Analysis of Active RoCoF Response Power of Gridforming System at Unit- and Plant-Level

This paper presents a model-based analysis of the active rate of change of frequency (RoCoF) response power in a grid-forming (GFM) system at both unit and plant levels. Each unit response is first analytically decomposed into three components: ramp-up/down, constant, and damped (oscillatory/exponential). It is then revealed that plant topology and variations in cable lengths among units can cause unit response power imbalances through power synchronization loops, leading to unit interactions. These interactions shape the dynamic characteristics of the damped component, at the unit level-affecting overshoot and settling time-while having only a minor effect at the plant level.