A control device is applied to a power conversion system including a first DDC and a second DDC connected in parallel with a common power supply target. The control device performs the equalization control of correcting, with an output correction voltage, at least any of a voltage command value of the first DDC and a voltage command value of the second DDC to equalize an output current. Moreover, while the equalization control is being performed, it is determined on which one of an output side of the first DDC or an output side of the second DDC abnormal disconnection has been caused based on the output correction voltage.