Innovative DC technology for a sustainable integration of modern charging infrastructure for electromobility

Schematic of a DC underlay grid

The conventional integration of fast charging stations always requires the installation of additional transformers and often the local expansion of power grids for aggregated high charging capacities. Charging processes are stochastically distributed throughout the day, so that rarely all charging points of a charging park are occupied. Since the electrical equipment must be designed for the maximum power of the charging park, its utilization is low. In addition, conventional fast-charging stations consist of an active rectifier, a DC-DC converter and a galvanic isolation. The latter is often implemented in the form of a galvanically isolated DC-DC converter. Due to the multi-stage energy conversions, there are higher losses as well as more material and space requirements of the fast-charging stations.

In the case of a DC power supply for charging stations, a cost and material reduction can be achieved by eliminating the rectifier and the corresponding control and sensor technology. The reduction in complexity also leads to increased reliability, higher efficiency and a smaller installation footprint for the charging stations.

Central rectifier units at the grid interconnection points (substations, local grid stations, etc.) significantly reduce the effort required to integrate the active rectifiers for grid support. This leads to a direct cost reduction for the charging infrastructure. Due to the flexibly designable number and structure of the feed-in points of local DC underlay grids, the charging power can be optimally transferred to all coupled network nodes. The goal is to utilize the transformers of the distribution grid stations in a more targeted manner, while at the same time supporting the low-voltage grid.

In this project, the Institute for Power Generation and Storage Systems (PGS) creates real-time simulation models of a local DC underlay grid that are used to design and verify the control algorithms for the active rectifier. Subsequently, these algorithms will be tested in real-time on a control-hardware-in-the-loop platform to verify the operation of the control algorithms on real hardware. Finally, the fast-charging stations developed by the project partners in the research project will be operated and verified in power-hardware-in-the-loop tests.

The IDEAL project is a joint research project under the consortium leadership of the PGS. Further research and project partners are:

  • elexon GmbH
  • Lehrstuhl für Controlling, RWTH Aachen University
  • Lehrstuhl für Energiesystemökonomik, RWTH Aachen University
  • paXos Consulting and Engineering GmbH & Co. KG
  • Siemens AG Technology (T) Research in Energy and Electronics

The project is funded by the Federal Ministry of Economics and Climate Action (BMWK).