Uninterruptible power supply, power system, control device, and control method

A control device which controls an uninterruptible power supply connectable to a power line via which electric power from a power grid is supplied to a load device, comprising:

• a monitor configured to monitor a state of charge of a storage battery in the uninterruptible power supply;
• and
• a controller configured to control charging the storage battery from the power line and discharging from the storage battery to the power line, based on the state of charge of the storage battery and a difference between a first frequency being operation frequency of the power grid and a second frequency being a reference operation frequency for the power grid.

A control method which controls an uninterruptible power supply connectable to a power line via which electric power from a power grid is supplied to a load device, comprising:

• monitoring a state of charge of a storage battery in the uninterruptible power supply;
• and
• controlling charging the storage battery from the power line and discharging from the storage battery to the power line, based on the state of charge of the storage battery and a difference between a first frequency being operation frequency of the power grid and a second frequency being a reference operation frequency for the power grid.