Abstract: To intensive study the low frequency oscillation mechanism of hydraulic turbine generator units and reveal the stability behaviors of the system, this study develops a dynamic model of a turbine generator unit coupling a hydraulic turbine model, a governor model, and a third order generator model. First, the dynamic model is verified against the prototype measurements of the turbine generator unit. Then, according to the damping characteristics of the unit, we optimize its PID parameters through numerical experiments and analyze the mechanism of low frequency oscillations and the stability characteristics of the system under different governor parameters. Finally, to evaluate quantitatively the influence of sensitive parameters on system stability, damping sensitivity of the system in the steady oscillation mode is examined, and key parameters significant to system stability are determined.

Key words: hydraulic turbine generator units, low frequency oscillation, controller, damping characteristics, sensitivity analysis, stability