A power conversion apparatus comprising: a rectifier configured to rectify an alternating-current voltage supplied from an alternating-current power supply; a converter unit including a reactor connected to an output terminal of the rectifier, a reverse current prevention element connected in series with the reactor, and a switching element connected between the reactor and the reverse current prevention element, and configured to raise a rectified voltage (Vd) rectified by the rectifier and output the rectified voltage (Vd) as an output voltage; a smoothing capacitor configured to smooth the output voltage output from the converter unit; a current detection unit configured to detect a reactor current flowing to the reactor; a voltage detection unit configured to detect the output voltage output from the converter unit; and a converter control unit configured to control operation of the switching element of the converter unit, wherein the converter control unit includes a switching command calculation unit configured to calculate a switching command value responsive to a ratio of the rectified voltage (Vd) to the output voltage in accordance with the output voltage detected by the voltage detection unit and the reactor current detected by the current detection unit, characterized by further comprising: a switching control unit configured to control operation of the switching element in accordance with the switching command value calculated by the switching command calculation unit, and a supply abnormality determination unit configured to determine occurrence of a momentary power failure or a momentary voltage sag in accordance with the switching command value, wherein, when the switching command value is larger than a set threshold value (Dref), the supply abnormality determination unit determines that a momentary power failure or a momentary voltage sag has occurred, and the switching command calculation unit outputs a preset restriction switching command value (Dr), and wherein the switching control unit is adapted to control driving of the switching element to repeat ON/OFF operation during a momentary stopping of current flow due to the momentary power failure or the momentary voltage sag in accordance with the restriction switching command value (Dr). a rectifier configured to rectify an alternating-current voltage supplied from an alternating-current power supply; a converter unit including a reactor connected to an output terminal of the rectifier, a reverse current prevention element connected in series with the reactor, and a switching element connected between the reactor and the reverse current prevention element, and configured to raise a rectified voltage (Vd) rectified by the rectifier and output the rectified voltage (Vd) as an output voltage; a smoothing capacitor configured to smooth the output voltage output from the converter unit; a current detection unit configured to detect a reactor current flowing to the reactor; a voltage detection unit configured to detect the output voltage output from the converter unit; and a converter control unit configured to control operation of the switching element of the converter unit, wherein the converter control unit includes a switching command calculation unit configured to calculate a switching command value responsive to a ratio of the rectified voltage (Vd) to the output voltage in accordance with the output voltage detected by the voltage detection unit and the reactor current detected by the current detection unit, characterized by further comprising: a switching control unit configured to control operation of the switching element in accordance with the switching command value calculated by the switching command calculation unit, and a supply abnormality determination unit configured to determine occurrence of a momentary power failure or a momentary voltage sag in accordance with the switching command value, wherein, when the switching command value is larger than a set threshold value (Dref), the supply abnormality determination unit determines that a momentary power failure or a momentary voltage sag has occurred, and the switching command calculation unit outputs a preset restriction switching command value (Dr), and wherein the switching control unit is adapted to control driving of the switching element to repeat ON/OFF operation during a momentary stopping of current flow due to the momentary power failure or the momentary voltage sag in accordance with the restriction switching command value (Dr). a switching control unit configured to control operation of the switching element in accordance with the switching command value calculated by the switching command calculation unit, and a supply abnormality determination unit configured to determine occurrence of a momentary power failure or a momentary voltage sag in accordance with the switching command value, wherein, when the switching command value is larger than a set threshold value (Dref), the supply abnormality determination unit determines that a momentary power failure or a momentary voltage sag has occurred, and the switching command calculation unit outputs a preset restriction switching command value (Dr), and wherein the switching control unit is adapted to control driving of the switching element to repeat ON/OFF operation during a momentary stopping of current flow due to the momentary power failure or the momentary voltage sag in accordance with the restriction switching command value (Dr).