A heart for electricity

Kiel research project HEART takes stock and transitions to practice phase

Substations for conventional energies from all over Europe, regional block-type thermal power stations, large commercial and small private plants, which all generate renewable energies: our energy network is dependent on many different factors that are finely tuned to each other. The smallest faults can lead to widespread power cuts, or even significant damage to the network. In particular, the naturally fluctuating output from renewable energies requires a rethinking of the technologies used in the energy network. This is driving research for a stable power grid, which should be durable, flexible, fault tolerant and efficient. The HEART (Highly Efficient And Reliable smart Transformer) project at Kiel University (CAU) has been pursuing this goal for five years. Funded by the European Research Council (ERC), Professor Marco Liserre from the Kiel Chair of Power Electronics launched the ambitious project to develop a smart transformer for the modern power grid. Today (Tuesday 29 October), he presented the results of the project, and how it will continue.

“We have developed a new kind of current transformer for the power grid, our smart transformer. It contains power semiconductors made from silicon carbide, which enable great efficiency," explained Professor Marco Liserre. "The special feature of our prototype is its modular design. This makes it usable as a transformer for the power grid. But individual components can also be used to better integrate charging stations into the power grid, or better connect DC networks from plants for the production of renewable energy to the central AC power grid. Our system can also be used in energy storage," emphasised Liserre.

Comprehensively tested

In order to test and further improve the reliability of their prototypes, the Kiel scientists created various test environments. While doing so, a key focus area was bringing the thermal impact on the individual components under control. To achieve this, they created the voltage of a power grid in the laboratory under realistic conditions, and applied the new methods developed in Kiel of "Active Thermal Control" and "Power Routing". These methods enable them to reduce the thermal impact of fluctuating current flow. Essential information can be gained by applying these methods in the lab. "From this information, we derive how we can influence the temperature, and thereby make the modules more stress-resistant to fluctuating power inputs," said Liserre.  

If the modules work in the laboratory environment, the question remains whether they can interact with the real power grid. "At the start of the project, we hoped to re-envisage our traditional power grid with a new kind of transformer," reported Liserre. The current power grid has used conventional transformers for over 100 years. Liserre is convinced: "Our innovative ideas have the potential to reinvent the power grid."

Therefore, a second test environment enables real time digital simulation (RTDS) of the power grid. A power amplifier produces the voltage of the power grid, and various current transformers function here as smart transformers. Liserre said: "In this way, we can test how the smart transformer will work in conjunction with the power grid, and whether it delivers the performance we expect." In addition, various other test scenarios are also possible using this test station: how the transformers function with wind energy systems, storage systems or solar cells, as well as their interaction with the power grid.

"Our project results are very promising. By further developing our prototypes, we were able to prove that the smart transformer can bring the different energy sources into the power grid better, and the process can be controlled better. On top of this, our transformer is more durable and more reliable than conventional transformers," said Liserre.

Interview with Prof Marco Liserre due to the project conclusion

A new medium-voltage laboratory and field test in Scotland

In order to subject the results of the HEART project to further tests, a new medium-voltage laboratory was built for the Chair of Power Electronics at the Faculty of Engineering, and officially opened today (29 October). In this laboratory, it will be possible to test prototypes of the transformers in the medium-voltage range between 10 kilovolts and 1 megawatt, and simultaneously conduct real-time simulations of power grids. Liserre said: "This enables us to also test real scenarios under lab conditions on a larger scale, which will bring us closer to our goal of deploying the smart transformer in the real power grid."

In parallel, an "LV Engine" (LV = Low Voltage) practical test is being carried out together with the partner Scottish Power (SPEN). Amongst other goals, they are planning a power grid test with the Kiel smart transformer by 2022. "We’re supporting the company with the transformer deployment, and hope to convince them of our transformer with the new results from the medium-voltage laboratory, but also with the field test results," said Liserre.

Next, the Kiel researchers want to determine the impact of the further expansion of renewable energies on nodes in the grid, and what interventions can be made by an intelligent transformer, without burdening the grid. In addition, an extension of the laboratory is planned to address the topic of energy storage. The new laboratory is supported financially by the Gesellschaft für Energie- und Klimaschutz Schleswig-Holstein (EKSH) and the Business Development and Technology Transfer Corporation of Schleswig-Holstein (WTSH).

Five years of excellent research

At the start of the project in 2014, the Kiel scientists received two million Euros from the European Research Council (ERC). In 2018, they received additional ERC funding to make key developments from the HEART project ready for the market. They are currently planning to market the transformer in cooperation with companies, but Marco Liserre can also imagine founding his own start-up.

The fact that they have a lot to offer research - but also the energy market - is proven by numerous awards, funding grants, publications and patents, as well as new projects which have also arisen as a result of the HEART project:

  • 167 publications to date (including 102 conference articles, 65 international research publications in renowned scientific journals)
  • six patents submitted on the basis of project results
  • two direct follow-up projects: LV Engine, U-HEART 
  • twelve related follow-up projects, which tackle sub-aspects of the project, such as involvement in the Copernicus project ENSURE and KielFlex
  • three IEEE Awards for Professor Marco Liserre, and second place for the IEEE Award Transaction of power electronics (IEEE is a global technical professional organisation for engineers in the field of electrical engineering and information technology)
  • eight awards for doctoral researchers in the project, awarded at international symposia
  • listing of Professor Marco Liserre in the "Science Citation Index by Thomson Reuters" for a high number of citations.
Liserre and guests at the lab
© Claudia Eulitz, Uni Kiel

In order to subject the results of the HEART project to further tests, Marco Liserre opened a new medium-voltage laboratory today (29 October) at the Faculty of Engineering.

© Claudia Eulitz, Uni Kiel

Durable, flexible, fault tolerant and efficient: the modular smart transformer promises innovative solutions for the power grid of the future.

circuit board
© Claudia Eulitz, Uni Kiel

With newly developed methods, the researchers can measure the thermal effect of fluctuating current flow.

Marco Liserre
© Claudia Eulitz, Uni Kiel

Marco Liserre

inside the lab
© Claudia Eulitz, Uni Kiel

Ready for use: in the new laboratory at the Faculty of Engineering, transformers can be tested in the medium-voltage range between 10 kilovolts and 1 megawatt.

© AG Liserre

Innovative solutions in power electronics can increase the reliability of transformers.

Claudia Eulitz
Head of Press, Digital and Science Communication