Due to decarbonization policies, continuous growth can be foreseen, in the years to come, for Inverter-Based Generators (IBGs), especially those fed with non-programmable renewable energy sources. IBGs can also be expected to be enrolled in ancillary service supply, to control grid frequency e.g., since traditional suppliers like large fossil-fueled synchronous generators are decreasing.

Therefore, in this work an estimate is made of flexibility, in terms of active power reserve margins available for a given number of hours, which could be harvested from IBGs, with reference to a 2030 Italian power system scenario. Computations focus on the minimum flexibility which could be guaranteed with probability 97.5%, i.e. the 2.5% percentile of the power margins that could be obtained, for durations up to 8 h.

Different IBG technologies are analysed: ground PV, rooftop PV, rooftop PV coupled with a battery energy storage system, onshore wind, offshore wind. For each technology, downward and upward flexibility is evaluated for each market zone and for different deloading levels with respect to the expected available power output, which, in turn, is obtained from annual stochastic power profiles with hourly time step.

Results show that flexibility mainly comes from PV technologies, due not only to their large installed capacity, but also to the smaller intrinsic variability of their primary energy source, compared to wind technologies. Besides, flexibility reduction as duration increases is mild for durations up to 4 h at least.