Research on transient performance changes during the non-simultaneous opening process of guide vanes in reversible pump-turbine units in pump mode

With the escalating global energy crisis, worldwide energy infrastructure is undergoing restructuring. Pumped storage power plants (PSPs) plays a pivotal role in balancing grid demands for photovoltaic, wind power integration due to its operational flexibility. Understanding the transient performance evolution of pump-turbines during the startup phase in pumping mode is critical for ensuring operational safety and stability. This study investigates a special operating condition involving non-synchronous guide vane opening, focusing on transient hydrodynamic characteristics under this strategy. Through validated computational fluid dynamics (CFD) simulations calibrated with experimental data, this study systematically analyzes variations in external parameters, internal flow interactions, and pressure pulsations, its internal performance changes in line with the general law, the efficiency gradually increased, the head gradually decreased, the flow rate also gradually increased, the internal flow state with the opening of the movable guide vane is also gradually stable. Results demonstrate that the non-synchronous guide vane opening strategy effectively suppresses large-scale vortex generation between guide vanes, mitigates hydraulic losses, and enhances unit stability. By analyzing the hydraulic losses of different components, it is obvious to see the change of the flow smoothness of the flow state of each component in the process of opening the guide vane. Entropy production theory (EPT) quantifies energy loss distribution, while short-time Fourier transform (STFT) analysis identifies dominant pressure pulsation frequencies (9fn = 180 Hz) and their amplitudes at monitoring points. This research provides theoretical guidance for optimizing guide vane control strategies in PSPs systems, offering engineering insights for renewable energy applications. Collectively, the findings advance the development of operational protocols for pumped turbine units(PTU) in modern power grids.