双馈式变速抽水蓄能机组(DF-VSPSU)作为电力系统柔性可控电源，在系统功率平衡、无功支撑方面发挥重要作用。然而，在远端电网故障时采用典型低电压穿越控制的DF-VSPSU可能会因平衡点不存在，而出现运行失稳现象。因此，以单DF-VSPSU无穷大系统为对象，建立了准稳态下DF-VSPSU机侧特性和网侧特性方程，刻画了不同电网条件下DF-VSPSU稳定运行边界及其可行域，并分别从远端电压跌落深度、电网短路比、电网阻抗角、机组无功支撑系数4个因素分析对其运行平衡点存在性的影响。基于MATLAB/Simulink仿真验证了理论分析的合理性。

As the flexible-controlled power source in the power system, the doubly fed-based variable speed pumped storage unit (DF-VSPSU) has a significant role in the power rebalance and the reactive power support. However, under remote grid faults, the DF-VSPSU with the conventional low-voltage ride through control employed may lose the stability due to the absence of equilibrium point. Thus, taking one DF-VSPSU infinite-bus system as a case, the quasi-steady models of the DF-VSPSU generator-side characteristic and the grid-side characteristic are established. The stable boundary and the available region of DF-VSPSU are fully descripted with different grid conditions. Then, together with the sag depth of the remote voltage, the grid short circuit ratio, the grid impedance angle, and the reactive support coefficient, the existence of the equilibrium point of the DF-VSPSU is analyzed. Finally, the MATLAB/Simulink demonstrates availability of the theoretical analysis.