Patent ID: 12191772

DESCRIPTION OF THE EMBODIMENTS

The present invention will be further described clearly and completely in combination with the accompanying drawings and embodiments.

FIG.2is a circuit diagram of a direct current power supply system for urban rail transit cascaded direct-hanging stations. As can be seen from the figure, the direct current distribution system for urban rail transit cascaded direct-hanging stations according to the present invention includes 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 an electric load in the subway station; a step-down transformer is installed between the 110 kV high-voltage power grid and the 35 kV medium-voltage power grid, and a standby power supply and direct current electric loads are respectively connected with the 650V-800V common direct current bus.

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; 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 includes n modules Γmiwith the same structure, that is, the cascaded H-bridge medium-voltage direct-hanging converter includes 3n modules Γmiwith the same structure in total, wherein m represents a phase sequence, m=A, B, C, i represents a serial number of the module Γmi, i=1, 2, 3 . . . n, and n is a positive integer greater than 1.

The module Γmiis formed by one H-bridge converter and one isolated DC/DC converter connected in series, and one direct current-side filter capacitor Cmi0of the H-bridge converter is connected in parallel at a direct current output end of the H-bridge converter.

The H-bridge converter is formed by two bridge arms connected in parallel, each bridge arm includes two switch tubes with anti-parallel diodes, such that the H-bridge converter includes four switch tubes with anti-parallel diodes in total, and these 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; in the two bridge arms of the H-bridge converter, a source electrode of the switch tube Smi1is connected with a drain electrode of the switch tube Smi2, and a connection point thereof is marked as point σmi1; a source electrode of the switch tube Smi3is connected with a drain electrode of the switch tube Smi4, a connection point thereof is marked as point σmi2, and the points amu and σmi2form an alternating current input end of the module Γmi.

In each phase of the cascaded H-bridge medium-voltage direct-hanging converter, the alternating current input ends of n modules Γmiare cascaded, such that in the cascaded H-bridge medium-voltage direct-hanging converter, three module strings formed by n modules Γmiare 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 three-phase star-connected 35 kV medium-voltage power grid through one filter inductor L.

In the cascaded H-bridge medium-voltage direct-hanging converter, direct current output ports of 3n modules Γmiare connected in parallel to form one 650V-800V common direct current bus.

The electric loads in the subway station include alternating current loads and direct current loads, the alternating current loads at least include a ventilation and air conditioning system10, a water supply and drainage system20, a firefighting system30and an escalator system (40), and the direct current loads at least include a communication and information system50, an operation control system60and an in-station lighting system70; input ends of the ventilation and air conditioning system10, the water supply and drainage system20, the firefighting system30and the escalator system40are 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; input ends of the communication and information system50, the operation control system60and the in-station lighting system70are respectively connected with the 650V-800V common direct current bus, and are respectively supplied with power through self-contained direct current converters.

The emergency power supply system includes 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.

As can be seen fromFIG.2, n=3 in the present embodiment. In addition, the topological structures of the modules Γmiand the H-bridge converter can be seen inFIG.3andFIG.4.

In the present embodiment, the isolated DC/DC converter is a DAB converter.FIG.3shows a topological diagram of the modules Γmiwhen the isolated DC/DC converter adopts the DAB converter. As can be seen fromFIG.3, the circuit topological structure of the DAB converter sequentially includes a primary side inverter bridge, an energy storage inductor Lmi0, a high-frequency isolation transformer Tmi, a secondary side controllable rectifier bridge and a direct current bus filter capacitor Cmi1from input to output.

The primary side inverter bridge is formed by two bridge arms connected in parallel, each bridge arm includes two switch tubes with anti-parallel diodes, such that the primary side inverter bridge includes four switch tubes with anti-parallel diodes in total, and the four switch tubes are marked as switch tubes Qmij; the secondary side controllable rectifier bridge is formed by two bridge arms connected in parallel, each bridge arm includes two switch tubes with anti-parallel diodes, such that the secondary inverter bridge includes four switch tubes with anti-parallel diodes in total, and the four switch tubes are marked as switch tubes Qmih, wherein h is a serial number of the switch tube, and h=5, 6, 7, 8; each switch tube Qmijin the primary side inverter bridge is connected in parallel with one parasitic capacitor; each switch tube Qmihin the secondary side controllable rectifier bridge is connected in parallel with one parasitic capacitor.

In the two bridge arms of the primary side inverter bridge, the switch tube Qmi1and the switch tube Qmi2are connected in series to form one bridge arm, the switch tube Qmi3and the switch tube Qmi4are connected in series to form the other bridge arm, specifically, a source electrode of the switch tube Qmi1is connected with a drain electrode of the switch tube Qmi2, a connection point thereof is connected with one end of the energy storage inductor Lmi0, the other end of the energy storage inductor Lmi0is connected with one end of a secondary side of the high-frequency transformer Tmi, a source electrode of the switch tube Qmi3is connected with a drain electrode of the switch tube Qmi4, and a connection point thereof is connected with the other end of a primary side of the high-frequency transformer Tmi; the two bridge arms of the primary side controllable rectifier bridge are connected in parallel with the direct current-side filter capacitor Cmi0of the H-bridge converter.

In the two bridge arms of the secondary side controllable rectifier bridge, the switch tube Qmi5and the switch tube Qmi6are connected in series to form one bridge arm, the switch tube Qmi3and the switch tube Qmi4are connected in series to form the other bridge arm, specifically, a source electrode of the switch tube Qmi7is connected with a drain electrode of the switch tube Qmi8, and a connection point thereof is connected with one end of the secondary side of the high-frequency transformer Tmi, the source electrode of the switch tube Qmi7is connected with the drain electrode of the switch tube Qmi8, and a connection point thereof is connected with the other end of the secondary side of the high-frequency transformer Tmi.

The direct current bus filter capacitor Cmi1is connected in parallel at an output side of the secondary side controllable inverter bridge, and a positive electrode and a negative electrode of the direct current bus filter capacitor Cmi1form the direct current output port of the module Γmi.

In the present embodiment, the isolated DC/DC converter is an LLC resonant converter.FIG.4shows a topological diagram of the modules Γmiwhen the isolated DC/DC converter adopts the LLC resonant converter. As can be seen fromFIG.4, the circuit topological structure of the LLC resonant converter sequentially includes a primary side inverter bridge, an excitation inductor Lmi0, a resonant inductor Lmi1, a resonant capacitor Cmi2, a high-frequency isolation transformer Tmi, a secondary side uncontrolled rectifier bridge and a direct current bus filter capacitor Cmi1from input to output.

The primary side inverter bridge is formed by two bridge arms connected in parallel, each bridge arm includes two switch tubes with anti-parallel diodes, such that the primary side inverter bridge includes four switch tubes with anti-parallel diodes in total, and the four switch tubes are marked as switch tubes Qmij; each switch tube Qmijin the primary side inverter bridge is connected in parallel with one parasitic capacitor; the secondary side uncontrolled rectifier bridge is formed by two bridge arms connected in parallel, each bridge arm includes two diodes, such that the secondary side uncontrolled rectifier bridge includes four diodes in total, and the four diodes are marked as diodes Dmij.

In the two bridge arms of the primary side inverter bridge, the switch tube Qmi1and the switch tube Qmi2form one bridge arm, the switch tube Qmi3and the switch tube Qmi4form the other bridge arm, specifically, a source electrode of the switch tube Qmi1is connected with a drain electrode of the switch tube Qmi2, a connection point thereof is marked as point σmi3, a source electrode of the switch tube Qmi3is connected with a drain electrode of the switch tube Qmi4, and a connection point thereof is marked as point σmi4; the resonant capacitor Cmi2is connected in series between the point σmi3and the resonant inductor Lmi1, and the other end of the resonant inductor Lmi3is connected with one end of a primary side of the high-frequency transformer Tmi; the other end of a secondary side of the high-frequency transformer Tmiis connected with the point σmi4; the excitation inductor Lmi0is connected in parallel with the primary side of the high-frequency transformer Tmi; the two bridge arms of the primary side inverter bridge are connected in parallel with the direct current-side filter capacitor Cmi0of the H-bridge converter.

In the two bridge arms of the secondary side uncontrolled rectifier bridge, the diode Dmi1and the diode Dmi2form one bridge arm, the diode Dmi3and the diode Dmi4form the other bridge arm, specifically, an anode of the diode Dmi1is connected with a cathode of diode Dmi2, a connection point thereof is connected with one end of the secondary side of high-frequency transformer Tmi, an anode of the diode Dmi3is connected with a cathode of the diode Dmi4, and a connection point thereof is connected with the other end of the secondary side of the high-frequency transformer Tmi.

The direct current bus filter capacitor Cmi1is connected in parallel with an output side of the secondary side uncontrolled rectifier bridge, and a positive electrode and a negative electrode of the direct current bus filter capacitor Cmi1form the direct current output port of the module Γmi.

In the present embodiment, the DC/DC converter in the emergency power supply system is a Buck-Boost bidirectional non-isolated DC/DC converter.FIG.5shows a topological diagram of the Buck-Boost bidirectional non-isolated DC/DC converter. As can be seen fromFIG.5, the topological structure of the Buck-Boost bidirectional non-isolated DC/DC converter includes two switch tubes SDC1and SDC2with anti-parallel diodes, an inductor LDC, an input capacitor CDC1and an output capacitor CDC2.

In the Buck-Boost bidirectional non-isolated DC/DC converter, the switch tube SDC1and the switch tube SDC2form one bridge arm, a source electrode of the switch tube SDC1is connected with a drain electrode of the switch tube SDC2, and a connection point thereof is marked as point σDC; an input side of the bridge arm formed by the switch tube SDC1and the switch tube SDC2is connected in parallel with the input capacitor CDC1, one end of the inductor LDCis connected with the point σDC, the other end of the inductor LDCis connected with a positive electrode of the output capacitor CDC2, and a negative electrode of the output capacitor CDC2is connected with a source electrode of the switch tube SDC2.

FIG.6shows the comparison between a traditional alternating current power supply mode for loads in a station and the direct current power supply mode for loads in a station according to the present invention. It can be seen fromFIG.2that by adopting the direct current load power supply system according to the present invention, alternating current electric energy has been converted into direct current electric energy through the cascaded modular medium-voltage direct-hanging converter at the previous stage, unit power factor control can be realized, and electrical devices need no rectification and power factor correction any more. Therefore, only the uncontrolled rectifier circuit and the PFC circuit at the previous stage in the existing device need to be removed, and only the converters at the later stage are reserved. For example, only the DC/AC converter is reserved for a ventilation air conditioner and a water pump to drive a motor through frequency modulation control, and the DC/DC converter is reserved for lighting and information systems to supply power to the device through constant voltage or constant current control.