A runaway transition after the pump power interruption and the simultaneous guide vane servomotor failure is one of the most dangerous and complex transitions for a pumped storage power system (PSPS). This paper analyzes the fluctuation behavior and mechanism of a PSPS during a runaway transition caused by the pump power interruption. The transient cavitation flow in the PSPS is simulated by using a one-dimensional and three-dimensional coupling flow simulation method for the runaway transition. Subsequently, the effects of the transient fluctuation of the radial hydraulic thrust on the runner and transient pressures are analyzed using the short-time Fourier transform method. Finally, the mechanisms are analyzed based on the analysis of the internal flow field. This study suggests that the extreme fluctuation generally occurs near the critical transformation points between the two operation modes. In addition, the extreme fluctuation behavior is primarily related to the local backflow near the runner inlet and the unstable cavitation phenomena in the runner and the draft tube. This finding helps for optimizing the runner design to resolve the instability problems of a PSPS.

泵电源中断和导叶伺服电机同时发生故障后的失控过渡是抽水蓄能发电系统 (PSPS) 最危险和最复杂的过渡之一。本文分析了PSPS在泵电源中断引起的失控过渡过程中的波动行为和机制。PSPS中的瞬态空化流是采用一维和三维耦合流模拟方法对失控过渡进行模拟的。随后，利用短时傅里叶变换方法分析了径向水推力瞬态波动对转轮和瞬态压力的影响。最后，在分析内部流场的基础上，对机理进行了分析。这项研究表明，极端波动通常发生在两种运行模式之间的临界转变点附近。此外，极端波动行为主要与转轮入口附近的局部回流以及转轮和导流管内不稳定的空化现象有关。这一发现有助于优化流道设计以解决 PSPS 的不稳定性问题。