The Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg has now begun operations at its 250m2 megawatt laboratory for photovoltaics inverters. The facility is currently the only laboratory in Europe where manufacturers can commission certification, in accordance with the medium-voltage grid codes that have applied since July 1st 2010, of inverters with a power rating of up to 1MW.
“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 Sönke Rogalla, the laboratory manager.
The new laboratory is equipped with three medium voltage transformers, each with a power rating of 1.25MW, which are connected to the 20kV grid. One transformer supplies power to the solar array simulators, which supply the inverters to be tested with a voltage of up to 1000V and a current of up to 1000A. The other two transformers are used to feed the electricity into the medium-voltage grid. The transformer voltage can be adjusted between 255 and 790V. This range covers all voltages that are commonly used internationally.
“Power is drawn and fed in via two separate mediumvoltage transformers”, said 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.”