Abstract: China's power system is currently at a crucial stage of transformation and development. The rapid expansion of ultra-high voltage (UHV) networks and the large-scale integration of renewable energy sources impose stringent demands on the secure and stable operation of the power grid. This study focuses on the Jiangxi power grid, a significant UHV receiving-end grid in Central China. By considering the power transmission requirements of UHV transmission channels and the generation characteristics of various clean energy sources, an 8760-hour hourly power simulation was conducted. This simulation rationally allocated thermal power, hydro power, wind power, photovoltaic (PV) power, and pumped storage hydropower (PSH), thereby establishing a quantitative combination model that integrates a multi-power source structure with power system transformation scenarios. Based on the "14th Five-Year Plan for Energy Development in Jiangxi Province" and forecast data such as the "2022-2030 Provincial (District, Municipal) Renewable Energy Non-Hydropower Consumption Responsibility Weight Expected Target Recommendations," this combination model constructs both a conventional demand model and a sensitive demand model for the Jiangxi power grid, corresponding to 16 transformation scenario models. Employing the Analytic Hierarchy Process-Entropy Weight Method, a comprehensive evaluation system encompassing economic and technical indicators was established. The study's findings indicate that the current pumped storage power stations in Jiangxi Province are inadequate to meet the system's characteristics of high coal consumption, high curtailment rates of renewable energy, and poor operational economy by 2030. When PSH serve as additional energy storage sources, the amount of curtailed renewable energy, new energy storage losses, thermal power installed capacity, and coal consumption decrease as the scale of PSH increases. Even with a pumped storage capacity increased to 5000 MW, the Jiangxi power grid in 2030 still faces a 60% peak regulation range and maintains a high level of renewable energy curtailment. The study reveals that the reasonable demand scale (economic scale) for pumped storage under the conventional scenario of Jiangxi's power grid in 2030 is approximately 10200 MW. Additionally, considering potential future scenarios of load growth, load rate reduction, and increased UHV access in Jiangxi, the reasonable demand scale (economic scale) for pumped storage under the sensitive scenario of Jiangxi's power grid in 2030 ranges from 7120 MW to 11200 MW. These research outcomes provide theoretical support and scientific research for the development of PSH, the orderly retirement of thermal power, and the efficient integration of wind and solar resources in the new power system.