Ancillary Services

Ancillary services are the grid support functions, such as frequency regulation, operating reserves, voltage support, and black start, that a grid operator buys to keep the system stable.

Batteries can provide most of them: regulation by following a fast signal, spinning and non spinning reserve by holding capacity ready to discharge, voltage support with reactive power, and black start by grid forming. Each service has its own market rules, performance measurement, and payment. An energy management system that stacks several of them against one state of charge earns more than one that does a single job.