German certification body M.O.E. has issued what it describes as the industry’s first prototype confirmation of grid-forming properties under VDE FNN guidance note 2.1. The confirmation covers SMA’s Sunny Central Storage UP-S 4600 inverter with the “Full Boost” current boost option, M.O.E. said on 2 October.
The result followed measurements, simulations and model validation. The M.O.E. test laboratory carried out the testing, and the M.O.E. certification body then assessed the results independently. Model validation was a main focus: the inverter’s real behaviour had to be reproduced with different modelling approaches, including EMT and RMS models. Narrow permitted deviations, measurement uncertainty and dynamic effects meant that additional evaluation tests were needed at several points, according to M.O.E.
The background is a structural change in the power system. As large synchronous generators retire, functions long tied to them have to be provided differently in a grid dominated by inverters. Grid-forming inverters can, under defined conditions, provide instantaneous reserve, among other services. That turns a battery storage system from a pure energy store into an active component of the grid.
“Manufacturer, test laboratory and certification body have put a young and technically demanding verification procedure into practical use,” said Tobias Busboom, managing director of M.O.E. and head of its certification body and test laboratory. M.O.E. said it will feed the project’s findings into further technical and guideline work together with VDE FNN, FGW and experts from grid operators, manufacturers and test bodies.
SMA’s Daniel Duckwitz, specialist for grid stability, pointed to the Blackhillock and Föhren projects, which he said had already shown what battery storage with grid-forming inverters can contribute to system stability. The confirmation, he said, creates the precondition for using these capabilities in the German market for instantaneous reserve. The press release does not say when market use could begin. M.O.E. is based in Itzehoe, Schleswig-Holstein.
