Power supply system network structure of rail transit with medium and low traffic volume and application method of power supply system network structure

Abstract

The invention relates to the technical field of rail transit power supply systems, and discloses a power supply system network structure of medium and low traffic volume rail transit and an application method of the power supply system network structure. The medium-voltage feed-out bus of the main substation leads out two paths of medium-voltage power to supply power to stations on the way of the whole rail transit line; a standby power supply with the same voltage grade as a medium-voltage network is introduced into the whole rail transit line along stations on the way, when the main transformer substation exits, the introduced standby power supply is used for supporting power supply, and the whole rail transit line is changed from a centralized power supply mode to a decentralized power supply mode. The method solves the problems that an urban rail transit power supply system excessively depends on a'large bilateral 'power supply mode to support power supply, so that site selection of a traction substation is difficult, investment is increased and the like, and has high popularization and application value in the field of urban rail transit power supply systems in China.

Description

Technical Field

[0001] The present invention relates to the technical field of rail transit power supply systems, and in particular to a power supply system network structure for medium and low-capacity rail transit and an application method thereof. Background Art

[0002] At present, with the continuous development of domestic rail transit, rail transit has entered a stage of high-quality development from a period of rapid development. The overall demand for urban rail transit industry is still strong, but the development trend has shifted from the original high-density, high-capacity urban rail lines to the development direction of medium and low-capacity rail transit.

[0003] At present, the power supply network of medium and low-capacity rail transit power supply systems still follows the requirements of GB50157-2013 "Metro Design Code". The entire power supply system, especially the power supply system related to locomotive operation, uses two independent power supplies to pursue uninterrupted and continuous power supply of the power supply system and meet the "N-1" criterion. According to this criterion, after any independent component of the N components of the power supply system (such as transmission lines, transformers, etc.) fails and is removed, the power supply system should be able to maintain continuous and stable operation and normal power supply.

[0004] like Figure 1 As shown in the figure, most of the current typical medium-voltage power supply systems for rail transit adopt a "centralized" three-level power supply mode. This mode introduces two independent power sources from the power grid, which are stepped down and operated separately by two main transformers in the main substation. Each rail transit line requires more than two main substations for power supply, which are divided into multiple medium-voltage power supply arms. The medium-voltage power supply arms of the two main substations are connected by a normally open circuit breaker, also known as a ring network contact switch. When a main substation fails and exits, the medium-voltage power of the entire rail transit line can be supplied to all substations along the line by another main substation through a ring network contact switch. The substations along the way are powered by two sections of medium-voltage busbars. The first and second sections of the substation busbars are connected by busbars. When one section of the busbar fails or loses power, the other section of the busbar provides support power supply between the stations. This medium-voltage network can quickly cut off the fault source while achieving the fastest support power supply. After the medium-voltage power is introduced into the substation, it is converted by the distribution transformer and the rectifier unit to realize the power supply of the station and the locomotive respectively.

[0005] The current typical rail transit locomotive power supply uses two sets of rectifier units and one set of regenerative power device to form a traction-feedback rail transit DC power supply system. When the locomotive draws current, the two sets of rectifier units provide power output, the rectifier units are in working state, and the regenerative power device is in standby state; when the train brakes, the train motor is equivalent to a generator, converting the braking energy into electrical energy and feeding it back to the contact network (rail), and the regenerative energy braking device absorbs the braking energy and feeds it back to the medium-voltage power supply network in the station for energy consumption. In this state, the rectifier unit is in standby state and the regenerative power device is in working state. The traction station uses two sets of 12-pulse rectifier units with phase-shifting coils, that is, under normal conditions, the two rectifier units run in parallel to form 24-pulse rectified DC power to reduce grid harmonics. At the same time, in fault mode, after one rectifier unit exits, the other rectifier unit can provide support power supply.

[0006] At present, the typical rail transit power supply system has been maturely used in large-capacity urban rails. In terms of safety, reliability and advancement, the typical rail transit power supply system has been fully verified in engineering.

[0007] The difference between medium and low-capacity rail transit systems and large-capacity urban rail transit systems is that the system's continuous power supply requirements in the event of a fault are not as strict as those of large-capacity urban rail transit systems, and the time required to restore power is also more tolerant. For example, the electrified highway power supply system in the medium and low-capacity segment does not carry too much passenger business at this stage, and is mostly aimed at freight lines, so the continuity requirements for the power supply system are not too high.

[0008] In the face of low- and medium-capacity rail transit, the direct application of the large-capacity urban rail power supply system network structure is no longer applicable in terms of economy and applicability. Therefore, it is necessary to propose a power supply system network that is more in line with low- and medium-capacity rail transit on the principle of meeting the "N-1" criterion of the power supply system. Summary of the invention

[0009] In view of the problems in the related technology, the present invention proposes a power supply system network structure for medium and low-capacity rail transit and an application method thereof to overcome the above-mentioned technical problems existing in the existing related technology.

[0010] To this end, the specific technical solution adopted by the present invention is as follows:

[0011] According to a first aspect of the present invention, there is provided a power supply system network structure for medium and low-capacity rail transit, the power supply system network structure comprising a main substation, the main substation introducing a high-voltage power supply, and the high-voltage power supply is supplied to a medium-voltage network after being stepped down by the main substation, the medium-voltage feeder bus of the main substation leads out two medium-voltage electric powers to supply power to stations along the entire rail transit line; wherein, the stations along the entire rail transit line introduce a backup power supply with the same voltage level as the medium-voltage network, and when the main substation exits, the introduced backup power supply is used for support power supply, and the entire rail transit line is changed from a centralized power supply to a decentralized power supply.

[0012] Furthermore, the stations along the entire rail transit line are equipped with traction substations and step-down substations; wherein, the traction substation connects the two bus sections through a bus tie circuit breaker, adopts a single bus segmentation form, and the incoming and outgoing lines of the traction substation, the two bus sections and the transformer connection cabinet are all connected by circuit breakers, and are equipped with protection devices; the step-down substation adopts two single busbars in a separate operation mode, without a bus tie cabinet, and the incoming and outgoing lines of the step-down substation are connected to the station distribution transformer by AC isolating switches.

[0013] Furthermore, a fuse is arranged in front of the distribution transformer of the step-down substation. When a short circuit or a large current overload occurs at the proximal end of the transformer, the fuse cuts off the power supply as a proximal protection to protect the distribution transformer. When a distribution transformer unit of the step-down substation is out of operation, the low-voltage bus circuit breaker provides support power supply.

[0014] Furthermore, when the power supplied to the locomotive by the traction substation is a DC power supply, a bidirectional converter is used to realize integrated rectification and inversion power supply.

[0015] Furthermore, the traction substation draws DC power from the positive DC busbar by two DC circuit breakers; one DC circuit breaker and two sets of DC disconnectors matched therewith jointly supply DC power to the left power supply arm of the traction substation power supply section for up and down directions; the other DC circuit breaker and two sets of DC disconnectors matched therewith jointly supply DC power to the right power supply arm of the traction substation power supply section for up and down directions; the left power supply arm and the right power supply arm together constitute a DC power supply arm, and the two ends of the DC power supply arm are respectively connected to the DC grid-connected power of this station and the DC grid-connected power of the neighboring station, forming a dual-power DC traction network; the left power supply arm and the right power supply arm are connected by an inter-zone disconnector, and the inter-zone disconnector connection is in a normally open state in the normal power supply mode. When the traction substation of this station exits, the DC power of the adjacent traction substations on the left and right sides of the faulty traction substation is connected through the inter-zone disconnector, and the bilateral support working condition of the neighboring station is formed through the contact network.

[0016] Furthermore, the network structure of the power supply system also includes establishing an independent protection network in the entire rail transit line to connect the protection devices of all traction substations, step-down substations and main substations on the entire line, and the power protection control information circulates separately in the protection network to collect all switch status information of the substation; wherein, the protection devices in the protection network can be accessed arbitrarily, and the substations on the entire line exchange information with maintenance personnel through power monitoring, and the priority of the protection control information is higher than the control information remotely released by general maintenance personnel. The control information remotely released by general maintenance personnel includes remote closing and opening information. If the operating conditions do not allow it, the closing and opening operation is not allowed and the operation is unsuccessful.

[0017] According to a second aspect of the present invention, there is provided a power supply method using the above-mentioned power supply system network structure applicable to medium and low-capacity rail transit when a medium-voltage AC network fails, the method comprising:

[0018] When the high-voltage side of the transformer loses power, the main switch in the main substation is turned on, and the control command allowing the closing of the switch is transmitted to the circuit breaker corresponding to the backup power supply through the protection dedicated network;

[0019] The protection dedicated network is used to automatically issue program control commands to control the closing of circuit breakers 101A and 102B of the traction substation;

[0020] The step-down substation receives the control command and controls the circuit breaker corresponding to the backup power supply to close. The station switches the circuit breakers in sequence, restores the power supply to the power supply section, and sets the main switch in the main substation to the locking condition.

[0021] According to a third aspect of the present invention, there is provided a power supply method using the above-mentioned power supply system network structure applicable to medium and low-capacity rail transit when a substation fails, the method comprising:

[0022] When a fault occurs in the traction substation, the AC medium voltage section II loses power, the circuit breaker 101B in the traction substation Q1 is disconnected, the circuit breaker 103 in the traction substation Q1 is closed, and the AC medium voltage section II is supported by the power of the AC medium voltage section I;

[0023] When the incoming line from the traction substation to the next traction substation II fails, the circuit breaker 102B in the traction substation Q1 and the circuit breaker 102B in the traction substation QA are disconnected, and the circuit breaker 103 in the traction substation QA is closed, so that the two sections of the medium-voltage busbars in the traction substation QA operate simultaneously;

[0024] When the AC medium voltage II section in the step-down substation J1 loses power, the low voltage circuit breaker 802 in the step-down substation J1 is disconnected, and the low voltage circuit breaker 803 in the step-down substation J1 is closed, so that the low voltage power supply can operate normally;

[0025] When the AC medium voltage II section bus in the step-down substation J1 fails, the circuit breakers 102B in the traction substation Q1 and 102B in the traction substation QA are disconnected, and the circuit breaker 103 in the traction substation QA is closed. The step-down substation J1 operates on a single bus, and the two sections of the medium voltage bus in the traction substation QA operate simultaneously;

[0026] When a distribution transformer in the traction substation fails, the distribution transformer is taken out of operation, and the circuit breaker 104B in the traction substation Q1 and the circuit breaker 802 in the traction substation Q1 are disconnected, and the low-voltage circuit breaker 803 in the traction substation Q1 is closed, so that the low-voltage power supply can operate normally.

[0027] According to a fourth aspect of the present invention, there is provided a power supply method using the above-mentioned power supply system network structure applicable to medium and low-capacity rail transit when a DC system fails, the method comprising:

[0028] When the traction substation Q1 loses its DC power supply capability, the circuit breaker 201 in the traction substation Q1 is disconnected, and the circuit breakers 211 and 212 in the traction substation Q1 are in the closed position. At this time, the circuit breaker 212 in the traction substation QA and the circuit breaker 211 in the traction substation Q2 jointly provide bilateral power supply to all sections between the traction substation QA and the traction substation Q2 through the DC busbar of the traction substation Q1.

[0029] When the bidirectional converter unit fails, the circuit breakers 201, 211, and 212 in the traction substation Q1 are disconnected, and the disconnector 2112 in the traction substation Q1 is closed. At this time, the circuit breaker 212 in the traction substation QA and the circuit breaker 211 in the traction substation Q2 are connected through the disconnector 2112 in the traction substation Q1 to provide traction power to all sections between the traction substation QA and the traction substation Q2.

[0030] When the uplink overhead line fails, disconnect the isolating switch 2111S in the traction substation QA and the isolating switch 2111S in the traction substation Q1, close the uplink driving section from the traction substation QA to the traction substation Q1, and start the fault mode, with the downlink driving section running unilaterally;

[0031] When a certain set of DC power supply capacity is lost in the traction substation QA, the disconnector 2112 in the traction substation QA is closed, and the R2 unit in the traction substation QA supports the power supply of the left power supply arm of the station. If the R2 unit is out of operation, the disconnector 2112 in the traction substation QA is closed, and the circuit breaker 211 in the traction substation QA and the circuit breaker 211 in the traction substation Q1 are combined through the disconnector 2112 in the traction substation QA to provide bilateral power supply to all the power supply arms between the traction substation QA and the traction substation Q1;

[0032] When the frame protection element FP-1 or frame protection element FP-2 in the traction substation QA fails, the disconnector 2112 in the traction substation QA is closed, and the R2 unit in the traction substation QA supports the left power supply arm of the station. If the R2 unit is out of operation, the disconnector 2112 in the traction substation QA is closed, and the circuit breaker 211 in the traction substation QA and the circuit breaker 211 in the traction substation Q1 are combined through the disconnector 2112 in the traction substation QA to provide bilateral power supply to all power supply arms between the traction substation QA and the traction substation Q1;

[0033] When the DC switch cabinet fails to touch the shell, the circuit breakers 201, 211 and isolating circuit breaker 212 on the DC bus will trip, and the isolating switch 2112 of this station will be closed, so that the power supply arm between the traction substation QA and the traction substation Q2 can support power supply through the isolating switch 2112.

[0034] The beneficial effects of the present invention are:

[0035] 1) The present invention enhances the reliability of the power supply of the traction substation itself from the perspectives of non-stop maintenance, primary and standby redundant support, and saving power supply system investment through the designed main wiring diagram of the power supply system traction substation, and solves the problems of difficulty in site selection and increased investment caused by the excessive reliance of the urban rail transit power supply system on the "large bilateral" power supply mode for power supply support. It has a high value of promotion and application in the field of urban rail transit power supply system in my country.

[0036] 2) In combination with the characteristics of medium and low-volume rail transit, the present invention proposes to use a bidirectional converter as an energy converter to replace the traditional rectifier unit and regenerative brake unit combination, while taking into account both economy and safety, and completing the rapid power supply under N-1 fault through switching operation. Simplifying the network structure and protection configuration of the power supply system, saving equipment costs, saving civil construction area, and facilitating the application of prefabricated assembled substations.

[0037] 3) The terminal station of the present invention adopts medium-voltage single bus segmentation and DC single bus segmentation operation mode, which can flexibly merge and decouple DC operation modes, and can ensure that the terminal station has at least one set of bidirectional converter units at the same time to form "bilateral power supply" with the adjacent traction station, thereby avoiding the traditional DC power supply system at the terminal. The terminal rectifier unit is mounted on the same section of AC bus. When the AC bus with the mounted rectifier unit is out of operation, the DC power supply to the locomotive of the terminal traction station fails. The "single-sided power supply" of the adjacent terminal station causes problems such as difficulty in locating the traction station, too long DC power supply arm, and reduced DC power supply quality.

[0038] 4) The present invention combines the characteristics of low-capacity rail transit step-down stations with low power consumption and short distances between step-down stations. The step-down station adopts a busbar-free switch, medium-voltage power distribution adopts a medium-voltage isolating switch, and the transformer adopts a fast fuse as a proximal protection solution; the traction station adopts a circuit breaker solution, which saves the investment of the entire power supply system and improves the self-healing ability of the rail transit system power supply system.

[0039] 5) The power supply system of the present invention adopts one high-voltage incoming line, one main substation, and one main transformer to provide centralized power supply for the entire line. It can also share the main transformer with the urban power grid according to actual conditions. In the event of a fault, it can be switched to a decentralized power supply mode, which ensures the rapid recovery capability of the power supply system and saves system investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 This is a typical AC system diagram of a rail transit power supply system;

[0042] Figure 2 is an AC network structure diagram applicable to a medium and low capacity rail transit power supply system according to an embodiment of the present invention;

[0043] Figure 3 is a main wiring diagram of an AC system of a medium and low capacity rail transit power supply system according to an embodiment of the present invention;

[0044] Figure 4 is a main wiring diagram of a DC system of a medium and low capacity rail transit power supply system according to an embodiment of the present invention;

[0045] Figure 5 is a connection diagram of a medium and low-capacity rail transit protection network according to an embodiment of the present invention;

[0046] Figure 6 is a diagram illustrating the transition of medium voltage AC network fault modes according to an embodiment of the present invention;

[0047] Figure 7 is a schematic diagram of supporting circuit breaker locking conditions corresponding to WA / WB / WC according to an embodiment of the present invention;

[0048] Figure 8 is a schematic diagram of the locking condition of the Zin circuit breaker of the main substation according to an embodiment of the present invention;

[0049] Fig. 9is a schematic diagram of locking conditions of an external power supply supporting a ring network connection switch according to an embodiment of the present invention;

[0050] Fig.10 is a diagram illustrating the support working condition of the substation AC system of the medium and low-capacity rail transit power supply system under a single component failure according to an embodiment of the present invention;

[0051] Fig.11 1 is a diagram illustrating the support working condition of the DC system of the medium and low capacity rail transit power supply system under a single component failure according to an embodiment of the present invention.

[0052] Fig.12 1 is a logic diagram of the locking operation of a DC isolation switch according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] To further illustrate each embodiment, the present invention provides drawings, which are part of the disclosure of the present invention and are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, ordinary technicians in the field should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0054] According to an embodiment of the present invention, a power supply system network structure for medium and low-capacity rail transit and an application method thereof are provided, including AC power distribution, interlocking operation and AC system power restoration under fault conditions of the power supply system, and also including DC power distribution, interlocking operation and DC power system restoration under fault conditions of the power supply system.

[0055] The present invention will now be further described with reference to the accompanying drawings and specific embodiments. Figure 2 As shown, a power supply system network structure for medium and low-capacity rail transit is provided, which is an AC network structure diagram suitable for medium and low-capacity rail transit power supply systems. The power supply system network structure includes a main substation, and the main substation introduces a high-voltage power supply (generally 110kV or / 220kV power supply can be introduced), and the high-voltage power supply is supplied to the medium-voltage network after being stepped down by the main substation (the medium-voltage network voltage level can be 35kV / 20kV / 10kV). This main transformer can supply medium-voltage power to medium and low-capacity rail transit alone, or it can be shared with the urban power grid. The medium-voltage feeder busbar of the main substation draws out two medium-voltage powers to supply power to the stations along the entire rail transit line; a backup power supply with the same voltage level as the medium-voltage network is introduced into the stations along the entire rail transit line, such as Figure 2WA, WB, and WC shown by the dotted lines are external backup power supplies. When the main substation of this line is shut down, the backup power supply can be directly introduced for support power supply. The traction substation and step-down substation of the entire line supply power to the distribution station, which is provided by two distribution transformers.

[0056] like Figure 3 As shown, the stations along the entire rail transit line are equipped with traction substations and step-down substations; among them, the traction substation connects two sections of busbars through a busbar circuit breaker, adopts a single busbar segmentation form, and the incoming and outgoing lines of the traction substation, the two sections of busbars and the transformer connection cabinet are all connected by circuit breakers, and are equipped with protection devices; the step-down substation adopts a two-single-busbar split operation mode, does not have a busbar cabinet, and the incoming and outgoing lines of the step-down substation and the station distribution transformer are connected by AC isolation switches. At the same time, a fuse is set in front of the distribution transformer of the step-down substation. When a transformer short circuit or high current overload occurs near the end, the fuse can be used as a near-end protection to cut off the power supply and protect the distribution transformer. When the distribution transformer unit of the step-down substation is out of operation, the low-voltage busbar circuit breaker 803 provides support power supply.

[0057] like Figure 2 and 4 As shown in the figure, when the power supplied by the traction substation to the locomotive is a DC power supply, a bidirectional converter is used to realize the integrated power supply of rectification and inversion. The traction substation of a typical station adopts a single-unit bidirectional converter for power supply. The bidirectional converter units of two adjacent traction substations are mounted on different buses, respectively, to balance the current of the two medium-voltage networks. The traction substation at the end of the line adopts a bidirectional converter unit with two sections of DC busbars for power supply.

[0058] The traction substation is composed of two DC circuit breakers 211 and 212, which draw DC power from the positive DC busbar; the DC circuit breaker 211 and the two sets of DC disconnectors 2111S and 2111X matched therewith form a power supply unit, which jointly supply DC power to the left power supply arm of the traction substation power supply section; the DC circuit breaker 212 and the two sets of DC disconnectors 2121S and 2121X matched therewith form a power supply unit, which jointly supply DC power to the right power supply arm of the traction substation power supply section; the two ends of the DC power supply arm are respectively connected to the DC grid-connected power of the station and the DC grid-connected power of the neighboring station, forming a dual-power DC traction network; the left power supply arm and the right power supply arm are connected through the cross-zone disconnector 2112, and the cross-zone disconnector 2112 connection is in a normally open state in the normal power supply mode. When the traction substation of the station is withdrawn, the DC power of the adjacent traction substations on the left and right sides of the faulty traction substation is connected through the cross-zone disconnector 2112, and the bilateral support working condition of the neighboring station is formed through the contact network (rail).

[0059] like Figure 5As shown, the network structure of the power supply system also includes establishing an independent protection network in the entire rail transit line to connect the protection devices of all traction substations, step-down substations and main substations in series, and the power protection control information circulates independently in the protection network to collect all switch status information of the substation. Each independent protection device can arbitrarily access another protection device in the protection network. The substations on the entire line exchange information with maintenance personnel through power monitoring. The priority of protection control information is higher than the control information remotely released by general maintenance personnel (general maintenance information refers to: remote closing and opening information. If the operating conditions do not allow it, it returns that closing and opening operations are not allowed and the operation is unsuccessful).

[0060] Protection devices and circuit breakers (actuators / actuator bodies) are core components to ensure the safe operation of the power grid. The coordinated work of the two determines whether faults can be isolated quickly and accurately.

[0061] The essence of the protection device is the "diagnostic system" of the power grid, which identifies anomalies by real-time monitoring of electrical quantities (current, voltage, phase, etc.) and triggers the circuit breaker to operate.

[0062] The essence of the collaboration between the two is the closed-loop control of "detection-decision-execution". The protection network refers to a network that links all protection devices and specifically transmits the above protection information. Its structure is as follows: Figure 5 As shown, it avoids the network that directly issues execution instructions to the circuit breaker without judging other information.

[0063] Description of the working status of the medium voltage system network:

[0064] like Figure 6 As shown in the figure, the whole rail transit line is equipped with a main substation to supply medium-voltage power. The main substation uses a main transformer, which supplies power to the whole line through the medium-voltage network of the whole line after voltage reduction. The whole line is equipped with three external support power supplies WA, WB, and WC. When the main substation is out of operation, it cooperates with WA, WB, and WC to change the whole line from centralized power supply to decentralized power supply.

[0065] Under normal operating conditions, the AC system is powered by a three-level centralized power supply network. The main substation introduces a high-voltage power supply, which is stepped down by the main substation and then supplied to the medium-voltage network. This main transformer can supply medium-voltage power to medium and low-capacity rail transit alone, or it can be shared with the city power grid. Two medium-voltage power lines are drawn out from the medium-voltage feeder bus of the main substation to supply power to stations along the way. At stations along the rail transit network, a backup power supply with the same voltage level as the medium-voltage network is introduced, as indicated by the dotted line in the figure. When the main substation exits, the introduced power supply can be directly used for support power supply. The power supply for the distribution of the traction substation and the step-down substation of the entire line is provided by two distribution transformers.

[0066] In the event of a fault, the corresponding switching operation is performed to quickly support the power supply of the low-voltage network of the power supply system. The specific steps are as follows:

[0067] 1) When the high-voltage side of the transformer loses power, the Zin main switch is turned on, and the information is transmitted to the corresponding support circuit breakers of WA, WB, and WC through the protection dedicated network, such as circuit breakers 111A and 111B located in step-down substation J1, allowing closing;

[0068] 2) Automatically issue program control commands through the protection dedicated network to block the closing of circuit breakers 102A and 102B of traction substation Q1;

[0069] 3) Subsequently, circuit breakers 111A and 111B are closed, and the station switches in sequence. The first power supply section is restored to power supply. The WB and WC external power supplies are also automatically switched synchronously, just like the WA line supporting this line, to achieve synchronous power supply to the second and third power supply sections. Zin sets the blocking condition and does not allow closing.

[0070] After the above steps, the power supply system network is converted from a centralized power supply mode to a distributed power supply mode, meeting the N-1 criterion when the main power station is out of service. The position of the ring network interconnection switch during external support, such as the circuit breakers 102A and 102B in the above steps, is selected by power supply calculation and pre-loaded in the automatic control program command of the entire network. The blocking conditions of the supporting circuit breakers (such as J1-111A) corresponding to WA / WB / WC are as follows: Figure 7 As shown; the locking conditions of the Zin circuit breaker in the main substation are as follows Figure 8 As shown; the locking conditions of the external power supply supporting the ring network contact switch (such as Q1-102A) are as follows Fig. 9 shown.

[0071] Description of substation work:

[0072] Under normal operating conditions, the traction station uses a busbar circuit breaker to connect the two busbars, and adopts a single busbar segmentation form. The step-down station adopts two single busbars in a separate operation mode. The incoming and outgoing lines of the traction station, the two busbars, and the transformer connection cabinet are all connected by circuit breakers and equipped with protection devices. The step-down station uses two single busbars in a separate operation mode, without a busbar cabinet. The incoming and outgoing lines are connected to the distribution transformer that distributes power to the station with AC isolating switches.

[0073] In case of a fault, the power supply system substation can quickly provide support power through the corresponding switching operation. A fuse is installed in front of the distribution transformer of the step-down substation. When a short circuit or high current overload occurs at the near end of the distribution transformer, the fuse can be used as a near-end protection to cut off the power supply and protect the distribution transformer. Fig.10 The figure shows the support working condition of the substation AC system of the medium and low-capacity rail transit power supply system designed in this embodiment under the failure of a single component;

[0074] The specific steps are as follows:

[0075] 1) When Fa fault occurs, that is, a fault occurs in the incoming line of the traction substation, the AC medium voltage section II loses power, the circuit breaker 101B in the traction substation Q1 is disconnected, the circuit breaker 103 in the traction substation Q1 is closed, and the AC medium voltage section II is supported by the AC medium voltage section I, meeting the N-1 criterion;

[0076] 2) When Fb fault occurs, that is, a fault occurs in the incoming line from the traction substation to the next traction substation II, the circuit breaker 102B in the traction substation Q1 and the circuit breaker 102B in the traction substation QA are disconnected, and the circuit breaker 103 in the traction substation QA is closed. The two sections of the medium-voltage busbar in the traction substation QA can operate simultaneously, meeting the N-1 criterion;

[0077] 3) When the AC medium voltage II section in the step-down substation J1 loses power, the low voltage circuit breaker 802 in the step-down substation J1 is disconnected, and the low voltage circuit breaker 803 in the step-down substation J1 is closed, and the low voltage power supply can operate as usual, meeting the N-1 criterion;

[0078] In addition, if the busbar transformer of section II of the step-down substation fails, disconnect the circuit breaker 102B in the traction substation Q1 and the circuit breaker 102B in the traction substation QA, close the circuit breaker 103 in the traction substation QA, and the step-down substation J1 will operate on a single busbar, and the two sections of the medium-voltage busbars of the traction substation QA will operate simultaneously. When an Fc fault occurs, that is, a distribution transformer of the traction substation fails and exits operation. At this time, disconnect the circuit breaker 104B in the traction substation Q1 and the circuit breaker 802 in the traction substation Q1, close the low-voltage circuit breaker 803 in the traction substation Q1, and the low-voltage power supply can operate as usual, without affecting the power supply circuit of the traction substation locomotive, and also meet the N-1 criterion.

[0079] DC system network working conditions description:

[0080] The power supply for locomotives from the traction station is a DC power supply. The location of the traction substation is generally calculated based on the power supply. Under the premise of meeting the power supply needs of the locomotive, it is built together with the station as far as possible within a reasonable range to reduce the breakpoints of the power supply network and improve the utilization efficiency of the station's civil engineering. A bidirectional converter is used to realize the integrated power supply of rectification and inversion. The traction station of a typical station adopts a single-unit bidirectional converter for power supply, and the bidirectional converter units of adjacent traction stations are mounted on different buses. The traction station at the end of the line adopts a bidirectional converter unit with two sections of DC busbars running separately for power supply. The typical station adopts a single-unit bidirectional converter, which can have better power quality control capabilities, less reactive power injected into the power grid, and less distortion of AC voltage and current. A set of bidirectional converters can replace the traditional dual rectifier units to form 24-pulse DC power, solving the problems of poor power quality and reactive power return of the rectifier units.

[0081] like Fig.11 As shown in the figure, under normal working conditions, the traction station uses two fast DC circuit breakers 211 and 212 to draw DC power from the positive DC busbar. The circuit breaker 211 and the disconnectors 2111S and 2111X form a power supply unit, which jointly supplies DC power to the left power supply arm of the traction station power supply section at the same time; the circuit breaker 212 and the disconnectors 2121S and 2121X form a power supply unit, which jointly supplies DC power to the right power supply arm of the traction station power supply section at the same time. The two ends of the DC power supply arm are respectively connected to the DC grid power of the station and the DC grid power of the neighboring station, forming a dual-power DC traction network. A typical traction station is equipped with two sets of frame protection elements, and the scope of action is respectively bidirectional converter units and DC switchgear; the end traction station, such as the QA traction station, is equipped with two sets of frame protection elements, and the scope of action is respectively two sets of independent bidirectional converter units. When a DC positive fault occurs to the equipment casing of the FP (frame protection element), it will trip quickly to protect the safety of personnel.

[0082] In case of a fault, the DC system of the power supply system can quickly provide support for power supply through corresponding switching operations. Fig.11 FIG. 1 is a diagram illustrating the support working condition of the DC system of the medium and low-capacity rail transit power supply system designed in this embodiment under a single component failure. Fig.12 A schematic diagram of the locking operation logic of the DC isolation switch designed in this embodiment;

[0083] The specific steps are as follows:

[0084] 1) When an Fd fault occurs, that is, the traction substation Q1 loses its DC power supply capability, the circuit breaker 201 in the traction substation Q1 is disconnected, and the circuit breakers 211 and 212 in the traction substation Q1 are in the closed position. At this time, the circuit breaker 212 in the traction substation QA and the circuit breaker 211 in the traction substation Q2 jointly provide bilateral power supply to all sections between the traction substation QA and the traction substation Q2 through the DC bus of the traction substation Q1, meeting the N-1 criterion; when a typical traction substation FP-1 trip occurs, it proves that the bidirectional converter unit has a fault, and the circuit breakers 201, 211, and 212 in the traction substation Q1 are disconnected, and the disconnector 2112 in Q1 is closed. At this time, the circuit breaker 212 in the traction substation QA and the circuit breaker 211 in the traction substation Q2 are connected through the traction substation Q1 contact disconnector 2112 to provide traction power to all sections between the traction substation QA and the traction substation Q2;

[0085] 2) When a Fe fault occurs, that is, an uplink contact network (rail) fault occurs, disconnect the disconnector 2111S in the traction substation QA and the disconnector 2111S in the traction substation Q1, and the uplink driving section from the traction substation QA to the traction substation Q1 is closed. In the fault mode, the downlink driving section is operated unilaterally (there is no N-1 backup in the contact network, and only unilateral operation can be achieved to achieve N-1 operation);

[0086] 3) When an Fg fault occurs, that is, when the end substation QA loses a set of DC power supply capacity (R1 unit is out of operation), the disconnector 2112 in the traction substation QA is closed, and the R2 unit in the traction substation QA supports the power supply of the left power supply arm of the station; if the R2 unit is out of operation, the disconnector 2112 in the traction substation QA is closed, and the circuit breaker 211 in the traction substation QA and the circuit breaker 211 in the traction substation Q1 are combined through the disconnector 2112 in the traction substation QA to support all the power supply between the traction substation QA and the traction substation Q1. The power arm is powered on both sides; when FP-1 or FP-2 fault occurs, the disconnector 2112 in the traction substation QA is closed, and the R2 unit in the traction substation QA supports the power supply of the left power supply arm of the station. If the R2 unit is out of operation, the disconnector 2112 in the traction substation QA is closed, and the circuit breaker 211 in the traction substation QA and the circuit breaker 211 in the traction substation Q1 are combined through the disconnector 2112 in the traction substation QA to provide bilateral power supply to all power supply arms between the traction substation QA and the traction substation Q1, meeting the N-1 criterion;

[0087] 4) When the typical traction substation FP-2 trips, that is, the DC switch cabinet touches the shell fault, the DC bus circuit breakers 201, 211, and 212 trip, and the local disconnector 2112 is closed, so that the power supply arm between the traction substation QA and the traction substation Q2 can support power supply through the disconnector 2112, meeting the N-1 criterion.

[0088] To sum up, with the help of the above-mentioned technical scheme of the present invention, the present invention enhances the reliability of the power supply of the traction substation itself from the perspective of non-stop maintenance, main and standby redundant support, and saving power supply system investment through the designed main wiring diagram of the power supply system traction substation, and solves the problems of difficulty in site selection of traction substation and increased investment caused by the excessive reliance of the urban rail transit power supply system on the "large bilateral" power supply mode to support power supply. It has a high value of promotion and application in the field of urban rail transit power supply system in my country.

[0089] In addition, the present invention combines the characteristics of medium and low-volume rail transit and proposes to use a bidirectional converter as an energy converter to replace the traditional rectifier unit and regenerative brake unit combination. While taking into account both economy and safety, the invention completes the rapid power supply under N-1 fault through switching operation. The network structure and protection configuration of the power supply system are simplified, equipment costs are saved, and civil construction area is saved, which is conducive to the application of prefabricated assembled substations.

[0090] In addition, the terminal station of the present invention adopts medium-voltage single bus segmentation and DC single bus segmentation operation mode, which can flexibly merge and decouple DC operation modes, and can ensure that the terminal station has at least one set of bidirectional converter units at the same time to form "bilateral power supply" with the adjacent traction station, thereby avoiding the traditional DC power supply system at the terminal. The terminal rectifier unit is mounted on the same section of AC bus. When the AC bus with the mounted rectifier unit exits operation, the DC power supply to the locomotive of the terminal traction station fails. The "single-sided power supply" of the adjacent terminal station causes problems such as difficulty in locating the traction station, too long DC power supply arm, and reduced DC power supply quality.

[0091] In addition, the present invention combines the characteristics of low-capacity rail transit step-down stations with low power consumption and short distances between step-down stations. The step-down station adopts a busbar-free switch, medium-voltage power distribution adopts a medium-voltage isolating switch, and the transformer adopts a fast fuse as a proximal protection solution; the traction station adopts a circuit breaker solution, which saves the investment of the entire power supply system and improves the self-healing ability of the rail transit system power supply system.

[0092] In addition, the power supply system of the present invention adopts one high-voltage incoming line, one main substation, and one main transformer to provide centralized power supply for the entire line. It can also share the main transformer with the urban power grid according to actual conditions. In the event of a fault, it can be switched to a decentralized power supply mode, which ensures the rapid recovery capability of the power supply system and saves system investment.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A power supply system network structure for medium and low-capacity rail transit, characterized in that: The network structure of the power supply system includes a main substation, which introduces a high-voltage power supply, and the high-voltage power supply is supplied to the medium-voltage network after being stepped down by the main substation. The medium-voltage feeder bus of the main substation leads out two medium-voltage electric powers to supply power to the stations along the entire rail transit line; Among them, the stations along the entire rail transit line introduce backup power supplies with the same voltage level as the medium-voltage network. When the main substation is shut down, the introduced backup power supply is used to provide support power supply, and the entire rail transit line is changed from a centralized power supply to a decentralized power supply.

2. According to claim 1, the power supply system network structure of a medium and low-capacity rail transit is characterized in that: The stations along the entire rail transit line are equipped with traction substations and step-down substations; The traction substation connects two busbars through a busbar tie breaker, adopts a single busbar segmentation form, and the incoming and outgoing lines of the traction substation, the two busbars and the transformer connection cabinet are all connected by circuit breakers and equipped with protection devices; The step-down substation adopts two single busbars in a separate operation mode, does not have a busbar cabinet, and the incoming and outgoing lines of the step-down substation are connected to the station distribution transformer using AC isolating switches.

3. According to claim 2, the power supply system network structure of a medium and low-capacity rail transit is characterized in that: A fuse is arranged in front of the distribution transformer of the step-down substation. When a short circuit or a large current overload occurs at the proximal end of the transformer, the fuse cuts off the power supply as a proximal protection to protect the distribution transformer. When a distribution transformer unit of the step-down substation stops running, the low-voltage bus circuit breaker provides support power supply.

4. According to claim 1, the power supply system network structure of a medium and low-capacity rail transit is characterized in that: When the power supplied to the locomotive by the traction substation is DC power, a bidirectional converter is used to achieve integrated rectification and inversion power supply.

5. The power supply system network structure of a medium and low-capacity rail transit according to claim 4 is characterized in that: The traction substation draws DC power from the positive DC busbar by two DC circuit breakers; One of the DC circuit breakers and the two sets of DC disconnectors that work with it jointly supply DC power to the left power supply arm of the traction substation power supply section for both upstream and downstream operations; Another DC circuit breaker and two sets of DC disconnectors working with it jointly supply DC power to the right power supply arm of the traction substation power supply section for both upstream and downstream operations; The left power supply arm and the right power supply arm together form a DC power supply arm, and the two ends of the DC power supply arm are respectively connected to the DC grid-connected power of the station and the DC grid-connected power of the neighboring station, forming a dual-power DC traction network; The left power supply arm and the right power supply arm are connected by an inter-zone isolating switch, and the inter-zone isolating switch is in the normally open state in the normal power supply mode. When the traction substation of this station is withdrawn, the DC power of the adjacent traction substations on the left and right sides of the faulty traction substation is connected through the inter-zone isolating switch, and the bilateral support working condition of the adjacent station is formed through the contact network.

6. The power supply system network structure of a medium and low-capacity rail transit according to claim 1 is characterized in that: The network structure of the power supply system also includes establishing an independent protection network in the entire rail transit line to connect in series the protection devices of all traction substations, step-down substations and main substations along the entire line, and the power protection control information is circulated separately in the protection network to collect all switch status information of the substation; Among them, the protection devices within the protection dedicated network can be accessed arbitrarily, and the substations along the entire line exchange information with maintenance personnel through power monitoring, and the priority of protection control information is higher than the control information released remotely by general maintenance personnel.

7. The power supply system network structure of a medium and low-capacity rail transit according to claim 6 is characterized in that: The control information remotely released by the general maintenance personnel includes remote closing and opening information. If the operating conditions do not allow, it will return that the closing and opening operations are not allowed and the operation is unsuccessful.

8. A power supply method for a power supply system network structure of medium and low-capacity rail transit when a medium-voltage AC network fails, using any one of claims 1-7, characterized in that: The method includes: When the high-voltage side of the transformer loses power, the main switch in the main substation is turned on, and the control command allowing the closing of the switch is transmitted to the circuit breaker corresponding to the backup power supply through the protection dedicated network; The protection dedicated network is used to automatically issue program control commands to control the closing of circuit breakers 101A and 102B of the traction substation; The step-down substation receives the control command and controls the circuit breaker corresponding to the backup power supply to close. The station switches the circuit breakers in sequence, restores the power supply to the power supply section, and sets the main switch in the main substation to the locking condition.

9. A power supply method for a power supply system network structure of medium and low-capacity rail transit when a substation fails, using any one of claims 1-7, characterized in that: The method includes: When a fault occurs in the traction substation, the AC medium voltage section II loses power, the circuit breaker 101B in the traction substation Q1 is disconnected, the circuit breaker 103 in the traction substation Q1 is closed, and the AC medium voltage section II is supported by the power of the AC medium voltage section I; When the incoming line from the traction substation to the next traction substation II fails, the circuit breaker 102B in the traction substation Q1 and the circuit breaker 102B in the traction substation QA are disconnected, and the circuit breaker 103 in the traction substation QA is closed, so that the two sections of the medium-voltage busbars in the traction substation QA operate simultaneously; When the AC medium voltage II section in the step-down substation J1 loses power, the low voltage circuit breaker 802 in the step-down substation J1 is disconnected, and the low voltage circuit breaker 803 in the step-down substation J1 is closed, so that the low voltage power supply can operate normally; When the AC medium voltage II section bus in the step-down substation J1 fails, the circuit breakers 102B in the traction substation Q1 and 102B in the traction substation QA are disconnected, and the circuit breaker 103 in the traction substation QA is closed. The step-down substation J1 operates on a single bus, and the two sections of the medium voltage bus in the traction substation QA operate simultaneously; When a distribution transformer in the traction substation is shut down, the distribution transformer is shut down, the circuit breaker 104B in the traction substation Q1 and the circuit breaker 802 in the traction substation Q1 are disconnected, and the low-voltage circuit breaker 803 in the traction substation Q1 is closed, so that the low-voltage power supply can operate normally.

10. A power supply method for a power supply system network structure of medium and low-capacity rail transit when a DC system fails, using any one of claims 1-7, characterized in that: The method includes: When the traction substation Q1 loses its DC power supply capability, the circuit breaker 201 in the traction substation Q1 is disconnected, and the circuit breakers 211 and 212 in the traction substation Q1 are in the closed position. At this time, the circuit breaker 212 in the traction substation QA and the circuit breaker 211 in the traction substation Q2 jointly provide bilateral power supply to all sections between the traction substation QA and the traction substation Q2 through the DC busbar of the traction substation Q1. When the bidirectional converter unit fails, the circuit breakers 201, 211 and 212 in the traction substation Q1 are disconnected, and the disconnector 2112 in the traction substation Q1 is closed. At this time, the circuit breaker 212 in the traction substation QA and the circuit breaker 211 in the traction substation Q2 are connected through the disconnector 2112 in the traction substation Q1 to provide traction power to all sections between the traction substation QA and the traction substation Q2. When the uplink overhead line fails, disconnect the isolating switch 2111S in the traction substation QA and the isolating switch 2111S in the traction substation Q1, close the uplink driving section from the traction substation QA to the traction substation Q1, and start the fault mode, with the downlink driving section running unilaterally; When a certain set of DC power supply capacity is lost in the traction substation QA, the disconnector 2112 in the traction substation QA is closed, and the R2 unit in the traction substation QA supports the power supply of the left power supply arm of the station. If the R2 unit is out of operation, the disconnector 2112 in the traction substation QA is closed, and the circuit breaker 211 in the traction substation QA and the circuit breaker 211 in the traction substation Q1 are combined through the disconnector 2112 in the traction substation QA to provide bilateral power supply to all the power supply arms between the traction substation QA and the traction substation Q1; When the frame protection element FP-1 or frame protection element FP-2 in the terminal traction substation QA fails, the disconnector 2112 in the traction substation QA is closed, and the R2 unit in the traction substation QA supports the power supply of the left power supply arm of the station. If the R2 unit is out of operation, the disconnector 2112 in the traction substation QA is closed, and the circuit breaker 211 in the traction substation QA and the circuit breaker 211 in the traction substation Q1 are combined through the disconnector 2112 in the traction substation QA to provide bilateral power supply to all power supply arms between the traction substation QA and the traction substation Q1; When the DC switch cabinet fails to touch the shell, the circuit breakers 201, 211 and isolating circuit breaker 212 on the DC bus will trip, and the isolating switch 2112 of this station will be closed, so that the power supply arm between the traction substation QA and the traction substation Q2 can support power supply through the isolating switch 2112.

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