Inertia in power systems refers to the energy stored in large rotating generators and some industrial motors, which gives them the tendency to remain rotating. This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www. Denholm, Paul, Trieu Mai, Rick Wallace Kenyon, Ben Kroposki, and Mark O'Malley. Inertia and the Power Grid: A Guide Without the Spin. Golden, CO: National Renewable Energy. This included an investigation of technical solutions for low-inertia systems, including system-wide inertia requirements and RoCoF limits, low-carbon sources of SIR such as synchronous en-ergy storage (ES) and synchronous condensers (SynCons), and fast frequency response (FFR) or grid-forming. RWE's first inertia-ready battery energy storage system (BESS) has started commercial operation on the site of the company's power plant in Moerdijk, the Netherlands. The BESS has an installed capacity of 7. It also outlines various factors and power system co ditions that affect inertial contribution from a grid-forming battery energy storage system. Determining optimal sizes of VSGs is a key factor to develop strategies that efficiently assure the capability. Abstract—Fast-frequency control strategies have been pro- strategies using energy storage systems (ESSs) have been posed in the literature to maintain inertial response of electric generation and help with the frequency regulation of the system. However, it is challenging to deploy such strategies.