This study compares the responses of large fixed-speed and variable-speed pumped-storage units to fast power fluctuations through numerical simulations. We examine their response characteristics under power fluctuations of nine sets different in amplitude and frequency. The power response characteristics of the units are analyzed using four quantitative evaluation indicators－mean and standard deviations of power differences

mean response time for power rise (fall)

and power delay. The results show that variable-speed generating units not only effectively respond to rapid fluctuations in the renewable energy output within seconds

but their response capabilities are superior to those of traditional large fixed-speed pumped-storage units. This further emphasizes the importance of variable speed units in coping with renewable energy fluctuations.