A power system comprising: an AC power supply; an AC filter circuit including an inductor having a first end and a second end, the first end being connected in series to an output end of the AC power supply, and a capacitor having a third end receiving a voltage at the second end of the inductor; an AC circuit breaker provided between the second end of the inductor and an electric power grid; a first switch provided between the third end of the capacitor and a first wiring connecting the second end of the inductor and the AC circuit breaker; and a controller for switching the first switch from a connected state, in which the first switch is turned on, to a disconnected state, in which the first switch is turned off, while the AC circuit breaker remains connected when the AC power supply is operated in a predetermined standby mode, in which power of the AC power supply is not supplied; characterized by further comprising: a charging circuit configured to charge the capacitor from the electric power grid; wherein the charging circuit comprises: a current limiting unit configured to adjust a current flowing into the third end of the capacitor; a second switch provided between a connection point and a second wiring, the connection point connecting the third end of the capacitor and the first switch, and the second wiring connecting the AC circuit breaker to the electric power grid; and a charging control circuit configured to make the second switch the disconnected state during the standby mode, to make the second switch the connected state while the first switch is in the disconnected state when the AC power supply returns from the standby mode to operation, and to make the second switch the disconnected state and make the first switch the connected state when a difference between a second voltage (V ACC) of the capacitor and a first voltage value (V grid) of the electric power grid is equal to or less than a predetermined first predetermined value, wherein the charging control circuit comprises a comparator, by which the difference between the second voltage (V ACC) of the capacitor and the first voltage value (V grid) of the electric power grid is determined. an AC power supply; an AC filter circuit including an inductor having a first end and a second end, the first end being connected in series to an output end of the AC power supply, and a capacitor having a third end receiving a voltage at the second end of the inductor; an AC circuit breaker provided between the second end of the inductor and an electric power grid; a first switch provided between the third end of the capacitor and a first wiring connecting the second end of the inductor and the AC circuit breaker; and a controller for switching the first switch from a connected state, in which the first switch is turned on, to a disconnected state, in which the first switch is turned off, while the AC circuit breaker remains connected when the AC power supply is operated in a predetermined standby mode, in which power of the AC power supply is not supplied; characterized by further comprising: a charging circuit configured to charge the capacitor from the electric power grid; wherein the charging circuit comprises: a current limiting unit configured to adjust a current flowing into the third end of the capacitor; a second switch provided between a connection point and a second wiring, the connection point connecting the third end of the capacitor and the first switch, and the second wiring connecting the AC circuit breaker to the electric power grid; and a charging control circuit configured to make the second switch the disconnected state during the standby mode, to make the second switch the connected state while the first switch is in the disconnected state when the AC power supply returns from the standby mode to operation, and to make the second switch the disconnected state and make the first switch the connected state when a difference between a second voltage (V ACC) of the capacitor and a first voltage value (V grid) of the electric power grid is equal to or less than a predetermined first predetermined value, wherein the charging control circuit comprises a comparator, by which the difference between the second voltage (V ACC) of the capacitor and the first voltage value (V grid) of the electric power grid is determined. a current limiting unit configured to adjust a current flowing into the third end of the capacitor; a second switch provided between a connection point and a second wiring, the connection point connecting the third end of the capacitor and the first switch, and the second wiring connecting the AC circuit breaker to the electric power grid; and a charging control circuit configured to make the second switch the disconnected state during the standby mode, to make the second switch the connected state while the first switch is in the disconnected state when the AC power supply returns from the standby mode to operation, and to make the second switch the disconnected state and make the first switch the connected state when a difference between a second voltage (V ACC) of the capacitor and a first voltage value (V grid) of the electric power grid is equal to or less than a predetermined first predetermined value, wherein the charging control circuit comprises a comparator, by which the difference between the second voltage (V ACC) of the capacitor and the first voltage value (V grid) of the electric power grid is determined.