A flexible direct back-to-back alternating field topology and power transfer method

Abstract

The application discloses a kind of flexible back-to-back AC field topology and power transfer method, topology includes: a group of double busbar;Each busbar is connected with the area through first switching unit respectively;Each busbar is connected with converter unit through second switching unit respectively;One end of two busbars is connected with each other through switching device, the other end of two busbars is connected into bus tie switch assembly, bus tie switch assembly is connected with single-ended single busbar converter module, and single-ended single busbar converter module is connected into the DC side of each converter unit.The application solves the problem that the structure of flexible back-to-back AC field is difficult to provide power support for fault power receiving area when permanent fault occurs in the prior art converter unit, and the double busbar in the topology can be flexibly connected with single-ended single busbar converter module or other double busbar to form cascade, which further improves the flexibility of the topology, forms more power transmission channel combinations, so as to provide timely power support for fault power receiving area when fault occurs.

Description

Technical Field

[0001] This invention relates to the field of flexible DC transmission technology, and in particular to a flexible DC back-to-back AC field topology and power transfer method. Background Technology

[0002] With the advancement of urbanization and the expansion of urban power grids, problems such as scarce transmission channel resources, significant gaps in regional power generation capacity, excessive short-circuit current levels at key grid nodes, and weak reactive power support in core load areas are becoming increasingly prominent. The safety margin of urban power grids is under continuous pressure, necessitating technical optimization and improvement. Flexible DC transmission technology based on voltage source converters (VSC-HVDC) offers advantages such as large transmission capacity, excellent operational controllability, strong system anti-disturbance capability, fast control response, no superposition of system short-circuit currents, provision of dynamic reactive power support, and adaptability to renewable energy grid integration. It has become one of the core technical routes for the upgrading and development of modern power systems. Its application in urban power grid expansion and grid transformation projects can effectively optimize the operation of urban power grids and significantly improve the level of urban power supply security.

[0003] Existing flexible DC back-to-back projects mostly adopt a single busbar and single converter unit wiring configuration on the AC side, relying solely on a single converter unit to provide power support to the corresponding load area. Once a converter unit experiences a permanent failure, the existing flexible DC back-to-back AC field wiring architecture cannot achieve power transfer and cannot continuously provide active and reactive power support to the faulty power receiving area. Summary of the Invention

[0004] This invention provides a flexible DC back-to-back AC field topology and power transfer method to solve the technical problem in the prior art that when a permanent fault occurs in the converter unit, the existing flexible DC back-to-back AC field structure is unable to continue to provide power support to the faulty power receiving area.

[0005] To address the aforementioned technical problems, embodiments of the present invention provide a flexible DC back-to-back AC field topology, comprising: a set of dual buses; each set of dual buses includes two buses; each bus is connected to a region via a first switching unit; each bus is connected to a converter unit via a second switching unit; and the DC sides of each converter unit are interconnected. One end of each of the two buses is connected to the other end of the bus via a switching device, and the other end of each bus is connected to a bus tie switch assembly. The bus tie switch assembly is connected to a single-ended single-bus converter module, and the single-ended single-bus converter module is connected to the DC side of each converter unit.

[0006] As a preferred option, it also includes: several sets of double busbars; Each group of double busbars is cascaded through the bus tie switch assembly; The two busbars at the beginning of the double busbar are interconnected at one end via the switching device; the other ends of the two busbars at the end of the double busbar are connected to the bus tie switch assembly and connected to the single-ended single busbar converter module via the bus tie switch assembly.

[0007] As a preferred option, it also includes: several sets of double busbars; Each group of double busbars is cascaded through the bus tie switch assembly; The two busbars at the beginning of the double busbar are connected to each other at one end via the switching device; the two busbars at the end of the double busbar are connected to each other at the other end via the switching device.

[0008] As a preferred embodiment, the first switching unit includes a first outgoing switch, a first disconnect switch, and a second disconnect switch; One end of the first outgoing switch is connected to the area; The other end of the first outgoing switch is connected to the first disconnect switch and the second disconnect switch, respectively; The first disconnector is connected to one of the two busbars; The second disconnector is connected to the other busbar in the dual busbar configuration.

[0009] As a preferred embodiment, the second switching unit includes a second outgoing switch, a third disconnect switch, and a fourth disconnect switch; One end of the second outgoing switch is connected to the converter unit; The other end of the second outgoing switch is connected to the third disconnect switch and the fourth disconnect switch respectively; The third disconnector is connected to one of the two busbars; The fourth disconnector is connected to the other busbar in the dual busbar system.

[0010] As a preferred embodiment, the bus tie switch assembly includes: two bus tie switch devices; When the bus tie switch assembly is used to connect the double busbar and the single-ended single busbar converter module, one bus tie switch device is connected to one busbar and the single-ended single busbar converter module respectively; another bus tie switch device is connected to another busbar and the single-ended single busbar converter module respectively. When the bus tie switch assembly is used to establish a connection between each of the double busbars, one of the bus tie switch devices is connected to one busbar in one double busbar and one busbar in another double busbar; the other bus tie switch device is connected to the other busbar in one double busbar and the other busbar in another double busbar.

[0011] As a preferred embodiment, it also includes: a diagonal bus tie switch assembly; The diagonally opposite buses in each pair of dual busbars are connected via the diagonal bus tie switch assembly.

[0012] As a preferred embodiment, the diagonal bus tie switch assembly includes: two diagonal bus tie switch devices; The diagonal bus tie switch group device is respectively connected to one bus in one double bus and the other bus in the other double bus; Another diagonal bus tie switch device is connected to another bus in one of the double busbars and one bus in the other double busbar.

[0013] Accordingly, the present invention also provides a power transfer method, implemented by any one of the above-mentioned flexible DC back-to-back AC field topologies, comprising: When any converter unit in the flexible DC back-to-back AC field topology fails, a fault transfer command is generated. The fault transfer command is analyzed to obtain the busbar to be connected and the transfer converter unit; The target power transfer bus is determined based on the connection relationship between the bus to be connected and the power transfer converter unit; Establish a connection path between the power transfer and converter unit and the target power transfer bus, and establish a connection path between the target power transfer bus and the bus to be connected, so that the power transfer and converter unit provides energy to the bus to be connected.

[0014] As a preferred embodiment, determining the target power transfer bus based on the connection relationship between the bus to be connected and the power transfer converter unit specifically includes: Determine the original busbar connected to the power supply converter unit under normal operating conditions; Determine whether the original busbar is directly connected to the busbar to be connected via a bus tie switch assembly or a diagonal bus tie switch assembly; If so, the original busbar is used as the target transfer busbar; If not, the non-original busbar in the target dual busbar is taken as the target transfer busbar, and the target dual busbar is the dual busbar where the original busbar is located.

[0015] As a preferred embodiment, when the target transfer bus is the original bus, the step of establishing a connection path between the transfer converter unit and the target transfer bus, and establishing a connection path between the target transfer bus and the bus to be connected, specifically includes: Determine whether the original busbar is in a dual busbar configuration; If so, the first switching unit connected between the original bus and the power receiving area of ​​the original bus shall be used as the first target switching unit; otherwise, in the single-ended single bus converter module, the switching unit connected between the original bus and the power receiving area of ​​the original bus shall be used as the first target switching unit. Determine whether AC loop-connection is allowed between the power receiving area of ​​the busbar to be connected and the power receiving area of ​​the original busbar; If so, close the first target switching device and open the second target switching device; If not, shut down the power supply converter unit, disconnect the second target switching device, and close the first target switching device, thereby starting the power supply converter unit; Wherein, the first target switching device is a switching device connected between the bus to be connected and the original bus in the bus tie switch assembly or the diagonal bus tie switch assembly; The second target switching device is the switching device in the first target switching unit that is in the on state.

[0016] As a preferred embodiment, when the target transfer bus is not the original bus, the step of establishing a connection path between the transfer converter unit and the target transfer bus, and establishing a connection path between the target transfer bus and the bus to be connected, specifically includes: Shut down the power transfer converter unit and the non-power transfer converter unit; wherein, the non-power transfer converter unit is the converter unit that provides energy to the non-original bus under normal operating conditions; Disconnect the first target outgoing switch and the second target outgoing switch; wherein, the first target outgoing switch is an outgoing switch connected between the original bus and the power receiving area of ​​the original bus; the second target outgoing switch is an outgoing switch connected between the non-original bus and the power receiving area of ​​the non-original bus. The system closes the third target switching device, disconnects the first target disconnector assembly, and closes the first target disconnector; it also disconnects the second target disconnector assembly and closes the third target disconnector assembly. The first target disconnector assembly includes a disconnector connected between the second target outgoing switch and the non-original busbar, and a disconnector connected between the non-original busbar and the non-transfer converter unit. The first target disconnector is a disconnector connected between the non-original busbar and the transfer converter unit. The third target switching device refers to a switching device located away from the fault point and used to connect the original busbar and the non-original busbar. The second target disconnector assembly includes a disconnector connected between the first target outgoing switch and the original busbar, and a disconnector connected between the original busbar and the transfer converter unit. The third target disconnector assembly includes a disconnector connected between the second target outgoing switch and the original busbar, and a disconnector connected between the original busbar and the non-transfer converter unit. Disconnect the third target switching device; A switching device that closes the connection between the non-original busbar and the busbar to be connected; Start the power supply converter unit and close the second target outgoing line switch to start the non-power supply converter unit.

[0017] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: In this invention, the flexible DC back-to-back AC field topology connects each busbar to a section via a first switching unit. This allows for flexible switching of the busbar connected to the section via the first switching unit, improving topology flexibility. Furthermore, each busbar connects to a converter unit via a second switching unit. This allows for flexible switching of the busbar connected to the converter unit via the second switching unit. Therefore, based on the first and second switching units, various connection combinations can be formed between the converter units, buses, and sections, creating multiple transmission channels and further enhancing topology flexibility. When the number of dual busbar groups is one, one end of the two buses is interconnected via a switching device, and the other end of the two buses is connected to a single-ended single-bus converter module via a bus tie switch assembly.

[0018] Furthermore, when the number of dual busbar groups is not one, each dual busbar is cascaded through the bus tie switch assembly; wherein, one end of the two buses of the dual busbar located at the first end is interconnected through the switching device; the other end of the two buses of the dual busbar located at the last end is used to connect to the bus tie switch assembly, and through the bus tie switch assembly to the single-ended single-bus converter module, or is used to connect to each other through the switching device, so that the dual buses in the topology can be flexibly cascaded with the single-ended single-bus converter module or with other dual buses, further improving the flexibility of the topology and forming more power transmission channel combinations. Thus, in the event of a fault, the states of the bus tie switch assembly, the first switching unit, the second switching unit, and the switching device are switched to conduct the corresponding power transmission channel, providing timely power support to the faulty power receiving area. This solves the technical problem that when the converter unit fails, the existing flexible DC back-to-back AC field structure cannot continue to provide power support to the faulty power receiving area.

[0019] The power transfer method of this invention generates a fault transfer command when any converter unit in the flexible DC back-to-back AC field topology fails. The command is then parsed to obtain the bus to be connected and the transfer converter unit, thus identifying the bus affected by the fault and the transfer converter unit to provide power support. Based on the connection relationship between the bus to be connected and the transfer converter unit, a target transfer bus is determined, enabling the determination of the power supply path for the transfer converter unit and timely establishing the connection between the transfer converter unit and the faulty power receiving area. Furthermore, a connection path is established between the transfer converter unit and the target transfer bus, and between the target transfer bus and the bus to be connected, allowing the transfer converter unit to provide energy to the bus to be connected. This enables the transfer converter unit to provide power support to the faulty power receiving area, solving the technical problem that the existing flexible DC back-to-back AC field structure cannot continue to provide power support to the faulty power receiving area. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a four-terminal flexible straight back-to-back AC field structure using a single-end single-busbar connection method in the prior art. Figure 2 This is a schematic diagram of the existing four-terminal flexible straight back-to-back AC field fault. Figure 3 This is a schematic diagram of a flexible, straight back-to-back AC field topology provided in an embodiment of the present invention; wherein, Figure 3 (a) shows the structure of the flexible straight back-to-back AC field topology when the number of double bus groups is one; Figure 3 (b) shows the structure of the flexible straight back-to-back AC field topology when the number of double bus groups is not one; Figure 4 This is a schematic diagram of the structure of a three-terminal flexible straight back-to-back AC field topology provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of a four-terminal flexible straight back-to-back AC field topology provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the five-terminal flexible straight back-to-back AC field topology provided in an embodiment of the present invention; Figure 7 This is another structural schematic diagram of the four-terminal flexible straight back-to-back AC field topology provided in an embodiment of the present invention; Figure 8 A flowchart illustrating the steps of a fault transfer method provided in an embodiment of the present invention; Figure 9 The fault transfer method provided in this embodiment of the invention is applied to Figure 5 The principle of topological time Figure 1 ;in, Figure 9(a) shows the topology state when the faulty converter unit is cell one. Figure 9 (b) shows the state of the topology when the first target switching device is closed. Figure 9 (c) shows the state of the topology when the second target switching device is disconnected; Figure 10 The fault transfer method provided in this embodiment of the invention is applied to Figure 5 The principle of topological time Figure 2 ;in, Figure 10 (a) shows the state of the topology when the power supply switching unit is turned off and the second target switching device is disconnected. Figure 10 (b) shows the state of the topology when the first target switching device is closed. Figure 10 (c) shows the state of the topology when the power supply converter unit is started; Figure 11 The fault transfer method provided in this embodiment of the invention is applied to Figure 5 The principle of topological time Figure 3 ; Figure 12 The fault transfer method provided in this embodiment of the invention is applied to Figure 5 The principle of topological time Figure 4 ;in, Figure 12 (a) shows the state of the topology when the power supply converter unit and the non-power supply converter unit are turned off, and the first target outgoing switch and the second target outgoing switch are disconnected; Figure 12 (b) shows the state of the topology when the third target switching device is closed, the first target disconnector assembly is opened, the first target disconnector assembly is closed, the second target disconnector assembly is opened, and the third target disconnector assembly is closed; Figure 12 (c) shows the topology when the third target switching device is disconnected and the switching device connected between the non-original bus and the bus to be connected is closed; Figure 12 (d) shows the state of the topology when the power supply converter unit is started, the second target outgoing switch is closed, and the non-power supply converter unit is started.

[0021] The reference numerals for the accompanying drawings in the specification are as follows: 1. Double busbar; 2. First switching unit; 3. Second switching unit; 31. Outgoing switch connected to area 3; 4. Converter unit; 41. Outgoing switch connected to area 4; 5. Switching device; 6. Bus tie switch assembly; 61. Another bus tie switch device; 62. Single-ended single busbar converter module; 7. Diagonal bus tie switch assembly; 8. Diagonal bus tie switch device; 82. Another diagonal bus tie switch device; K5. Switching device K5 connecting busbar #5M and busbar #6M; d1, d2, d3, d4, d5, d6, and d7 are disconnect switches. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Currently, there are relatively few multi-terminal flexible DC back-to-back projects in operation. To meet the requirement of non-loop operation under normal AC outgoing line conditions, DC converters need to be connected to different areas to achieve DC isolation and interconnection. Therefore, the current AC field wiring method of flexible DC back-to-back systems is a single busbar single converter unit wiring, with no electrical connection between the individual buses. Under normal operating conditions, the existing single-terminal single busbar flexible DC back-to-back AC field can provide power support. However, if a single-terminal converter unit experiences a permanent fault and is difficult to repair and restore, the existing flexible DC back-to-back AC field cannot continue to provide power support to the faulty receiving area, making it difficult to guarantee power support for the core receiving area.

[0024] Taking the existing four-terminal flexible DC back-to-back AC field as an example, its AC field wiring is a single-terminal single busbar connection, such as... Figure 1 As shown, the rectangle represents the outgoing switch, the smaller circle connected to the outgoing switch is the disconnect switch, the two overlapping circles represent the flexible DC converter transformer, and #2M, #1M, #5M, and #6M represent the respective buses. This flexible DC back-to-back AC field has four converters, VSC1 to VSC4. Each converter is connected to a bus via a flexible DC converter transformer, an outgoing switch, and a disconnect switch, and then transmits power to a specific receiving area via the bus.

[0025] Taking a single-end permanent fault (such as converter failure, converter transformer failure, etc.) in a converter unit as an example, such as... Figure 2 As shown, a power shortage will occur in the first power receiving area, and the other converter units will be unable to switch power transmission channels to ensure power support for the first power receiving area.

[0026] Therefore, when a converter unit experiences a permanent failure, the existing flexible DC back-to-back AC field structure is unable to continue providing power support to the faulty power receiving area. This invention provides a flexible DC back-to-back AC field topology and power transfer method to address the technical problem that the existing flexible DC back-to-back AC field structure is unable to continue providing power support to the faulty power receiving area when a converter unit experiences a permanent failure.

[0027] Example 1 Please refer to Figure 3The present invention provides a flexible DC back-to-back AC field topology, comprising: a set of dual buses 1; each set of dual buses 1 includes two buses; each bus is connected to a region through a first switching unit 2; each bus is connected to a converter unit 4 through a second switching unit 3; and the DC sides of each converter unit 4 are interconnected. One end of each of the two buses is connected to the other end of the bus via a switching device 5. The other end of each of the two buses is connected to a bus tie switch assembly 6. The bus tie switch assembly 6 is connected to a single-ended single-bus converter module 7. The single-ended single-bus converter module 7 is connected to the DC side of each of the converter units 4.

[0028] In this embodiment, as Figure 3 As shown in (a), when the number of groups of the double busbar 1 is one, one end of the two busbars is connected to each other through the switching device 5, and the other end of the two busbars is connected to the single-ended single busbar converter module 7 through the bus tie switch assembly 6 respectively.

[0029] It should be noted that the first switching unit 2 is equipped with an outgoing switch and a disconnector, which have both on and off states. In practical applications, by switching the states of the various devices inside the first switching unit 2, the connection relationship between the two buses in the double busbar 1 and the area is adjusted. The second switching unit 3 works similarly to the first switching unit 2. In practical applications, by switching the states of the switching devices 5 inside the second switching unit 3, the connection relationship between the two buses in the double busbar 1 and the converter unit 4 is adjusted.

[0030] In this embodiment, each first switching unit 2 is connected to one area, and each second switching unit 3 is connected to one converter unit 4. In a set of dual buses 1, one bus can connect two first switching units 2 and connect to two areas respectively through the two first switching units 2, and one bus can connect two second switching units 3 and connect to two converter units 4 respectively through the two second switching units 3.

[0031] The converter unit 4 includes a converter and a converter transformer. The converter and the converter transformer are connected, and the converter transformer is connected to the second switching unit 3. In this embodiment, the DC sides of each converter are interconnected.

[0032] The number of groups of dual busbars 1 can be determined according to actual conditions. When the number of groups of dual busbars 1 is one, one end of the two buses is connected to each other through a switching device 5, and the other end of the two buses is connected to a single-ended single-bus converter module 7 through a bus tie switch assembly 6, so that the overall topology forms a three-terminal flexible DC back-to-back AC field. In this embodiment, the switching device 5 connecting the two buses can be a bus tie switch device, which has on and off states. The single-ended single-bus converter module 7 refers to a circuit that provides power to a region in the existing flexible DC converter field topology, for example, such as... Figure 1 As shown, the outgoing switches, disconnectors, unit 1, and bus #2m used to provide power support for area 1 can constitute a single-ended single-bus converter module 7.

[0033] The bus tie switch assembly 6 is equipped with a bus tie switch device. The two buses of the double busbar 1 are respectively connected to the busbar in the single-ended single busbar converter module 7 through the bus tie switch device. Therefore, in practical applications, by switching the state of the bus tie switch device inside the bus tie switch assembly 6, the single-ended single busbar converter module 7 and the double busbar 1 can be connected, so that in the event of a fault, power support can be provided to the faulty area in a timely manner.

[0034] As a preferred embodiment, the first switching unit 2 includes a first outgoing switch, a first disconnect switch, and a second disconnect switch; one end of the first outgoing switch is connected to the area; the other end of the first outgoing switch is connected to the first disconnect switch and the second disconnect switch respectively; the first disconnect switch is connected to one of the two busbars 1; and the second disconnect switch is connected to the other busbar 1.

[0035] It should be noted that in practical applications, the power supply to the area is maintained or stopped by switching the on / off state of the first outgoing switch. The busbar supplying power to the area is switched by switching the on / off state of the first disconnect switch and the second disconnect switch. For example, when the first disconnect switch is open and the second disconnect switch is closed, the other busbar in the double busbar 1 supplies power to the area; when the second disconnect switch is open and the first disconnect switch is closed, one busbar in the double busbar 1 supplies power to the area.

[0036] As a preferred embodiment, the second switching unit 3 includes a second outgoing switch, a third disconnect switch, and a fourth disconnect switch; one end of the second outgoing switch is connected to the converter unit 4; the other end of the second outgoing switch is connected to the third disconnect switch and the fourth disconnect switch respectively; the third disconnect switch is connected to one of the two busbars 1; and the fourth disconnect switch is connected to the other busbar 1.

[0037] As a preferred embodiment, the bus tie switch assembly 6 includes two bus tie switch devices. When the bus tie switch assembly 6 is used to connect the double busbar 1 and the single-ended single busbar converter module 7, one bus tie switch device is connected to one of the buses and the single-ended single busbar converter module 7 respectively; the other bus tie switch device is connected to the other busbar and the single-ended single busbar converter module 7 respectively. When the bus tie switch assembly 6 is used to establish a connection between each of the double busbars 1, one bus tie switch device is connected to one busbar in one double busbar 1 and one busbar in another double busbar 1 respectively; the other bus tie switch device is connected to the other busbar in one double busbar 1 and the other busbar in another double busbar 1 respectively.

[0038] It should be noted that when the double busbars 1 are grouped together, the two buses of the double busbars 1 can be connected to the single busbar in the single-ended single busbar converter module 7 respectively through the bus tie switch assembly 6. Each of the two buses in the double busbars 1 is connected to a corresponding bus tie switch device, and is connected to one side of the single busbar through the corresponding bus tie switch device. For example... Figure 4 As shown, taking a three-terminal flexible DC back-to-back AC field as an example, the bus tie switch assembly 6 is equipped with bus tie switch device 61 and bus tie switch device 62. The bus #1M and #2M in the double bus 1 are connected to the single bus #5M in the single-terminal single bus converter module 7 through bus tie switch device 61 and bus tie switch device 62, respectively.

[0039] Implementing the above embodiments has the following effects: In this invention, the flexible DC back-to-back AC field topology connects each busbar to a section via a first switching unit. This allows for flexible switching of the busbar connected to the section via the first switching unit, improving topology flexibility. Furthermore, each busbar connects to a converter unit via a second switching unit. This allows for flexible switching of the busbar connected to the converter unit via the second switching unit. Therefore, based on the first and second switching units, various connection combinations can be formed between the converter units, buses, and sections, creating multiple transmission channels and further enhancing topology flexibility. When the number of dual busbar groups is one, one end of the two buses is interconnected via a switching device, and the other end of each busbar is connected to a single-ended single-bus converter module via a bus tie switch assembly. Example 2 As a preferred option, it also includes: several sets of double busbars 1; Each group of double busbars 1 is cascaded through the bus tie switch assembly 6; Among them, one end of the two busbars of the first double busbar 1 is connected to each other through the switching device 5; the other end of the two busbars of the last double busbar 1 is connected to the bus tie switch assembly 6 and connected to the single-ended single busbar converter module 7 through the bus tie switch assembly 6.

[0040] As a preferred option, it also includes: several sets of double busbars 1; Each group of double busbars 1 is cascaded through the bus tie switch assembly 6; Among them, one end of the two busbars of the first double busbar 1 is connected to each other through the switching device 5; the other end of the two busbars of the last double busbar 1 is connected to each other through the switching device 5.

[0041] In this embodiment, when the number of groups of dual busbars 1 is not one, each of the dual busbars 1 is cascaded through the bus tie switch assembly 6. Therefore, one end of the two buses of one group of dual busbars 1 is connected to one end of the two buses of another group of dual busbars 1 through the bus tie switch assembly 6, and the other end of the other group of dual busbars 1 is connected to one end of the two buses of the next group of dual busbars 1 through the bus tie switch assembly 6, and so on, forming a chain connection structure, so that the topology as a whole constitutes a multi-terminal flexible straight back-to-back AC field.

[0042] In this chain-connection structure, one end of each of the two buses of the first double busbar 1 is interconnected via the switching device 5. The other end of each of the two buses of the last double busbar 1 is connected to the bus tie switch assembly 6, and through the bus tie switch assembly 6 to the single-ended single busbar converter module 7, or interconnected via the switching device 5 (this part...). Figure 1 (Not shown). Therefore, one end of the two buses of the double busbar 1 at the end is connected to the previous double busbar 1 through the bus tie switch assembly 6, while the other end is an idle end, which can be connected to the single-ended single busbar converter module 7 or mutually closed-loop connected according to actual needs.

[0043] Therefore, in the topology provided in this embodiment, each busbar is connected to a region via a first switching unit 2, thereby allowing for flexible switching of the busbar connected to the region through the first switching unit 2 in practical applications, improving the flexibility of the topology. Furthermore, each busbar is connected to a converter unit 4 via a second switching unit 3, allowing for flexible switching of the busbar connected to the converter unit 4 in practical applications. Therefore, in this invention, based on the first switching unit 2 and the second switching unit 3, various connection combinations can be formed between each converter unit 4, each busbar, and each region, thereby constituting various power supply channel combinations and further improving the flexibility of the topology. In this invention, when the number of groups of the dual busbars 1 is one, one end of the two buses is interconnected via a switching device 5, and the other end of the two buses is connected to a single-ended single-busbar converter module 7 via a bus tie switch assembly 6. When the number of groups of the dual busbars 1 is not one, each dual busbar 1 is connected via a... The bus tie switch assembly 6 is cascaded; wherein, one end of the two buses of the first double bus 1 is interconnected through the switching device 5; the other end of the two buses of the last double bus 1 is used to connect to the bus tie switch assembly 6, and through the bus tie switch assembly 6 to the single-ended single bus converter module 7, or to be interconnected through the switching device 5, so that the double bus 1 in the topology can be flexibly cascaded with the single-ended single bus converter module 7 or with other double bus 1, further improving the flexibility of the topology and forming more power channel combinations. Thus, in the event of a fault, the states of the bus tie switch assembly 6, the first switching unit 2, the second switching unit 3, and the switching device 5 are switched to conduct the corresponding power transmission channel, so as to redistribute the power support of the converter unit 4 to different areas, and provide timely power support to the faulty power receiving area. This solves the technical problem that the existing flexible DC back-to-back AC field structure is difficult to continue to provide power support to the faulty power receiving area.

[0044] In this embodiment, when there are multiple sets of dual busbars 1, the two buses in each set of dual busbars 1 are respectively connected to two bus tie switching devices, and are connected to the next set of dual busbars 1 through the two bus tie switching devices. The two buses in the next set of dual busbars 1 are also respectively connected to two bus tie switching devices 5, and are connected to the next set of dual busbars 1 through the two bus tie switching devices, and so on, forming a chain structure. Each busbar is connected to a first switching unit 2 and a second switching unit 3, and is connected to the corresponding area through each first switching unit 2, and to the corresponding converter unit 4 through each second switching unit 3, so that the overall topology forms a multi-terminal flexible DC back-to-back AC field structure. Among them, one end of the two buses of the first set of dual busbars 1 (i.e., the end not connected to the bus tie switching devices) is connected to each other through the switching devices 5, while the other end of the two buses of the last set of dual busbars 1 (i.e., the end not connected to the previous set of dual busbars 1) can be connected to the single-ended single bus converter module 7 through the bus tie switching assembly 6, or connected to each other through the switching devices 5.

[0045] like Figure 5 As shown, taking the constructed four-end flexible straight back-to-back AC field as an example, Figure 5 The diagram shows the two buses of the end double busbar 1 being interconnected via a switching device 5. Figure 5 In the diagram, units one through four are converter units 4. The DC sides of each converter unit 4 are interconnected. VSC1 through VSC4 represent the respective converters. In the first switching unit 2 and the second switching unit 3, rectangles represent outgoing line switches, circles represent disconnectors, shaded areas represent on, and unshaded areas represent off. Figure 5 This shows the operating status of each outgoing switch, each disconnector, each bus tie switch, and each switch device 5 under normal operating conditions.

[0046] Specifically, Figure 5 In this configuration, two buses #1M and #2M of the first double busbar 1 are interconnected at one end via switching device 5, and their other ends are respectively connected to bus tie switch assembly 6. These buses are then connected to one end of buses #5M and #6M in the next double busbar 1 via bus tie switch assembly 6, and the other ends of buses #5M and #6M are interconnected via switching device 5. Each busbar is connected to two first switching units 2, and through these two units, to two different zones. Furthermore, each busbar is connected to two second switching units 3, and through these units, to two converter units 4.

[0047] Following the order from left to right, the two sets of double busbars 1 on the left and right sides of the diagram can be divided into the first set of double busbars 1 and the second set of double busbars 1. The structure of the first set of double busbars 1 is similar to that of the second set of double busbars 1. This example uses... Figure 5Taking the second group of double busbars 1 as an example, busbar #5M connects to two first switching units 2 respectively. Busbar #5M is connected to area four through the disconnect switch and outgoing switch in the first switching unit 2 on the left, and to area four through the disconnect switch and outgoing switch in the first switching unit 2 on the right. It is also connected to unit four through the disconnect switch and outgoing switch in the second switching unit 3 on the left, and to unit three through the disconnect switch and outgoing switch in the second switching unit 3 on the right. Figure 5 As shown, under normal operating conditions, in the second switching unit 3 on the right, the outgoing switch and disconnector connected to bus #5M are in the conducting state, and in the first switching unit 2 on the right, the outgoing switch and disconnector connected to area 3 are in the conducting state. Therefore, unit 3 provides energy to bus #5M, and bus #5M provides energy to area 3.

[0048] Similarly, busbar #6M connects to the disconnect switch of the first switching unit 2 on the left, and is connected to area four based on the connection relationship between the disconnect switch and the outgoing switch. Busbar #6M connects to the disconnect switch of the first switching unit 2 on the right, and is connected to area three based on the connection relationship between the disconnect switch and the outgoing switch. Busbar #6M connects to the disconnect switch of the second switching unit 3 on the left, and is connected to unit four based on the connection relationship between the disconnect switch and the outgoing switch. Busbar #6M connects to the disconnect switch of the second switching unit 3 on the right, and is connected to unit three based on the connection relationship between the disconnect switch and the outgoing switch. Figure 5 As shown, under normal operating conditions, in the second switching unit 3 on the left, the outgoing switch and disconnector connected to bus #6M of unit 4 are in the ON state. In the first switching unit 2 on the left, the outgoing switch and disconnector connected to area 4 of bus #6M are in the ON state. Therefore, unit 4 provides energy to bus #6M, and bus #6M provides energy to area 4. In the event of a fault, the ON / OFF state of the bus tie switch devices, the first switching unit 2, and the second switching unit 3 can be controlled to allow the converter unit 4, which provides power support, to establish a connection with the area experiencing a power shortage due to the fault, thereby enabling the converter unit 4 to provide power support to that area.

[0049] It is understood that the topology provided in this embodiment is not limited to a three-terminal flexible DC back-to-back AC field or a four-terminal flexible DC back-to-back AC field. Based on the wiring principle of the topology provided by this invention, a multi-terminal flexible DC back-to-back AC field can be constructed according to actual needs. For example, Figure 6 A five-terminal flexible DC back-to-back AC field topology is shown, wherein the other end of the dual busbar 1 at the end is connected to busbar #9M in the single-ended single-busbar converter module 7.

[0050] As a preferred embodiment, it further includes: a diagonal bus tie switch assembly 8; The diagonally opposite buses in each pair of the double busbars 1 are connected by the diagonal bus tie switch assembly 8.

[0051] It should be noted that when the number of double busbars 1 is not one, each pair of double busbars 1 is connected by bus tie switch assembly 6 and diagonal bus tie switch assembly 8. The two busbars in each pair of double busbars 1 are arranged in a longitudinal direction, and the two pairs of double busbars 1 are arranged in a transverse direction. Therefore, in the four double busbars 1, each pair of busbars is adjacent in the transverse direction, and each pair of busbars is located at a diagonal position.

[0052] In this embodiment, the bus tie switch assembly 6 is used to connect adjacent busbars; the diagonal bus tie switch assembly 8 is used to connect busbars located diagonally opposite each other.

[0053] As a preferred embodiment, the diagonal bus tie switch assembly 8 includes: two diagonal bus tie switch devices; The diagonal bus tie switch device 81 is respectively connected to one bus in the one double busbar and the other bus in the other double busbar; Another diagonal bus tie switch device 82 is connected to another bus in one of the double busbars and one bus in the other double busbar.

[0054] It should be noted that in this embodiment, one bus in one double busbar 1 and another bus in another double busbar 1 are located diagonally and are connected by a diagonal bus tie switch device 81. The other bus in one double busbar 1 and one bus in another double busbar 1 are also located diagonally and are therefore connected by a diagonal bus tie switch device 82.

[0055] For example, as Figure 7 The following is an example of a four-terminal flexible back-to-back AC field topology. Buses #1M and #5M are adjacent buses, therefore, they are connected via bus tie switch 61. Buses #1M and #6M are diagonal buses, connected via diagonal bus tie switch 81. Buses #2M and #6M are adjacent buses, therefore, they are connected via another bus tie switch 62. Buses #2M and #5M are diagonal buses, connected via another diagonal bus tie switch 82.

[0056] This embodiment further enhances the flexibility of the topology by adding diagonal bus tie-in switching devices, so that in the event of a fault, the converter unit 4 can be more easily and flexibly deployed to support the faulty power receiving area, making the power transfer operation simpler.

[0057] Implementing the above embodiments has the following effects: When the number of dual busbar groups is not one, the dual busbars are cascaded through the bus tie switch assembly. One end of each of the two buses of the first dual busbar is interconnected through the switching device. The other end of each of the two buses of the last dual busbar is connected to the bus tie switch assembly and, through the bus tie switch assembly, to the single-ended single-bus converter module, or interconnected through the switching device. This allows the dual buses in the topology to be flexibly cascaded with the single-ended single-bus converter module or with other dual buses, further improving the flexibility of the topology and forming more power transmission channel combinations. In the event of a fault, the states of the bus tie switch assembly, the first switching unit, the second switching unit, and the switching device are switched to activate the corresponding power transmission channel, providing timely power support to the faulty power receiving area. This solves the technical problem that the existing flexible DC back-to-back AC field structure cannot continue to provide power support to the faulty power receiving area when the converter unit fails.

[0058] Example 3 The present invention also provides a power transfer method, implemented by the flexible DC back-to-back AC field topology described in any of the preceding claims, comprising the following steps S101-S104: S101: When any converter unit in the flexible DC back-to-back AC field topology fails, a fault transfer command is generated.

[0059] In this embodiment, real-time data are collected on the DC-side voltage, DC current, active and reactive power output of each converter, arm current, submodule operating status, and AC bus operating conditions of each converter. The collected data is then compared and analyzed in real-time with normal operating baseline thresholds, parallel current sharing deviation limits, module communication heartbeat signals, and switch fault alarm information. When any converter exhibits fault characteristics such as sudden current changes, parallel current sharing imbalance, abnormal operating voltage, device protection activation, or module offline shutdown, a fault in the converter module can be determined, and the faulty outgoing branch can be quickly and accurately located. Based on this, information on the power receiving area awaiting support, the target commissioned converter unit, and the power support type is encapsulated to generate corresponding power support control commands.

[0060] S102: Parse the fault transfer command to obtain the bus to be connected and the transfer converter unit.

[0061] It should be noted that when a fault transfer command is received, it indicates that a converter unit fault has occurred in the topology, and power support needs to be provided to the area where a power shortage has occurred due to the fault (hereinafter referred to as the fault-receiving area). The fault transfer command carries information about the bus to be connected and the transfer converter unit. Therefore, by parsing the fault transfer command, the bus to be connected and the transfer converter unit used to provide power support can be identified.

[0062] Among them, the busbar to be connected refers to the busbar that is connected to the faulty power receiving area and transmits power to the faulty power receiving area.

[0063] S103: Determine the target power transfer bus based on the connection relationship between the bus to be connected and the power transfer converter unit.

[0064] It should be noted that after determining the bus to be connected and the power transfer converter unit, the target power transfer bus can be determined based on their connection relationship in the topology. The target power transfer bus is the intermediate connecting line between the power transfer converter unit and the bus to be connected, used to connect the two buses. This allows the power transfer converter unit to connect to the bus to be connected via the target power transfer bus, thereby providing power to the affected area through the bus to be connected.

[0065] S104: Establish a connection path between the power transfer converter unit and the target power transfer bus, and establish a connection path between the target power transfer bus and the bus to be connected, so that the power transfer converter unit provides energy to the bus to be connected.

[0066] It should be noted that after the target power transfer bus is determined, a connection path is established between the power transfer converter unit and the target power transfer bus, and a connection path is established between the target power transfer bus and the bus to be connected. This ensures that the power supply channel between the power transfer converter unit and the target power transfer bus is in a conductive state, and the power supply channel between the target power transfer bus and the faulty power receiving area is in a conductive state. This allows the power transfer converter unit to transmit power to the target power transfer bus, the target power transfer bus to transmit power to the bus to be connected, and the bus to be connected to transmit power to the faulty power receiving area, thus completing power support and enabling the faulty power receiving area to operate normally.

[0067] Therefore, the power transfer method provided by this invention, upon receiving a fault transfer command, parses the command to obtain the bus to be connected and the transfer converter unit, thus determining the bus affected by the fault and the transfer converter unit used to provide power support; and determines the target transfer bus based on the connection relationship between the bus to be connected and the transfer converter unit, thereby determining the power supply path of the transfer converter unit and establishing a timely connection between the transfer converter unit and the faulty power receiving area; and establishes a connection path between the transfer converter unit and the target transfer bus, and between the target transfer bus and the bus to be connected, enabling the transfer converter unit to provide energy to the bus to be connected, thereby providing power support to the faulty power receiving area. This solves the technical problem that the existing flexible DC back-to-back AC field structure is unable to continue providing power support to the faulty power receiving area.

[0068] In a preferred embodiment of this invention, determining the target power transfer bus based on the connection relationship between the bus to be connected and the power transfer converter unit specifically includes: S21: Determine the original busbar connected to the power supply converter unit under normal operating conditions.

[0069] It should be noted that in the topology under normal operating conditions, the power transfer converter unit is connected to the corresponding primary bus. Therefore, based on the connection relationship of the power transfer converter unit in the topology, the primary bus connected to the power transfer converter unit can be determined.

[0070] S22: Determine whether the original busbar is directly connected to the busbar to be connected through a bus tie switch assembly or a diagonal bus tie switch assembly.

[0071] S23: If so, the original busbar is used as the target transfer busbar.

[0072] S24: If not, take the non-original busbar in the target dual busbar as the target transfer busbar, where the target dual busbar is the dual busbar where the original busbar is located.

[0073] It should be noted that when the original busbar and the busbar to be connected are connected through a bus tie switch assembly or a diagonal bus tie switch assembly, it means that by closing the corresponding switching device in the bus tie switch assembly or the diagonal bus tie switch assembly, a connection channel can be established between the original busbar and the busbar to be connected. Under this structure, the original busbar can be used as the target transfer busbar.

[0074] When the original busbar and the busbar to be connected cannot be directly connected via the bus tie switch assembly, it indicates that there is no basis for connection between the original busbar and the busbar to be connected, and it cannot be used as the target transfer busbar. Since a double busbar includes two busbars, based on the aforementioned topology, if the original target is not connected to the busbar to be connected, it means that the other non-original busbar in the double busbar is directly connected to the busbar to be connected via the bus tie switch assembly. Therefore, in this case, the non-original busbar is used as the target transfer busbar.

[0075] Implementing the above embodiments has the following effects: The power transfer method of this invention generates a fault transfer command when any converter unit in the flexible DC back-to-back AC field topology fails. The command is then parsed to obtain the bus to be connected and the transfer converter unit, thus identifying the bus affected by the fault and the transfer converter unit to provide power support. Based on the connection relationship between the bus to be connected and the transfer converter unit, a target transfer bus is determined, enabling the determination of the power supply path for the transfer converter unit and timely establishing the connection between the transfer converter unit and the faulty power receiving area. Furthermore, a connection path is established between the transfer converter unit and the target transfer bus, and between the target transfer bus and the bus to be connected, allowing the transfer converter unit to provide energy to the bus to be connected. This enables the transfer converter unit to provide power support to the faulty power receiving area, solving the technical problem that the existing flexible DC back-to-back AC field structure cannot continue to provide power support to the faulty power receiving area.

[0076] Example 4 In another preferred embodiment, when the target transfer bus is the original bus, the step of establishing a connection path between the transfer converter unit and the target transfer bus, and establishing a connection path between the target transfer bus and the bus to be connected, specifically includes: S311: Determine whether the original busbar is in a dual busbar configuration; if so, use the first switching unit connected between the original busbar and the power receiving area of ​​the original busbar as the first target switching unit; otherwise, in a single-ended single busbar converter module, use the switching unit connected between the original busbar and the power receiving area of ​​the original busbar as the first target switching unit. S312: Determine whether AC looping is allowed between the power receiving area of ​​the busbar to be connected and the power receiving area of ​​the original busbar; if yes, close the first target switch device and open the second target switch device; if no, shut down the power transfer and switching unit, open the second target switch device, and close the first target switch device, thereby starting the power transfer and switching unit. Wherein, the first target switching device is a switching device connected between the bus to be connected and the original bus in the bus tie switch assembly or the diagonal bus tie switch assembly; the second target switching device is a switching device in the first target switching unit that is in the conducting state.

[0077] It should be noted that the power receiving area of ​​the bus to be connected refers to the area that receives the electrical energy transmitted by the bus to be connected.

[0078] When the receiving section of the bus to be connected and the receiving section of the original bus are allowed to be closed in AC loop, it indicates that the power transfer and switching unit can operate without power interruption. At this time, first close the bus tie switch or diagonal bus tie switch connected between the bus to be connected and the original bus to establish a connection between the bus to be connected and the original bus. Then, by disconnecting the second target switch, the connection path between the original bus and the receiving section of the original bus is broken, so that the original bus stops transmitting power to the receiving section of the original bus and transmits it to the bus to be connected, and then transmits it to the faulty receiving section through the bus to be connected.

[0079] When the receiving section of the bus to be connected and the receiving section of the original bus are not allowed to be connected in an AC loop, the converter unit connected to the original bus (i.e., the transfer converter unit) is first shut down to stop its operation. Then, the bus tie switch or diagonal bus tie switch connected between the bus to be connected and the original bus is closed to establish a connection path between the bus to be connected and the original bus. The second target switch is then disconnected to break the connection path between the original bus and the receiving section of the original bus. After that, the transfer converter unit is started, so that it transmits power to the original bus. The original bus transmits the received power to the bus to be connected, and the bus to be connected transmits power to the faulty receiving section. This isolates the faulty converter unit and allows the faulty receiving section to operate normally.

[0080] The method provided in this embodiment will be further explained below with reference to specific topology examples.

[0081] by Figure 5 Taking the four-end flexible straight back-to-back AC field shown as an example, such as Figure 5As shown, under normal operating conditions, Unit 1 is connected to busbar #2M, and busbar #2M is connected to area 1, with Unit 1 supplying power to area 1. Units 1 and 2, after exiting via converter transformers and switches, are each connected to busbars #1M and #2M via two disconnect switches. Units 3 and 4, after exiting via converter transformers and switches, are each connected to busbars #5M and #6M via two disconnect switches. Busbar #1M is connected to busbar #2M, and busbar #6M to busbar #5M via switching devices; busbar #2M is connected to busbar #6M, and busbar #5M to busbar #1M via bus tie switching devices. Busbars #1M and #2M each supply power to area 1 and area 2 via two different disconnect switches, while busbars #5M and #6M each supply power to area 3 and area 4 via two different disconnect switches. Under normal operating conditions, the output line of converter VSC1, after passing through the converter transformer and the outgoing switch, supplies power to bus #2M via a disconnect switch. The disconnect switch on the power supply channel between converter VSC1 and bus #1M is in the open state. Bus #2M supplies power to area one via the disconnect switch, and the disconnect switch connecting bus #2M to area two is open. Similarly, unit two supplies power to area two via bus #1M, unit three supplies power to area three via bus #5M, and unit four supplies power to area four via bus #6M. The outgoing switches and disconnect switches on the power transmission channels are closed, while the remaining disconnect switches are open. All switching devices and bus tie switching devices used to connect the bus are disconnected. Compared to the existing four-terminal flexible DC back-to-back AC field, this topology adds four switches and eight disconnect switches. Therefore, when a converter unit fails, this topology can redistribute the power support from the converter unit to different areas by switching the states of the switches and disconnect switches, providing timely power support to the faulty power-receiving area.

[0082] Specifically, assuming that Area 1, Area 2, and Area 3 are the core power receiving areas and their power needs to be guaranteed, Unit 4 can be flexibly allocated to support the faulty power receiving areas in the event of other converter failures. That is, it is the transfer power supply unit. The original bus of the transfer power supply unit is #6M, and the power receiving area of ​​the original bus is Area 4.

[0083] See Figure 9 Assuming the faulty converter unit is Unit 1, the bus to be connected is Bus #2M, and the power receiving area of ​​the bus to be connected is Area 1. The original bus #6M and the bus to be connected #2M are directly connected via bus tie switch device 62. Therefore, the original bus #6M is the target transfer bus. Figure 9 As shown in (a).

[0084] When short-term AC loop closure is permitted between Zone 1 and Zone 4, the loop closure power of the two zones can be pre-controlled by scheduling, and then the bus tie switch device 62 between bus #2M and #6M can be closed to achieve loop closure of the power in the two zones. Figure 9As shown in (b). Finally, disconnect the outgoing switch (i.e., the one in the ON state) of connection area four. Figure 9 (b) The shaded rectangle connecting section four and the disconnect switch connecting the outgoing line (i.e. Figure 9 (b) The shaded circle below the rectangle connected to section four ensures that section four provides power support only to section one, thus enabling section one to operate normally, as shown in the image. Figure 9 As shown in (c). It can be seen that, based on the topology and method provided in this embodiment, power support for faulty power-receiving areas can be implemented relatively simply.

[0085] See Figure 10 When short-term AC loop closing is not allowed in areas one and four, firstly, a command is issued to disconnect unit four online (i.e., shut down converter VSC4), and then the outgoing line switch and disconnector connected to area four that are in the conducting state are disconnected. At this time, the topology is as follows: Figure 10 As shown in (a). Next, the bus tie switch 62 between bus #2M and bus #6M is closed to establish a connection between bus #6M and area one, as shown. Figure 10 As shown in (b). Finally, a command is issued to put Unit 4 into operation online (i.e., start converter VSC4), connecting Unit 4 with Area 1, thereby completing power support for Area 1. At this time, the power supply channel is as follows: Figure 10 As shown in (c).

[0086] Example 5 In another preferred embodiment, when the target power transfer bus is not the original bus, since there is no direct conductive path between the non-original bus and the power transfer converter unit under normal operating conditions, a connection between the non-original bus and the power transfer converter unit can be established by switching the states of each switching device. The establishment of the connection path between the power transfer converter unit and the target power transfer bus, and the establishment of the connection path between the target power transfer bus and the bus to be connected, specifically includes: S321: Shut down the power transfer converter unit and the non-power transfer converter unit; wherein, the non-power transfer converter unit is the converter unit that provides energy to the non-original bus under normal operating conditions.

[0087] It should be noted that this embodiment improves the safety of power transfer by shutting down the power transfer converter unit and the non-power transfer converter unit, thereby disconnecting the energy source of the original bus and the non-original bus.

[0088] S322: Disconnect the first target outgoing switch and the second target outgoing switch; wherein, the first target outgoing switch is an outgoing switch connected between the original bus and the power receiving area of ​​the original bus; the second target outgoing switch is an outgoing switch connected between the non-original bus and the power receiving area of ​​the non-original bus.

[0089] It should be noted that in this embodiment, the power transmission channel between the original busbar and the original busbar receiving area is disconnected by disconnecting the first target outgoing switch; and the power transmission channel between the non-original busbar and the non-original busbar receiving area is disconnected by disconnecting the second target outgoing switch, so as to facilitate the subsequent interchange of the original busbar receiving area and the non-original busbar receiving area.

[0090] S323: Close the third target switching device, disconnect the first target disconnector assembly, close the first target disconnector; and disconnect the second target disconnector assembly, and close the third target disconnector assembly; wherein, the first target disconnector assembly includes a disconnector connected between the second target outgoing switch and the non-original bus, and a disconnector connected between the non-original bus and the non-transfer converter unit; the first target disconnector is a disconnector connected between the non-original bus and the transfer converter unit; the third target switching device refers to a switching device far from the fault point and used to connect the original bus and the non-original bus; the second target disconnector assembly includes a disconnector connected between the first target outgoing switch and the original bus, and a disconnector connected between the original bus and the transfer converter unit; the third target disconnector assembly includes a disconnector connected between the second target outgoing switch and the original bus, and a disconnector connected between the original bus and the non-transfer converter unit.

[0091] It should be noted that in the topology, one end of the original bus and the non-original bus are connected to the double busbar containing the bus to be connected via a bus tie switch assembly, while the other end can be connected to other devices. Therefore, the end connected to other devices can be marked as the end furthest from the fault point. Thus, the third target switch device is the switch device located at the other end of the original bus and the non-original bus, and can be used to connect the original bus and the non-original bus.

[0092] For example: Suppose that the other end of the original busbar and the non-original busbar is connected to only one switching device, and the third target switching device is that switching device through the interconnection of the switching devices.

[0093] For example, suppose the other ends of the original bus and the non-original bus are connected to one end of double bus 1 via bus tie switches or diagonal bus tie switches, and the other end of double bus 1 is cascaded to one end of double bus 2. The other end of double bus 2 is cascaded to a single-ended single-bus converter module or interconnected via switches. In this topology, the third target switch includes switches that connect the original bus and the non-original bus to double bus 1, switches that connect double bus 1 to double bus 2, and switches that connect two buses in double bus 2. Therefore, by closing the third target switch, the original bus, double bus 1, double bus 2, and the non-original bus can be connected, thus achieving a connection between the original bus and the non-original bus. When the other ends of the original bus and the non-original bus are cascaded to more double buses, the switches included in the third target switch can be determined based on the above principle.

[0094] This embodiment connects the original busbar and the non-original busbar by closing the third target switching device. It then completely disconnects the non-original busbar from area three and from the non-power transfer converter unit by opening the first target disconnector. Closing the first target disconnector connects the non-original busbar and the power transfer converter unit, allowing the power transfer converter unit to transmit power to the non-original busbar. Opening the second target disconnector completely disconnects the original busbar from its area and the power transfer converter unit from the original busbar. Closing the third target disconnector connects the original busbar to the non-power transfer converter unit, allowing the original busbar to replace the non-original busbar in connecting to its power receiving area.

[0095] Therefore, this step achieves the exchange of the original bus and the non-original bus, thereby connecting the original bus to the non-power transfer unit, receiving power from the non-power transfer unit, and providing power to the receiving area of ​​the non-original bus, thus connecting the non-original bus to the power transfer unit and receiving power transmitted by the power transfer unit. S324: Disconnect the third target switching device.

[0096] It should be noted that this step disconnects the third target switching device to break the connection between the original bus and the non-original bus.

[0097] In one example, when the third target switching device contains multiple switching devices, they are turned off in reverse order of the conduction sequence. The conduction sequence can be based on the distance between each device and the original bus and non-original bus, and they are turned on from near to far.

[0098] S325: A closing switching device connected between the non-original busbar and the busbar to be connected.

[0099] It should be noted that in this step, the bus tie switch device connected between the non-original bus and the bus to be connected is closed, so that the power transfer converter unit is connected to the bus to be connected through the non-original bus, and connected to the power receiving area of ​​the bus to be connected through the bus to be connected, thereby constructing a power transmission channel from the power transfer converter unit to the power receiving area of ​​the bus to be connected.

[0100] S326: Start the power supply converter unit and close the second target outgoing line switch to start the non-power supply converter unit.

[0101] It should be noted that this step activates the power transfer and conversion unit, enabling the power transfer and conversion unit to provide power support to the receiving section of the bus to be connected based on the power transmission channel constructed in step S325, so that the receiving section of the bus to be connected can operate normally.

[0102] Example 6 This embodiment will further illustrate the method provided in the above embodiment with specific topology examples.

[0103] by Figure 5 Taking the four-terminal flexible straight back-to-back AC field shown as an example, the topology of the four-terminal flexible straight back-to-back AC field can be referred to the description of the previous embodiment, and will not be repeated here.

[0104] Assuming that Zone 1, Zone 2, and Zone 3 are the core power receiving zones and their power needs to be guaranteed, Unit 4 can be flexibly deployed to support the faulty power receiving zones in the event of other converter failures; that is, it is a power transfer converter unit. Therefore, the original bus of the power transfer converter unit is #6M, the power receiving zone of the original bus is Zone 4, the non-power transfer converter unit is Unit 3, and the non-original bus is #5M. Under normal operating conditions, Unit 2 is connected to bus #1M, and bus #1M is connected to Zone 2; Unit 2 supplies power to Zone 2.

[0105] like Figure 11 As shown, assuming the faulty converter unit is Unit 2, the bus to be connected is Bus #1M, and the power receiving area of ​​the bus to be connected is Area 2. There is no connection between the original bus #6M and the bus to be connected #1M. In the double busbar where the original bus #6M is located, bus #5M and the bus to be connected #1M are connected via a bus tie switch. Therefore, bus #5M is designated as the target transfer bus, and a connection is established between the target transfer bus and the transfer converter unit, as well as between the target transfer bus and the bus to be connected.

[0106] like Figure 12As shown in (a) to (d), the first target outgoing switch is outgoing switch 41 connected to area four, the second target outgoing switch is outgoing switch 31 connected to area three, the third target switching device is switching device K5 connecting bus #5M and bus #6M, the first target disconnector assembly includes disconnector d1 and disconnector d2, the first target disconnector is disconnector d3, the second target disconnector assembly includes disconnector d4 and disconnector d5, and the third target disconnector assembly includes disconnector d6 and disconnector d7.

[0107] The specific setup steps include: First, issuing a command to disconnect Unit 3 and Unit 4 from the network (i.e., shutting down converters VSC3 and VSC4). Then, disconnecting the outgoing switch 31 connected to Area 3 and the outgoing switch 41 connected to Area 4, thus de-energizing the outgoing lines of Area 3 and Area 4. At this time, the topology is as follows: Figure 12 As shown in (a).

[0108] Then, the switch K5 between busbars #5M and #6M is closed, and simultaneously the disconnectors d1 connecting busbar #5M and Unit 3, and d2 connecting busbar #5M and Area 3 are disconnected. The disconnector d3 connecting busbar #5M and Unit 4 is closed, and simultaneously the disconnectors d4 connecting busbar #6M and Unit 4, and d5 connecting busbar #6M and Area 4 are disconnected. The disconnectors d6 connecting busbar #6M and Area 3, and d7 connecting busbar #6M and Unit 3 are closed. At this point, the topology is as follows: Figure 12 As shown in (b).

[0109] Afterwards, disconnect switch K5 between busbars #5M and #6M, and then close bus tie switch MK1 between busbars #5M and #1M. At this time, the topology is as follows. Figure 12 As shown in (c).

[0110] Finally, the command unit four is put into online operation, enabling it to provide power support to area two via busbars #5M and #1M. For area three, the outgoing switch 31 of area three is closed, and a command is issued to put unit three into online operation. Unit three then restores power support to area three via busbar #6M. At this point, the topology is as follows: Figure 12 As shown in (d).

[0111] Therefore, in this example, the power transfer operation involves the start-up and shutdown of three buses, two outgoing switches, and two converter units. During the process of switching between the original bus and the non-original bus, Unit 3 suspends power support to Area 3 to improve the safety of the power transfer.

[0112] In summary, the flexible DC back-to-back AC field topology and power transfer method provided by this invention can flexibly regulate the power of different power receiving areas. Thus, when a converter unit fails, normal converter units can be deployed to provide power support to the faulty power receiving area, enabling the faulty power receiving area to operate normally and isolating the faulty converter unit. This can cope with the special working condition of power transfer from a line with a permanent converter unit failure, and solves the technical problem that the existing flexible DC back-to-back AC field structure cannot continue to provide power support to the faulty power receiving area when the converter unit fails.

[0113] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0114] In the several embodiments provided in this application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection of devices or units may be electrical, mechanical, or other forms.

[0115] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0116] Furthermore, in the various embodiments of the present invention, the functional units can be integrated into one processing unit, or each functional unit can be a separate physical entity, or two or more functional units can be integrated into one processing unit. The integrated unit described above can be implemented in hardware or as a software functional unit.

[0117] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0118] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0119] It should also be noted that in the description of this invention, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0120] Finally, it should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0121] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A flexible, straight back-to-back AC field topology, characterized in that, include: A set of dual busbars; each set of dual busbars includes two busbars; each busbar is connected to a section via a first switching unit; each busbar is connected to a converter unit via a second switching unit; the DC sides of each converter unit are interconnected. One end of each of the two buses is connected to the other end of the bus via a switching device, and the other end of each bus is connected to a bus tie switch assembly. The bus tie switch assembly is connected to a single-ended single-bus converter module, and the single-ended single-bus converter module is connected to the DC side of each converter unit.

2. The flexible, straight back-to-back AC field topology as described in claim 1, characterized in that, Also includes: Several sets of double busbars; Each group of double busbars is cascaded through the bus tie switch assembly; The two busbars at the beginning of the double busbar are interconnected at one end via the switching device; the other ends of the two busbars at the end of the double busbar are connected to the bus tie switch assembly and connected to the single-ended single busbar converter module via the bus tie switch assembly.

3. The flexible, straight back-to-back AC field topology as described in claim 1, characterized in that, Also includes: Several sets of double busbars; Each group of double busbars is cascaded through the bus tie switch assembly; The two busbars at the beginning of the double busbar are connected to each other at one end via the switching device; the two busbars at the end of the double busbar are connected to each other at the other end via the switching device.

4. A flexible, straight back-to-back AC field topology as described in any one of claims 1-3, characterized in that, The first switching unit includes a first outgoing switch, a first disconnect switch, and a second disconnect switch; One end of the first outgoing switch is connected to the area; The other end of the first outgoing switch is connected to the first disconnect switch and the second disconnect switch, respectively; The first disconnector is connected to one of the two busbars; The second disconnector is connected to the other busbar in the dual busbar system.

5. A flexible, straight back-to-back AC field topology as described in any one of claims 1-3, characterized in that, The second switching unit includes a second outgoing switch, a third disconnect switch, and a fourth disconnect switch; One end of the second outgoing switch is connected to the converter unit; The other end of the second outgoing switch is connected to the third disconnect switch and the fourth disconnect switch respectively; The third disconnector is connected to one of the two busbars; The fourth disconnector is connected to the other busbar in the dual busbar system.

6. A flexible, straight back-to-back AC field topology as described in any one of claims 1-3, characterized in that, The bus tie switch assembly includes: two bus tie switch devices; When the bus tie switch assembly is used to connect the double busbar and the single-ended single busbar converter module, one bus tie switch device is connected to one busbar and the single-ended single busbar converter module respectively; another bus tie switch device is connected to another busbar and the single-ended single busbar converter module respectively. When the bus tie switch assembly is used to establish a connection between each of the double busbars, one of the bus tie switch devices is connected to one busbar in one double busbar and one busbar in another double busbar; the other bus tie switch device is connected to the other busbar in one double busbar and the other busbar in another double busbar.

7. The flexible, straight back-to-back AC field topology as described in claim 6, characterized in that, Also includes: diagonal Bus tie switch assembly; The diagonally opposite buses in each pair of dual busbars are connected via the diagonal bus tie switch assembly.

8. The flexible, straight back-to-back AC field topology as described in claim 7, characterized in that, The diagonal bus tie switch assembly includes: two diagonal bus tie switch devices; The diagonal bus tie switch group device is respectively connected to one bus in one double bus and the other bus in the other double bus; Another diagonal bus tie switch device is connected to another bus in one of the double busbars and one bus in the other double busbar.

9. A power conversion method, characterized in that, Implemented by any one of claims 1-8, the flexible straight back-to-back AC field topology includes: When any converter unit in the flexible DC back-to-back AC field topology fails, a fault transfer command is generated. The fault transfer command is analyzed to obtain the busbar to be connected and the transfer converter unit; The target power transfer bus is determined based on the connection relationship between the bus to be connected and the power transfer converter unit; Establish a connection path between the power transfer and converter unit and the target power transfer bus, and establish a connection path between the target power transfer bus and the bus to be connected, so that the power transfer and converter unit provides energy to the bus to be connected.

10. A power conversion method as described in claim 9, characterized in that, The step of determining the target power transfer bus based on the connection relationship between the bus to be connected and the power transfer converter unit specifically includes: Determine the original busbar connected to the power supply converter unit under normal operating conditions; Determine whether the original busbar is directly connected to the busbar to be connected via a bus tie switch assembly or a diagonal bus tie switch assembly; If so, the original busbar is used as the target transfer busbar; If not, the non-original busbar in the target dual busbar is taken as the target transfer busbar, and the target dual busbar is the dual busbar where the original busbar is located.

11. A power conversion method as described in claim 10, characterized in that, When the target transfer bus is the original bus, establishing a connection path between the transfer converter unit and the target transfer bus, and establishing a connection path between the target transfer bus and the bus to be connected, specifically includes: Determine whether the original busbar is in a dual busbar configuration; If so, the first switching unit connected between the original bus and the power receiving area of ​​the original bus shall be used as the first target switching unit; otherwise, in the single-ended single bus converter module, the switching unit connected between the original bus and the power receiving area of ​​the original bus shall be used as the first target switching unit. Determine whether AC loop-connection is allowed between the power receiving area of ​​the busbar to be connected and the power receiving area of ​​the original busbar; If so, close the first target switching device and open the second target switching device; If not, shut down the power supply converter unit, disconnect the second target switching device, and close the first target switching device, thereby starting the power supply converter unit; Wherein, the first target switching device is a switching device connected between the bus to be connected and the original bus in the bus tie switch assembly or the diagonal bus tie switch assembly; The second target switching device is the switching device in the first target switching unit that is in the on state.

12. The power conversion method as described in claim 10, characterized in that, When the target transfer bus is not the original bus, the establishment of a connection path between the transfer converter unit and the target transfer bus, and the establishment of a connection path between the target transfer bus and the bus to be connected, specifically includes: Shut down the power transfer converter unit and the non-power transfer converter unit; wherein, the non-power transfer converter unit is the converter unit that provides energy to the non-original bus under normal operating conditions; Disconnect the first target outgoing switch and the second target outgoing switch; wherein, the first target outgoing switch is an outgoing switch connected between the original bus and the power receiving area of ​​the original bus; the second target outgoing switch is an outgoing switch connected between the non-original bus and the power receiving area of ​​the non-original bus. Close the third target switching device, disconnect the first target disconnector assembly, close the first target disconnector; and disconnect the second target disconnector assembly, and close the third target disconnector assembly; wherein, the first target disconnector assembly includes a disconnector connected between the second target outgoing switch and the non-original bus, and a disconnector connected between the non-original bus and the non-transfer converter unit; the first target disconnector is a disconnector connected between the non-original bus and the transfer converter unit; the third target switching device refers to a switching device located away from the fault point and used to connect the original bus and the non-original bus; the second target disconnector assembly includes a disconnector connected between the first target outgoing switch and the original bus, and a disconnector connected between the original bus and the transfer converter unit; the third target disconnector assembly includes a disconnector connected between the second target outgoing switch and the original bus, and a disconnector connected between the original bus and the non-transfer converter unit; Disconnect the third target switching device; A switching device that closes the connection between the non-original busbar and the busbar to be connected; Start the power supply converter unit and close the second target outgoing line switch to start the non-power supply converter unit.

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