ROCOF IMPORTANCE IN ELECTRIC POWER SYSTEMS WITH HIGH RENEWABLES SHARE: A SIMULATION CASE FOR CROATIA

By integrating the new production technologies into the electric power system (EPS) which are mainly inverter-based, the characteristics of the conventional bulk EPS are significantly changed leading to a reduction of synchronous inertia which causes faster frequency dynamics. Synchronous inertia directly affects the maximum value of the rate of change of frequency (ROCOF). The importance of ROCOF is vital: ROCOF is the main parameter for Loss of Mains relay, it is used as an input parameter for Fast Frequency Response and Synthetic Inertial Response control algorithms and can be used as a metric parameter for underfrequency load shedding. In this paper, the importance of ROCOF in the inverter rich EPS will be described in detail, different grid code versions concerning ROCOF will be presented and the results of ROCOF analysis in Croatian EPS with respect to the future renewable energy source (RES) share scenarios will be shown.