Diesel multiple unit, and electricity supply system and traction control method therefor

A power supply system for a diesel multiple-unit train, comprising:

• a diesel power pack;
• a traction inverter connected to a traction motor;
• an auxiliary inverter connected to a train load;
• a direct current chopper;
• and a supercapacitor, wherein the diesel power pack Is configured to output variable-voltage direct current power, the direct current chopper is configured to step down the variable-voltage direct current power and charge the supercapacitor by using the stepped-down variable-voltage direct current power, a first-voltage side of the direct current chopper is connected to the diesel power pack, a second-voltage side of the direct current chopper is connected to the supercapacitor, wherein the first voltage is higher than the second voltage, and the supercapacitor is connected to the traction inverter and the train load, wherein power flows bi-directionally between the supercapacitor and the traction inverter, the supercapacitor is connected in a main circuit consisting of the diesel power pack, the direct current chopper, the traction inverter connected to the tractor motor, and the auxiliary inverter connected to the train load, and there is only one direct current chopper in the main circuit, wherein an isolating contactor is connected between the supercapacitor and the direct current chopper and is configured to provide overcurrent protection for the supercapacitor, and a second isolating contactor is connected between the diesel power pack and the direct current chopper, wherein the isolating contactor and the second isolating contactor is controlled to open or close based on whether there is an overcurrent signal detected.