The traction converter is internally integrated with three traction inverter modules, the main purpose of which is to convert the DC voltage obtained from the converter into three-phase voltage with frequency conversion and transformation, which is used to control the traction motor to drive the vehicle to run in traction, inertia and braking conditions. The IGBT semiconductor devices of the traction converter are effectively cooled by circulating water cooling, and the structure of the inverter is very compact. Through internal and external cooling cycles, the heat of the inverter is effectively transferred out to prevent overheating. Two traction inverter modules and one auxiliary inverter module are integrated in the traction/auxiliary converter. Apart from the traction drive function, it also takes on the function of auxiliary power supply, which can convert DC voltage into three-phase sine wave voltage and supply power for vehicle AC load.