Unstable behaviour of pump-turbines and its effects on power regulation capacity of pumped-hydro energy storage plants

A detailed review of the studies published in literature on the topic revealed the main characteristics of the hydraulic instabilities and the influence of one or more geometrical parameters on their onset. Even though some geometry modifications aimed at improving the RPT's stability in one operating mode were proposed in literature, the definition of a comprehensive design strategy, globally optimizing the pump-turbine design by considering simultaneously the complexity of the phenomena in both the operating modes, still represents a challenge.