© Fraunhofer IEE

Researchers develop novel power converters for the grid-serving operation of electrolysers

In the medium term, large-scale electrolysis capacities are to be built up both in Germany and worldwide. This requires new types of power converters that not only meet the requirements of powerful electrolysers, but also those of the power grids. The Fraunhofer Institute for Energy Economics and Energy System Technology (IEE) is now developing such power converters together with partners in the H₂Giga project HyLeiT. Special emphasis is placed on the system integration of the converters. The aim of the project is to halve the costs compared to the state of the art, to guarantee a high direct current quality and to enable the grid-serving use of electrolysers.

As coordinator of HyLeiT, Fraunhofer IEE is collaborating on this project with SMA, Infineon, TU Dresden and Bonn-Rhein-Sieg University of Applied Sciences. The project has a duration of 4 years. It is funded by the Federal Ministry of Research and Education.

HyLeiT is part of the lead project H2Giga coordinated by DECHEMA. It aims to advance the series production of electrolysers. “Within H2Giga, HyLeiT contributes in particular to the topics of grid integration and the electrical system technology of electrolysers,” says Dr. Philipp Strauß, deputy director of Fraunhofer IEE, who coordinates the H₂Giga project HyLeiT together with Dr. Norbert Henze.

Modelling of the network and the electrolysers

As part of HyLeiT, the experts are initially developing laboratory prototypes of power converters. Infineon is contributing novel semiconductors that are being made suitable for use in converters. They meet the requirements of both the electrolyzers and the power grid better than the classic thyristor semiconductors.

In order to be able to test and optimize the power converters in the system context, the Fraunhofer researchers are creating real-time simulation models of the power grid and the electrolysis stacks. They also take into account the ageing of the electrolyzers, as these change their electrical behaviour in the course of their life cycle. This must be taken into account when designing the power converters.

These models are then incorporated into a “hardware in the loop” platform. The scientists are thus testing the developed converter concepts on all common electrolysis technologies. The focus is on the interactions of the power converter with both the electrolysis stacks and the power grid. “As the link between the electrolyser and the grid, the power converter is of central importance for the energy transition. That’s why it’s essential to take the entire system into account when developing and optimizing power converters,” says Henze.

Power converters enable electrolysis to serve the grid

The research team expects that the project will succeed in halving the system costs of electrical engineering from the grid connection point to the DC connection at the electrolyser compared to the state of the art. A modular and standardised production of the power converters using optimised semiconductor components is the main factor contributing to the reduction in costs. Thanks to new circuitry techniques for power converters, passive components such as heat sinks can also be made smaller.

Another goal of the H₂Giga project HyLeiT is to design the power converters in such a way that the electrolysers can behave in a grid-serving manner. Provided that they are designed accordingly, they should even actively contribute to the stabilization of the grids in the future by reacting to critical grid situations at short notice.

Last but not least, the project also aims to improve the DC quality for the electrolyser, especially in dynamic operating situations. This increases reliability and safety and also extends the service life of the system.

New building offers best conditions for HyLeiT

In this project, the Fraunhofer researchers benefit from the technical equipment provided by the institute’s new building in Kassel. “The new building offers us ideal conditions. Among other things, we have a gas laboratory at our disposal where we can build stacks, as well as a well-equipped laboratory for power electronics and grid integration,” says Strauß. The new building is scheduled to be occupied at the end of 2021.

Fraunhofer IEE has been dealing with questions of grid integration of electrical equipment and systems for many years. The researchers also have a great deal of expertise and experience in modelling, for example in the simulation of battery cells.

About the hydrogen lead projects:

The hydrogen lead projects are the largest research initiative of the Federal Ministry of Education and Research (BMBF) on the subject of the energy transition to date. In the industry-led lead projects, industry and science are jointly developing solutions for the German hydrogen economy: series production of large-scale electrolysers (H2Giga), production of hydrogen at sea (H2Mare), technologies for the transport of hydrogen (TransHyDE).

The BMBF-funded hydrogen lead projects are the result of an ideas competition: science, industry and civil society were invited to submit ideas for large-scale hydrogen projects. More than 240 partners have come together in this way and are to receive a total of around 740 million euros in funding. The lead projects are funded over a period of four years.