Control device, conversion device, control method, and electricity distribution system

1. A control device that controls power to be supplied to a specific load from at least one of a converter that has a power generator and a storage battery both connected thereto and converts DC power into AC power, and a commercial power supply, wherein

the control device determines whether the commercial power supply is in a power failure state or a power distribution state, and wherein:

when determining that the commercial power supply is in a power distribution state, the control device causes both of the converter and the commercial power supply to be connected to the specific load;

when determining that the commercial power supply has made a transition from a power distribution state to a power failure state, the control device causes the commercial power supply to be disconnected from the specific load while maintaining connection between the converter and the specific load; and

when determining that the commercial power supply has made a transition from a power failure state to a power distribution state, the control device causes the converter to be disconnected from the specific load and the commercial power supply to be connected to the specific load.

2. The control device according to claim 1 further comprising:

a detection unit that determines whether the commercial power supply is in a power failure state or a power distribution state; and

a load connection controller that switches, in accordance with a determination result of the detection unit, the connection between the converter and the specific load and the connection between the commercial power supply and the specific load.

3. The control device according to claim 2 further comprising a setting unit that sets a frequency of AC power to be generated by the converter from DC power, wherein:

when a determination result of the detection unit is a power distribution state, the setting unit sets the frequency to be synchronized with frequency of the commercial power supply;

when a determination result of the detection unit makes a transition from a power distribution state to a power failure state, the setting unit sets the frequency to be changed from the frequency synchronized with the frequency of the commercial power supply to a frequency asynchronous with that; and

when a determination result of the detection unit makes a transition from a power failure state to a power distribution state, the setting unit maintains the frequency asynchronous with the frequency of the commercial power supply.

4. A conversion device comprising:

a converter that is connected to a power generator and a storage battery and that converts DC power into AC power; and

a control device that controls power to be supplied to a specific load from at least one of the converter and a commercial power supply; wherein

the control device includes: a detection unit that determines whether the commercial power supply is in a power failure state or a power distribution state; and a load connection controller that switches, in accordance with a determination result of detection unit, connection between the converter and the specific load and connection between the commercial power supply and the specific load, and wherein:

when the detection unit determines that the commercial power supply is in a power distribution state, the load connection controller causes both of the converter and the commercial power supply to be connected to the specific load;

when the detection unit determines that the commercial power supply has made a transition from a power distribution state to a power failure state, the load connection controller causes the commercial power supply to be disconnected from the specific load while maintaining the connection between the converter and the specific load; and

when the detection unit determines that the commercial power supply has made a transition from a power failure state to a power distribution state, the load connection controller causes the converter to be disconnected from the specific load and the commercial power supply to be connected to the specific load.

5. A power distribution system comprising:

a power generator;

a storage battery that stores power from at least one of the power generator and a commercial power supply;

a converter that is connected to the power generator and the storage battery and that converts DC power into AC power;

a control device that controls power to be supplied to a specific load from at least one of the converter and the commercial power supply;

a switch that turns on or off connection between the converter and the commercial power supply; and

a power source switching unit that selectively connects the specific load to either a first pathway branched from a point between the switch and the converter or a second pathway branched from a point between the switch and the commercial power supply, wherein

the control device includes: a detection unit that determines whether the commercial power supply is in a power failure state or a power distribution state; and a load connection controller that controls, in accordance with a determination result of the detection unit, turning on and off of the switch and switching of the power source switching unit, and wherein:

when the detection unit determines that the commercial power supply is in a power distribution state, the load connection controller causes the switch to be turned on and causes the power source switching unit to connect the specific load to the second pathway;

when the detection unit determines that the commercial power supply has made a transition from a power distribution state to a power failure state, the load connection controller causes the switch to be turned off and causes the power source switching unit to connect the specific load to the first pathway; and

when the detection unit determines that the commercial power supply has made a transition from a power failure state to a power distribution state, the load connection controller maintains the off state of the switch and causes the power source switching unit to connect the specific load to the second pathway.

6. A method of controlling power to be supplied to a specific load from at least one of a converter that has a power generator and a storage battery both connected thereto and converts DC power into AC power, and a commercial power supply, the method comprising:

determining whether the commercial power supply is in a power failure state or a power distribution state;

causing, when it is determined that the commercial power supply is in a power distribution state, both of the converter and the commercial power supply to be connected to the specific load;

causing, when it is determined that the commercial power supply has made a transition from a power distribution state to a power failure state, the commercial power supply to be disconnected from the specific load while maintaining the connection between the converter and the specific load; and

causing, when it is determined that the commercial power supply has made a transition from a power failure state to a power distribution state, the converter to be disconnected from the specific load and the commercial power supply to be connected to the specific load.