»Solutions from research for sustainable grids in times of the energy transition«

Power HIL - Hardware-in-the-Loop for electric grids and plants


Hardware-in-the-loop (HIL) is a method of combining laboratory and simulation environments with each other. The benefits of grid simulation are integrated into the labora-tory infrastructure to not only test the full range of functions of initial concepts as well as extensive smart grid technologies, but also analyze the contribution of distributed generators to grid stability and grid operation in a realistic testing environment.

In the industry, the tests serve to bridge the gap between standardized laboratory tests and expensive field tests, because they allow forinvestigating a wide range of possible scenarios in advance, which can otherwise only be depicted in field tests. The reduced need for field testing and preoptimization saves plenty of time and resources.

In research, HIL systems are used specifically for the further development of prototypes and/or the development of innovative strategies for new grid components to ensure general grid stability.

Why Power HIL


With the help of a real-time system, grid models for electromagnetic or electromechanical phenomena are simulated and can be transmitted to a power amplifier via an interface or directly connected to the test object. The power amplifier serves as the source/sink for the respective test object and generates realistic grid events according to the parameters of the real-time system. Measurement sensors feed the dynamic behavior of the test object back into the grid simulation of the real-time system to establish a bidirectional and thus realistic relationship. A special signal amplifier, which can transmit up to 6 (voltage or current) signals to protection devices, is used for testing protection devices.

The system is capable of supplying three test objects with ± 90 kVA each or one test object with ± 270 kVA and of testing protection devices with flexible voltage or current signals:

  • Setup of a system for calculating real-time grids for grid operators for grid monitoring/planning
  • Demonstration of contribution of prototypes and test components
  • Plant tests up to 270 kVA and 460 V integrated in grid simulations (for extensive functional testing)
  • Analysis of dynamic interaction between up to 3 plants (operational compatibility of several plants)
  • Testing the contribution of prototypes for grid operation and grid stability
  • Grid studies of interconnected, transmission and distribution grids in a laboratory test environment (global, detailed test scenarios)
  • Realistic scaling of contribution of real test compo-nents into simulated grid models (future scenarios)
  • Testing of protection devices/functions and dependencies
  • Functional testing of novel control units and
    elements under realistic grid conditions Hardware-under-Test (HUT):
    • Loads (non-linear)
    • Distributed generators
    • Transformers
    • Prototypes
    • Protection devices
    • Control units, controllers


The Fraunhofer IEE offers a comprehensive system for testing energy grids by providing real grid data or using reference grids, which serves to ensure grid stability with the help of real plants while enabling extensive functional testing of real plants under laboratory field conditions:

  • Integration of distributed generators into a realistic grid simulation
  • Setup of real-time systems for grid monitoring and planning
  • Expansion of testing guidelines for full functional testing
  • Setup of future grid scenarios through simulated grid adjustment or performance scaling of the real generators
  • Testing of interactions between several (up to three) real generators or control units under real grid conditions
  • Qualified support in prototype development and testing of conventional and future grid stability by
    the Fraunhofer IEE