A propulsion control device is connected to each converter as a load. A carrier phase table, in which, when load states of propulsion control devices capable of being determined to be equivalent to each other are grouped in a same group, setting values of phase angles in the same group are given for each group, is provided in a phase-angle determination unit providing a desired phase angle between signal wave and carrier wave. The phase-angle determination unit refers to the carrier phase table based on a load state signal indicating a load state of each propulsion control device and an own-vehicle ID signal, determines a phase angle provided to each converter, and outputs it to a PWM control unit. The PWM control unit changes a phase angle of the carrier wave based on the phase angle determined by the phase-angle determination unit.