Load-frequency control

In sudden power surges, load-frequency control stabilizes the grid. LFC's goals are to nullify steady-state frequency error after load changes and maintain each area's scheduled tie-line power flow.

Area Control Error, combining tie-line power flow deviations and frequency error, guides adjustments to each turbine governor's reference power setting.

Commands to raise or lower these settings occur every few seconds, allowing new steady-state operations when all settings and ACE of all areas are zero.

Frequency bias should be high enough for area contribution to frequency control without causing instability through high integrator gain.

Additional LFC objectives include controlling 60-Hz motor-driven clocks' timing and energy transfers by nullifying frequency and net tie-line errors.

During normal load and frequency changes, LFC maintains control.

Adjusting turbine governors' reference power settings accomplishes LFC and economic dispatch objectives.

In a coordinated automatic generation control strategy, ACE is computed first, with a share allocated to each unit.

Then, deviations of total generation from the desired are computed and allocated, dictating each unit's raise or lower signals.