The solar PV inverter laboratory at Fraunhofer ISE is the first and currently the only laboratory in Europe where manufacturers can commission certification in accordance with the medium-voltage grid codes that have applied since 1 July 2010, of solar PV inverters with a power rating of up to 1 MW.

The laboratory is equipped with three mediumvoltage transformers, each with a power rating of 1.25 MW, which are connected to the 20 kV grid.

One transformer supplies power to the solar array simulators, which supply the inverters to be tested with a voltage of up to 1 kV and a current of up to 1 kA.

The other two transformers are used to feed the electricity into the medium-voltage grid. Their voltage can be adjusted between 255 and 790 V. This range covers all voltages that are commonly used internationally in solar PV systems.

In addition to the tests required by regulations, the laboratory offers analytical facilities in order to optimise solar PV inverters. For example, the Fraunhofer researchers measure not only the conversion efficiency but also the MPP tracking efficiency; this quantity quantifies the ability of a solar PV inverter to extract the maximum power from the connected solar cells at all times.