Instability of Reversible Pump Turbines and Its Physical Origin

Currently, reversible pump turbines are being developed worldwide in the pumped hydro energy storage power plants. One of the paramount technical problems of the reversible pump turbines is the instabilities during the off-design working conditions. For example, in generating modes, significant pressure fluctuation has been observed in the reversible pump turbines with prominent systematic vibrations. In the present paper, several examples of the measured instabilities of reversible pump turbines are given for both the prototype and model type turbines. Based on those experimental data, the basic features of the instabilities are revealed together with the paramount influencing parameters (e.g. guide vane opening). Numerical simulations has also been performed to further investigate the physical origins of the instability. Finally, some recent progress are also briefly discussed for relieving the instability.