A wind power generation system including: 1. - a group of wind turbine generators, 2. - a power storage system constituted by more than one power storage device, 3. - a generated power detector (6, 8) to detect the power generated by the group of wind turbine generators, 4. - a superior controller to control the group of wind turbine generators and the power storage system, 5. wherein the superior controller comprises: 6. - a power memory to record the sum of the power generated by the group of wind turbine generators and the charge and discharge power of the power storage system, 7. - a charge and discharge power command computing device for computing a command for the power storage system in a predetermined period from the present to a moment in the future (second period), by making use of: 7.1 - information computed in an output power recording memory about the output power in a predetermined period from a moment in the past to the present (the first period) and 7.2 - information about the present value recorded in the output power recording memory, and 8. - a charge and discharge power control device for controlling the charge and discharge power by the power storage system according to the charge and discharge power command, characterized by 9. - a maximum value and minimum value computing unit for determining the maximum value and the minimum value of the output power recorded in the output power memory in a first predetermined period from a moment in the past to the present, 10. - wherein the charge and discharge power command computing unit obtains an 10.1- upper limit value of an output range of the output power in the second predetermined period by adding a predetermined value to the minimum value determined by the maximum value and minimum value computing unit and 10.2- a lower limit value of the output range of the output power in the second predetermined period by subtracting a predetermined value from the maximum value determined by the maximum value and minimum value computing unit. 1. - a group of wind turbine generators, 2. - a power storage system constituted by more than one power storage device, 3. - a generated power detector (6, 8) to detect the power generated by the group of wind turbine generators, 4. - a superior controller to control the group of wind turbine generators and the power storage system, 5. wherein the superior controller comprises: 6. - a power memory to record the sum of the power generated by the group of wind turbine generators and the charge and discharge power of the power storage system, 7. - a charge and discharge power command computing device for computing a command for the power storage system in a predetermined period from the present to a moment in the future (second period), by making use of: 7.1 - information computed in an output power recording memory about the output power in a predetermined period from a moment in the past to the present (the first period) and 7.2 - information about the present value recorded in the output power recording memory, and 7.1 - information computed in an output power recording memory about the output power in a predetermined period from a moment in the past to the present (the first period) and 7.2 - information about the present value recorded in the output power recording memory, and 8. - a charge and discharge power control device for controlling the charge and discharge power by the power storage system according to the charge and discharge power command, characterized by 9. - a maximum value and minimum value computing unit for determining the maximum value and the minimum value of the output power recorded in the output power memory in a first predetermined period from a moment in the past to the present, 10. - wherein the charge and discharge power command computing unit obtains an 10.1- upper limit value of an output range of the output power in the second predetermined period by adding a predetermined value to the minimum value determined by the maximum value and minimum value computing unit and 10.2- a lower limit value of the output range of the output power in the second predetermined period by subtracting a predetermined value from the maximum value determined by the maximum value and minimum value computing unit.