A DC/AC system interconnection device that is able to bidirectionally and directly perform power conversion between three-phase AC power and DC power, the device comprising: a bidirectional switch circuit that comprises a bidirectional switch group with six bidirectional switches (SRP, SSP, STP, SRN, SSN, STN) and is provided between a three-phase AC power supply and a DC power supply and turns on and off said bidirectional switches (SRP, SSP, STP, SRN, SSN, STN) of which each is provided for connecting a different combination of one phase of the three-phase AC power supply and one of two lines to the DC power supply; a control unit that is configured to generate, in a predetermined switching cycle, a first carrier waveform pattern, which has a pattern that varies for each mode, according to a plurality of modes divided according to a magnitude relation between voltages in each phase in the three-phase AC power, that is configured to perform virtual AC/DC conversion processing to acquire a plurality of interline voltage generation sections, in which two phases of the three-phase AC power are selected, based on the first carrier waveform pattern in the predetermined switching cycle and a first control signal corresponding to a phase of the three-phase AC power, that is configured to generate a second carrier waveform pattern, which varies according the plurality of modes, corresponding to the plurality of interline voltage generation sections acquired from the virtual AC/DC conversion processing, and that is configured to generate a switching pattern of the bidirectional switch circuit to perform virtual DC/DC conversion processing, which varies according to the plurality of modes, on an interline voltage across two phases selected from the plurality of interline voltage generation sections based on the generated second carrier waveform pattern and a second control signal corresponding to a phase of the DC power; a current setting unit that is configured to input a current set value indicating a current direction and an amount of current which flows between the DC power supply and the bidirectional switch circuit; a current detection unit that is configured to detect the current direction and an amount of current which flows between the DC power supply and the bidirectional switch circuit; and a current adjustment unit that is configured to generate the second control signal which increases and decreases a signal level such that the current direction and the amount of current detected by the current detection unit become the current set value. a bidirectional switch circuit that comprises a bidirectional switch group with six bidirectional switches (SRP, SSP, STP, SRN, SSN, STN) and is provided between a three-phase AC power supply and a DC power supply and turns on and off said bidirectional switches (SRP, SSP, STP, SRN, SSN, STN) of which each is provided for connecting a different combination of one phase of the three-phase AC power supply and one of two lines to the DC power supply; a control unit that is configured to generate, in a predetermined switching cycle, a first carrier waveform pattern, which has a pattern that varies for each mode, according to a plurality of modes divided according to a magnitude relation between voltages in each phase in the three-phase AC power, that is configured to perform virtual AC/DC conversion processing to acquire a plurality of interline voltage generation sections, in which two phases of the three-phase AC power are selected, based on the first carrier waveform pattern in the predetermined switching cycle and a first control signal corresponding to a phase of the three-phase AC power, that is configured to generate a second carrier waveform pattern, which varies according the plurality of modes, corresponding to the plurality of interline voltage generation sections acquired from the virtual AC/DC conversion processing, and that is configured to generate a switching pattern of the bidirectional switch circuit to perform virtual DC/DC conversion processing, which varies according to the plurality of modes, on an interline voltage across two phases selected from the plurality of interline voltage generation sections based on the generated second carrier waveform pattern and a second control signal corresponding to a phase of the DC power; a current setting unit that is configured to input a current set value indicating a current direction and an amount of current which flows between the DC power supply and the bidirectional switch circuit; a current detection unit that is configured to detect the current direction and an amount of current which flows between the DC power supply and the bidirectional switch circuit; and a current adjustment unit that is configured to generate the second control signal which increases and decreases a signal level such that the current direction and the amount of current detected by the current detection unit become the current set value.