Influence of Initial Rotational Speed of Variable-Speed Pump Storage Units on the Hydraulic Interference for Fixed-Speed Units During Pump Power-Off

Addressing the issue of hydraulic interference caused by variable-speed pumped storage units to individual units with a shared water delivery system, this study conducts numerical simulation research on fixed-variable speed pumped storage units with a shared water delivery system. It explores the patterns of hydraulic interference on fixed-speed units when the pump experience power-off at different initial rotational speeds. The results indicate that within the selected range of initial rotational speed variations (varies from 96% to 104%), the maximum spiral case pressure and the rate of draft tube inlet pressure decrease in the disturbed fixed-speed unit positively correlate with the initial rotational speeds of the variable-speed unit, while the minimum draft tube inlet pressure negatively correlates with it. When the initial rotational speed decreases from 104% to 96%, the input power setting time, overshoot, and amplitude variation rate of the disturbed unit decrease by 3.57 seconds, 6.65%, and 21.51%, respectively. The results demonstrate that the input power stability of the disturbed fixed-speed unit negatively correlates with the initial rotational speed of the disturbing variable-speed unit. The higher the initial rotational speed of the variable-speed unit, the more intense the flow rate and pressure changes. As the initial rotational speed of the variable-speed unit decreases, the stability of the disturbed unit improves.