The auxiliary power supply system of urban rail vehicle is the heart of the rail traffic control system. Its power supply quality and reliability will directly affect the safety of vehicle operation and the degree of passenger comfort. Urban rail transit train power is not very large, the power supply range is small, the power supply lines are in the urban construction group, so the supply voltage should not be too high to ensure safety. Considering the same voltage level, the DC system AC voltage loss is small (no reactance voltage drop), so the urban rail transit adopts DC power supply system. In the provisions of IEC and UIC, there are four kinds of DC voltage system that are 600V,750V,1500V,3000V and one kind of alternating current pressing of 25KV,50Hz.

The auxiliary power supply modes of urban rail vehicles are distributed power supply and centralized power supply.

The decentralized power supply scheme is shown below (taking 6 car marshalling as an example):

The capacity of the single car auxiliary inverter is about 75 to 80KVA, and the power supply of the DC110V is about 25KW. Decentralized power supply redundancy, balanced axle load, configuration, but the cost of large, high total weight.

The centralized power supply diagram is as follows (taking 6 car marshalling as an example):