Risk assessment and mitigation on area-level RoCoF for operational planning

The integration of various renewable energy sources (RESs) leads to more severe frequency fluctuation, i.e., the rate of change of frequency (RoCoF) than before, which threats the safe operation of the modern power system. Besides, the RoCoF responses and its associated risk actually vary with different areas of the system owing to the uneven distribution of system inertia and RESs. Therefore, this paper aims to assess and then mitigate the risk of area-level RoCoF violation of a large power system in a probabilistic manner for operational planning. First, a sensitivity-based method, instead of traditionally time-consuming Monte Carlo-based simulation, is proposed to achieve a fast calculation on probabilistic distribution of area-level RoCoF, which is evaluated by the risk assessment matrix (RAM) established according to grid code. Additionally, the assessed high risk is mitigated by increasing inertia determined by the proposed RAM-based inertia identification method (RIIM), which allows a small probability of RoCoF violation according to the RAM and further reduces the required inertia demand and thus the cost for enhancement. Finally, six different allocation plans (AP) are proposed to distribute the calculated area-level inertia demand to individual plants in the region according to various considerations, i.e., technical feasibility and individual cost and RoCoF performance. The risk assessment and mitigation are critically validated via scenario-based simulation (SBS).