fully operational after 12.5 minutes and must be available for at least 5 minutes. The responsibility for providing this reserve and managing imbalances is assigned every 15 minutes to different Balancing Service Providers (BSPs) through auctions.

What Kinds of Ancillary Services Are There? What Are the Differences?

As we mentioned before, mFRR is a type of ancillary service. Just as aFRR and FCR - These three all describe different balancing services. These products vary in their activation times and the way they work to balance energy.

FCR stands for Frequency containment reserve and is also known as primary reserve. Primary reserve is used to quickly stabilise the grid in 30 seconds (automatically activated in the generator of the power plant). For instance, hydropower plants and battery generators instantly adjust the amount of electricity available in response to a frequency deviation throughout Europe. Primary reserve is used only for initial stabilisation and is augmented by secondary control as soon as possible so that FCR can be prepared for the next activation. 


aFRR stands for automatic Frequency Restoration Reserve and is also known as secondary reserve. Secondary reserves must be activated in either 7.5 minutes or 5 minutes depending on the country. aFRR is provided by many different device types, the main requirement is that they can be fully activated within the required time. It is possible to combine devices together, such as a battery and biogas plant to create one device that is both quick to activate and also able to be activated for a longer duration.

mFRR stands for manual Frequency Restoration Reserve also known as tertiary reserve. Devices operating on mFRR must be activated within 15 or 12.5 minutes depending on local laws. These devices are activated manually, meaning a dispatcher will alert the device operator to activate the device at the specified time.

How Can I Participate in Ancillary Services?

As an energy asset owner, you may be interested in finding ways to create more value from your assets. Nano Energies has expertise in ancillary services and can help you optimize the operation of your assets and increase their value. By partnering with us, you can take advantage of our advanced technology and expertise to make informed decisions about how to best manage your energy assets. If you want to learn more about how we can help you, don't hesitate to contact us for more information. We would be happy to speak with you and answer any questions you may have.

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