Network control network

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Figure 1: The figure shows an example of the horizontal structure of individual control areas (RZ A to E). The “control programs” describe the planned exchange of energy using timetables. In the case of congested borders, the free capacities (NTC congestion) between the individual control areas must be taken into account. The planned energy exchange must not exceed the capacities.

The term network control network (NRV) describes a concept that optimizes the balance between consumption and generation of electrical power (system balance) in interconnected power grids by avoiding the simultaneous activation of positive and negative control power , provided that the network capacities and network security allow it .

Figure 2: The horizontal structure of the control areas (RZ) was supplemented by the NRV ("NRV programs", green arrows). The previous exchange according to Figure 1 remains. Control areas that are undercover (red) receive additional energy from control areas that are covered (blue) as part of module 1. The opposite call for control power between the individual control areas is avoided. The free capacities are still taken into account. Power flows resulting from modules 2-4 are treated identically.

Principle of the network control network

Figure 3: Modules of the network control network

The network control network consists of four modules (see Figure 3), each of which pursues different technical and economic optimizations:

Module 1: Avoidance of counter reserve activation

It is inevitable that there will be times when control areas lack power while other control areas simultaneously have excess power. The aim of module 1 is the consistent avoidance of the counteracting activation of control reserve through controlled and targeted energy exchange between the control areas. The savings potential lies in the reduction of the counteracting control power work and the associated costs.

Module 2: Common control reserve dimensioning

The aim of module 2 is the common, cross-control area dimensioning of the control power and thus the reduction of the power to be provided and the corresponding costs. In the example of the four German control areas, the dimensioning after the implementation of Module 2 is identical to a fictitious German control area.

Module 3: Joint procurement of secondary control reserve

Module 3 enables the participating transmission system operators to procure secondary control power from providers in all participating control areas. Each provider only needs to have a telecontrol connection with a transmission system operator. The savings potential with module 3 lies in the cost reduction through more competition as a result of the reduction of the technical effort for the providers. In addition, a close link between system responsibility and the physical effect of the use of control reserve is achieved. This close coupling is advantageous when it comes to assessing control power flows, for example, and especially in the event of a fault, for example in the case of an island network.

For tertiary control power ( minute reserve ), joint procurement has existed for a long time, as no telecontrol connection is required.

Module 4: Cost-optimized control reserve activation

As with a control area, the use of the control reserve is cost-effective for the whole of Germany. In the event of impending network bottlenecks, the transmission system operators can restrict or suspend the exchange of services between the control areas depending on the direction. The aim of module 4 is therefore the cross-control area, economic optimization of the control reserve activation. The savings potential therefore lies in the reduction of the costs for regular work.

Technical functionality

Figure 4: Basic principle of the SRL optimization

The basic principle of the network control network is based on "optimization software". The coordinating functions are shown in Figure 4.

The principle of operation is generally as follows: Due to fluctuations in consumption and generation that are unknown a priori, the power balance of a control area deviates from the required setpoint. The resulting balance error must be compensated for by activating secondary control power. The secondary control reserve requirements of the participating control areas are reported to the optimization software. This calculates a correction value that is added to the setpoint of the corresponding control zone. The input variable of the secondary controller changes accordingly. The sum of all correction values ​​for all control areas participating in the network control network is zero at all times.

The correction activation is calculated in a short cycle according to the corresponding algorithms.

System security and congestion management

The coordinated operation of several secondary regulators in the network control network leads to additional current flows in the network of the control zones involved and in their neighborhood. In the event of grid congestion, the cross-control area energy exchange must be restricted. Every transmission system operator therefore has the option of defining import and export barriers for the energy exchange resulting from the optimization and changing them at any time with immediate effect during operation. In an emergency, it is also possible to temporarily exit the network control network.

The network control network thus makes the most of network security and the use of synergies in the transmission network (see Figure 2).

Economic benefits of the network control network

The economic benefit of the network control network generally depends on the disturbances in the power balance in the control areas involved and the prices for control power and control energy. Since the factors vary, the savings from the network control network can only be assessed qualitatively.

An expert opinion commissioned by the Federal Network Agency in 2009 puts the savings for Germany by avoiding opposing activation of the control power (module 1) at around EUR 120 million per year. In addition, there are further savings through the reduction of the control reserve (module 2) of approx. 140 million euros per year [3,6], which directly benefit the network users.

Through the joint procurement (module 3) and the cross-control area cost optimization (module 4) of the use of secondary control power and tertiary control power ( minute reserve ), the network control network achieves a further cost-reducing effect. Simulation studies for module 4 show that the corresponding savings are in the double-digit million range.

Another advantage of the network control network is the introduction of the cross-control area uniform balancing energy price (reBAP). This means that the balancing group deviations in all German control areas are settled with the same balancing energy price.

Participants in the network control network

Figure 5: Distribution of the TSO control areas in Germany

The network control network was put into operation in Germany starting with module 1 in December 2008 and gradually expanded to include additional modules. The four transmission system operators active in Germany have set up a connection between their power-frequency controllers for this purpose. However, every network operator still has a fully functional power-frequency regulator and, in an emergency, is able to keep its control area self-sufficient in power balance.

The network control network can gradually be expanded to other control areas. The following control areas are currently participating in the network control network:

Figure 6: Germany has been a common control energy market since the NRV

Participants from abroad (only module 1)

  • Denmark: Energinet.dk since October 2011
  • Netherlands: TenneT since February 2012
  • Switzerland: swissgrid since March 2012
  • Czech Republic: ČEPS since June 2012
  • Belgium: Elia System Operator since October 2012
  • Austria: APG since April 2015
  • France: RTE since February 2016
  • Slovenia: ELES since February 2019
  • Croatia: HOPS since February 2019

International cooperation (Grid Control Cooperation, GCC)

Figure 7: Planned international expansion of the network control network

In the continental European network (→ ENTSO-E RG CE, formerly UCTE ) there are currently over 30 control areas. These are independently responsible for their performance balance. The self-sufficient network control has the advantage of a defined energy exchange and a predictable network load, but causes higher costs. Accordingly, there is also an interest in the concept of the network regulation network introduced in Germany at European level.

The easiest way to avoid activating the control power in the opposite direction (module 1) is to avoid it. Such a cooperation has been implemented with Denmark, the Netherlands, Switzerland and Belgium. A wide variety of economic, regulatory and technical harmonizations are necessary for the other modules, which is why these are usually only implemented in a second step.

Historical development of the network control network

In December 2008, three of the four German transmission system operators - EnBW Transportnetze AG (today: TransnetBW GmbH), E.ON Netz GmbH (today: TenneT TSO GmbH) and Vattenfall Europe Transmission GmbH (today: 50Hertz Transmission GmbH) - launched the first module of the Network control network put into operation. This serves to avoid an opposing call for control power.

Module 2 followed in May 2009. Among other things, this allows the transmission system operators to dimension the control power that corresponds to that of a single control area.

The formation of a uniform control reserve market for secondary control reserve (module 3) followed in July 2009 and was supplemented in September 2009 by the cost-optimized demand for secondary control reserve across control areas (module 4).

Since July 2010, the four German TSOs have also been calling up the minute reserve across all four control areas at optimal prices (except in the event of network bottlenecks or other disruptions).

Following the decision by the Federal Network Agency to implement the nationwide introduction of the network control network by May 31, 2010 at the latest, the fourth German transmission system operator, Amprion GmbH, joined the network control network in May 2010.

literature

  • Press release of May 4, 2010 , EnBW Transportnetze AG, EnBW Energie Baden-Württemberg AG, accessed on April 29, 2011.
  • P. Zolotarev, M. Treuer, T. Weißbach, University of Stuttgart; M. Gökeler, EnBW Transportnetze AG: Network control network, coordinated use of secondary control power . VDI reports 2080, VDI-Verlag, 2009, ISBN 978-3-18-092080-1 .
  • Pavel Zolotarev, University of Stuttgart (IFK), Melchior Gökeler, EnBW Transportnetze AG: Netzregelverbund - Coordinated use of secondary control power , Grid Control Cooperation - Coordination of Secondary Control, March 2011.
  • TU Dortmund, E-Bridge Consulting GmbH: Scientific report: Optimizing the adjustment of performance imbalances , 2009.

Individual evidence

  1. ↑ a b c d e P. Zolotarev, M. Treuer, T. Weißbach, University of Stuttgart; M. Gökeler, EnBW Transportnetze AG: Network control network, coordinated use of secondary control power . VDI reports 2080, VDI-Verlag GmbH, 2009, ISBN 978-3-18-092080-1 , pp. 2-4
  2. ↑ a b c d e f g Pavel Zolotarev, University of Stuttgart (IFK), Melchior Gökeler, EnBW Transportnetze AG: Netzregelverbund - Coordinated use of secondary control power , Grid Control Cooperation - Coordination of Secondary Control, March 2011. pp. 5–7
  3. ↑ ENTSO-E Member Companies. In: entsoe.eu. Retrieved February 2, 2018 .
  4. ↑ Decision in the administrative procedure due to the determination of the use of control energy. (PDF) Az BK6-08-111. Ruling Chamber 6 of the Federal Network Agency , March 16, 2010, pp. 5–11 , accessed on February 2, 2018 .
  5. ↑ Federal Network Agency orders network regulation for the German power grids. (PDF) press release. Federal Network Agency , March 16, 2010, accessed on February 2, 2018 .