City rail vehicle auxiliary power system is an important part of the control system, its main task is to meet the low voltage power supply, vehicle control for passenger lighting, air conditioning and ventilation unit, low-voltage electrical equipment required for various voltage and electric power. The power supply quality and reliability of the auxiliary power supply system will directly affect the safety of vehicle operation and the degree of passenger comfort.

The auxiliary power supply system of urban rail vehicle has many kinds of inverter forms, and the typical block inversion principle is as follows: