The continuous increase in grid-connected generation using inverters (Inverter-Based Generation – IBG), such as Photovoltaic (PV), wind, and Electrochemical Storage (ES) systems, reduces the resources that traditionally contributed to grid inertia and frequency regulation, i.e., large conventional systems equipped with synchronous generators, thus causing larger and faster frequency deviations from the nominal value.
Therefore, special attention was paid here to the potential for flexibility that IBG could provide in the future to support stable and safe system operation.

Firstly, with a view to developing and validating converter control methodologies for providing a new fast Synthetic Inertia (IS) support capability, a literature search was conducted on Grid-Forming control (GFM), which is faster and more robust than the already established Grid-Following (GFL) control. In fact, unlike GFLs, GFMs can synchronize automatically (not requiring a Phase-Locked Loop – PLL for the purpose), thus emulating the behavior of traditional synchronous generators. The analysis identified three main classes of GFM controllers: Droop-Based, Virtual Synchronous Generator (VSG) Swing-Based, and VSG High-Order. In the latter, a scheme that does not require the PLL and is able to distinguish between IS, damping, and primary frequency regulation appears particularly promising.

In addition, assuming that IBG participates in traditional services, an initial estimate of potential flexibility (downward and upward power margins for different levels of deloading), by hour of the day and month and by market area, of PV systems (with and without SdA) and onshore and offshore wind systems was made for a national development scenario through 2030 with 93.5 GW of installed IBG.

Focusing on the 2.5% percentile of power margins that these technologies can statistically present, in the most relevant zone, the NORTH, the maximum margin that can fall between 0% and 10% in the case of deloading varies between 2.5 and 6 GW in the winter months, reaching up to about 10-12 GW in the summer months. The other zones reach a maximum of up to 2.5-5 GW. For the maximum upward margin, the largest contribution is still from the NORTH zone, with values of 1.5 GW and 3 GW for deloading of 5% and 10% respectively in all or nearly all months; the other zones contribute a maximum of 1 to 2 GW.