Real - Time Generation Control

ower system loads are sensitive to frequency and following system frequency changes the aggregate load change follows the frequency deviation. When a generating unit is tripped or additional load is added to the system, the power mismatch is initially compensated by an extraction of the kinetic energy from the system inertial storage (the spinning masses) that causes a system frequency drop. As the frequency decreases the power consumed by loads also decreases. Equilibrium for large systems can be obtained when the frequency sensitive reduction of loads balances the power output of the tripped unit or that delivered to the additional load resulting in the new frequency. This effect could stop the frequency decline in less than a couple of seconds. However, if the mismatch causes the frequency to deviate beyond the governor deadband of the generating units their output will be increased by governor action. For such mismatches, equilibrium is obtained when the reduction in power consumed by loads plus the increased generation due to governor action compensates the mismatch. Such equilibrium is normally obtained within a dozen seconds of the frequency incident.