Grid Ancillary Services

What Are Ancillary Services?

Grid ancillary services refer to functions that help grid operators balance and support the transmission of energy from generators to consumers. Ancillary service markets maintain a reliable electricity system by controlling the proper flow and direction of electricity, addressing supply and demand imbalances and helping the power system recover after catastrophic events.

Types of Ancillary Services

• Regulation Service: Regulation service is the continuous balancing of resources to maintain the scheduled interconnection frequency at 60 Hertz. Regulation also tracks minute-to-minute fluctuations in consumer electricity use in order to fine-tune the grid frequency.
• Synchronized Reserve Service: This grid ancillary service is designed to ensure that there is enough unutilized energy to increase output when abrupt electrical demands need to be met. Synchronized reserve services supply energy when the grid has an unexpected need for power on short notice.
• Day-Ahead Scheduling Reserve (DASR): The DASR market is designed to clear existing day-ahead scheduling reserve requirements and ensure a sufficient quantity of resources are available to provide 30-minute reserve service in the real-time market. The purpose of DASR is to encourage generation and demand resources to be flexible and capable of providing half-hour reserves.
• Black Start Service: This ancillary service is paid to certain generating resources that can begin providing electricity to the grid for system restoration without any external energy supply. In the event that there are large blackouts on the power system, or the entire grid loses power, black start is necessary.
• Voltage Control: Just like frequency, voltage must be kept within a certain range to ensure the safety of people, equipment and the devices requiring power. Grid operators are responsible for maintaining voltage levels within acceptable limits by responding to shifts in generation and demand.
• Reactive Service: Reactive power services also work to maintain the voltage levels on the system by instructing generators to either absorb or generate reactive power.