Frauenhofer’s megawatt laboratory for PV inverters begins operation

It is the first and currently only laboratory in Europe where manufacturers can commission certification, says the institute, in accordance with the medium-voltage grid codes that have applied since July 1, of inverters with a power rating of up to one MW.

The 250 m2 megawatt laboratory is equipped with three medium-voltage 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 1,000 V and a current of up to 1,000 A. 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.

“Power is drawn and fed in via two separate medium-voltage transformers,” explains Prof. Bruno Burger, in charge of power electronics development at Fraunhofer ISE. “This prevents the solar simulators and inverters from mutually affecting each other, and avoids measurement errors.”

The control unit for the megawatt laboratory resembles the control room of a power station, according to the institute. The scientists can reportedly connect and disconnect 20 kV transformers by remote control and create voltage dips of varying depth and duration.

“With a so-called ‘Low-Voltage Ride-Through’ test unit, we can investigate the performance of inverters with regard to voltage dips in the medium-voltage grid, as is required by the new regulations,” stated laboratory manager, Sönke Rogalla.