Method, device and medium for controlling voltage switching of a branch of a flexible direct current converter station

Abstract

The application provides a flexible direct current converter station branch control voltage switching method, device and medium. The flexible direct current converter station comprises a converter transformer, a flexible direct current converter valve and a flexible direct current branch, the flexible direct current branch is connected between the flexible direct current converter valve and the converter transformer, and comprises at least one branch connected in parallel. When the flexible direct current converter station is running, the method comprises the following steps: determining the conduction state of each branch; and determining the voltage of the branch with a normal conduction state as a control voltage only when the conduction state of one branch is normal.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a method, equipment, and medium for switching control voltage in a flexible DC converter station branch. Background Technology

[0002] Flexible DC transmission technology is a new generation of high-voltage DC transmission technology. Its characteristics include the ability to independently control active and reactive power without requiring the short-circuit capacity of the AC power grid to support phase switching. This solves the problem of connecting clean energy sources such as wind power and photovoltaics to the power grid and has good development prospects.

[0003] A two-terminal flexible DC transmission system mainly includes islanded converter stations and constant DC voltage converter stations. The islanded converter station is the sending-end converter station. To enhance system reliability, reduce converter transformer capacity, and facilitate converter station maintenance, the AC side can adopt a dual-branch or multi-branch topology, such as... Figure 1 The diagram illustrates the composition of a dual-branch topology flexible DC transmission system. In this topology, the choice of which branch's grid-side voltage to use as the control voltage for the islanded converter station control system is crucial. When a branch voltage anomaly occurs, due to the variety of anomaly types and branch connection methods, selecting the appropriate control voltage under different connection methods and anomaly types requires comprehensive design. This ensures the control system can always switch to the optimal branch voltage for control, guaranteeing the system's safe and stable operation. Currently, converter stations employing dual-branch or multi-branch topologies are rare, and strategies for switching control voltage between dual branches are not yet available.

[0004] Therefore, it is necessary to find a control voltage measurement point switching method suitable for islanded converter stations with dual or multi-branch topologies, which can actively select the control voltage according to the branch connection status and voltage fault type to ensure the safe and stable operation of the flexible DC transmission system. Summary of the Invention

[0005] This application provides a method for switching the control voltage of a branch in a flexible DC converter station. The flexible DC converter station includes a converter transformer, a flexible DC converter valve, and a flexible DC branch. The flexible DC branch is connected between the flexible DC converter valve and the converter transformer, and includes at least one branch connected in parallel. When the flexible DC converter station is running, the method includes: determining the conduction state of each branch; when only one branch has a normal conduction state, determining the voltage of the branch with a normal conduction state as the control voltage.

[0006] According to some embodiments, the control method further includes: when the conduction states of at least two of the branches are normal, determining the voltage of the branch with normal conduction state and normal operating voltage state as the control voltage.

[0007] According to some embodiments, the control method further includes: when the conduction state and operating voltage state of at least two of the branches are normal, determining the voltage of the branch with normal conduction state, normal operating voltage state, and normal measured voltage state as the control voltage.

[0008] According to some embodiments, the control method further includes: when the conduction state, operating voltage state, and measured voltage state of at least two of the branches are all normal, determining the voltage of the branch with normal conduction state, normal operating voltage state, normal measured voltage state, and higher priority as the control voltage.

[0009] According to some embodiments, the operating voltage state includes the valve-side operating voltage state or the grid-side operating voltage state of the converter transformer of the branch.

[0010] According to some embodiments, the operating voltage status includes at least one of the following: normal operating voltage status, voltage circuit breaker in the sensor terminal box of the branch is open, voltage circuit breaker in the control and protection panel of the branch is open, and fiber optic communication between the control host and the voltage measurement IO host of the branch is abnormal.

[0011] According to some embodiments, the measured voltage status includes the valve-side measured voltage status or the grid-side measured voltage status of the converter transformer of the branch.

[0012] According to some embodiments, the measured voltage state includes at least one of the following: normal measured voltage state, abnormal sampling, voltage imbalance, and sensor short circuit.

[0013] This application also provides an electronic device, including one or more processors and a memory, wherein the memory is used to store one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors perform the method described above.

[0014] This application also provides a computer-readable storage medium storing a computer program thereon, wherein when the computer program is executed by a processor, the processor performs the method described above.

[0015] The technical solution provided in this application embodiment can switch to the optimal branch voltage for control when different branch connection states and abnormal branch voltage occur, thereby ensuring the safe and stable operation of the system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a dual-branch topology flexible DC transmission system.

[0018] Figure 2 This is a schematic flowchart of a dual-branch control voltage switching method for a flexible DC converter station according to an embodiment of this application.

[0019] Figure 3 This is a schematic diagram of the primary wiring of a dual-branch flexible DC converter station according to an embodiment of this application.

[0020] Figure 4 This is a schematic flowchart of another flexible DC converter station dual-branch control voltage switching method according to an embodiment of this application.

[0021] Figure 5 This is a schematic diagram of another flexible DC converter station dual-branch control voltage switching method according to an embodiment of this application.

[0022] Figure 6 This is a schematic flowchart of another flexible DC converter station dual-branch control voltage switching method according to an embodiment of this application.

[0023] Figure 7 This is a block diagram of the functional composition of an electronic device provided in an embodiment of this application. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0026] Figure 1 This is a schematic diagram of a flexible DC transmission system according to an embodiment of this application.

[0027] The flexible DC transmission system includes an offshore wind farm 1, an offshore flexible DC converter station 2, and an onshore flexible DC converter station 3. Offshore wind farm 1 includes an AC step-up substation 11. Offshore flexible DC converter station 2 includes a station service power supply 21, a converter transformer 22, a flexible DC converter valve 23, and flexible DC branch lines. Offshore flexible DC converter station 2 is connected to the AC step-up substation 11 of offshore wind farm 1. The flexible DC converter valve 23 of flexible DC converter station 2 is connected to the onshore flexible DC converter station 3.

[0028] The flexible DC branch is connected between the converter transformer 22 and the flexible DC converter valve 23, and includes at least one branch connected in parallel. For example... Figure 1 As shown, this embodiment includes two AC branches, namely branch 241 and branch 242.

[0029] Figure 2 This is a schematic flowchart of a branch control voltage switching method for a flexible DC converter station according to an embodiment of this application, which includes the following process.

[0030] In S11, the conduction status of each branch of the flexible DC converter station is determined.

[0031] The primary wiring diagram of the AC side branch of the offshore flexible DC converter station is as follows: Figure 3 As shown, when the converter station is in operation, it can operate with multiple branches or with only one branch.

[0032] In S12, when only one branch is in a normal conduction state, the voltage of the branch in a normal conduction state is determined as the control voltage.

[0033] Operating voltage status includes the valve-side operating voltage status or grid-side operating voltage status of the converter transformer in the branch.

[0034] Figure 4 This is a schematic flowchart of another flexible DC converter station branch control voltage switching method according to an embodiment of this application, which includes the following process.

[0035] In S21, the conduction status of each branch of the flexible DC converter station is determined.

[0036] The primary wiring diagram of the AC side branch of the offshore flexible DC converter station is as follows: Figure 3 As shown, when the converter station is in operation, it can operate with multiple branches or with only one branch.

[0037] In S22, when the conduction state of at least two branches is normal, the voltage of the branch with normal conduction state and normal operating voltage state is determined as the control voltage.

[0038] Operating voltage includes, but is not limited to, the valve-side operating voltage or grid-side operating voltage of the converter transformer in the branch.

[0039] Operating voltage status includes at least one of the following: normal operating voltage status of the branch, open circuit breaker in the sensor terminal box of the branch, open circuit breaker in the control and protection panel of the branch, and abnormal fiber optic communication between the control host and the voltage measurement IO host of the branch, but is not limited to these.

[0040] When the conduction status of multiple branches is normal, determine the operating voltage status of multiple branches, and select the voltage of the branch with normal operating voltage status as the control voltage.

[0041] Figure 5 This is a schematic flowchart of another flexible DC converter station branch control voltage switching method according to an embodiment of this application, which includes the following process.

[0042] In S31, the conduction status of each branch of the flexible DC converter station is determined.

[0043] The primary wiring diagram of the AC side branch of the offshore flexible DC converter station is as follows: Figure 3 As shown, when the converter station is in operation, it can operate with multiple branches or with only one branch.

[0044] In S32, when the conduction state of at least two branches is normal, the operating voltage state of the at least two branches is determined.

[0045] Operating voltage includes, but is not limited to, the valve-side operating voltage or grid-side operating voltage of the converter transformer in the branch.

[0046] Operating voltage status includes at least one of the following: normal operating voltage status of the branch, open circuit breaker in the sensor terminal box of the branch, open circuit breaker in the control and protection panel of the branch, and abnormal fiber optic communication between the control host and the voltage measurement IO host of the branch, but is not limited to these.

[0047] In S33, when the conduction state and operating voltage state of at least two branches are normal, the measured voltage state of the at least two branches is determined.

[0048] The voltage status measurement includes the valve-side voltage status of the converter transformer in the branch or the grid-side voltage status.

[0049] The voltage measurement status includes at least one of the following: normal voltage measurement status, abnormal sampling, voltage imbalance, and sensor short circuit, but is not limited to these.

[0050] In S34, the voltage of the branch with normal conduction state, normal operating voltage state, and normal measured voltage state is determined as the control voltage.

[0051] When the conduction status and operating voltage status of multiple branches are normal, the voltage of the branch with normal measured voltage status is selected as the control voltage.

[0052] Figure 6 This is a schematic flowchart of another flexible DC converter station branch control voltage switching method according to an embodiment of this application, which includes the following process.

[0053] In S41, the conduction status of each branch of the flexible DC converter station is determined.

[0054] The primary wiring diagram of the AC side branch of the offshore flexible DC converter station is as follows: Figure 3 As shown, when the converter station is in operation, it can operate with multiple branches or with only one branch.

[0055] In S42, when the conduction state of at least two branches is normal, the operating voltage state of the at least two branches is determined.

[0056] Operating voltage includes, but is not limited to, the valve-side operating voltage or grid-side operating voltage of the converter transformer in the branch.

[0057] Operating voltage status includes at least one of the following: normal operating voltage status of the branch, open circuit breaker in the sensor terminal box of the branch, open circuit breaker in the control and protection panel of the branch, and abnormal fiber optic communication between the control host and the voltage measurement IO host of the branch, but is not limited to these.

[0058] In S43, when the conduction state and operating voltage state of at least two branches are normal, the measured voltage state of the at least two branches is determined.

[0059] The voltage status measurement includes the valve-side voltage status of the converter transformer in the branch or the grid-side voltage status.

[0060] The voltage measurement status includes at least one of the following: normal voltage measurement status, abnormal sampling, voltage imbalance, and sensor short circuit, but is not limited to these.

[0061] In S44, when the conduction state, operating voltage state, and measured voltage state of at least two branches are all normal, the priority of the at least two branches is determined.

[0062] When the conduction status, operating voltage status, and measured voltage status of multiple branches are all normal, the branch voltage with the highest priority is selected as the control voltage.

[0063] Priorities are pre-configured based on branch conditions.

[0064] In S45, the voltage of the branch with normal conduction status, normal operating voltage status, normal measured voltage status, and high priority is determined as the control voltage.

[0065] According to some embodiments, status words are set during the control process. For example... Figure 3As shown, a branch 241 connection indicates that WS.Q1, WS.Q11, and WS.Q12 are all closed; otherwise, branch 241 is isolated. A branch 242 connection indicates that WS.Q2, WS.Q13, and WS.Q14 are all closed; otherwise, branch 242 is isolated.

[0066] The status of the grid-side operating voltages US1 and US2 of the converter transformer is collected.

[0067] Two status words are defined. Status word A, from high to low bits, represents the conduction status of branch 241, the operating voltage of branch 241, and the measured voltage of branch 241, with a high priority (value 1). Status word B, from high to low bits, represents the conduction status of branch 242, the operating voltage of branch 242, and the measured voltage of branch 242, with a low priority (value 0). See Table 1 below.

[0068] Table 1

[0069]

[0070] When the flexible DC converter station is running, determine the values ​​of status words A and B in Table 1. When the branch conduction status is "on", BIT:3 is 1; otherwise, it is 0. When the branch operating voltage is normal, BIT:2 is 1; otherwise, it is 0. When the branch measured voltage is normal, BIT:1 is 1; otherwise, it is 0.

[0071] Compare the values ​​of two status words A and B. If status word A is greater than status word B, select the voltage of the converter control voltage selection branch 241; otherwise, select the voltage of the control voltage selection branch 242.

[0072] As can be seen from the above branch voltage switching method, when the converter station is operating with a single branch, the voltage of that single branch is selected as the control voltage. For example, if branch 242 is connected and branch 241 is not connected, the status word A is 0111 and the status word B is 1110. Since status word A < status word B, the voltage of branch 2 is selected as the control voltage.

[0073] When both branches are connected and one branch has an abnormal operating voltage, for example, when status word A is 1111 and status word B is 1000, and status word A > status word B, the voltage of the branch 241 with normal operating voltage is selected as the control voltage.

[0074] When both branches are connected, both branches are conducting and their operating voltages are normal, but the measured voltage of a branch is abnormal, for example, status word A is 1101 and status word B is 1110, status word A < status word B, then the voltage of branch 242 is selected as the control voltage.

[0075] When both branches are connected, if one branch experiences a measured voltage abnormality and the other experiences an operating voltage abnormality, the voltage of the branch with the abnormal measured voltage is selected as the control voltage. For example, if branch 1 experiences a measured voltage abnormality and branch 2 experiences an operating voltage abnormality, status word A is 1101 and status word B is 1010, where status word A > status word B. In this case, the voltage of branch 241 is selected as the control voltage.

[0076] When both branches are connected, and the operating voltage and measured voltage of both branches are normal, the voltage of the branch with the higher priority is selected as the control voltage.

[0077] The technical solution provided in this application embodiment enables the control system to switch to the optimal branch voltage for control when abnormalities occur in different branch connection states, thereby ensuring the safe and stable operation of the system.

[0078] Figure 7 This is a block diagram of the functional composition of an electronic device provided in an embodiment of this application.

[0079] The electronic device may include an output unit 301, an input unit 302, a processor 303, a memory 304, a communication interface 305, and a memory unit 306.

[0080] Memory 304, as a non-transitory computer-readable storage device, can be used to store software programs, computer-executable programs, and modules. When one or more programs are executed by one or more processors 303, the one or more processors 303 perform the methods described above.

[0081] The memory 304 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the electronic device. Furthermore, the memory 304 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 304 may optionally include memory remotely located relative to the processor 303, and these remote memories may be connected to the electronic device via a network.

[0082] The above embodiments are only for illustrating the technical concept of this application and should not be used to limit the scope of protection of this application. Any modifications made to the technical solution based on the technical concept proposed in this application shall fall within the scope of protection of this application.

Claims

1. A method for switching the control voltage of a branch circuit in a flexible DC converter station, the flexible DC converter station comprising a converter transformer, a flexible DC converter valve, and a flexible DC branch circuit, the flexible DC branch circuit being connected between the flexible DC converter valve and the converter transformer, including at least one branch circuit connected in parallel, the method comprising: Determine the conduction status of each of the aforementioned branches; When only one of the branches is in a normal conduction state, the voltage of the branch in a normal conduction state is determined as the control voltage; When at least two of the branches are in normal conduction states, the voltage of the branch with normal conduction state and normal operating voltage state is determined as the control voltage; When the conduction state and operating voltage state of at least two of the branches are normal, the voltage of the branch with normal conduction state, normal operating voltage state, and normal measured voltage state is determined as the control voltage; When the conduction state, operating voltage state, and measured voltage state of at least two of the branches are normal, the voltage of the branch with the highest priority among those with normal conduction state, normal operating voltage state, normal measured voltage state, is determined as the control voltage.

2. The method as described in claim 1, wherein, The operating voltage status includes the valve-side operating voltage status or the grid-side operating voltage status of the converter transformer of the branch.

3. The method as described in claim 1, wherein, The measured voltage status includes the valve-side measured voltage status or the grid-side measured voltage status of the converter transformer of the branch.

4. An electronic device, characterized in that, include: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors perform the method as described in any one of claims 1 to 3.

5. A computer-readable storage medium having a computer program stored thereon, wherein, When the computer program is executed by a processor, the processor performs the method as described in any one of claims 1 to 3.

Images