CFD-based hydraulic-mechanical-electrical coupled simulation method for variable-speed pumped storage units

Compared to traditional fixed-speed units, variable-speed pumped storage units (VSPSUs) exhibit faster response and greater operational flexibility. However, their dynamic characteristics—including pressure pulsations, unit vibrations, and runner forces—may deteriorate under improper control. Accurate prediction of these characteristics is essential for ensuring safety. Nevertheless, existing mainstream numerical simulation methods, such as the transfer function method, primarily focus on macro parameters, failing to capture the complex dynamic characteristics. Therefore, this study proposes a novel computational fluid dynamics (CFD)-based method for simulating the dynamic characteristics of VSPSUs during transient processes, which couples three subsystems: (1) waterway system—employing one-dimensional method of characteristics (1D MOC) to simulate water hammer fluctuations in pipeline system; (2) hydromechanical system—utilizing three-dimensional (3D) CFD method to simulate the pump-turbine flow characteristics when the guide vanes adjust and the governor regulates, coupled with the waterway system through 1D-3D coupling approach; (3) electrical system—integrating models of doubly-fed induction machine and converter into the speed and power control strategies. These three system models are coupled and solved together in OpenFOAM, with implementation details provided. The method's high accuracy is validated through comparisons with field and model test data from pumped-storage plants, despite the relatively high computational costs. This method proves valuable for revealing instability mechanisms, mitigating vibration, and extending service life of VSPSUs.