Online emergency control to suppress frequency oscillations based on damping evaluation using dissipation energy flow

When a frequency oscillation occurs, effective control measures should be taken to suppress the oscillation as soon as possible to avoid subsequent failures caused by the oscillation. Prime movers, including governors and turbines, with negative damping are the major cause of frequency oscillations, and quitting the primary frequency regulations of these units can increase the damping ratio of the system mode and make the oscillation decay. The dissipation energy flow method is further developed to evaluate the damping of prime movers for emergency control. The dissipation energy flow into the prime movers is computed online using phasor measurement data of 2-3 oscillation periods and is then used to evaluate the damping of the prime movers. The primary frequency regulations of the units with the lowest damping are quit to suppress the oscillation. The procedure of online emergency control is presented. Test results verify the validity of the proposed approach.