Urban rail transit full flexible direct current power supply system

Abstract

The application discloses a kind of urban rail transit full flexible DC power supply systems, including centralized power supply system and decentralized power supply system, centralized power supply system includes at least two independent main substation, and is supplied to multiple substations by medium voltage network, and main substation is accessed two-way external power supply and is respectively output to I section medium voltage bus, Ⅱ section medium voltage bus by converter device;I section medium voltage bus, Ⅱ section medium voltage bus are connected with the medium voltage bus of substation;Decentralized power supply system is provided with at least two settings in substation opening and closing station, and is supplied to adjacent substation by medium voltage network, and opening and closing station is accessed two-way external power supply and is output to the medium voltage bus of substation by converter device;The medium voltage network of two kinds of power supply systems is connected with double loop network scheme or loop network scheme;Substation is provided with two energy routers for mutual standby, and the input end of energy router is respectively connected I section medium voltage bus or / and Ⅱ section medium voltage bus.

Description

Technical Field

[0001] This invention belongs to the technical field of rail transit power supply systems, specifically relating to a fully flexible DC power supply system for urban rail transit. Background Technology

[0002] Domestic power distribution networks generally adopt AC power supply system. While fulfilling the task of supplying power to the load, traditional AC distribution networks also face many challenges.

[0003] On the one hand, electricity demand is becoming more diversified, with an increase in DC load. Most household appliances, office automation equipment, and industrial and commercial loads (such as LED lighting, data centers, electric locomotives, air conditioners, elevators, etc.) are actually powered by DC. Therefore, traditional power distribution networks need to be equipped with a large number of power electronic converters. However, the extensive use of converters not only increases equipment costs but also reduces the overall efficiency and reliability of power.

[0004] On the other hand, due to the need for system redundancy, a large number of cables and transformers require redundant configuration, resulting in low utilization rates of AC power distribution equipment in my country's AC distribution network. Simultaneously, under the influence of AC current, the presence of eddy currents in the cable's metallic sheath generates active power losses, which, combined with the reactive power losses of the AC system itself, make the line losses of the AC power grid significantly higher than those of the DC distribution network. The increasing proportion of high-tech industries in my country's industrial structure leads to a growing number of sensitive loads in the power grid. These sensitive loads have high requirements for power quality, demanding high-quality power with stable voltage amplitude and frequency, and free from surges and harmonics. In traditional urban distribution networks, most sensitive load users rely on power electronic devices such as UPS, APF, and SVG to improve power quality, further increasing system complexity and cost.

[0005] In addition, the demand for access to new energy equipment is increasing. Small wind turbines, photovoltaic cells, diesel generators, fuel cells, energy storage power stations, electric vehicle charging stations and other units mostly output electrical energy in the form of DC or can be converted into DC through simple rectification. They must be connected to the AC distribution network through DC-AC converters and supplemented by complex controllers, which will also reduce the overall efficiency of the system and increase its complexity.

[0006] Compared to AC distribution networks, DC distribution networks have the following advantages: high power supply reliability, high power quality, easy access to new energy equipment, low line loss, high equipment utilization, conducive to power optimization and dispatch, and more flexible power configuration. The DCization of distribution networks will inevitably become an important direction for the future transformation and upgrading of urban distribution networks.

[0007] Researching DC power distribution network technologies for urban rail transit is of great significance for building a more reliable, stable, economical, and clean modern intelligent rail transit system. Summary of the Invention

[0008] The purpose of this invention is to provide a fully flexible DC power supply system for urban rail transit. Currently, urban rail transit power supply systems typically use a three-phase AC system for medium-voltage networks, with voltage levels generally at AC35kV or AC10kV. Two rectifier units are installed in the traction substation, and the voltage is stepped down and rectified before being supplied to the DC traction network. The contact network voltage level is generally DC1500V or DC750V. Compared to the existing three-phase AC medium-voltage system and uncontrolled DC traction system, the fully flexible DC power supply system proposed in this invention adopts a system architecture of DC medium-voltage system and controllable DC traction system, offering advantages such as high reliability and high power quality.

[0009] This invention achieves this objective through the following technical solution:

[0010] A flexible DC power supply system for urban rail transit is categorized into two types based on the external power supply method: a centralized power supply flexible DC power supply system and a distributed power supply flexible DC power supply system.

[0011] The centralized power supply mode fully flexible DC power supply system includes at least two independently set main substations. The main substations supply power to multiple substations through a medium-voltage network. The main substations are connected to two external power sources, which are output to the main substation's Section I medium-voltage busbar and Section II medium-voltage busbar respectively through the main substation's converter device. The main substation's Section I medium-voltage busbar and Section II medium-voltage busbar are both connected to the substation's medium-voltage busbar.

[0012] The distributed power supply method fully flexible DC power supply system has at least two switching stations. The switching stations are located in the substation and supply power to the adjacent substation through the medium voltage network. The switching stations are connected to two external power sources, which are output to the medium voltage bus of the substation through the converter device of the switching station.

[0013] Both the centralized power supply mode fully flexible DC power supply system and the decentralized power supply mode fully flexible DC power supply system adopt a double-ring network connection scheme or a ring network connection scheme for their medium-voltage networks; the medium-voltage network is a hybrid network of traction power and lighting, with the medium-voltage ring network fully connected.

[0014] The substation includes a step-down substation, a traction substation, and a traction-step-down hybrid substation. The substation is equipped with two energy routers that serve as backups for each other. The input terminals of the energy routers are respectively connected to the I-section medium-voltage bus and / or the II-section medium-voltage bus. Both energy routers output multiple voltage standards.

[0015] Furthermore, both the energy router and the converter simultaneously output three different voltage standards: the first is three-phase AC 400V, the second is DC ±375V, and the third is DC 1500V / 750V. The AC 400V bus adopts a single-bus segmented wiring scheme, with normally open bus tie switches. The two bus segments are respectively connected to the AC 400V output side of the two energy routers. The DC ±375V bus adopts a single-bus segmented wiring scheme, with normally open bus tie switches between the two positive bus segments and between the two negative bus segments. The two positive bus segments are respectively connected to the DC +375V output side of the two energy routers, and the two negative bus segments are respectively connected to the DC -375V output side of the two energy routers. The positive and negative bus segments are grounded through a resistor or capacitor. The DC 1500V / 750V bus adopts a single-bus scheme, with the two bus segments respectively connected to the DC +1500V / +750V and 0V output sides of the two energy routers.

[0016] Furthermore, the DC medium-voltage network adopts a unipolar symmetrical connection method, and the positive and negative buses of the medium-voltage network are grounded through resistors or capacitors; the medium-voltage bus adopts a single bus segmentation scheme, and the positive medium-voltage ring network structure is the same as the negative medium-voltage ring network structure.

[0017] Furthermore, for the centralized power supply system with a double-ring network connection scheme for medium-voltage networks, bus tie switches are installed between the sectional busbars in the main substation and the first and last substations of the line. The bus tie switches in the main substation are normally open, while the bus tie switches in the first and last substations of the line are normally closed. No bus tie switches are installed between the two busbar sections in the intermediate substations of the line. Except for the first and last substations of the line, all other substations are equipped with two incoming lines and two outgoing lines to connect to the first section of medium-voltage power supply in the intermediate substations. The line has two incoming lines at the beginning and end substations. The medium-voltage ring network cable of section I is led out from the medium-voltage busbar of section I of the main substation and connected to the medium-voltage busbar of section I of each substation in sequence. The medium-voltage ring network cable of section II is led out from the medium-voltage busbar of section II of the main substation and connected to the medium-voltage busbar of section II of each substation in sequence. Both sections I and II of the medium-voltage ring network are fully connected and provide power to each substation on both sides. The outgoing line of the medium-voltage busbar of the main substation is connected to the medium-voltage busbar of the two substations as the substation incoming line.

[0018] Furthermore, for the centralized power supply system with a loop connection scheme in the medium-voltage network, bus tie switches are installed on the busbars of the main substation and each substation along the line. The bus tie switches of the main substation and the two access substations connected to the main substation are normally open, while the bus tie switches of the remaining substations are normally closed. A ring network tie switch is installed between the first and last substations of the line and their adjacent substations; this ring network tie switch is normally closed. Each substation along the line, except for the access substations, has one incoming line and one outgoing line. The two outgoing cables of the medium-voltage busbar in section I of the main substation... The two busbars of the main substation are connected to two sections of the medium-voltage busbar in section II, and the two outgoing cables of the medium-voltage busbar in section II of the main substation are connected to two sections of the busbar in the adjacent substation. The medium-voltage ring network cable in section I of the line has two outgoing lines from the medium-voltage busbar in section I of the substation, and each line connects to the medium-voltage busbar in section I of the next substation every other substation. The medium-voltage ring network cable in section II of the line has two outgoing lines from the medium-voltage busbar in section II of the substation, and each line connects to the medium-voltage busbar in section II of the next substation every other substation. The medium-voltage ring network forms a loop connection, providing power to each substation on the line from both sides.

[0019] Furthermore, for the distributed power supply system with a dual-ring network scheme for medium-voltage networks, a bus tie switch is installed between the busbars of the switching stations and the substations at the beginning and end of the line. The bus tie switch of the switching station is normally open, while the bus tie switch of the substations at the beginning and end of the line is normally closed. No bus tie switch is installed between the two busbars of the other substations in the middle of the line. Except for the substations at the beginning and end of the line, each substation is equipped with two incoming lines and two outgoing lines, which are used to connect the I-section medium-voltage busbar and the II-section medium-voltage busbar of each intermediate substation. The substations at the beginning and end of the line are equipped with two incoming lines. The I-section medium-voltage ring network cable is led out from the I-section medium-voltage busbar of the switching station and connected to the I-section medium-voltage busbar of each substation in sequence. The II-section medium-voltage ring network cable is led out from the II-section medium-voltage busbar of the switching station and connected to the II-section medium-voltage busbar of each substation in sequence. Both the I-section and II-section medium-voltage ring networks are fully connected, providing bilateral power supply to each substation on the line.

[0020] Furthermore, for the distributed power supply system with a ring-connection scheme in the medium-voltage network, each substation section busbar in the line is equipped with a bus tie switch. The two bus tie switches connecting to the outgoing lines of the switching substation are normally open, while the bus tie switches of the remaining substations are normally closed. Except for the connecting substations, each of the other substations on the line has one incoming line and one outgoing line. The two outgoing cables of the converter unit in the switching substation are respectively connected to two busbar sections of one connecting substation, and the other converter unit in the switching substation... The device's two outgoing cables are respectively connected to two busbars of an adjacent substation. The I-section medium-voltage ring network cable on the line has two outgoing lines from the I-section medium-voltage busbar of the substation, each line connecting to the I-section medium-voltage busbar of the next substation every other substation. The II-section medium-voltage ring network cable has two outgoing lines from the II-section medium-voltage busbar of the substation, each line connecting to the II-section medium-voltage busbar of the next substation every other substation. The medium-voltage ring network forms a loop connection, providing bilateral power supply to each substation on the line.

[0021] Furthermore, the two converter units of the switching station are located in the same access substation or in two adjacent access substations respectively.

[0022] Compared with the prior art, the beneficial effects of this invention are as follows:

[0023] I. This invention proposes to use a fully flexible DC power supply system to supply power to urban rail transit lines. By employing DC-DC conversion and DC-AC conversion technologies, the power flow of the power supply system is adjustable and controllable, improving the reliability of the medium-voltage power supply network and effectively reducing line losses.

[0024] Second, this invention employs an energy router to undertake power supply and transformation tasks in traction substations and step-down substations, which improves the flexibility of system operation, simplifies the main wiring structure of substations, reduces the number of switches, and lowers system investment costs.

[0025] Third, the low-voltage network of the system in this invention adopts DC power supply, which provides an interface for the access of new energy and energy storage equipment, realizes the local consumption of new energy power generation, helps to reduce the back transmission of train regenerative power to the urban power grid, and enables the train regenerative braking energy to be consumed within the power supply system.

[0026] Fourth, this invention is applicable to networked power supply for urban rail transit. The DC medium-voltage network is fully connected, and there is no problem of balanced current in AC network loop power supply. This is beneficial for extending the power supply distance and improving the system's power supply capacity. Attached Figure Description

[0027] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the positive terminal of the fully flexible DC power supply system with centralized power supply mode in the dual-ring network scheme of this invention;

[0029] Figure 2 This is a schematic diagram of the positive terminal of the fully flexible DC power supply system with centralized power supply method in the loop connection scheme of the present invention;

[0030] Figure 3 This is a schematic diagram of the main substation structure in this invention;

[0031] Figure 4 This is a schematic diagram of the substation structure in the middle position of the fully flexible DC power supply system with centralized power supply mode in the dual-ring network scheme of this invention;

[0032] Figure 5 This is a schematic diagram of the positive terminal of the fully flexible DC power supply system with distributed power supply method in the dual-ring network scheme of this invention;

[0033] Figure 6 This is a schematic diagram of the positive terminal of the fully flexible DC power supply system with distributed power supply method in the loop connection scheme of this invention;

[0034] Figure 7 This is a schematic diagram of the opening and closing structure in this invention. Detailed Implementation

[0035] Exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] Currently, the medium-voltage power supply network of urban rail transit in China generally adopts a three-phase AC system with a voltage level of AC35kV or AC10kV. Two rectifier units are installed in the traction substation, and the voltage is stepped down and rectified before being supplied to the DC traction network. The voltage level of the contact network is generally DC1500V or DC750V. The three-phase AC medium-voltage network uses a lot of cables, has a large line power loss, and the power flow of the power supply system is difficult to control. The fully flexible DC power supply system proposed in this invention adopts a DC-DC system architecture. The power flow of the power supply system is adjustable and controllable, the line loss is low, the operation mode is flexible, and it can provide interfaces for the access of new energy and energy storage equipment, which is conducive to extending the system power supply distance and improving the system power supply capacity.

[0037] The external power supply of the fully flexible DC power supply system adopts either a centralized or decentralized power supply method, and the medium-voltage ring network adopts a double-ring network connection scheme or a ring connection scheme. Taking a certain engineering line as an example, the fully flexible DC power supply system schemes under centralized and decentralized power supply methods were adopted respectively. The line has a total of 11 substations. If the centralized power supply method is adopted, 2 main substations are required. If the decentralized power supply method is adopted, 4 switching stations are required. Figure 1 This is a schematic diagram of the positive terminal of the fully flexible DC power supply system with centralized power supply in the dual-ring network scheme of this project. Figure 2 This is a schematic diagram of the positive terminal of the fully flexible DC power supply system with centralized power supply in the ring connection scheme of this project. Figure 5 This is a schematic diagram of the positive terminal of the fully flexible DC power supply system with a distributed power supply method in the dual-ring network scheme of this project. Figure 6 This is a schematic diagram of the positive terminal of the fully flexible DC power supply system with a distributed power supply scheme for the ring connection of this project.

[0038] Example 1

[0039] like Figure 1 As shown, for the medium-voltage network, a dual-ring network centralized power supply system with fully flexible DC power supply is adopted. A separate main substation is constructed along the line to supply power to the loads on the line, serving as the interface between the urban rail transit's internal power supply system and the external power source. The main substation is directly interconnected with a high-capacity, high-voltage power system, and its external power supply voltage level can be three-phase AC 110kV. A schematic diagram of the main substation structure is shown below. Figure 3 As shown (the main substation structure is the same for both the dual-ring network and ring-connection schemes), each main substation is equipped with two external power supplies and two sets of converters. The external power supplies are stepped down and rectified from three-phase 110kV or three-phase 35kV to DC±35kV / DC±20kV / DC±10kV or DC±20kV / DC±10kV, outputting DC power to the DC medium-voltage bus. The DC medium-voltage network adopts a single-pole symmetrical connection method, and both the positive and negative buses of the medium-voltage network are grounded through resistors or capacitors. The medium-voltage network is a hybrid network for traction power and lighting, with the entire DC medium-voltage ring network connected.

[0040] All substations along the main substation and the lines (including traction substations, step-down substations, and hybrid traction-step-down substations) adopt a single busbar segmented connection scheme. A busbar tie switch is installed between the segmented busbars of the main substation and the first and last substations of the line. The busbar tie switch of the main substation is normally open, while the busbar tie switches of the first and last substations of the line are normally closed. The remaining substations along the line adopt a single busbar segmented connection scheme, and no busbar tie switch is installed between the two busbar segments. Except for the first and last substations of the line, all other substations are equipped with two incoming lines and two outgoing lines to connect to the Section I and Section II medium-voltage busbars of the intermediate substations, respectively. The first and last substations of the line are equipped with two incoming lines. Section I ring network cable is led out from the Section I medium-voltage busbar of the main substation and connected to the Section I medium-voltage busbars of the two access substations. The outgoing lines of the Section I DC busbars of the access substations serve as incoming lines to adjacent substations, forming a ring network between the main substation and the Section I DC medium-voltage busbars of each substation. Section II ring network cable is led out from the Section II medium-voltage busbar of the main substation and connected to the Section II DC busbars of the two adjacent access substations. The outgoing lines of the Section II DC busbars of the access substations serve as incoming lines to adjacent substations, forming a ring network between the main substation and the Section II DC medium-voltage busbars of each substation. The substations located at both ends of the line have direct access to the Section I DC bus and the Section II DC medium-voltage bus. Both Section I and Section II medium-voltage ring networks are fully continuous, providing power to each substation on both sides of the line. The positive and negative medium-voltage ring network structures are identical.

[0041] Under normal operating conditions, the two external power supplies of a main substation operate simultaneously, with all main substations sharing the traction load and power / lighting load on the lines. When one incoming power supply to a main substation fails or a converter unit malfunctions, the busbar tie switch of that substation is closed, and the other power supply supplies power to the loads on the line. When one ring network cable connecting a section of busbar within a substation fails, the other ring network cable supplies power to the loads on that section of busbar. When both incoming power supplies to a main substation fail, that main substation is taken out of operation, and the loads on the entire line are supplied by an adjacent main substation. When both ring network cables on a section of busbar within a substation fail, that section of busbar is disconnected, and the loads within that substation are supplied power by the other section of busbar.

[0042] The structure of non-starting and non-ending substations in a medium-voltage double-ring network is as follows: Figure 4As shown, two sets of energy routers are installed in each substation along the line. The energy routers receive DC power from the medium-voltage bus and can output three different voltage standards and magnitudes: the first is three-phase AC 400V, the second is DC ±375V, and the third is DC 1500V or DC 750V. The AC400V busbar adopts a single-busbar segmented wiring scheme, with normally open busbar tie switches. The two busbar segments connect to the AC400V output side of each of the two energy routers. The DC±375V busbar also adopts a single-busbar segmented wiring scheme, with normally open busbar tie switches between the two positive busbar segments and between the two negative busbar segments. The two positive busbar segments connect to the DC+375V output side of each of the two energy routers, and the two negative busbar segments connect to the DC-375V output side of each of the two energy routers. The positive and negative busbars are grounded via a resistor or capacitor. The DC1500V / 750V busbar adopts a single-busbar scheme, with the two busbar segments connecting to the DC+1500V / +750V and 0V output sides of each of the two energy routers. The two energy routers are redundantly configured; when one energy router is out of service, the busbar tie switches are closed, and the other energy router takes over the power supply for the unit's load.

[0043] Example 2

[0044] like Figure 2As shown, for a centralized power supply system with a loop connection scheme in the medium-voltage network, the main substation adopts a single busbar segmented scheme, with a busbar tie switch installed between the two busbar segments. This busbar tie switch is normally open. All substations on the line adopt a single busbar segmented connection scheme. Busbar tie switches are installed on the segmented busbars within the main substation and each substation along the line. The busbar tie switches for the main substation and the two connecting substations whose outgoing lines connect to the main substation are normally open, while the busbar tie switches for the remaining substations are normally closed. A ring network tie switch is installed between the first and last substations of the line and their respective adjacent substations. This ring network tie switch is normally closed. Except for the access substation, each substation on the line has one incoming line and one outgoing line. The two outgoing cables of the medium-voltage busbar section I of the main substation are connected to the two busbar sections of one access substation, and the two outgoing cables of the medium-voltage busbar section II of the main substation are connected to the two busbar sections of another access substation. The two access substations are adjacent stations. The section I ring network cable of each substation is led out from the section I medium-voltage busbar of the access substation and connects to the section I medium-voltage busbar of the other substation every other substation. The section II ring network cable of each substation is led out from the section II medium-voltage busbar of the access substation and connects to the section II medium-voltage busbar of the other substation every other substation. The medium-voltage ring network forms a loop connection, providing bilateral power supply to each substation on the line. The medium-voltage ring network is fully connected along the entire line. Under normal operating conditions, all main substations share the traction load and power / lighting load on the line. The positive and negative medium-voltage ring network structures are identical. When one incoming power line to a main substation fails or one converter unit malfunctions, the bus tie switch of that substation is closed, and power is supplied to the loads on the line from another power source. When a section of the ring network cable connecting the busbar in a substation fails, power is supplied to the loads in that substation from another ring network cable. When the substation busbar fails or both ring network cables fail, the substation is taken out of operation.

[0045] Example 3

[0046] like Figure 5 As shown, for a distributed power supply system with a dual-ring network scheme in the medium-voltage network, the external power supply voltage level can be three-phase AC 35kV or three-phase AC 10kV. A switching station is set up as the interface between the rail transit line power supply system and the external power supply. The switching station and substation are built together, and the external power supply three-phase AC 35kV or three-phase AC 10kV is rectified to DC±35kV / DC±20kV / DC±10kV or DC±10kV. For example... Figure 7 As shown in (a), for the switching station with a dual-ring network scheme, the switching station is equipped with two external power supplies and two sets of converter devices. The DC medium-voltage network adopts a single-pole symmetrical connection method, and both the positive and negative buses of the medium-voltage network are grounded through resistors or capacitors. The medium-voltage network is a hybrid network of traction power and lighting, and the entire DC medium-voltage ring network is connected.

[0047] The switching stations and substations at the beginning and end of the line adopt a single busbar segmented scheme, with busbar tie switches installed between the segmented busbars. The busbar tie switches at the switching stations are normally open, while those at the beginning and end of the line are normally closed. Substations in the middle of the line adopt a single busbar segmented connection scheme, without busbar tie switches between the two busbar segments. Except for the substations at the beginning and end of the line, all other substations have two incoming lines and two outgoing lines, used to connect to the I-section and II-section medium-voltage busbars of the intermediate substations, respectively. The substations at the beginning and end of the line have two incoming lines. The I-section ring network cable originates from the I-section medium-voltage busbar of the switching station and connects sequentially to the I-section medium-voltage busbars of each substation. The II-section ring network cable originates from the II-section medium-voltage busbar of the switching station and connects sequentially to the II-section medium-voltage busbars of each substation. Both I-section and II-section medium-voltage ring networks are fully continuous, providing bilateral power supply to each substation on the line. In a medium-voltage network, the positive and negative poles have the same medium-voltage ring network structure.

[0048] Under normal operating conditions, the two incoming power supplies of a switching station operate separately, with all switching stations sharing the traction load and power / lighting load on the line. When one incoming power supply to a switching station fails or a converter unit malfunctions, the busbar tie switch of that station is closed, and the other power supply supplies power to the load on the line. When one ring network cable connecting a section of busbar within a substation fails, the other ring network cable supplies power to the load on that section of busbar. When both incoming power supplies to a switching station fail, that switching station is taken out of operation, and the load on the entire line is supplied by an adjacent switching station. When both ring network cables on a section of busbar in a substation fail, that section of busbar is disconnected, and the load on that substation is supplied power by the other section of busbar.

[0049] Example 4

[0050] like Figure 6 As shown, for a distributed power supply system with a loop connection scheme in a medium-voltage network, the switching station and substation are built together, and the external power supply of three-phase AC 35kV or three-phase AC 10kV is rectified to DC±35kV / DC±20kV / DC±10kV or DC±10kV. For example... Figure 7 As shown in (b), for the switching station with a dual-ring network scheme, the switching station is equipped with two external power supplies and two sets of converters. The two sets of converters can be located in the same substation or in two adjacent substations. The outgoing lines of the two sets of converters are connected to different substations. The DC medium-voltage network adopts a single-pole symmetrical connection method, and both the positive and negative buses of the medium-voltage network are grounded through resistors or capacitors. The medium-voltage network is a hybrid network of traction power and lighting, and the entire DC medium-voltage ring network is connected.

[0051] The substations connected to the switching station and the remaining substations on the line all adopt a single busbar segmented connection scheme. Each substation segmented busbar on the line is equipped with a busbar tie switch. The busbar tie switches for the two substations connected to the switching station's outgoing line are normally open, while the busbar tie switches for the remaining substations are normally closed. Except for the connecting substations, each of the remaining substations on the line has one incoming line and one outgoing line. The two outgoing cables of the switching station's converter unit are respectively connected to two busbar segments of one connecting substation. The other converter unit of the switching station... The two outgoing cables are respectively connected to two busbars of an adjacent substation. The first section of the medium-voltage ring network cable on the line has two outgoing lines from the first section of the medium-voltage busbar of the substation, each connecting to the first section of the medium-voltage busbar of the next substation every other substation. The second section of the medium-voltage ring network cable has two outgoing lines from the second section of the medium-voltage busbar of the substation, each connecting to the second section of the medium-voltage busbar of the next substation every other substation. The medium-voltage ring network forms a loop connection, providing bilateral power supply to each substation on the line. Under normal operating conditions, all switching stations share the traction load and power and lighting load of the entire line. When one incoming power supply to a switching station fails, that switching station is taken out of operation, and other switching stations supply power to the loads within the fault area. When a section of the ring network cable connecting the busbar in a substation fails, the other ring network cable supplies power to the loads on that section of the busbar. When the substation busbar fails, that substation is taken out of operation.

[0052] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0053] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

Claims

1. A fully flexible DC power supply system for urban rail transit, characterized in that, Based on the external power supply method, fully flexible DC power supply systems are divided into centralized power supply systems and distributed power supply systems. The centralized power supply mode fully flexible DC power supply system includes at least two independently set main substations. The main substations supply power to multiple substations through a medium-voltage network. The main substations are connected to two external power sources, which are output to the main substation's Section I medium-voltage busbar and Section II medium-voltage busbar respectively through the main substation's converter device. The main substation's Section I medium-voltage busbar and Section II medium-voltage busbar are respectively connected to the section I medium-voltage busbar and Section II medium-voltage busbar connected to the substations. The distributed power supply method fully flexible DC power supply system has at least two switching stations. The switching stations are located in the substation and supply power to the adjacent substation through the medium voltage network. The switching stations are connected to two external power sources, which are output to the I section medium voltage bus and II section medium voltage bus connected to the substation through the converter device of the switching station respectively. Both the centralized power supply mode fully flexible DC power supply system and the decentralized power supply mode fully flexible DC power supply system adopt a double-ring network connection scheme or a ring DC distribution network connection scheme for their medium-voltage networks; the medium-voltage network is a hybrid network of traction power and lighting, with the medium-voltage ring network fully connected; The substation includes a step-down substation, a traction substation, and a hybrid traction-step-down substation. The substation is equipped with two energy routers that serve as backups for each other. The input terminals of the energy routers are respectively connected to the medium-voltage busbar of section I or section II of the substation. Both energy routers output multiple voltage standards.

2. The fully flexible DC power supply system for urban rail transit according to claim 1, characterized in that, The energy router simultaneously outputs three different voltage standards: the first is three-phase AC 400V, the second is DC ±375V, and the third is DC 1500V / 750V. The AC 400V bus adopts a single-bus segmented wiring scheme, with normally open bus tie switches. The two bus segments are connected to the AC 400V output sides of the two energy routers respectively. The DC ±375V bus adopts a single-bus segmented wiring scheme, with normally open bus tie switches between the two positive bus segments and between the two negative bus segments. The two positive bus segments are connected to the DC +375V output sides of the two energy routers respectively, and the two negative bus segments are connected to the DC -375V output sides of the two energy routers respectively. The positive and negative bus segments are grounded through a resistor or capacitor. The DC 1500V / 750V bus adopts a single-bus scheme, with the two bus segments connected to the DC +1500V / +750V and 0V output sides of the two energy routers respectively.

3. The fully flexible DC power supply system for urban rail transit according to claim 1, characterized in that, The medium-voltage network adopts a single-pole symmetrical wiring method, and the positive and negative buses of the medium-voltage network are grounded through resistors or capacitors; the medium-voltage bus adopts a single-bus segmented scheme, and the positive medium-voltage ring network structure is the same as the negative medium-voltage ring network structure.

4. The fully flexible DC power supply system for urban rail transit according to claim 3, characterized in that, For a centralized power supply system with a double-ring network connection scheme for medium-voltage networks, a bus tie switch is installed between the sectional busbars in the main substation and the first and last substations of the line. The bus tie switch in the main substation is normally open, while the bus tie switches in the first and last substations of the line are normally closed. No bus tie switch is installed between the two busbar sections in the intermediate substations of the line. Except for the first and last substations of the line, all other substations are equipped with two incoming lines and two outgoing lines to connect to the first section of the medium-voltage busbars of each intermediate substation. The line has two incoming lines at the first and last substations, namely Section I medium-voltage busbar and Section II medium-voltage busbar. Section I medium-voltage ring network cable is led out from Section I medium-voltage busbar of the main substation and connected to Section I medium-voltage busbar of each substation in sequence. Section II medium-voltage ring network cable is led out from Section II medium-voltage busbar of the main substation and connected to Section II medium-voltage busbar of each substation in sequence. Both Section I and Section II medium-voltage ring networks are fully connected and provide power to each substation on both sides of the line. The outgoing line of the medium-voltage busbar of the main substation is connected to the medium-voltage busbar of the two substations as substation incoming lines.

5. A fully flexible DC power supply system for urban rail transit according to claim 3, characterized in that, For a centralized power supply system with a ring DC distribution network connection scheme in the medium-voltage network, a bus tie switch is installed on the busbars of the main substation and each substation along the line. The bus tie switches of the main substation and the two access substations connected to the main substation are normally open, while the bus tie switches of the remaining substations are normally closed. A ring network tie switch is installed between the first and last substations of the line and their adjacent substations; this ring network tie switch is normally closed. Each substation along the line, except for the access substations, has one incoming line and one outgoing line. The two outgoing lines of the medium-voltage busbar in section I of the main substation are also included. The cables are respectively connected to two busbars of a substation. The two outgoing cables of the medium-voltage busbar of section II of the main substation are respectively connected to two busbars of another adjacent substation. The medium-voltage ring network cable of section I on the line has two outgoing lines from the medium-voltage busbar of section I of the substation, and each line connects to the medium-voltage busbar of section I of the next substation every other substation. The medium-voltage ring network cable of section II has two outgoing lines from the medium-voltage busbar of section II of the substation, and each line connects to the medium-voltage busbar of section II of the next substation every other substation. The medium-voltage ring network forms a loop connection, providing power to each substation on the line from both sides.

6. A fully flexible DC power supply system for urban rail transit according to claim 3, characterized in that, For a distributed power supply system with a double-ring network connection scheme for medium-voltage networks, a bus tie switch is installed between the busbars of the switching stations and the first and last substations of the line. The bus tie switch of the switching station is normally open, and the bus tie switch of the first and last substations of the line is normally closed. No bus tie switch is installed between the two busbars of the remaining substations in the middle of the line. Except for the first and last substations of the line, each substation is equipped with two incoming lines and two outgoing lines, which are used to connect the first and second section medium-voltage busbars of the intermediate substations, respectively. The first and last substations of the line are equipped with two incoming lines. The first section medium-voltage ring network cable is led out from the first section medium-voltage busbar of the switching station and connected to the first section medium-voltage busbar of each substation in sequence. The second section medium-voltage ring network cable is led out from the second section medium-voltage busbar of the switching station and connected to the second section medium-voltage busbar of each substation in sequence. The first and second sections of the medium-voltage ring network are fully connected and provide bilateral power supply to each substation on the line.

7. A fully flexible DC power supply system for urban rail transit according to claim 3, characterized in that, For a distributed, fully flexible DC power supply system using a ring DC distribution network wiring scheme in a medium-voltage network, each substation section busbar in the line is equipped with a bus tie switch. The two bus tie switches connecting to the outgoing lines of the switching station are normally open, while the bus tie switches of the remaining substations are normally closed. Each substation on the line, except for the connecting substations, has one incoming line and one outgoing line. The two outgoing cables of one converter unit in the switching station are respectively connected to two busbar sections of one connecting substation, and the other... The two outgoing cables of the converter unit are respectively connected to the two busbars of another adjacent substation. The medium-voltage ring network cable of section I on the line has two outgoing lines from the medium-voltage busbar of section I of the substation, and each line connects to the medium-voltage busbar of section I of the next substation every other substation. The medium-voltage ring network cable of section II has two outgoing lines from the medium-voltage busbar of section II of the substation, and each line connects to the medium-voltage busbar of section II of the next substation every other substation. The medium-voltage ring network forms a loop connection, providing power to each substation on the line from both sides.

8. A fully flexible DC power supply system for urban rail transit according to claim 7, characterized in that, The two converter units of the switching station are located in the same access substation or in two adjacent access substations respectively.

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