Evaluation of Generator Damping Using Oscillation Energy Dissipation and the Connection With Modal Analysis

A newly proposed oscillation energy analysis method for power system low frequency oscillation is further developed. The oscillation energy flow in a generator and the energy dissipations of the field winding and the damper winding are studied. The oscillation energy flows into the field winding and the damper winding actually correspond to the electric energy transferred to the windings. The average powers of energy dissipation for oscillation modes with different frequencies are decoupled. For an individual mode, the energy dissipation of generator is computed using eigenvector and energy dissipation coefficient is obtained. The real-part of eigenvalue is negatively proportional to the sum of energy dissipation coefficients of all generators. It means the composite damping of the system comes from the energy dissipations of all generators. Especially in the single-machine system, the energy dissipation coefficient is equal to the damping torque coefficient. The consistency of oscillation energy analysis with damping torque analysis and modal analysis is verified. The energy dissipation leads to a new understanding of damping in power system and can be used for quantitative evaluation of generator damping in both offline and online applications.