Abstract: Sensitivity analysis of a hydroelectric generating system is of great significance to the application and improvement of the modeling technologies. To describe the unbalanced hydraulic forces acting on the turbine blades, this paper presents analytical expressions that play a key role in linking the models of the governing system and generator units. And based on this, we develop a unified model of the hydroelectric generating system and conduct a sensitivity analysis of its 27 parameters using the extended Fourier amplitude sensitivity test (EFAST), focusing on the parameters sensitive to the angular speed and rotor centroid of the generator. Results show that 1) the generator angular speed sensitive parameters include unit self-adjustment coefficient, the penstock diameters of the runner inlet and outlet, rated flow, and rated main servomotor displacement. 2) The sensitive parameters to the rotor centroid at horizontal deflection offset are the mass eccentricity of the rotor and runner, self-adjustment coefficient, the diameters of the runner outlet and outlet, and rated servomotor displacement. 3) An obvious difference exists between the interaction effects of the global sensitivity parameters and other parameters on the oscillation swings in X-direction and Y-direction. 4) The sensitivity to oscillation offset is stronger than that to the parameters of generator speed. Hence, when using the unified model to analyze the vibration evolution, the generator speed should be adjusted first, then the generator rotor parameters.

Key words: unbalanced hydraulic forces, hydroelectric generating system, generator speed, oscillation throw, sensitivity analysis