Power supply apparatus, power supply system, and control method of power supply apparatus

A power supply system interconnected to a grid comprising:

• a power generation apparatus, a solar cell, a storage battery, and a power supply apparatus, wherein
• the power supply apparatus is provided with
• an inverter configured to convert DC power from the solar cell and the storage battery into AC power,
• a first relay configured to switch on or off a connection between the inverter and the grid,
• an AC-DC converter capable of converting AC power from the power generation apparatus into DC power and supplying the DC power to the storage battery during an grid-independent operation, and
• a controller configured to control, at the time of recovery of the grid from power outage, such that the AC-DC converter starts operating, that the first relay is switched on, and that the AC-DC converter keeps operating until a reverse power flow to the grid is detected.

A control method of a power supply apparatus interconnected to a grid together with a power generation apparatus, and configured to control a solar cell and a storage battery, the control method comprising:

• at the time of recovery of the grid from power outage,
• a step of converting AC power from the power generation apparatus into DC power and supplying the DC power to the storage battery;
• a step of switching on a connection between an inverter that converts DC power from the solar cell and the storage battery into AC power and the grid;
• and
• a step of controlling so as to maintain an operation to convert the AC power from the power generation apparatus into the DC power until a reverse power flow to the grid is detected.