  This paper presents a dynamic Frequency Regulation (FR) model of a large
interconnected power system including Energy Storage Systems (ESSs) such as
Battery Energy Storage Systems (BESSs) and Flywheel Energy Storage Systems
(FESSs), considering all relevant stages in the frequency control process.
Communication delays are considered in the transmission of the signals in the
FR control loop and ESSs, and their State of Charge (SoC) management model is
considered. The system, ESSs and SoC components are modelled in detail from a
FR perspective. The model is validated using real system and ESSs data, based
on a practical transient stability model of the North American Eastern
Interconnection (NAEI), and the results show that the proposed model accurately
represents the FR process of a large interconnected power network including
ESS, and can be used for long-term FR studies. The impact of communication
delays and SoC management of ESS facilities in the Area Control Error (ACE) is
also studied and discussed
