OpSim: test- and simulation-environment for grid control and aggregation strategies

OpSim is a test- and simulation-environment with applications ranging from developing prototype controllers to testing operative control software in the smart grid domain. OpSim is created by Fraunhofer IEE and University of Kassel and enables users to connect their software to simulated power systems, or test it in conjunction with other software. The power grid simulator of OpSim is capable of emulating large power systems with multiple voltage levels and substantial amounts of generators, storages and loads.

The core of OpSim is a flexible message bus architecture; it allows arbitrary co-simulations in which power system simulators, controllers and operative control software can be coupled together.

© Fraunhofer IEE

Particular features

  • APIs to connect various simulation tools such as pandapower, PYPOWER, MATPOWER, OPAL-RT, PowerFactory, PSS Sincal or custom scripts in MATLAB, Python and Java.
  • Standard interfaces: Websocket, REST, IEC 61850, IEC 60870-5-104, CIM, VHPready
  • Enables combined power/gas- and power/heat-simulations
  • Scalable environment - runs on desktop PCs and clusters.
  • Interfaces for hardware-in-the-loop (HIL) tests.
  • Users can easily switch between real-time and offline simulations.
  • Geographically plausible time series based on meteorological data, for arbitrary grid regions.

Because of these features, OpSim can be applied to a wide variety of research topics.
In the “applications” section below, we showcase current areas of use.

Applications of the OpSim-environment


Test of grid operation strategies




Benchmark tests of
control concepts


Research of smart grid cyber security risks


Interaction tests
between different actors
in the smart grid


Annual simulations for economic studies


Development and test of controller concepts



22nd Power Systems Computation Conference PSCC 2022

J. Ringelstein, M. Vogt, A.M. Khavari, R. Ciavarella, M. Di Somma, Giorgio Graditi

A methodology for improved TSO-DSO coordination in grid operation planning

ETG-Kongress 2021

A. Schoen, J. Ringelstein, I. Hammermeister, M. Braun, B. Wille-Haussmann, S. Marchand, S. Ruhe, S. Nicolai

Testing Automated Operation and Control Algorithms for Distribution Grids Using a Co-simulation Environment

17th International Conference on the European Energy Market (EEM), 2020

M. Grasenack, L. Jürgens, A. C. Meißner, A. Dreher, K. Knorr, P. Giron, M. Vogt

Design and evaluation of a last-minute electricity market considering local grid limitations

European Guide to Power System Testing, 2020 

V. H. Nguyen, Q. T. Tran, E. Guillo-Sansano, P. Kotsampopoulos, C. Gavriluta, G. Lauss, T. I. Strasser, T. V. Jensen, K. Heussen, O. Gehrke, Y. Besanger, T. L. Nguyen,  M. H. Syed, R. Brandl, G. Arnold

Hardware-in-the-Loop Assessment Methods

16th International Conference on the European Energy Market (EEM) 2019  

A. C. Meißner, A. Dreher, K. Knorr, M. Vogt, H. Zarif, L. Jürgens, M. Grasenack

A co-simulation of flexibility market based congestion management in Northern Germany

IEEE Milan PowerTech 2019

M. Vogt, F. Marten, J. Montoya, C. Töbermann, M. Braun

A REST based co-simulation interface for distributed simulations

International ETG-Congress 2019

F. Schäfer, M. Scharf, M. Braun

Comparison of electrical storage system operation within a framework for time-series-based power system planning

CIRED, 2019

F. Schäfer, J.H. Menke, F. Marten, M. Braun

Time Series Based Power System Planning Including Storage Systems and Curtailment Strategies

2018 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe)

S. Wende - von Berg, F. Marten, M. Braun

Quadratic programming-based grid optimization algorithms for real-time applications

Workshop on Modeling and Simulation of Cyber-Physical Energy Systems (MSCPES), 2018

S.R. Drauz, C. Spalthoff, M. Würtenberg, T.M. Kneikse, M. Braun

A modular approach for co-simulations of integrated multi-energy systems: Coupling multi-energy grids in existing environments of grid planning & operation tools

Zweites PTJ-Statusseminar »Zukunftsfähige Stromnetze«, 2018

F. Marten, F. Schäfer, J.H. Menke, M. Vogt, C. Töbermann, M. Braun

OpSimEval – Integration von Netzplanung und Betriebsführungen im Smart Grid

IECON, 2018

J. Montoya, R. Brandl, M. Vogt, F. Marten, M. Maniatopoulos

Asynchronous Integration of a Real-Time Simulator to a Geographically Distributed Controller through a Co-Simulation Environment

IEEE SmartGridComm, 2018

J.H. Menke, F. Schäfer, M. Braun

Performing a Virtual Field Test of a New Monitoring Method for Smart Power Grids

IEEE SmartGridComm, 2018

F. Schäfer, J.H. Menke, M. Braun

Contingency Analysis of Power Systems with Artificial Neural Networks

Applied Energy, 2018

M. Vogt, F. Marten, M. Braun

A survey and statistical analysis of smart grid co-simulations

IEEE PES Innovative Smart Grid Technologies ISGT Asia 2017

V. Hoa Nguyen, Y. Besanger, Q.T. Tran, T. Lam Nguyen, C. Boudinet, R. Brandl, F. Marten, A. Markou, P. Kotsampopoulos, A. A. van der Meer, E. Guillo-Sansano, G. Lauss, T.I. Strasser, K. Heussen

Real-Time Simulation and Hardware-in-the-Loop Approaches for Integrating Renewable Energy Sources into Smart Grids: Challenges & Actions

Computer Science - Research and Development, 2017

F. Marten, A. Mand, A. Bernard, B.K. Mielsch, M. Vogt

Result processing approaches for large smart grid co-simulations

CIM Users Group – European Meeting 2017. Herzogenaurach, Germany

S. Wende - von Berg, B. Requardt, B. Ernst, M. Braun

CIM CGMES Applications in research projects for DER

International Journal of Electrical Power & Energy Systems, 2017

J.H. Menke, J. Hegemann, S. Gehler, M. Braun

Heuristic monitoring method for sparsely measured distribution grids

4. Konferenz „Zukünftige Stromnetze für erneuerbare Energien“, 31.01.-01.02.2017, Berlin

S. Wende – von Berg, F. Marten, B. Requardt, H. Wang, M. Vogt, M. Braun

Technische Bewertung von Betriebsführungen mithilfe einer Echtzeit-Simulationsumgebung, am Beispiel des Verbundforschungsprojektes SysDL2.0

14. Symposium Energieinnovation, 10.-12.02.2016, Graz/Austria

S. Wende-von Berg, N. Bornhorst, S. Gehler, E. Schneider, H. Hänchen, Th. Pilz, K. Seidl, U. Zickler, M. Braun, U. Schmidt, T. Wagner, J. Götz,
J. Schwedler, E. Habermann

SysDL 2.0 - Systemdienstleistungen aus Flächenverteilnetzen: Methoden und Anwendungen

Statuskonferenz "Zukunftsfähige Stromnetze", Berlin

F. Marten, M. Braun

OpSimEval - Ziele, Ergebnisse, Status & nächste Schritte


E. Drayer, J. Hegemann, S. Gehler, M. Braun.

Resilient Distribution Grids - Cyber Threat Scenarios and Test Environment.

Opal-RT RT16 International User Conference, München

F. Marten, S. Wende-von Berg, M. Vogt, C. Töbermann.

Testing an IEC 61850 compliant voltage control algorithm for Smart Grids, using a real-time simulation.

ETG Congress 2015 - Die Energiewende

H. Wang, T. Stetz, F. Marten, M. Kraiczy, S. Schmidt, C. Bock, M. Braun.

Controlled Reactive Power Provision at the Interface of Medium- and High Voltage Level: First Laboratory Experiences for a Bayernwerk Distribution Grid using Real-Time-Hardware-in-the-Loop-Simulation

Opal-RT RT15 Regional User Group Event, Barcelona

F. Marten und J.-Christian Töbermann.

OpSim - a smart grid co-simulation environment

PowerTech Eindhoven 2015

M. Vogt, F. Marten, L. Löwer, D. Horst, K. Brauns, D. Fetzer, J.-H. Menke, M. Troncia, J. Hegemann, C. Töbermann, M. Braun.

Evaluation of interactions between multiple grid operators based on sparse grid knowledge in context of a smart grid co-simulation environment

E-World SmartER-EUROPE 2015

F. Marten, M. Vogt, M. Widdel, M. Wickert, A. Meinl, M. Nigge-Uricher und J.-Christian Töbermann.

Real-time simulation of Distributed Generators, for testing a Virtual Power Plant software.

ETG Fachtagung: von Smart Grids zu Smart Markets 2015

F. Marten, M. Vogt, M. Widdel, M. Nigge-Uricher, A. Meinl und J.-Christian Töbermann.

Echtzeit Simulationsplattform OpSim: Systemtests der Software eines virtuellen Kraftwerks durch simulierte Anlagenpools.

18th Power Systems Computation Conference PSCC2014

F. Marten, L. Löwer, C. Töbermann, M. Braun.

Optimizing the reactive power balance between a distribution and transmission grid through iteratively updated grid equivalents.

A framework for distributed simulations

© Fraunhofer IEE

OpSim is a framework for the distributed simulation of complex electric energy systems. The present structure of OpSim is shown in the illustration. The core is an intelligent central middleware, which controls the simulation and enables the communication between different simulation components (e.g. power grid simulation, virtual power plant, distribution/transmission grid optimization). This flexible framework was motivated by a concept of Faschang et al. (IECON 2013) and allows arbitrary configurations of simulation components or extensions by new simulation components. In addition, OpSim provides standard interfaces (IEC61850, VHPready,…) for external industrial software. For example, we have successfully connected an operative energy management with an OpSim real-time simulation!

Realistic time series and forecasts

© Fraunhofer IEE

To simulate future energy systems, a solid scenario dataset is indispensable: renewable generators, consumers, but also conventional power plants and storages are continually changing and must be simulated with dedicated models and time series.

In case of renewable generators, the spatial and temporal generation profiles are chiefly determined by meteorological factors. The OpSim “scenario generator” takes these effects into account: based on historical weather data and the geographic location of the power grid region, this tool creates realistic time series for generators and loads.

OpSim is used as a testing platform for novel control strategies (e.g. virtual power plant or grid optimization). Some of the strategies require forecasts of electric generation and demand: these forecasts can also be created by the scenario generator, based on time series and error distributions.

Power system simulation

© Opal-RT

An important simulation component of OpSim is a high performance grid simulation, which emulates a detailed distribution grid (consisting of low-, medium- and high-voltage) and a section of transmission grid. The simulation contains a large variety of dynamic models of generators, storages and loads, which are partly parameterized with time series data of the OpSim scenario generator (see previous section). Large power grid models with up to 10.000 buses can be simulated. For this task, solutions from e.g. OPAL-RT Technologies were commissioned. Besides the implementation of the power system simulator, an interface to the remaining OpSim-architecture (containing virtual power plant and distribution/transmission grid operation strategies) was developed.

Further development of transmission grid operation strategies

In the OpSim project, control strategies for the transmission grid were further developed:

  1. Algorithms for technical and bus-specific set point optimization (e.g. reactive power, voltage,…).
  2. Curative redispatch-algorithms involving classical (grid security) and economic optimization.
  3. Development of an interface to the remaining OpSim-architecture.

A novel aspect is the involvement of flexible generators in distribution grids, to resolve transmission grid congestions.

In summary, the following results were achieved in this working package:

  1. Algorithms for set point optimization in normal grid operation and curative redispatch control.
  2. Interface between these algorithms and the power system simulator, as well as interfaces to other control strategies (e.g. distribution grid control).

Virtual power plant

© Fraunhofer IEE

The virtual power plant (VPP) of Fraunhofer IEE was extended with mechanisms to couple it to the OpSim system. Simulated power plants from OpSim can now be dynamically added to the VPP. This is realized through a standard communication interface (VHPready) in the OpSim system which can convey data from OpSim’s simulation components to external applications.

In the extension of the VPP, energy management modules from other projects (e.g. RegModHarz and Kombikraftwerk 2) were updated and implemented. Hence, OpSim also provides a testing environment for developers of aggregation strategies.

Further development of distribution grid operation strategies

OpSim enables users to simulate the operation of future distribution grids in a holistic manner. One could investigate agreement structures between a distribution grid operator (DSO) and aggregators of decentral units (e.g. virtual power plants) to reach a technically and economically optimal grid state. One can also use OpSim to investigate ancillary service provision from the distribution grid to the transmission grid. Existing distribution grid control strategies from previous projects at Fraunhofer IEE were further developed and integrated into the OpSim environment:

  1. Development of interfaces and mechanisms for direct and indirect (e.g. via an aggregator) set points from a distribution grid control strategy to simulated decentral units in OpSim.
  2. Integration of algorithms to optimize (re)active power at the connection point to the upstream voltage level.
  3. Standard interfaces (CIM, IEC61850) to connect an operative grid control software to OpSim.

Industry advisory board

During and beyond the projects "OpSim" and "OpSimEval", the further development and application of our simulation environment is accompanied by an industry advisory board of grid operators, equipment manufacturers, operators of virtual power plants and manufacturers of control systems.

Requirements from the industry advisory board ensure that the OpSim environment fulfills the technical conditions to tackle issues of industrial partners. We want to ensure that OpSim can be used in follow-up projects with minimal effort and can directly be applied to tasks from industrial practice. First applications from advisory board members were already addressed during the project period, e.g. in form of functional tests.

The industry advisory board thus offers a valuable exchange of information between the various actors from the energy supply field.

Participating in the advisory board is free of charge and we appreciate more participants at any time, to drive forward the development of OpSim.

Signing up is easy: an email to the project manager (Contact per email) with some details about your company and reason for your interest in the project is sufficient.

Examples of companies which have participated during the project


Some of the companies which are currently participating

OpSim Press review


InnoVisions | 13.12.2018
Smart Test für Smart Grid - Test- und Simulationsumgebung für Stromnetze


HNA | 11.06.2014
Stromnetz soll stabiler sein – Kasseler Forscher entwickeln System für gleichmäßige Netzbelastung.


Göttinger Tagesblatt – de | 03.05.2014, Seite 32
Intelligentes Netz –
Forschungsprojekt will Stromversorgung aus erneuerbaren Energien verbessern.


Behörden Spiegel – de | 02.05.2014, Seite 4
Wissen, was passiert – Kasseler Forscher entwickeln Test- und Simulationswerkszeuge


Pressemitteilung Fraunhofer IWES | 15.04.2014


Pressemitteilung Universität Kassel | 15.04.2014


SONNE WIND & WÄRME | 07.03.2014, Seite 28
Netzinfrastruktur: Planungstools


Contact Press / Media

Dr. Frank Marten

Fraunhofer IEE
Joseph-Beuys-Straße 8
34117 Kassel, Germany

Phone +49 561 7294-444

Contact Press / Media

Mike Vogt

Fraunhofer IEE
Joseph-Beuys-Straße 8
34117 Kassel, Germany

Phone +49 561 7294-119