Inertial Response of Electrical Power Systems

Abstract

Following loss of generation events and during the period prior to the deployment of automatic generation control, the stabilization of system frequency above load shedding levels rests solely on the system inertia, self regulation, and governor response. This paper focuses on system inertia. The physics of inertia is reviewed and it is shown that increased amounts of inertia, and thus increased amounts of inertial response, can be provided only by increasing the mass of the machines rotating on the system or by redistributing it farther away from its axis of rotation. It is shown that controls that inject power into the system, such as synthetic inertia controls, do not provide inertial response. These controls only change the generation minus load imbalance. A one machine equivalent of a power system is developed and the calculation of equivalent system values for inertia, self regulation, and governor droop is discussed. Results of simulations that illustrate the impacts of different values of inertia on frequency recovery are presented. These results demonstrate that governor controls become unstable at some critical low value of inertia.