Control power (power grid)

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The control power , also known as reserve power , ensures that electricity customers are supplied with exactly the electrical power they need in the event of unforeseen events in the power grid . For this purpose, output adjustments can be carried out at short-term in controllable power plants , quickly starting power plants (e.g. gas turbine power plants ) or pumped storage power plants can be used. Alternatively, certain electricity customers can be disconnected from the grid with load control . This separation is often only possible for a maximum period of time, so the control energy is limited as with pumped storage.

Control reserve is part of the compensation that is required in the context of the provision of energy to cover losses and to compensate for differences between feed-in and feed- out ( Section 3 EnWG ). Control reserve or control energy is the energy that the transmission system operators purchase to provide system services. The costs for the procurement of control energy are allocated by the transmission system operator to the actors responsible for load deviations in the power grid (the so-called balancing group managers ) based on the size and sign of the respective balancing energy .

In addition, the transmission system operator can automatically disconnect loads from the grid or assign setpoints to power plants to maintain system security in special operating conditions . In this way, the supply network can be stabilized and thus prevented, in extreme cases, from a load shedding and the resulting smaller regionally limited power outages or a large-scale power outage.

Need for regulation

Variation of the network frequency over 48 hours in some European and Asian countries

Via the control mechanism of the balancing group management , the market participants (balancing group managers) in the electricity markets are obliged, based on daily load forecasts, to procure as much energy on the energy markets or to generate it in their own assigned power plants as they supply metering points assigned to their balancing group or sell on the energy markets to have. As balancing group managers, the distribution network operators are also obliged to procure forecast transmission losses on the energy markets.

However, the actual load deviates from the forecast load, and this deviation must be compensated for. This follows from the physical necessity that electrical power grids cannot store energy and therefore the power fed in must correspond to the sum of the power drawn and the power loss due to transport at all times. Deviations from this result in a change in the network frequency in AC voltage networks , which is uniform (synchronous) in the entire AC voltage network: If there is an oversupply of power, there is a deviation in the network frequency above the nominal frequency; if there is an undersupply, there is a so-called underfrequency .

The deviation can be caused by both the entry and exit points. Examples are power plant failures, non-compliant reference profiles of large consumers, forecast errors in the performance of wind energy or photovoltaic systems as well as the loss of consumers in the event of power grid failures.

If there is a power deficit, i.e. additional power is necessary to bring the network frequency back to the target frequency, one speaks of positive control power . This additional power can be provided by connecting additional generation power and / or limiting consumers. In the opposite case, one speaks of negative control power , which can be provided by limiting generation power and / or additional electricity consumption. The larger a control area, the smaller the relative demand for control energy, since the causes for the fluctuations are mostly independent of one another and therefore partially compensate for one another.

Fluctuations in the mains voltage and deviations from the nominal value of the mains voltage, on the other hand, are largely determined by regional consumption and supply and are compensated for in certain areas , for example by technical equipment such as tap changers for power transformers , which are housed in substations . This ensures that the consumers connected to the network can draw an electrical voltage within a tolerance range around the nominal voltage, almost independently of the load flow.

Technical structure of the frequency control

European network systems, color-coded network networks. The spatial area of ​​the continental European network is blue. The frequency is the same at every location within a network.

The ENTSO-E (Association of European Transmission System Operators ) is responsible for coordinating operations and expanding the European network. The ENTSO-E represents 41 transmission system operators from 34 European countries.

The transmission networks regulated by the ENTSO-E are not all linked. The UCTE network, which is synchronized with a standard frequency of 50 Hz, is referenced as a "UCTE synchronous area" within the framework of the ENTSO-E specifications.

A safe and smooth network operation assumes the maintenance of the balance between energy supply and consumption. A disturbance of this balance inevitably leads to changes in the network frequency. Since a constant network frequency within a specified tolerance range is the basis of a secure energy supply, the use of mechanisms that are coordinated with one another to maintain the frequency is necessary in the event of a fault.

Frequency control in the UCTE

As part of the UCTE synchronous area, the ENTSO-E sets certain standards for frequency control. This includes the division of the task of frequency maintenance into different control levels, rules on minimum reserve capacities and cross-border energy flows. A distinction is made between the following control levels:

  • Inertia, stability without control intervention as a result of the inertial masses involved in the distributed active generator systems
  • Primary control, for active power balance, primarily via the speed control on the electrical generators of the power plants involved.
  • Secondary control, serves to maintain frequency stability. In interconnected networks such as the UCTE also for load flow control and load distribution
  • Tertiary control, also referred to as minute reserve, serves to optimize the economy in operation
  • Quaternary control, to compensate for the rate error , which is triggered by accumulated deviations in the network frequency over long periods of time
and display information about the image
Scheme of the temporal use of the different types of control reserve, idealized representation

The necessary control reserve is procured for the German transmission system operators via a common platform for standardized control reserve products within the framework of the network control network (NRV). In the course of the further coupling of neighboring markets, part of the required control power for Belgium, the Netherlands, Switzerland and Austria will also be procured on this platform.

Apart from this, the standard reserve products and tender conditions may still differ across Europe despite the standardization promoted by ENTSO-E.

Primary control

Frequency control scheme in the UCTE network

The primary control serves to compensate imbalances between physical supply and demand, with the aim of restoring a stable network frequency. By coupling the PRL markets of Germany, Belgium, the Netherlands, Switzerland and Austria, the largest primary control power market (PRL market) in Europe is created with a total requirement of over 750 MW. In a further step, the Danish network operator Energinet.dk is also planned to participate.

Since mid-January 2017, the French transmission system operator has also been participating in the international cross-border PRL cooperation between the transmission system operators in Belgium, Germany, Austria, Switzerland and the Netherlands. Since then, PRL's tender conditions for the French market have also been adjusted in accordance with the rules of cooperation. Despite a shared platform, the provision of PRL must always be carried out to a large extent on a rule-zone-specific basis. PRL imports to France are limited to 30% of RTE's requirements of 561 MW, PRL exports to 15% of RTE's requirements.

Not every power plant participates in the primary control; rather, reliable power provision must be proven through so-called prequalification.

The provision of primary reserve by participating power plants is automatically triggered by the deviation of the grid frequency from the target value. The network frequency for the proportional primary controller of the power plants participating in the primary control is compared with the setpoint frequency. If there is a discrepancy, the primary control power is activated according to the control characteristic and the frequency is supported in this way (in the event of a sudden increase in load) or a further increase in frequency (in the event of a decrease in load) is prevented.

The power plants participating in the primary control must be able to provide the entire primary control power within 30 seconds with a quasi-stationary frequency deviation of ± 200 mHz, i.e. H. Increase or decrease the power output linearly and maintain this power for up to 15 minutes. The primary control power available, the so-called primary control band, must correspond to at least 2% of the nominal power of the system.

Wind parks, solar systems and other fluctuating, renewable energy sources only contribute to the control reserve if they are combined with storage capacities to form a so-called "virtual power plant" , such as B. "Next Pool" from Next Kraftwerk GmbH or the virtual power plant from Statkrafts .

In most nuclear power plants, especially in light water reactors, a rapid load adjustment in the range of 40-100% is possible at a rate of 2% / minute. A reduction to 30% power and a rate of 5% / minute are possible if the control rods are specially designed for this. Starting up from a shutdown power plant takes several hours and, due to xenon poisoning , up to a week after an emergency shutdown. For physical reasons, nuclear power plants are therefore usually not suitable for primary control.

If the deviation is less than 10 mHz, the primary control will not be activated depending on the primary control provision used. This means that there is a dead band (insensitivity range) of 50 Hz ± 10 mHz (49.99 Hz to 50.01 Hz) in which there is no control. Within the dead band, the balance between power generation and power demand takes place exclusively via the inertia in the power system, in particular by kinetic energy (of rotation) of the electric generators and coupled to these turbomachines such as steam and gas turbines. The ability of an electricity system to cover fluctuations caused by inertia is also known as instantaneous reserve .

The frequency dependence on certain loads is advantageous for the primary control. For example, the relationship applies to an asynchronous motor . While the motor demands a higher power from the mains when the frequency increases , this effect takes place with the opposite sign when the frequency is underfrequent .

In the course of the coupling of further markets, Belgium, the Netherlands, Switzerland and Austria are also tendering part of their required primary control power on the platform www.regelleistung.net.

Secondary regulation

The secondary control also has the task of restoring the balance between physical electricity supply and demand after a difference has occurred. In contrast to primary control, only the situation in the respective control area including the exchange of electricity with other control areas is considered here. For this purpose, the planned with the actual power flows to other control areas are compared and adjusted. It must be ensured that the secondary and primary control always work in the same direction, which is ensured by monitoring the grid frequency. Primary and secondary control can start at the same time; the secondary control process should have replaced the primary control process after 15 minutes at the latest in accordance with the specifications of the network control network, so that the primary control is available again.

The amount of secondary power made available depends on the one hand on the network code and the frequency deviation, and on the other hand on the difference between the actual exchange services with neighboring networks and the exchange services declared as the schedule. The secondary control power is called up automatically; for this purpose, the corresponding generating units are connected to the transmission system operator via control technology. Generator units that provide secondary control power have to meet special requirements. The entire control power must be able to be provided within a maximum of 5 minutes, the rate of load change must be at least 2% of the nominal power per minute. For example, pumped storage power plants or conventional combined cycle or hard coal power plants are used .

Tertiary control (minute reserve)

With tertiary control (minute reserve), a distinction is made between negative and positive control energy; it primarily serves to optimize the economy. In the past, the transmission network operator requested the minute reserve from the supplier by telephone. Since July 3, 2012, the minute reserve has been automatically retrieved from the Merit Order List server (MOLS). It must be possible to provide the minute reserve capacity in full within 15 minutes, using conventional power plants or other generating units, as well as controllable loads. Electric arc furnaces in steelworks or night storage heaters are used as controllable loads .

Two options are available for the negative minute reserve:

  • The activation of additional loads in the network in the form of pumped storage power plants.
  • The partial or complete shutdown of power plants. In addition to throttling large power plants , negative control power can also be provided by the collective shutdown of combined heat and power plants (CHP systems) in the form of a virtual power plant . Such CHP systems are particularly suitable, the heat supply of which does not have to be guaranteed continuously. However, their fed-in electricity may not be remunerated according to the EEG, because parallel marketing is currently contrary to the EEG. By wind power negative minutes reserve can now be provided. For this purpose, wind turbines in a virtual power plant are regulated downwards as required using remote control and on the basis of meteorological data, the generation output of the systems and the respective signals from the network operator.

Quaternary regulation

Mains frequency deviations can accumulate over a longer period of time and cause a clock error in synchronous clocks . The limitation of the deviation is sometimes called quaternary regulation, is not necessary for the technical operation of an interconnected network, but is also available in many interconnected networks. In Europe, Swissgrid records the deviations from the coordinated universal time (UTC) on behalf of the UCTE electricity network and coordinates the correction of the phase errors according to the following rule: If the grid frequency is exceeded by ± 20 seconds, the setpoint of the grid frequency (nominal grid frequency) is increased by 10 mHz with a leading grid time to 49 .99 Hz reduced, increased to 50.01 Hz with lagging network time. Without taking into account further deviations from the target frequency, the return of a time deviation of 20 seconds then takes 100,000 s or a good day (27.77 hours).

Frequency control in Northern Europe

In Northern Europe, frequency control is based on a control strategy that differs from that in continental Europe. The first two control loops are activated automatically.

Frequency controlled normal operation reserve

Frequency controlled normal operation reserve (abbreviated FCR-N or FNR) means roughly frequency - controlled normal operating reserve . The FCR-N is activated when the frequency deviates by ± 0.1 Hz from the nominal frequency of 50 Hz. The FCR-N is designed for a change in output of 6000 MW / Hz.

The total demand for the Nordic network is 600 MW and is divided between the transmission system operators of the countries according to the annual load: In 2013 Sweden had 230 MW, Norway 210 MW, Finland 138 MW and Denmark-East 22 MW.

Frequency controlled disturbance reserve

Frequency controlled disturbance reserve (abbreviated FCR-D or FDR) translates as frequency - controlled disturbance reserve . The FCT-D is designed so that it is activated linearly between 49.9 Hz and 49.5 Hz. When the frequency drops to 49.5 Hz, FCR-D must be 50% activated within five seconds and fully activated after 30 seconds.

The need for FCR-D depends on the N-1 criterion and is usually 1000 MW. The design case is normally the failure of one of the Swedish nuclear power plant blocks Forsmark 3 or Oskarshamn 3 or a cross connection. The amount required is determined on a weekly basis. The entire FDR requirement is again divided among the TSO according to the internal N-1 security.

Fast active disturbance reserve

Fast active disturbance reserve translated means that the disturbance reserve activated quickly must be activated within 15 minutes. The aim is to restore the primary regulation.

Demand is determined at the level of each individual transmission system operator, taking into account local conditions such as network bottlenecks and design errors. Of this, Sweden has 1290 MW, Norway 1200 MW, Finland 1000 MW and Denmark 900 MW (of which 600 MW must actually be in the Denmark-East control area).

Slow active disturbance reserve

Slow active disturbance reserve roughly means slowly activated disturbance reserve and must only be able to provide power after 15 minutes.

Control areas

Germany

German transmission network from 50Hertz , Amprion , TenneT and TransnetBW

The network control network of the Federal Republic of Germany managed by Amprion is divided into four control areas, in each of which a transmission system operator is responsible for the balance of feed- in and feed-out in the electricity network. In Germany, a total of 7,000 megawatts of positive control power (additional power in the event of a bottleneck) and 5,500 megawatts of negative control power (reduction in production or artificial increase in consumption) are available. The costs for this amount to around 40 percent of the total transmission network fee.

On May 1, 2010, by order of the Federal Network Agency in Germany, the previously existing network control network of the three transmission system operators 50Hertz Transmission (formerly: Vattenfall Europe Transmission), TransnetBW (formerly: EnBW Transportnetze), Tennet TSO (formerly: E.ON Netz) were added to the fourth control area of Amprion (formerly: RWE Transportnetz Strom) expanded, so that there has been a uniform Germany-wide network control network since then. This is to prevent so-called counter-regulation, in which both positive and negative control energy is used in different control areas at the same time. As a result of the control network, less control reserve has to be kept and less control energy used, because the power surpluses and requirements of the four control areas partially offset each other. According to the Federal Network Agency, this should bring about savings in the three-digit million range.

The Federal Network Agency does not rule out even more intensive cooperation between the transmission system operators in the future. The control network could also be expanded in the direction of neighboring European countries.

Switzerland

Up until the turn of the year 2008/2009 there were a total of eight control areas in Switzerland. These were brought together under Swissgrid .

Austria

Austria was divided into two zones until December 31, 2011: Vorarlberg belonged to the control area VKW-Netz AG (which in turn belonged to the German control area block), the remaining federal states belong to the control area Austrian Power Grid (APG). Until December 31, 2010, Tyrol was part of the TIWAG network control area, but this was integrated into the APG control area on January 1, 2011 ; In the same way, on January 1, 2012, Vorarlberg was integrated into the APG network.

Northern Europe

The transmission system operators Energinet.dk (Denmark), Fingrid (Finland), Statnett (Norway) and Svenska kraftnät (Sweden) together form the Nordic control area ( NORDEL ).

Denmark is a special case

There is a special feature in Denmark: The country is divided into two control areas, both of which are operated by Energinet.dk:

  • Denmark East (also known as DK2 , includes Zealand ) is part of the Nordic network.
  • Denmark-West (also known as DK1 , includes Jutland and Funen ), on the other hand, runs synchronously with the continental European network . Accordingly, the requirements for the control power of the continental European network must also be met in DK1.

The two Danish sub-networks are only connected directly via the HVDC submarine cable Great Belt Power Link , and indirectly via the surrounding countries: there are lines to Sweden and Germany from both DK1 and DK2.

Procurement of control power

The procurement of control reserve is carried out by the operators of the transmission networks.

Procurement in the German network control network

In Germany, as in most European countries, a tendering process must be carried out, which must be non-discriminatory and transparent ( Section 22 (2) EnWG). The German operators of transmission networks have set up an internet platform for tenders for control energy, via which a joint tender for the types of control power is processed. Since December 1, 2006, the minute reserve (tertiary regulation) has been tendered daily on a joint Internet platform and since December 1, 2007, the primary and secondary regulation has been jointly tendered monthly. Since May 2010 the four German transmission system operators have been united in the optimized network control network. On June 27, 2011, the primary and secondary regulation was switched from monthly to weekly tenders. The need for secondary control power and minute reserve is regularly checked and the tenders are adjusted accordingly; in Germany this is done quarterly.

The network uniformly regulates the dimensioning and the actual procurement as well as the use and billing of control power in all network areas. Since then, the so-called “cross-control area uniform balancing energy price” (reBAP) has applied to all control areas, via which the costs for control power are passed on to the balancing group managers . At the same time, situations are avoided in which previously positive (energy supply) and negative control power (reduction of power plant feed-in) were used in neighboring control areas.

Potential providers of control power must first pre- qualify with one of the four TSOs, i.e. they have to prove that they can actually meet the technical requirements for providing one or more types of control power. In July 2017, 64 providers were prequalified, 24 of them for primary control power, 37 for secondary control power and 52 for the provision of minute control power. The range of providers includes power plant operators and municipal utilities as well as large industrial plants.

The tendering process for control power is pay-as-bid, i.e. H. each provider receives the price offered by him when the bid is accepted. The income that different providers have achieved for an offer of identical control power can therefore vary widely in the result. The remuneration is based on a power price in € / MW, with which the provision of control power is remunerated and, in the case of secondary and minute reserve power, additionally via an energy price in € / MWh, which is paid when the control power is actually used. In the first step, the provision is assigned to the providers with the lowest service prices; in the next step, the available providers with the cheapest working prices are called depending on the current demand.

Procurement in Austria

In Austria, control power is tendered by Austrian Power Grid through regular tenders. The tendering of primary control power is regulated in Section 68 of the Electricity Industry and Organization Act (ElWOG), its cost shift in Section 67 ElWOG and the tendering and cost shift for secondary control power in Section 66 ElWOG.

Procurement in Switzerland

In Switzerland, Swissgrid has been procuring the required control power since 2009 through regular tenders on the control power market. The tenders were initially monthly, in 2012 they were replaced by weekly and daily tenders.

Control energy and renewable energy sources

With increased use of wind energy , the required control power increases; In particular, the need for negative control power (absorption of production peaks) increases. Although renewable energies can potentially provide control reserve, the current legal regulation is different: The Renewable Energy Sources Act prohibits the technically obvious solution of reducing overproduction at the source during wind peaks by shutting down the power output of the wind turbines; rather, it is legally stipulated that all available wind power is fed into the grid and remunerated. A curtailment according to § 11 EEG is currently only allowed in the case of grid congestion.

In reality, however, it has been shown that the provided control power has decreased slightly in recent years. Although the installed capacity of wind power and photovoltaic systems in Germany has tripled from 27 to 78 GW and both technologies together now produce 15% of German electricity, the required control power fell by 15% between 2008 and 2014, and the costs for control power even fell by about 50%. The causal factors for this include: a. Improved feed-in forecasts and demand forecasts, fewer generator failures and organizational improvements were considered. Even if this trend is not a causal relationship, these results indicate that there is no direct relationship between the feed-in of renewable energies and the increased control power requirement and that other factors dominate the control power demand even with a high proportion of variable feeders.

Photovoltaics with its peak power at midday can, depending on the amount of solar radiation, have a dampening effect on the demand for energy from medium-load and expensive peak-load power plants and thus also have a secondary effect on the control power, which is particularly required in the middle of the day. For the feed-in from photovoltaics, forecast programs have also been developed since 2010/2011 due to the increasing total installed capacity. In addition, the medium-voltage directive was adapted and, in July 2011, the directive for generation systems in the low-voltage network, with transition to the beginning of 2012, in order to gradually make the potential of photovoltaic systems usable for network control.

A particular problem arises in Germany from the large expansion of power generation systems with power converters , in particular photovoltaic systems. In the past, based on applicable standards, solar inverters were designed in such a way that they were automatically disconnected from the grid at a grid frequency of 50.2 Hz (i.e. the upper limit of what can be covered by the primary control power). These standards originated from times when photovoltaic systems only had a marginal share in electricity generation. Today, however, this means that when the grid frequency of 50.2 Hz is reached - which can certainly be reached in the event of a major grid disruption - a large part of the generation capacity is suddenly disconnected from the grid. This problem is avoided for new systems that were and will be built after April 1, 2011: The manufacturers of solar inverters now have to set the switch-off frequency equally between 50.2 Hz and 51.5 Hz or implement a frequency-dependent active power reduction. On July 26, 2012, the System Stability Ordinance (SysStabV) came into force. This regulates the retrofitting of certain photovoltaic systems. According to this, the retrofitted photovoltaic systems will no longer be permanently disconnected from the grid at a frequency of 50.2 Hertz (Hz), but in a stepped process.

Costs for control reserve

The costs for control power can be considerable, as it is covered by peak load power plants (which can often be ramped up in less than a minute) , the production costs of which are comparatively high. Depending on the supply situation in the power grid , up to 1.50 euros per kilowatt hour - six times more than end consumers pay - can be charged by the energy suppliers. As a rule, however, the average balancing energy price is at the level of the electricity exchange price, since undercover control areas are offset by overcovered ones.

The increased demand for control reserve required by the expansion of renewable energies was in the range of approx. 300 to 600 million euros for the control area Germany in 2006, whereby transaction costs and other non-related cost factors are included in this total.

literature

  • Panos Konstantin: Practical book energy industry. Energy conversion, transport and procurement in the liberalized market . Springer, Berlin 2007, ISBN 978-3-540-35377-5 , Chapter 9.1.5 Control and balancing energy.
  • Tobias Weißbach: Improvement of the power plant and grid control behavior with regard to schedule changes on the trading side . Stuttgart 2009, ISBN 978-3-18-358606-6 ( elib.uni-stuttgart.de [accessed on December 13, 2014] dissertation ).
  • ENTSO-E (Ed.): P1 - Policy 1: Load Frequency Control and Performance [C] . ( entsoe.eu [PDF; 339 kB ; accessed on April 4, 2017]).
  • Tobias Weißbach: Improvement of the power plant and grid control behavior with regard to trading-side schedule changes Dissertation, Faculty of Energy, Process and Biotechnology of the University of Stuttgart, 2009, elib.uni-stuttgart.de (PDF; 3.0 MB).

Web links

Individual evidence

  1. ^ P1 - Policy 1: Load Frequency Control and Performance [C]. (PDF) Retrieved January 5, 2017 .
  2. ↑ Network control network. Retrieved January 1, 2017 .
  3. ↑ Market for control power in Germany. Retrieved January 1, 2017 .
  4. ↑ a b International PRL cooperation - coupling the markets of Germany, Belgium, the Netherlands, Switzerland and Austria. Retrieved January 1, 2017 .
  5. ↑ Joint PRL tender with RTE from January 2017. Accessed on January 5, 2017 .
  6. ↑ prequalification. Retrieved January 1, 2017 .
  7. ↑ a b TransmissionCode 2003 Appendix D 1: Documents for prequalification for the provision of primary control power for the TSO (as of August 2003). Association of network operators VDN e. V. at VDEW, accessed on March 10, 2015 .
  8. ↑ Federal Ministry for Economic Affairs and Energy Germany: What actually is a "virtual power plant"? Retrieved January 28, 2019 . in connection with pre-qualified providers for each type of control energy. Amprion , TenneT , TransnetBW and 50Hertz , December 20, 2018, accessed on January 28, 2019 .
  9. ↑ Load-changing capability of German nuclear power plants, International Magazine for Nuclear Energy, 2010 ( Memento of the original from July 10, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / de.areva.com
  10. ↑ German Energy Agency [dena] (Ed.): System services 2030 . Summary of the central results of the study "Safety and reliability of a power supply with a high proportion of renewable energies" by the project steering group. Berlin February 11, 2014, Chapter 3.1 Momentary reserve, p. 8–10 ( dena.de [PDF; 438 kB ; accessed on March 10, 2015]). dena.de ( Memento of the original from 23 September 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.dena.de
  11. ↑ momentary reserve. In: EnArgus: Zentrales Informationssystem Energieforschungsförderung. Archived from the original on March 10, 2015 ; accessed on March 10, 2015 .
  12. ↑ Primary control, secondary control, minute reserve. Amprion, accessed July 7, 2013 .
  13. ↑ Joint tender for minute reserve capacity. 50Hertz, Amprion, Transnet BW, Tennet, accessed December 5, 2014 .
  14. ↑ Christoph Speckamp: Merit-Order-List-Server - nationwide uniform management of minute reserve capacity. In: http://www.soptim.de/de/blog/detail/Software-von-SOPTIM-managt-zuverlaessig-Markt-fuer-M Minutenreservleistungs-13T/
  15. ↑ Minute reserve power - control energy from wind. In: www.statkraftdirektvermarktung.de. Retrieved September 22, 2016 .
  16. ↑ swissgrid on grid time deviation ( memento of the original dated August 31, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.swissgrid.ch
  17. ↑ a b c d e f g h i Agreement (Translation) regarding operation of the interconnected Nordic power system (System Operation Agreement) . (PDF) ENTSO-E, June 13, 2006. Appendix 2 - Operational security standards of April 25, 2013; accessed on December 13, 2014.
  18. ↑ a b c d e Christer Bäck (Svenska Kraftnät): Current balancing method's in Nordel area. ( Memento of the original from December 14, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF, pp. 10-21). Nordic System Operation Workshop, April 13, 2010, Arlanda, accessed December 13, 2014. @1@ 2Template: Webachiv / IABot / www.entsoe.eu
  19. ↑ "Against each other" is a thing of the past in Germany - network regulation network implemented nationwide since May 1, 2010 . ( Memento of the original from January 12, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. EnBW, May 1, 2010; Retrieved January 1, 2011 @1@ 2Template: Webachiv / IABot / www.enbw.com
  20. ↑ Federal Network Agency for Electricity, Gas, Telecommunications, Post and Railways: Network regulation network for German electricity networks. April 4, 2010, archived from the original on July 29, 2012 ; Retrieved May 14, 2010 (press release).
  21. ↑ Swissgrid is taking over the Swiss transmission network ( memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 974 kB) @1@ 2Template: Webachiv / IABot / www.swissgrid.ch
  22. ↑ APG press release: APG control area manager for all of Austria from 2012
  23. ↑ a b E Agreement (Translation) regarding the operation of the interconnected Nordic power system (System Operation Agreement) . (PDF) ENTSO-E, June 13, 2006; accessed on December 13, 2014.
  24. ↑ a b Electricity interconnections . ( Memento of the original from February 9, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Energieset.dk; Retrieved December 13, 2012. @1@ 2Template: Webachiv / IABot / www.energinet.dk
  25. ↑ a b www.regelleistung.net
  26. ↑ Determination of the need for secondary control power and minute reserve . regelleistung.de
  27. ↑ Prequalification for the provision and provision of control power . regelleistung.de; Retrieved September 12, 2013.
  28. ↑ Prequalified providers for each type of control energy . As of July 14, 2017, regelleistung.de; accessed on October 6, 2017.
  29. ↑ Marianne Diem: What revenues does the balancing energy market offer. Retrieved January 5, 2017 .
  30. ↑ Grid control. Austrian Power Grid, accessed on July 6, 2013 .
  31. ↑ System services. Swissgrid, archived from the original on August 31, 2011 ; Retrieved July 6, 2013 .
  32. ↑ Adjustments in the AS market. (PDF; 35 kB) (No longer available online.) Swissgrid, July 23, 2012, archived from the original on December 7, 2015 ; Retrieved July 6, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.swissgrid.ch
  33. ^ Lion Hirth, Inka Ziegenhagen: Balancing power and variable renewables: Three links . In: Renewable and Sustainable Energy Reviews . tape 50 , October 2015, p. 1035-1051 , especially p. 1041 , doi : 10.1016 / j.rser.2015.04.180 .
  34. ↑ Markus Fürst: The 50.2Hz problem. (PDF; 713 kB) January 19, 2011, accessed on July 7, 2013 (presentation at the BMWi discussion platform “Future-proof networks and system security” ).
  35. ↑ Forum Netztechnik / Netzbetrieb im VDE [FNN] (Ed.): Framework conditions for a transitional regulation for frequency-dependent active power control of PV systems on the LV grid . Technical note. Berlin March 2011 ( vde.com [PDF; accessed on January 23, 2017]).
  36. ↑ BDEW: System Stability Ordinance, July 2012
  37. ↑ Overtime / underflow billing for electricity. BDEW
  38. ↑ Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU): Background information on the EEG experience report 2007. ( Memento of December 29, 2009 in the Internet Archive ) (PDF; 124 kB).