Frequency Support from Multiple Utility-Scale Grid-Forming Battery Energy Storage Systems

The large-scale integration of renewable energy sources has led to challenges related to frequency stability in low-inertia power systems. Utility-scale battery energy storage systems (BESSs) based on grid-following (GFL) and grid-forming (GFM) inverters are being explored to enhance networks’ resilience. For example, by providing new frequency control ancillary services (FCAS) such as fast frequency response (FFR) and simulated inertia. However, only a limited number of delivered utility-scale BESS projects with GFM technology have been reported, while GFM for microgrid or small island applications have been well studied, it is rare in large-scale power grid studies. This paper studies the FFR and simulated inertia services of utility-scale GFL and GFM BESSs. The dynamic study is performed by using an existing large-scale power network with two renewable penetration levels. The theoretical differences between a set of BESSs with GFL and GFM inverters have been validated based on simulation studies for critical generation trip events. The results demonstrate that the simulated inertia of GFM-BESSs benefits the FFR service in terms of frequency nadir, power reserve and the rate of change of frequency (RoCoF). This research contributes to the appropriate assimilation of new frequency control mechanisms of utility-scale BESSs towards converter dominated grids.