Comparison of Control Indices in Evaluating Coordinated V2G-Fuel Cells for Frequency Support

Frequency stability is critical to power system operation, especially in modern grids with high renewable energy penetration. Vehicle-to-Grid (V2G) and Fuel Cells (FC) have emerged as practical solutions to enhance frequency support due to their fast response capabilities. However, evaluating their effectiveness requires appropriate performance indices that capture different aspects of frequency control. This study conducts a comparative analysis of control indices for coordinated V2G and FC frequency support, focusing on key metrics that assess system stability. In addition to conventional indices, this study proposes new indices, including Integral of Cubed Error (ICE) and its time-weighted variants (ITCE, IT2SE, IT2AE, IT2CE, IT3SE, IT3AE, IT3CE). These indices comprehensively evaluate frequency deviation characteristics, response duration, and transient performance, including the Rate of Change of Frequency (RoCoF), a crucial factor in power system resilience. In order to ensure fairness in evaluation, all indices are benchmarked against the Frequency Disturbance Severity Index (FDSI), an independent metric integrating deviation magnitude, disturbance duration, and RoCoF impact. Genetic Algorithm (GA) optimisation is applied to fine-tune the control parameters of V2G and FC, ensuring optimal frequency response. The results provide insights into the effectiveness of different indices and highlight the importance of selecting suitable metrics for evaluating frequency support strategies. This study contributes to developing robust frequency regulation frameworks by guiding the selection of optimal indices for assessing ancillary services in power systems.