Frequency Droop

Frequency droop is a control rule that changes a plant’s active power in proportion to the grid frequency’s deviation from nominal, raising output when frequency falls and lowering it when frequency rises.

Droop is expressed as a percentage: a five percent droop means a frequency change of five percent of nominal would move the plant through its full rated power. A deadband around nominal keeps the plant from reacting to normal jitter. Droop is how synchronous generators have always shared load, and IEEE 2800 and IEEE 1547 require inverter based resources to provide it. The power plant controller or the inverters themselves implement it, in milliseconds to seconds.

Also called: Frequency-watt, Primary frequency response, Droop control