Train power supply system and method

The invention discloses a train power supply system and method. The system comprises a main power supply loop, a branch power supply loop and a control unit. The main power supply loop comprises a traction transformer, a first rectification unit, a middle supporting capacitor, an inversion unit, an isolation filtering unit, an alternating current contactor and train electric equipment which are connected in sequence, the traction transformer converts a high-voltage alternating current obtained from a pantograph into a low-voltage alternating current, and rectification, voltage stabilization, inversion and isolation filtering processing are carried out successively and then the alternating current is output; and the alternating current is provided when the alternating current contactor is controlled to be closed through the control unit. The branch power supply loop comprises a second rectification unit and a direct current contactor, a direct current is obtained through rectification of the second rectificati