A wind power generation system with a power storage device, comprising: a wind power generation system part that includes a wind power generator, a first power conversion circuit adapted to convert electric power generated by the wind power generator, a first control circuit adapted to control the first power conversion circuit, a filter capacitor provided at an output side of the first power conversion circuit, and a circuit breaker interposed between the filter capacitor and a grid connection point, the wind power generation system part being configured to output electric power converted by the first power conversion circuit to an electric power gird via the grid connection point; a power storage device system part (40, 140) that includes a power storage device, a second power conversion circuit interposed between the power storage device and the grid connection point, and a second control circuit (44, 144) adapted to control the second power conversion circuit adapted to perform load leveling operation () between the power storage device and the electric power gird via the grid connection point; and reactive power control means (13, 144) configured to provide a reactive power command value (Qref) to the second control circuit (44, 144) for causing the second power conversion circuit to perform reactive power compensation operation in a state in which the filter capacitor is connected to the grid connection point by making the circuit breaker connected and stopping the first power conversion circuit, the reactive power compensation operation being an operation in which the second power conversion circuit receives reactive power from the filter capacitor via the grid connection point. a wind power generation system part that includes a wind power generator, a first power conversion circuit adapted to convert electric power generated by the wind power generator, a first control circuit adapted to control the first power conversion circuit, a filter capacitor provided at an output side of the first power conversion circuit, and a circuit breaker interposed between the filter capacitor and a grid connection point, the wind power generation system part being configured to output electric power converted by the first power conversion circuit to an electric power gird via the grid connection point; a wind power generator, a first power conversion circuit adapted to convert electric power generated by the wind power generator, a first control circuit adapted to control the first power conversion circuit, a filter capacitor provided at an output side of the first power conversion circuit, and a circuit breaker interposed between the filter capacitor and a grid connection point, the wind power generation system part being configured to output electric power converted by the first power conversion circuit to an electric power gird via the grid connection point; a power storage device system part (40, 140) that includes a power storage device, a second power conversion circuit interposed between the power storage device and the grid connection point, and a second control circuit (44, 144) adapted to control the second power conversion circuit adapted to perform load leveling operation () between the power storage device and the electric power gird via the grid connection point; and a power storage device, a second power conversion circuit interposed between the power storage device and the grid connection point, and a second control circuit (44, 144) adapted to control the second power conversion circuit adapted to perform load leveling operation () between the power storage device and the electric power gird via the grid connection point; and reactive power control means (13, 144) configured to provide a reactive power command value (Qref) to the second control circuit (44, 144) for causing the second power conversion circuit to perform reactive power compensation operation in a state in which the filter capacitor is connected to the grid connection point by making the circuit breaker connected and stopping the first power conversion circuit, the reactive power compensation operation being an operation in which the second power conversion circuit receives reactive power from the filter capacitor via the grid connection point.