Ancillary services support the basic electrical services and are essential for the reliability and operation of the electric power system.
The electrical services that are supported include generating capacity, energy supply, and the power delivery system. FERC requires six ancillary services, including system control, regulation (frequency), contingency reserves (both spinning and supplemental), voltage control, and energy imbalance.
In addition, load following, backup supply, network stability, system ‘‘black-start’’, loss replacement, and dynamic scheduling are necessary for the operation of the system.
Utilities have been performing these functions for decades, but as vertically integrated regulated monopoly organizations. As these begin to disappear, and a new structure with multiple competing parties emerges, distributed utilities might be able to supply several of these.