Resistant medium and low voltage grids

Project state
Oben links: Messtechnik in Kabelverteilerschränken übermittelt Netzparameter via Glasfaser oder GPRS, oben rechts: Verteilte Rechner in den Ortsnetzstationen übernehmen die dezentralen Steuerungsaufgaben, unten links: elektrische Heizelemente in Warmwasserspeichern schaffen eine Verknüpfung zwischen Strom- und Wärmenetz, unten rechts: BSI-konforme Messsysteme bei Anschlussnutzern ergänzen das Messkonzept
Top left: Measurement technology in cable distribution cabinets transmits grid parameters via fibre optics or GPRS; top right: Distributed computers in secondary substations take on the decentralised control tasks; bottom left: Electric heating elements in hot water storage tanks create a link between the electricity and heating network; bottom right: BSI-compliant measuring systems for connection users supplement the measurement concept

In the PolyEnergyNet project, developers led by project coordinator Dr Ralf Levacher are focussing on constructing a resilient grid at the medium- and low-voltage level.

The increasingly decentralised infeed of renewable energy into the grid is not only presenting the energy supply companies with new challenges but is also offering new opportunities. The engineers in the PolyEnergyNet project see one of these opportunities in the ability to form autonomous sub-grids. These have the advantage that they can supply themselves in the event of disruptions in the low-voltage grid. The production plants available in these so-called holons then supply the loads until the superordinate grid is running stably again. The holons can then be integrated into the grid.

Another approach being taken by the project group is the project’s name-giving PolyNet concept, in which the electricity, gas and heating networks are intended to be linked with a superordinate fibre optic network. That should make it possible to ride through supply failures by using gas-fired cogeneration units, hot water storage systems and solar power storage systems. This would increase the supply security.

The developed concepts will be tested in a real test area as part of the integrative field trial. For this purpose, measuring sensors were installed on the basis of a measurement concept in the field test area in Saarlouis, and intelligent measuring systems installed with connection users. The automation technology is decentrally distributed in PolyEnergyNet. For example, the grid state of automation systems is detected in secondary substations that can also determine and control the appropriate holon formations and control interventions. The most important technologies for linking the energy grids in the field trial are CHP and Power-to-Heat plants. In periods of high solar radiation or strong winds, surplus electrical energy can be converted into heat and stored.

What is a holon?

Holons are variable cells that can dynamically adapt to the respective grid situation. In the project, holons are defined as autonomously supplied sub-grids that re-form in accordance with the grid situation via disconnect points, and thus create an optimal supply situation.

Resilient local grids for greater security

The aim of the project is to research and realise exemplary resilient local grids, i.e. grids that are protected against external interference. These are characterised by a robust grid operation that can respond to both the volatility of the decentralised renewable energy fed into the grid as well as to unforeseen events that even include cyber attacks. For the researchers, an essential aspect is the creation of a common information basis that, by means of appropriate measures, makes it possible to detect and rectify critical grid conditions. In addition, it is intended that the supply should be maintained in emergency operation as widely as possible and that, if required, parts of the local grid shall be placed under quarantine until these can be re-integrated into the overall system.

In order to achieve the goals, experts from different fields are working together. Therefore at the beginning it was particularly important to define a common work process, to make the expertise from the other specialist disciplines as transparent as possible within the consortium and to develop a theoretical basis as a foundation for the further considerations. In this regard, sharing experience gained from other research projects as well as the basic principles relating to the systems theory behind holons proved to be useful. The engineers have set three milestones during the course of the project:

  • The conceptual model, the functional requirements and the scenarios for resilient, holonic poly-grids are available in their initial versions. Based on this, initial concepts for the grid planning and operation, energy and data management as well as the resilience of the grid should have been designed.
  • All requirements are known and the analysis is complete. The main core functionalities are fully developed. Initial prototypes for the grid planning and operation, energy and data management as well as the attack detection will be presented. There is a plan for the field trials.
  • A complete demonstrator is implemented, evaluated in field trials and the results published.

The project partners at a glance

  • B.A.U.M. Consult is coordinating the basic activities for modelling resilient poly-grids. Through on-site consulting, it is supporting the actual identification and integration of operational flexibilities for both the model and the final field test.

  • The German Research Centre for Artificial Intelligence (DFKI) is developing three main components as part of the project: in addition to aggregation and analysis tools for poly-grids, it is creating forecasting software for poly-grids as well as network management systems for resilient poly-grids.

  • As part of the project, Karlsruhe Institute of Technology (KIT) is developing a scalable, highly available cloud infrastructure/platform and is also designing and realising the integration and management of internet-distributed data management systems. In addition, it is also developing software components for monitoring and for the event-triggered automatic scaling of services.

  • In this context, Scheer Management is contributing basic concepts for the system architecture in the data management area. The aim is to combine the real-time capability and bulk data within an energy data hub to enable decoupled operation and ensure the reliability at almost all times.

  • The Stadtwerke Saarlouis municipal utility company is focussing, in particular, on the energy industry-compliant design of the models and scenarios. In addition, the utility company is also designing and supervising the integrative field trial.

  • Within the project, the TU Berlin is concerned with the management of distributed data, taking into account specific quality requirements such as the scalability and resilience within poly-grids. Firstly, a corresponding distributed database management system for measurement data will be developed and implemented prototypically. Secondly, new methods for quantitatively determining the critical quality characteristics of database management systems will be developed for measurement data within poly-grids.

  • Within the project, the TU Darmstadt is focussing on resilient grids, secure ICT infrastructures and collaborative attack detection.

  • As part of the project, the [ui!] is focussing on the taxonomy/ontology, the overall architecture, the protocol specification of components and services used as well as on automatic responses to attacks/emergency operation and prioritisation.

  • VOLTARIS is largely responsible for developing the measurement concept. In addition, VOLTARIS is also responsible for selecting and procuring measurement systems consisting of meters, gateways and control boxes, which in the field trial will be installed in the individual holons or households. In addition, VOLTARIS will be responsible for designing and implementing the necessary backend systems, the gateway administrator system and the system for the energy industry-related measurement data management.

  • VSE Verteilnetz is identifying the tasks and requirements for a multi-discipline grid control centre and is developing appropriate solutions. VSE Verteilnetz is also bringing its expertise in the network planning and operation field into the project and is thereby supporting the partners.

Project duration

09/2014 – 08/2017


Dr. Ralf Levacher
Project coordinator and energy grid operation
Stadtwerke Saarlouis GmbH
Holtzendorffer Str. 12
66740 Saarlouis, Germany

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