According to one embodiment, there is provided a power-fluctuation reducing apparatus in a power generation system to control a converter connected to the power generation system and connected to secondary batteries. The power-fluctuation reducing apparatus includes adjusting direct current voltages output from the secondary batteries, respectively, detecting the directing current voltages output from the secondary batteries, respectively, controlling to adjust the direct current voltages output from the secondary batteries to make the direct current voltages uniform, based on the detected direct current voltages, and controlling the converter to reduce power fluctuations in the power generation system.