Influence of Rotor Damping Structures on Damping Torque Coefficient of Turbo-Generator during Low-Frequency Oscillation Caused by Large Disturbance

The damping structures of turbo-generators, such as rotor damping bars, core, and slot wedges, can provide positive damping effect for the low-frequency oscillation of power system. However, the magnetic saturation, distortion, and skin effect of generators make nonlinear damping effects during the low-frequency oscillation caused by large disturbance. In order to quantitatively describe the damping effect of the three damping structures, the damping torque coefficient (DTC) during the low-frequency oscillation is calculated by coupling time-stepping finite element method with the polynomial approximation method. The DTCs of turbo-generator with different rotor damping structures are obtained by comparing the individual and combined effect of the three damping components. Since there are several material options for the rotor slot wedges and damping bars, the influence of these materials on DTC is studied. A rotor damping structure that can not only improve the symmetry of rotor damping structure, but also enhance the DTC of turbo-generator is proposed. The results provide theoretical basis for power system stability enhancement by improving the rotor damping structures of turbo-generator.