A review of pressure fluctuation in pump-turbines for pumped hydro energy storage with ultra-large head variation: Mechanisms, research methods, and control measures

As the most mature and widely deployed long-duration energy storage solution, pumped storage hydropower (PSH) faces hydraulic stability challenges under wide head variations that constrain its regulation capability and efficiency. Through statistical analysis of 113 existing PSH stations, this paper establishes a quantitative criterion for defining “ultra-large head variation” using the dual-operating condition ratio λ_H (maximum pumping head to minimum turbine net head). Incorporating head-level classifications, we delineate thresholds for normal, large, and ultra-large ranges: for low-head plants, λ_H ≤ 1.2557 (normal), 1.2557–1.3213 (large), and > 1.3213 (ultra-large); for high-head plants, corresponding thresholds are 1.1580 and 1.1870. Increased head variation intensifies rotor-stator interaction in pump-turbines, inducing unstable flow regimes (e.g., rotating stall and flow separation) that generate high-amplitude, low-frequency pressure pulsations—critically threatening cycle efficiency and structural integrity. This review systematically examines pressure pulsation mechanisms under ultra-large head variations, synthesizes advances in experimental, numerical, and intelligent algorithm approaches, and elucidates correlations among pressure pulsations, operational strategies, and structural vibrations. Critical analysis of hydraulic optimization methods suggests that integrating machine learning and data-driven techniques into multi-objective intelligent design platforms represents the future direction for addressing pressure pulsation challenges. By establishing linkages between hydraulic phenomena and energy storage performance, this work underscores the enabling role of advanced control strategies in enhancing PSH system efficiency and stability.