In view of the problem that a hydro-power plant will have V/Hz limiting protection action and start emergency shutdown after load rejection and cannot meet the demand for auxiliary power protection of the unit

a method combining fast response and advanced pre-judgment is proposed. The PID control system principle is used to improve the startup and load rejection logic

so that the low frequency can be theoretically improved in response speed. Taking the optimized load rejection control system as the test content

the V/Hz limiting protection action is avoided

which indicates that the proposed method has universal applicability for suppressing frequency overshoot.