Power supply apparatus and power system

A power supply apparatus comprising:

• a charge/discharge cable to which a vehicle is connected, the charge/discharge cable including a pair of power lines, a protective earth line at ground potential, and a control line;
• a grid-side switch provided between a grid-side input/output end and the charge/discharge cable, the grid-side input/output end being electrically connected to a power grid via a first distribution board;
• an islanded-side switch provided between an output end for islanded operation and the charge/discharge cable, the output end for islanded operation being electrically connected to a second distribution board different from the first distribution board;
• and
• a second control circuit configured to
• control operations of the grid-side switch and the islanded-side switch, and
• communicate, via the control line, with a first control circuit of a power conversion device provided in the vehicle, wherein
• a pair of voltage lines of the grid-side input/output end is electrically connected to a pair of power lines of the charge/discharge cable via the grid-side switch,
• a pair of voltage lines of the output end for islanded operation is electrically connected to the pair of power lines of the charge/discharge cable via the islanded-side switch,
• the pair of power lines of the charge/discharge cable is electrically connected to a pair of power lines of an AC-side input/output end of the power conversion device in the vehicle, the AC-side input/output end serving to input and output AC power,
• a neutral line of the grid-side input/output end and the protective earth line of the charge/discharge cable are connected to ground potential,
• the second control circuit is configured to, when the vehicle is connected via the charge/discharge cable,
• establish conduction between the first distribution board and the charge/discharge cable by turning on the grid-side switch, and
• control a grid-connected supply operation or a grid-interconnection operation while keeping the conduction between the first distribution board and the charge/discharge cable, the grid-connected supply operation being operation in which AC power at a first voltage supplied from the power grid via the first distribution board is supplied to the vehicle, the grid-interconnection operation being operation in which AC power at the first voltage supplied from the vehicle via the charge/discharge cable is supplied to the first distribution board,
• the second control circuit is configured to, when a power failure of the power grid is detected,
• establish conduction between the second distribution board and the charge/discharge cable by turning on the islanded-side switch,
• output a control signal instructing the islanded operation to the first control circuit of the power conversion device while keeping the conduction between the second distribution board and the charge/discharge cable, and
• control islanded operation in which AC power supplied from the vehicle via the charge/discharge cable is supplied to the second distribution board, and
• the control signal instructing the islanded operation specifies, as an output voltage value, a second voltage that is a potential difference between each line of the pair of voltage lines of the grid-side input/output end and the neutral line of the grid-side input/output end in the grid-connected supply operation or the grid-interconnection operation.