Following the significant increase in the installation of generation plants fed by renewable sources and the corresponding reduction in the use of conventional generation plants, the Italian Regulatory Authority ARERA approved Resolution 300/2017/R/eel, which constitutes the first opening of the market for the dispatching service to electricity demand, to generation units from renewable sources and to storage systems. In this context, it is essential to develop control functions that also allow wind and photovoltaic systems to participate in frequency regulation.

This report first presents a model-based predictive control strategy to enable a generating unit consisting of wind generators and electrochemical storage systems to perform synthetic inertia service. The strategy is designed to minimise the impact on the electrical system of restoring the initial conditions of wind generators, after providing a support in case of underfrequency: this restoration typically results in an additional frequency perturbation (rebound effect).

Next, the report proposes a control strategy to enable photovoltaic generation systems to provide upward frequency regulation service. This service is guaranteed provided that the system is set to operate in a de-loaded way i.e., in the absence of frequency imbalances, it does not deliver the maximum available power.

Both proposed controllers have been tested, by means of digital simulation, to show their effectiveness in containing the grid frequency deviation in the event of significant disturbances. Finally, it should be noted that the final aim of the three-year research project activity is to verify the control logics developed also by means of HIL (Hardware in the Loop) simulation.

The Report is available on the Italian site