Prof. Dr. Eberhard Waffenschmidt und Prof. Dr. Ingo Stadler vom Cologne Institute for Renewable Energy der Fakultät für Informations-, Medien- und Elektrotechnik der TH Köln leiteten das Projekt. Foto: Henrike Klehr/TH Köln

Successful project at TH Köln: Grid-friendly swarm charging

The switch to electric mobility for passenger cars could push distribution grids to their performance limits in some cases. To prevent overload, researchers at TH Köln have developed a solution for communicating charging stations. An algorithm controls optimal utilization based on grid status data, while also taking into account the charging preferences of users. The application is patented in the US and is still being reviewed in the EU.

“If many households in a residential area purchase electric cars, charging the vehicles can pose challenges for the stability of the power grid. There are two complex options for preventing overload: one is costly and time-consuming grid expansion, and the other is equipping buildings with complex measurement technology, which is often difficult to implement due to regulatory requirements. We are pursuing a simpler way to coordinate charging processes and control them in a way that benefits the grid,“ says project manager Prof. Dr. Eberhard Waffenschmidt from the Cologne Institute for Renewable Energy (CIRE) at the Faculty of Information, Media and Electrical Engineering at TH Köln. ”Our solution is based on the swarm principle.”

The application developed collects measurement data from charging stations already installed in buildings and can determine the current grid status on this basis. This is an essential prerequisite for controlling charging processes in such a way that the distribution grids, i.e., cables and transformers, are not overloaded and the permitted voltage ranges, i.e., the upper and lower voltage limits, are not exceeded or undershot. “Our solution does not require a connection to the grid operator’s control room. An additional control device to distribute the available charging power is also not required. We rely on a charging infrastructure that manages itself after installation without a central authority taking control. This means less effort in planning and coordination,” explains the second project manager, Prof. Dr. Ingo Stadler from CIRE.

Algorithm coordinates grid-friendly charging processes: To test the solution, the project team designed a distribution network in the laboratory with several hundred meters of cable and six simulated households, which were replicated using electrical components such as inverters, batteries, and measuring and control units. Three racks were equipped with a wallbox. The system was controlled by an algorithm whose basic functions were developed in the previous project.

“Our algorithm can determine the state of the grid. It uses measurement data such as electrical voltage and current, as well as standard load profiles, to determine the aggregate power consumption of appliances such as ovens or washing machines within a household. Based on this, the program distributes free grid capacity to electric cars that need charging. In doing so, specified voltage limits are maintained at all points in the grid,” explains research assistant André Ulrich.

In addition, owners of electric vehicles can select at the wall boxes the time by which a certain charge level should be reached. Using this data, as well as information on the grid topology and the current grid status, the algorithm is able to determine the optimal operating mode for the entire system.

Functional expansion and planned practical test: In a follow-up project, the application tested in the laboratory is to be expanded to include an energy management system so that other controllable power consumers, such as heat pumps, can be incorporated. In addition, a real-world test with a grid operator is planned.

About the project: The GridMaximizer project was led by Prof. Dr. Eberhard Waffenschmidt and Prof. Dr. Ingo Stadler from the Cologne Institute for Renewable Energy at the Faculty of Information, Media and Electrical Engineering at TH Köln. The project team included research assistants André Ulrich, Marcel Krämer, and Sven Lorre. The project ran for 18 months. The state of North Rhine-Westphalia and the European Regional Development Fund (ERDF), as well as a predecessor project of the Electronic Components and Systems for European Leadership Joint Undertaking, funded the project with over €800,000.

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