A dynamic, virtual future for the power plant

We are all well aware that the sun, wind and water are the energy sources of the future, whereas coal- and gas-operated power plants will gradually disappear. What is less well known is that the energy supply system first requires conversion in order to ensure that decentrally-fed renewable energies (RE) not only supplement conventional energy generation, as is currently the case, but gradually replace it. Four engineering scientists at HTW Berlin are currently focusing on this transformation process in their research.

Ten partners in four European countries

The fact that this conversion is anything but insignificant is underscored by the fact that Prof. Dr. Horst Schulte and his research assistants Dr. Stephan Kusche, Florian Pöschke as well as Prof. Dr. Jens Fortmann, Prof. Dr Norbert Klaes and Prof. Dr Jochen Twele collaborate with ten partners from four EU countries in the “POSYTYF” (POwering SYstem flexibiliTY in the Future through RES) project funded by the H2020 programme of the European Commission. Says Prof. Dr Horst Schulte: “We have to think in European dimensions when it comes to energy supply.” After all, more solar energy can be generated in the South and more wind energy in the North.

Even milliseconds count

Because no matter where the energy is generated and where it is fed in, the power system must be stable, i.e. it must display a continual frequency of 50 hertz and constant voltage at different levels. Even an interruption of just a few milliseconds is highly problematic, which is logical if one considers the precision requirements of electronically controlled high-speed trains, operations in hospitals, elevator rides or services provided by large data centres, to name just a few examples.

Current must flow without interruption

Ensuring this stability is a challenge. The 30 or so large conventional power plants currently generating energy in Germany based on coal, gas or nuclear power are able to compensate for even major fluctuations with robust synchronous machines. On the other hand, renewable energies fluctuate and feed energy into the grid by means of sensitive power electronics. Sometimes the sun shines, sometimes it doesn’t, a strong wind might be followed by a lull, a fallen tree can paralyze an entire subgrid. But the current must flow evenly.

The dynamic, virtual power plant

The solution: the dynamic, virtual power plant. “This is a sophisticated control strategy capable of forming a portfolio of frequency- and voltage-variable current and voltage sources and optimally reallocate resources in the event of meteorological and system-related fluctuations,” explains Prof. Dr Horst Schulte. Simply put, if wind farm A reports that no additional energy can be produced, a large biogas plant must step in without delay, for instance.

Ten partners from four countries

The precise details of the control strategy will be developed on the basis of complex methods and mathematical models in the context of the POSYTYF project, which is due for completion by May 2023. Ten partners in Germany, Spain, France and Switzerland share the work. Four universities and industrial partners are also involved, including Bachmann Electronic GmbH, and the French transmission grid operator Reseau de Transport d’Électricité (RTE).

The standard interface already exists

The HTW team has already reached a significant milestone, and Prof. Dr. Horst Schulte is satisfied. As renewable energies cannot simply be subjected to a “one-size-fits-all” approach, considering that photovoltaic systems, wind turbines, solar thermal plants, hydropower, and biogas differ in behavior, so-called response time and technology, they were subdivided as generation units, with separate strategies modeled but the interface itself standardized.

Realistic scenarios for subgrids are now available

The second milestone was achieved by scientists from the University Politechnica de Catalunya (UPC) in Barcelona, Spain: realistic scenarios for subgrids, e.g. for the Canary Islands, the Atlantic coast, and the North Sea, including southern Scandinavia. Although these power plants are virtual, i.e. location-independent, they always combine particularly profitable energies in the respective region. The different types of power plants are linked via the standard interface already mentioned. As a result, the two key dimensions – power or frequency on the one hand, and voltage on the other – can be controlled flexibly at any time. The German-Spanish findings will be presented and published jointly at a conference in 2022.

Key industry partner in Bochum

No less important for the HTW team is its working relationship with Austrian company Bachmann Electronic GmbH, which specializes in automatic control and automation, or, to be more precise, the university’s collaboration with the latter’s development department located in Bochum. The company has great expertise in the control of renewable-based hybrid power plants, which Prof. Dr. Schulte describes as a kind of preliminary step for the dynamic, virtual power plants. Their Smart Power Plant Controller was integrated within the university’s 300-m² test stand, “concealed” in the windowless brick building between the WaschBar and Building G on the Wilhelminenhof campus. There, the simulations are subject to continuous testing.

Goals achieved by 2023

Prof. Dr. Schulte is confident that the project goals will be achieved by 2023. After all, they are a well-coordinated team and are not starting from scratch, having already addressed the topic in-depth in a previous project entitled “Wind Power Plant”, which received the HTW Berlin Research Award in 2019.