Frequency regulation

Also called automatic generation control (AGC), frequency regulation is used to manage the second-by-second fluctuations in the system balance between supply and loads. AGC units are ramped up and down remotely by the system operations software and are used within successive five-minute periods to keep supply and demand in balance. Typical sources of AGC include hydropower, gas combustion turbines, gas combined-cycle turbines, gas, or coal steam turbine units that are providing energy from a portion of their capacity but that have additional unused capacity. In some control areas, batteries, fly wheels, and flexible loads also provide frequency regulation.