The load rejection imposes a danger in the pumped storage hydropower plants (PSPs), especially when two or more pump turbines reject their loads simultaneously. In this paper, the simultaneous load rejection scenarios in the PSPs are simulated and analyzed by using a 1-D, 3-D coupling method. The PSP pipe system is modeled by using the 1-D method of characteristics (MOC) and one pump turbine is modeled by using the 3-D computational fluid dynamics (CFD). The simulated flow and head are transmitted between the 1-D, 3-D regions through the interfaces between these two regions. By assuming that the installed pump turbines are of the same type and the corresponding branch pipes have the same properties, the variations of the transient pressures and the flowrates in different pump turbines will be identical. Therefore, only one pump turbine is modeled by the CFD in this study. A new branching junction boundary is proposed to assign the simulated dynamic pressures and flowrates obtained by the 3-D model to other pump turbines. The 1-D-3-D coupling method is validated by experiments with only one pump turbine rejecting its load. The simultaneous load rejection of two pump turbines is then simulated and validated by comparing the results with those of the 1-D simulation. By building only one pump turbine 3-D model, a large amount of computational resources can be saved. The simultaneous load rejection scenario is then analyzed and compared with the single load rejection scenario. Higher water hammer pressures and a larger rotational speed occur in the simultaneous load rejection scenario, which leads to larger pressure pulsations in the pump turbine. The larger pressure pulsations can be further explained by the flow patterns in the runner channels, in which heavier flow separations and vortexes can be observed in the simultaneous load rejection scenario.

甩负荷给抽水蓄能水电站 (PSP) 带来危险，尤其是当两个或更多泵水轮机同时甩负荷时。在本文中，使用一维、三维耦合方法模拟和分析了 PSP 中的同时甩负荷情况。PSP 管道系统使用一维特性法 (MOC) 建模，一台泵涡轮机使用 3-D 计算流体动力学 (CFD) 建模。模拟的流量和水头通过这两个区域之间的界面在 1-D、3-D 区域之间传输。假设安装的水泵水轮机类型相同，对应的支管具有相同的特性，那么不同水泵水轮机的瞬态压力和流量的变化将是相同的。所以，在本研究中，CFD 只模拟了一个水泵涡轮机。提出了一个新的分支结边界，以将 3-D 模型获得的模拟动态压力和流量分配给其他水泵涡轮机。1-D-3-D 耦合方法通过实验得到验证，只有一个泵涡轮拒绝其负载。然后通过将结果与一维模拟的结果进行比较来模拟和验证两个泵水轮机的同时甩负荷。通过仅构建一个泵轮机 3-D 模型，可以节省大量计算资源。然后分析同时甩负荷情况并与单一甩负荷情况进行比较。更高的水锤压力和更大的转速发生在同时甩负荷的情况下，这会导致泵涡轮机中更大的压力脉动。