Calculation of grid forming energy storage configuration for island grids based on virtual inertia sufficiency probability

Due to their unique geographical conditions, island grids face challenges, such as isolated operation, load fluctuations, and variability in renewable energy generation under high renewable energy penetration. Traditional grid-following energy storage systems struggle to provide sufficient inertia support and frequency stability, compromising grid security and power supply reliability. To address these issues, this paper first compares the fundamental attributes and control methods of gridforming and grid-following energy storage systems to analyze the applicability of grid-forming energy storage in island power systems. Subsequently, probabilistic modeling of net load fluctuations and interconnection line power is conducted using historical data, and the Gaussian kernel density estimation is applied to derive the probability density functions and calculate imbalance power. Furthermore, an energy storage configuration model is proposed, and it incorporates inertia sufficiency, which is considered by the requirements of the rate frequency change and maximum frequency deviation. Based on the imbalance power with a specified confidence probability, the model is used to determine the required energy storage capacity for the configuration. Finally, an empirical analysis is performed using a domestic island grid as a case study. The results show that the proposed energy storage configuration method can satisfy the system's inertia sufficiency requirements and align with mainstream engineering practices.