All about Frequency Control

Ancillary services ensure a proper operation of the power grid. The grid operators (transmission grid operators and distribution grid operators) are responsible for ancillary services. To ensure a reliable power supply, it is necessary that frequency, voltage, and power load remain within certain limits. This does not happen automatically, but through continuous corrections: namely, ancillary services. The most renowned service is probably the frequency control/balancing energy. Even in the event of a blackout, ancillary services help restart the power grid as quickly as possible. Ancillary services can be divided into four sections : Frequency measure, voltage measure, supply reconstruction, and operational management.

mFRR is the manual Frequency Restoration Reserve that helps to stabilize the frequency of the electricity grid. In most countries the TSO (Transmission System Operator) is responsible for its procurement and activation. The mFRR (also R3 or tertiary reserve) helps to restore the required grid frequency of 50 Hz (or in some countries of 60 Hz). This tertiary control reserve intervenes when there are longer lasting deviations in the power grid that cannot be resolved solely by the other upstream balancing services (FCR or aFRR). 

mFRR must be, according to the guidelines proposed by the European Network of Transmission System Operators of TSO in Europe (ENTSO-E), fully deployable after 12.5 minutes and has a minimum duration period of 5 minutes. Different auctions determine which Balancing Service Provider (BSP) holds back capacities and/or delivers the reserve in case of imbalances for each quarter hour.

When Next Kraftwerke expanded its operations to Belgium in 2014, one of its goals was to convince the transmission grid operator Elia to open its automatic Frequency Restoration Reserve (aFRR) market for all technologies. aFRR, also known as secondary reserve, has historically been provided by a handful of gas fired power plants operated by two or three companies.

The COVID-19 pandemic shakes up the world – but the power grid in Europe remains stable. What ensures this stability and how do the electricity markets in Germany and Europe react to the situation?

Ecotricity from Great Britain is the first green electricity company providing green energy solutions since 1996. For their future projects, the Stroud based company turned to Next Kraftwerke for setting up a Virtual Power Plant based on its software-as-a-solution NEMOCS. We asked Mark Meyrick, Head of Trading and Smart Grids at Ecotricity, and Tobias Weghorn, NEMOCS product specialist at Next Kraftwerke, about the first steps in setting up a VPP of their own.

In the energy industry, the term ‘merit order’ describes the sequence in which power plants are designated to deliver power, with the aim of economically optimizing the electricity supply. The merit order is based on the lowest marginal costs. These are incurred by a power plant and refer to the cost of producing a single megawatt hour under recent conditions. The merit order is separate from the fixed costs associated with a power generation technology. According to the merit order, power plants that continuously produce electricity at very low prices are the first to be called upon to supply power. Power plants with higher marginal costs are subsequently added until demand is met.

The merit order is just one possible model for creating a functional electricity market. It assumes that power plant operators are always trying to cover the cost of the next megawatt hour produced; they would not produce it otherwise. Power plants with low marginal costs can therefore offer a lower price for their electricity, and they are in turn called upon more often than power plants with higher marginal costs. The merit order is designed to shed light on how pricing works on the electricity market; it is not a fixed "law" that coordinates the use of power plants.

It is well-know that household alternating current (AC) in Germany and Europe has a frequency of 50 Hertz (Hz), while other parts of the world run on 60 Hz. What is less known is that this utility frequency (also known as mains frequency or grid frequency) also provides information about the ratio of electricity generation to electricity consumption in a power grid. If the frequency drops too low, there is not enough electricity in the grid; if the frequency increases too much, there is too much electricity in the grid. An intelligent supply-demand mechanism and a functional system for ancillary services to compensate for frequency deviation is necessary to keep the utility frequency at a stable 50 or 60 Hz.