The spread of non-dispatchable renewable generation presents challenges for the safe operation of the power system, including reduced inertia, frequency regulation margins, and short-circuit power. Evaluations of these parameters are particularly necessary for the Sardinian system, which is significantly affected by the energy transition. The document presents three main areas of activity.

The first development concerns the “SeTA” (SErvizi innovativi: Tuning Automatico) procedure for estimating the minimum amounts of possible new fast primary regulation services and synthetic inertia needed to achieve acceptable frequency responses in the event of imbalances. The procedure has been evolved to account for delays, measurement uncertainties, and nonlinear characteristics of controllers.

Application to a 2030 Sardinian scenario demonstrated that fast primary regulation is crucial in situations of low or high export to the mainland. The four synchronous compensators considered (4×250 MVA), along with the Sarroch plant, proved sufficient to ensure adequate inertia. In the event of unavailability of compensators, synthetic inertia with an implementation delay of less than 100 ms was found to adequately limit the frequency gradient.

The second development involves the refinement of frequency regulation models for upward frequency response by wind generation, based on the temporary release of accumulated kinetic energy. Simulations of transient under-frequency conditions in the Sardinian grid operation for 2030 showed high sensitivity of the system’s response to the tuning of parameters for this innovative regulation.

The third development involves the creation of a function to estimate short-circuit power levels, based on static calculations that account for the low contribution to short-circuit currents from generation connected via power electronics. Spanning 8,760 annual hours, the function lays the groundwork for adequacy assessments of short-circuit power resources, particularly for the stability of HVDC connections to the mainland. Application to a 2030 Sardinian scenario highlighted the effectiveness of installing three new synchronous compensators (3×250 MVA) planned on the island by the network development plan.