Ancillary services from area distribution grids
Ancillary services keep the electricity grid stable. With the increased construction of renewable, volatile generation plants, the market for ancillary services is changing. This is because, in comparison with conventional power plants, renewables have some considerable differences. The topology for the generation is also changing. This is because renewable energy sources such as the sun and wind make the most sense where the environmental conditions are favourable. This means that electricity power lines must transport the energy from the generators to the load centres. This then guarantees consistent supply security.
Challenges in the electricity transmission grid
- Electricity, in particular when generated from wind energy, needs to be transported from the north and east to the load centres in southern and western Germany
- Transits are created by European electricity trading
- Continued expansion and predominant connection of small-scale generation systems to the distribution grids and thus further decentralisation of the electricity generation
- Significant expansion and innovation required in order to avoid overloading the grid resources and breaching the voltage limits
However, what changes are required by the existing system for it to meet the new conditions? Conventional power plants, which still predominantly provide the preliminary services to ensure stable grid operation, will in future be online for increasing fewer hours. This therefore also reduces the possibility for these energy sources to provide ancillary services. The result is that the scope, type and provision of upstream products for ensuring selected ancillary services such as maintaining the voltage and operational management must change.
The SysDL 2.0 research project (ancillary services from area distribution grids) is focussing on developing and validating the system-based principles for the coordinated provision of ancillary-service upstream products. To this end, the project participants are incorporating the third-party operated generation systems available in the distribution grid. In addition, a field test is also being conducted in different distribution grids taking into regard the respective grid topology.
Grid management strategy for transmission and distribution system operators
The basis for the investigations in the SysDL 2.0 project is provided by the data determined from grid-stabilising voltage, reactive and active power corrections (modes Q/U/P), which are made for specific applications at defined transfer points between the transmission system operators and the distribution system operators.
The grid management strategies to be developed, the so-called SysDL 2.0 coordinators, support the close and real time-capable coordination of the distribution system operators’ requirements with the requirements of the transmission system operators. The strategies always incorporate the decentralised resources available at this time from third-party power generation systems.
Field trial serves as basis for project success
Following a kick-off meeting, the focus is on developing concepts for providing contributions to ancillary services from 110-kV distribution grids in preparation for the field trial. The TU Dresden together with Fraunhofer IWES and Siemens are actively in charge here, with the support of all project partners, particularly the grid operators (Drewag NETZ, MITNETZ, TEN and 50Hertz).
The project partners expect the initial results and milestones at the beginning of the second quarter of 2015. By then it is intended that there shall be a preliminary selection of algorithms for providing ancillary service contributions, the potential for the investigated 110-kV grids shall be determined and the technical requirements for generation systems for providing ancillary service contributions shall be defined.
Other core tasks of the SysDL 2.0 project
- The development of optimisation algorithms (for the control variables voltage/reactive power/active power (U/Q/P) and specifications for the modes U/Q/P) for the distributed provision of upstream ancillary services and their topological effectiveness
- The development of appropriate, fault-tolerant system architecture and its comparison with reference architectures in the international IEC standardisation
- The definition of a unified, automated interface for distribution/transmission system operators
- The simulation and subsequent implementation of the SysDL 2.0 system concept in a demonstrator in the grid areas belonging to EVD (EnergieVerbund Dresden: DREWAG NETZ and ENSO NETZ), MITNETZ, TEN and 50Hertz
A subsequent project stage will model future requirements for a range from 10 to 20 years within the 50-Hertz control area or alternatively synthetic network models for the distribution system operators. Using expansion scenarios for further generation systems, the upstream ancillary services requirements and potential shall also be determined. The robustness of the developed operating modes for use with further comparable grid groups shall be verified using grid classes that shall also be determined.
To round off the project, the prerequisites for the market roles involved and their business models will be determined. Based on this it will be possible to derive policy recommendations on the scalability of the solution demonstrated within Germany, in compliance with European conformity requirements.
10/2014 - 09/2017
DREWAG Netz GmbH