Meaning
Power system control strategy forces generators to reduce output proportionally as frequency rises above nominal thresholds. Active power droop stabilizes grids by sharing load imbalances automatically across multiple connected units without central dispatch commands. Grid codes specify frequency response curves where a four percent droop setting drops generator output from full capacity to zero when frequency increases from fifty hertz to fifty two hertz.
Boundaries apply at islanded microgrids where sudden load rejection forces extreme frequency excursions that exceed normal droop governor capabilities.
Frequency Response
Governors measure local electrical frequency at generator terminals through internal phase locked loops. Turbine controllers calculate speed error signals continuously against established setpoints. Real power injection decreases linearly once network frequency crosses deadband limits.
Primary reserve margins depend entirely on available headroom across participating assets.
Load Sharing
Parallel generation units divide demand changes proportionately according to individual droop parameter settings. Larger machines assume greater shares of transient shifts when droop percentages match system capacity ratings. Impedance mismatches between feeders cause unequal power distribution despite identical governor configurations.
Communication links remain absent because governors react exclusively to local voltage angle shifts.
Grid Stability
Uncontrolled frequency spikes threaten rotating machinery integrity and consumer electronics safety. Droop mechanisms arrest decay rates during sudden generation loss events before secondary reserves activate. Frequency nadirs improve measurably when spinning reserves operate under tight droop curves.
System operators verify compliance through periodic injection tests during scheduled maintenance outages.
