The increase of renewable energy generation penetration rate exerts a passive impact on the power system. A pumped-storage plant (PSP) is a proper technology to depress power fluctuation and regulate the frequency of the power system. Variable-speed PSP (VSPSP) is a relatively novel technology and has unique advantages when participating in power and frequency regulation. This study focuses on the generating phase modulation of VSPSP and fixed-speed PSP (FSPSP). The integrated

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... al-electrical models of FSPSP and VSPSP are built and vector control theory is introduced in the model of VSPSP. Based on these two models, this study analyses operational performance and power response under generating phase-modulation mode. The results reveal that the power regulation ability of VSPSP is more accurate and rapid. In addition, the operation of VSPSP is not restricted by a stability limit and the range of power regulation is expanded. Eventually, it could be observed that weak coupling between the mechanical and electrical system in VSPSP helps to increase efficiency and prolong life-span of pumped-turbine. The results and conclusions obtained from this study help to mitigate power fluctuation and improve strategies of power regulation of hybrid power systems with PSP.