The trend, which has been underway for a number of years now, whereby generation from renewable energy sources is replacing large fossil-fueled generation plants, means that there is an increasingly reduced regulatory capacity and mechanical inertia of the power system. Therefore, in order to ensure the safe operation of the system, proposals are being made by transmission system operators to allow renewable plants to participate in frequency containment in the event of imbalance between generation and load.

To this regard, this three-year System Research project seeks to address this issue by considering the possibility that wind and photovoltaic plants can participate in upward frequency regulation.
In particular, this report proposes a control strategy for wind generators. The proposed approach—whereby the variation in power output is not constant, but a function of the magnitude of the frequency error and the deviation of the rotor speed from its minimum permissible value—prevents frequency imbalances, which may occur if the wind speed is low due to the restoration of the optimal pre-fault operating conditions of the wind turbine.

In addition, a procedure is proposed for optimal calibration of wind power control parameters both considered in isolation and in synergy with ultra-fast regulation (which is assumed to be provided by electrochemical storage systems). The nadir distance from the nominal frequency value and the minimum frequency value tolerable by the electricity system under normal operating conditions, respectively, are used as the objective function to be minimized in the calibration. Simulation results for a 2030 scenario for the Sardinian system show that the restoration-related issue is completely resolved and that the sizing of ultra-fast regulation—due to the greater efficiency of the wind support—can be lower than in the case of coordination with constant-power wind regulation.

In the following research year, a possible strategy for upward grid frequency support by photovoltaic systems will be explored.