A power conversion device includes a smoothing capacitor, an input voltage detection unit, a power conversion unit, and a controller. The input voltage detection unit detects a voltage value of the input voltage. The power conversion unit converts a direct-current voltage smoothed by the smoothing capacitor into an alternating-current voltage to output the alternating-current voltage to a power system. The controller has a first operation mode of outputting active power to the power system, has a second operation mode of outputting reactive power to the power system, determines whether or not the voltage value is one of equal to and higher than a determination value, and makes a transition from the first operation mode to the second operation mode within a predetermined time from a time point when it is determined that the voltage value is lower than the determination value.