Fraunhofer Team Validates Megawatt Charging Without Upgrading the Grid

Researchers at the Fraunhofer Institute for Solar Energy Systems have demonstrated that megawatt-scale charging for heavy electric vehicles can work without reinforcing the grid connection — a result confirmed during trials in Freiburg under the HV-MELA-BAT research programme. Partners included Motion Control & Power Electronics and Mercedes-Benz Energy.

The core challenge the project addressed is that existing infrastructure cannot handle the loads imposed by heavy transport under conventional charging architectures. The team’s solution centres on a shared DC bus that links the AC grid, a second-life EV battery buffer, and the charging output. During testing, a 500 kW grid tie-in sustained charging output above 1 MW; the additional power was drawn from the battery storage, reducing peak demand on the transmission line.

Several design choices set the system apart:

• Modular converters — up to four 250 kW units in parallel — let capacity scale to a site’s specific needs.
• A galvanically isolated DC-DC converter runs at switching frequencies up to 200 kHz, yielding power density of 9 kW per litre and peak efficiency of 99.26 percent.
• The shared bus also allows local solar generation to feed directly into the buffer or the charger.
• The architecture supports both legacy and newer connection standards.

The Freiburg trials confirmed consistent grid-to-vehicle transfer efficiency across varying operating conditions. By replacing the need for grid-node reinforcement with modular, battery-buffered hardware, the project advances the technical case for electrifying heavy road transport at scale.

Source: pv Europe