Renewable power integration in Sicily: Frequency stability issues and possible countermeasures

The exploitation of Renewable Energy Sources (RES) allows to reduce the electricity energy supplied by fossil fuelled power plants but introduces significant issues in power system planning and operation. Especially for small islanded systems, a larger share of load covered by RES, mainly wind and photovoltaic (PV) plants, implies lower inertia and reduced regulation resources to address frequency stability issues. The paper focuses on frequency stability criticalities of the power system of Sicily operated as an electric island. Starting from the reconstruction of a real incident occurred in 2011, several scenarios are analyzed, characterized by different countermeasures (e.g. PV retrofitting, advanced controls on wind farms). The aim is to evaluate the benefit on security brought about by the introduction of these solutions. The study relies on the dynamic simulation of the control/defense/protection systems relevant for frequency stability.