In recent years, the scale of renewable energy sources such as wind, solar, and hydropower has continued to expand, and pumped storage has emerged as the most reliable and cleanest energy storage method at this stage, with its role becoming increasingly prominent. The power system has imposed higher requirements on the safety and response speed of pumped storage. Most pumped storage units in China employ constant-speed units, which are known to involve multiple systems, have complex signal interactions, require longer startup times in the water pump mode, and have slower response speeds. To address these issues associated with constant-speed units, China has introduced doubly-fed variable-speed units, which have been successfully operated. By comparing the structures of constant-speed and variable-speed units and their startup modes in the water pump direction, this paper concludes that variable-speed units involve fewer systems, have simpler processes, and achieve faster startup speeds . This makes them more conducive to fulfilling the capabilities of peak shaving, valley filling, energy storage, frequency regulation, phase adjustment, and emergency backup for the power system.