A power supply system for urban rail transit cascaded direct-hanging stations, wherein the power supply system comprises a 110 kV high-voltage power grid, a 35 kV medium-voltage power grid, three identical filter inductors L, a cascaded H-bridge medium-voltage direct-hanging converter, a 650V-800V common direct current bus, an emergency power supply system and electric loads in a subway station, wherein a step-down transformer is installed between the 110 kV high-voltage power grid and the 35 kV medium-voltage power grid,
- wherein the cascaded H-bridge medium-voltage direct-hanging converter is divided into three phases with the same structure, which are respectively marked as an A-phase cascaded H-bridge medium-voltage direct-hanging converter, a B-phase cascaded H-bridge medium-voltage direct-hanging converter and a C-phase cascaded H-bridge medium-voltage direct-hanging converter, wherein each phase of the A-phase cascaded H-bridge medium-voltage direct-hanging converter, the B-phase cascaded H-bridge medium-voltage direct-hanging converter and the C-phase cascaded H-bridge medium-voltage direct-hanging converter comprises n modules Γmi with the same structure, such that the cascaded H-bridge medium-voltage direct-hanging converter comprises 3n modules Γmi with the same structure in total, wherein m represents a phase sequence, m=A, B, C, i represents a serial number of the modules Γmi, i=1, 2, 3 . . . n, and n is a positive integer greater than 1,
- wherein each of the modules Γmi is formed by an H-bridge converter and an isolated DC/DC converter connected in series, and a direct current-side filter capacitor Cmi0 of the H-bridge converter is connected in parallel at a direct current output end of the H-bridge converter, wherein the H-bridge converter is formed by two bridge arms connected in parallel, each bridge arm comprises two switch tubes with anti-parallel diodes, such that the H-bridge converter comprises four switch tubes with anti-parallel diodes in total, and the four switch tubes are marked as switch tubes Smij, wherein j represents a serial number of the switch tube, and j=1, 2, 3, 4, wherein in the two bridge arms of the H-bridge converter, a source electrode of the switch tube Smi1 is connected with a drain electrode of the switch tube Smi2, and a connection point of the source electrode of the switch tube Smi1 and the drain electrode of the switch tube Smi2 is marked as point σmi1, wherein a source electrode of the switch tube Smi3 is connected with a drain electrode of the switch tube Smi4, a connection point of the source electrode of the switch tube Smi3 and the drain electrode of the switch tube Smi4 is marked as point σmi2, and the points σmi1 and σmi2 form an alternating current input end of each of the modules Γmi,
- wherein in each phase of the cascaded H-bridge medium-voltage direct-hanging converter, the alternating current input ends of n modules Γmi are cascaded, such that in the cascaded H-bridge medium-voltage direct-hanging converter, three module strings formed by the n modules Γmi are formed, certain ends of the three module strings are connected together to form a common point, and the other ends of the module strings are respectively connected with the 35 kV medium-voltage power grid that is three-phase star-connected through one filter inductor L,
- wherein in the cascaded H-bridge medium-voltage direct-hanging converter, direct current output ports of the 3n modules Γmi are connected in parallel to form one 650V-800V common direct current bus,
- wherein the electric loads in the subway station comprise alternating current loads and direct current loads, wherein the alternating current loads at least comprise a ventilation and air conditioning system, a water supply and drainage system, a firefighting system and an escalator system, and the direct current loads at least comprise a communication and information system, an operation control system and an in-station lighting system, wherein input ends of the ventilation and air conditioning system, the water supply and drainage system, the firefighting system and the escalator system are respectively connected with the 650V-800V common direct current bus, and respectively convert direct current into alternating current by self-contained frequency modulation control apparatuses for operation, wherein input ends of the communication and information system, the operation control system and the in-station lighting system are respectively connected with the 650V-800V common direct current bus, and are respectively supplied with power through self-contained direct current converters,
- wherein the emergency power supply system comprises a non-isolated DC/DC converter and a standby power supply, wherein an output end of the non-isolated DC/DC converter is connected with the 650-800 V common direct current bus, and an input end of the non-isolated DC/DC converter is connected with an output end of the standby power supply.