Ground Conversion Method, System, Storage Medium, Electronic Device and Computer Program Product for Multi-Site Cascade HVDC Transmission System

Abstract

The present application discloses a grounding conversion method, system, storage medium, electronic device and computer program product for a multi-site cascaded DC power transmission system. The grounding conversion method for the multi-site cascaded DC power transmission system includes: receiving a first instruction from a first converter station; determining a first current value of a first switching device of a second converter station according to the first instruction; determining that the first current value meets a first preset condition, and then sending a second instruction to a third converter station so that the third converter station closes a grounding switch of the third converter station in response to the second instruction; collecting a second current value of the first switching device in response to a third instruction from the third converter station; determining that the second current value meets a second preset condition, and then sending a fourth instruction to the second converter station so that the second converter station opens a second switching device of the second converter station in response to the fourth instruction.

Description

Technical Field

[0001] The present application relates to the technical field of DC power transmission systems, and particularly to a grounding conversion method, system, storage medium, electronic device and computer program product for a split-site cascaded DC power transmission system. Background Art

[0002] Figure 1 The topological structure diagram of a split-site cascaded DC power transmission system is shown. Refer to Figure 1 , split-site cascaded DC is a typical series connection mode of multi-terminal DC. The split-site cascaded DC power transmission system includes two poles, namely the first pole and the second pole. The high-voltage converters of the first pole and the second pole are arranged in the high-end converter station, and the low-voltage converters of the first pole and the second pole are arranged in the low-end converter station. The high-end converter station and the low-end converter station are connected by a DC line.

[0003] In Figure 1 In the system shown, grounding electrode lines are configured on both the high-end converter station side and the low-end converter station side. The DC current on the high-voltage converter station side can be grounded through the grounding electrode line on the low-end converter station side or through the grounding electrode line on the high-end converter station side. The two grounding methods can be directly converted, thereby improving the availability and reliability of the DC power transmission system. The above connection mode is adopted in the currently under-construction split-site cascaded UHV DC power transmission system in China.

[0004] However, the inventors of the present application have found that in some operating modes of the split-site cascaded DC power transmission system (such as the operation mode through the metallic return line), during the process of the DC current at the sending end switching from grounding through the grounding electrode line of the high-end converter station to grounding through the grounding electrode of the low-end converter station, the control system of the split-site cascaded DC power transmission system may not be able to identify whether the transfer branch is effectively established because the DC current flowing through the transfer switch in the transfer branch does not reach the set protection value, thus resulting in the problem of conversion failure. Summary of the Invention

[0005] According to one aspect of the present application, a grounding conversion method for a split-site cascaded DC power transmission system is provided. The grounding conversion method includes: receiving a first instruction from a first converter station; determining a first current value of a first transfer switch of a second converter station according to the first instruction; determining that the first current value meets a first preset condition, and then sending a second instruction to a third converter station to cause the third converter station to close the grounding switch of the third converter station in response to the second instruction; collecting a second current value of the first transfer switch in response to a third instruction from the third converter station; determining that the second current value meets a second preset condition, and then sending a fourth instruction to the second converter station to cause the second converter station to open a second transfer switch of the second converter station in response to the fourth instruction.

[0006] According to one aspect of the present application, a grounding conversion method for a multi-site cascaded HVDC transmission system is provided. The grounding switch of the third converter station includes a first grounding switch and a second grounding switch. The grounding device of the first grounding switch is arranged within the area of the third converter station, and the grounding device of the second grounding switch is arranged outside the area of the third converter station. The grounding conversion method includes: collecting a third current value of the converter of the second converter station; determining a first current value of a first switching device of the second converter station according to the third current value; receiving a first instruction from the first converter station; determining that the first current value meets a first preset condition according to the first instruction, and then sending a second instruction to the third converter station to cause the third converter station to close the second grounding switch in response to the second instruction; in response to a third instruction from the third converter station, sending a sixth instruction to the second converter station to cause the second converter station to close the first switching device in response to the sixth instruction; collecting a second current value of the first switching device; determining that the second current value meets a second preset condition, and then sending a fourth instruction to the second converter station to cause the second converter station to open a second switching device of the second converter station in response to the fourth instruction.

[0007] According to one aspect of the present application, a grounding conversion system for a multi-site cascaded HVDC transmission system is further provided. The grounding conversion system includes a processing module and a collection module. The processing module receives a first instruction from the first converter station. The collection module receives the first instruction transmitted by the processing module and collects a first current value of a first switching device of the second converter station according to the first instruction. The processing module further receives and determines the first current value, and determines that the first current value meets the first preset condition, then sends a second instruction to the third converter station to cause the third converter station to close the grounding switch of the third converter station in response to the second instruction. The processing module receives a third instruction from the third converter station. The collection module receives the third instruction transmitted by the processing module and collects a second current value of the first switching device according to the third instruction. The processing module further determines that the second current value meets the second preset condition, then sends a fourth instruction to the second converter station to cause the second converter station to open a second switching device of the second converter station in response to the fourth instruction.

[0008] According to one aspect of the present application, a non-volatile computer-readable storage medium is further provided, on which a computer program is stored. When the computer program is executed by a processor, it can implement the grounding conversion method of the multi-site cascaded HVDC transmission system as described above.

[0009] According to one aspect of the present application, an electronic device is further provided, including: one or more processors; a storage device for storing one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors can implement the grounding conversion method of the multi-site cascaded HVDC transmission system as described above.

[0010] According to an aspect of the present application, there is also provided a computer program product, including: a computer program stored on a computer-readable storage medium; the computer program includes program instructions that, when executed by a computer, cause the computer to execute the grounding conversion method of the address-separated cascaded HVDC transmission system as described above.

[0011] According to an aspect of the present application, there is also provided a non-volatile computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it can implement the grounding conversion method of the address-separated cascaded HVDC transmission system as described above.

[0012] According to an aspect of the present application, there is also provided an electronic device, including: one or more processors; a storage device for storing one or more programs, and when the one or more programs are executed by the one or more processors, the one or more processors can implement the grounding conversion method of the address-separated cascaded HVDC transmission system as described above.

[0013] According to an aspect of the present application, there is also provided a computer program product, including: a computer program stored on a computer-readable storage medium; the computer program includes program instructions that, when executed by a computer, cause the computer to execute the grounding conversion method of the address-separated cascaded HVDC transmission system as described above.

[0014] Through the above technical solutions, when it is determined that the first current value of the first switch meets the first preset condition, the grounding switch of the third converter station is closed to increase the current value flowing through the first switch, so that the computer system can effectively identify the effective establishment of the transfer branch. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0016] Figure 1 Shows a schematic diagram of the topological structure of this address-separated cascaded HVDC transmission system;

[0017] Figure 2 Shows a schematic diagram of the grounding electrode conversion of the topological structure of the address-separated cascaded HVDC transmission system in the metal return line state;

[0018] Figure 3 Shows a schematic flowchart of the grounding conversion method 1000 of the address-separated cascaded HVDC transmission system according to an embodiment of the present application;

[0019] Figure 4Schematic diagram showing the grounding conversion method 2000 of a multi-site cascaded HVDC transmission system according to an embodiment of the present application;

[0020] Figure 5 Schematic diagram showing one process of step S230 according to an embodiment of the present application;

[0021] Figure 6 Schematic diagram showing another process of step S230 according to an embodiment of the present application;

[0022] Figure 7 Schematic diagram showing another process of step S230 according to an embodiment of the present application;

[0023] Figure 8 Schematic diagram showing another process of step S230 according to an embodiment of the present application;

[0024] Figure 9 Schematic diagram showing the process of step S260 according to an embodiment of the present application;

[0025] Figure 10 Schematic diagram showing the grounding conversion method 3000 of a multi-site cascaded HVDC transmission system according to an embodiment of the present application;

[0026] Figure 11 Schematic diagram showing the process of step S350 according to an embodiment of the present application;

[0027] Figure 12 Schematic diagram showing the structure of the grounding conversion system 4000 of a multi-site cascaded HVDC transmission system according to an embodiment of the present application.

[0028] Reference numerals:

[0029] Sending end 1; receiving end 2; first DC line 3.

[0030] First converter station 11; second converter station 12; second DC line 13; first switch 14; second switch 15; first ground electrode line 16; second ground electrode line 17; low-voltage converter 18; high-voltage converter 19.

[0031] Third converter station 21; grounding switch 22; first grounding switch 23; second grounding switch 24; receiving-end converter 25.

[0032] First DC line 31 of the first pole; first DC line 32 of the second pole.

[0033] Grounding conversion system 4000 of a multi-site cascaded HVDC transmission system.

[0034] Processing module 4100; acquisition module 4200. Detailed implementation manners

[0035] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. Like reference numerals in the figures denote like or similar parts, and thus their repetitive description will be omitted.

[0036] The features, structures, or characteristics described may be combined in one or more embodiments in any suitable manner. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present disclosure. However, those skilled in the art will realize that the technical solutions of the present disclosure can be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. may be used. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.

[0037] Furthermore, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0038] The terms "first", "second", etc. in the description and claims of this application and the above drawings are used to distinguish different objects, rather than to describe a specific order.

[0039] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative efforts fall within the scope of protection of this application.

[0040] According to one aspect of this application, a grounding conversion method 1000 for a multi-site cascaded HVDC system is provided. Refer to Figure 3 , the grounding conversion method 1000 includes steps S110 - step S150. Exemplarily, the grounding conversion method 1000 can be executed by a computer system, and the computer system can be a client device (such as a host, etc.) with data processing capabilities.

[0041] Figure 1 The topological structure diagram of the multi-site cascaded HVDC system is shown. Refer to Figure 1, the sending end 1 has a split-site cascaded DC layout, and the receiving end 2 has a conventional UHVDC layout. The low-voltage converter at the sending end 1 is installed in the first converter station 11, i.e., the low-end converter station. The first converter station 11 is provided with a low-voltage converter 18, AC filters, and DC filters (Direct Current Filters, DCF); the high-voltage converter 19 at the sending end 1 is installed in the second converter station 12, i.e., the high-end converter station. The second converter station 12 is provided with a high-voltage converter 19, AC filters, and DC filters (DCF).

[0042] The first converter station 11 and the second converter station 12 are connected by a DC line 13. The first converter station 11 and the second converter station 12 are respectively configured with a pole bus zone and a bipolar bus zone DC field. The first converter station 11 and the second converter station 12 are connected to a common grounding electrode through their respective grounding electrode leads. The converter station at the receiving end 2 is the third converter station 21, and the third converter station 12 is provided with a receiving-end converter 25, AC filters, and DC filters (DCF).

[0043] The third converter station 21 and the second converter station 12 are connected by a first DC line 3. The first pole 4 of the split-site cascaded DC transmission system is provided with a first DC line 31 of the first pole, and DC current flows from the second converter station 12 through the first DC line 31 of the first pole into the third converter station 21. The second pole 5 of the split-site cascaded DC transmission system is provided with a first DC line 32 of the second pole. DC current flows from the third converter station 21 through the first DC line 32 of the second pole into the second converter station 12, thus forming a transmission loop for DC current.

[0044] Figure 2 The schematic diagram shows the grounding electrode conversion of the topological structure of the split-site cascaded DC transmission system in the metal return line state. Figure 2 In Figure 1 On the basis, equipment and areas that do not participate in operation or are unimportant are omitted.

[0045] See Figure 2 , the second converter station 12 may include a first transfer switch 14 and a second transfer switch 15. The first transfer switch 14 is connected to the first converter station 11 through the DC line 13. The first converter station 11 is connected to the first grounding electrode line 16. The second transfer switch 15 is connected to the second grounding electrode line 17.

[0046] When the valve group of the first converter station 11 at the sending end 1 is not in operation and is in the bypass state, and the valve group of the second converter station 12 at the sending end 11 is in operation, the DC current of the second converter station 12 can be grounded through the grounding electrode line on its own side, that is, connected to the grounding device through the second transfer switch 15 - the second grounding electrode line 17; the DC current of the second converter station 12 can also be grounded through the grounding electrode line of the first converter station 11, that is, connected to the grounding device through the first transfer switch 14 - the second DC line 13 - the first converter station 11 - the first grounding electrode line 16.

[0047] When the valve group of the first converter station 11 at the sending end 1 is bypassed, and the DC current of the second converter station 12 is converted from being grounded through the grounding electrode line on its own side to being grounded through the grounding electrode line of the first converter station 11, there will be a situation where two branches are in parallel. After the DC current flows into the second converter station 12 at the sending end 1 through the first DC line 32 of the second pole, it flows through the first branch: the second grounding electrode line 17 - the first grounding electrode line 16 - the first converter station 11 - the second DC line 13 - the first transfer switch 14 and into the high-voltage converter 19 of the second converter station 12; the DC current also flows through the second branch: the second transfer switch 15 and into the high-voltage converter 19 of the second converter station 12 at the same time.

[0048] Since both the grounding electrode line and the DC line have resistance, and the resistance of the second branch is basically 0, the second branch can share all the DC current, and the current flowing through the first branch is basically 0, resulting in the current flowing through the first transfer switch 18 being less than the set protection value, causing the control system of the split-site cascaded HVDC transmission system to be unable to identify whether the transfer branch (the first grounding electrode line 16 - the first converter station 11 - the second DC line 13 - the first transfer switch 14) is effectively established, and thus not allowing the second transfer switch 15 to be disconnected, resulting in a conversion failure.

[0049] In step S110, a first instruction from the first converter station is received.

[0050] According to the exemplary embodiment, the first instruction can be instruction information for the first converter station to be put into operation. The first instruction can be generated and sent by the first converter station.

[0051] For example, in step S110, the computer system receives a first instruction from the first converter station. The grounding method of the second converter station needs to be converted from being grounded through the grounding electrode line on its own side to being grounded through the grounding electrode line of the first converter station. For example, see Figure 2 , the grounding method of the second converter station 12 needs to be converted from being connected to the grounding device through the second transfer switch 15 - the second grounding electrode line 17 to being connected to the grounding device through the first transfer switch 14 - the second DC line 13 - the first converter station 11 - the first grounding electrode line 16.

[0052] In step S120, according to the first instruction, determine the first current value of the first switching device of the second converter station.

[0053] According to the exemplary embodiment, after receiving the first instruction, the computer system closes the first switching device of the second converter station in response to the first instruction. After the first switching device is closed, the computer system establishes a ground transfer branch of the second converter station, that is, establishes a branch for the second converter station to be grounded through the grounding electrode line of the first converter station.

[0054] The computer system can collect the first current value flowing through the first switching device by means of an electronic current transformer or an optical current transformer according to the first instruction. For example, in step S120, refer to Figure 2 , the computer system can collect the first current value of the first switching device 14 as 10 amperes by means of an electronic current transformer.

[0055] In step S130, if it is determined that the first current value satisfies the first preset condition, send a second instruction to the third converter station so that the third converter station closes the grounding switch of the third converter station in response to the second instruction.

[0056] According to the exemplary embodiment, the first preset condition may be that the first current value of the first switching device is less than the protection value of the first switching device. The protection value of the first switching device can be determined according to the zero drift value of the current measurement point beside the first switching device.

[0057] According to the exemplary embodiment, the second instruction may be instruction information for closing the grounding switch of the third converter station. After the third converter station closes the grounding switch of the third converter station in response to the second instruction, the DC current flows into the grounding device of the second converter station through the grounding device of the third converter station, and then the DC current flows into the high-voltage converter of the second converter station through the grounding electrode line and the second switching device of the second converter station; the DC current also flows into the high-voltage converter of the second converter station through the grounding electrode line of the first converter station, the first converter station, the DC line between the first converter station and the second converter station, and the first switching device.

[0058] For example, in step S130, refer to Figure 2 , the first current value is 10 amperes, the protection value of the first switching device 14 is 20 amperes, and the computer system determines that the first current value is less than the protection value of the first switching device. Then the computer system sends a second instruction to the third converter station 21 so that the third converter station 21 closes the grounding switch 22 of the third converter station 21 in response to the second instruction.

[0059] Refer to Figure 2, the third converter station 21 closes the grounding switch 22 of the third converter station 21 in response to the second instruction. After the DC current flows into the grounding device of the second converter station 12 through the grounding device of the third converter station 21, it flows into the high-voltage converter 19 of the second converter station 12 through the third branch: the second grounding electrode line 17 - the second switch 15; the DC current also flows into the high-voltage converter 19 of the second converter station through the fourth branch: the first grounding electrode line 16 - the first converter station 11 - the second DC line 13 - the first switch 14.

[0060] See Figure 2 , the third branch and the fourth branch are in parallel. Compared with the second branch, the fourth branch adds a second grounding electrode line 17, making the resistance value of the fourth branch larger than that of the second branch. Compared with the first branch, the third branch reduces a second grounding electrode line 17, making the resistance value of the third branch smaller than that of the first branch. Thus, the current value flowing through the first switch 14 increases.

[0061] In step S140, in response to the third instruction from the third converter station, the second current value of the first switch is collected.

[0062] According to the exemplary embodiment, the third instruction may be the feedback instruction information generated after the third converter station closes the grounding switch.

[0063] According to the exemplary embodiment, after the computer system receives the third instruction, in response to the third instruction, the current value flowing through the first switch can be collected by means of an electronic current transformer or an optical current transformer. For example, in step S140, see Figure 2 , the computer system can collect the second current value of the first switch 14 as 1500 amperes by means of an electronic current transformer.

[0064] In step S150, if it is determined that the second current value meets the second preset condition, a fourth instruction is sent to the second converter station to cause the second converter station to disconnect the second switch of the second converter station in response to the fourth instruction.

[0065] According to the exemplary embodiment, the second preset condition may be that the second current value of the first switch is greater than or equal to the protection value of the first switch.

[0066] The fourth instruction may be the instruction information for disconnecting the second switch generated when the computer system determines that the second current value meets the second preset condition. After the second switch is disconnected, the computer system disconnects the branch connected by the second converter station through the grounding electrode line on its own side, thereby completing the conversion process of the second converter station from grounding through the grounding electrode line on its own side to grounding through the grounding electrode line of the first converter station.

[0067] For example, in step S150, referring to Figure 2 , the second current value is 1500 amperes, and the protection value of the first switch 14 is 20 amperes. The computer system determines that the second current value is greater than or equal to the protection value of the first switch. The computer system sends a fourth instruction to the second converter station 12 to cause the second converter station 12 to disconnect the second switch 15, thereby completing the conversion process of the second converter station 12 from being connected to the grounding device through the second switch 15 - the second grounding electrode line 17 to being connected to the grounding device through the first switch 14 - the second DC line 13 - the first converter station 11 - the first grounding electrode line 16.

[0068] Through the above embodiments, when the computer system determines that the first current value of the first switch satisfies the first preset condition, the grounding switch of the third converter station is closed to increase the current value flowing through the first switch, so that the computer system can effectively identify the effective establishment of the transfer branch.

[0069] The technical solution of the present application can avoid the problem that the computer system cannot identify whether the transfer branch is effectively established because the current value flowing through the first switch is less than the protection setting value of the first switch, thereby causing the interruption of the grounding electrode line conversion.

[0070] Optionally, in the topological structure of the multi-site cascaded HVDC transmission system, the receiving end can also be a multi-site cascaded DC layout.

[0071] Optionally, in the topological structure of the multi-site cascaded HVDC transmission system, the sending end is a conventional UHVDC layout, and the receiving end is a multi-site cascaded DC layout.

[0072] Optionally, the present application also provides a grounding conversion method 2000 for a multi-site cascaded HVDC transmission system. Referring to Figure 4 , the grounding conversion method 2000 includes steps S210 - S260. Exemplarily, the grounding conversion method 2000 can be executed by a computer system, and the computer system can be a client device with data processing capabilities (such as a host, etc.).

[0073] Referring to Figure 4 , steps S210 - S250 in the grounding conversion method 2000 are the same as steps S110 - S150 in the grounding conversion method 1000, and will not be elaborated here.

[0074] In step S260, a fifth instruction is sent to the third converter station to cause the third converter station to disconnect the grounding switch in response to the fifth instruction.

[0075] According to an exemplary embodiment, the fifth instruction may be generated after the computer system completes the conversion of the grounding electrode line of the second converter station, and the fifth instruction may include instruction information for disconnecting the grounding switch of the third converter station.

[0076] For example, in step S260, the computer system sends the fifth instruction to the third converter station 21 so that the third converter station 21 disconnects the grounding switch in response to the fifth instruction, thereby avoiding the situation where a large current flows through the grounding device connected to the third converter station 21 for a long time.

[0077] Optionally, the first instruction may include a conversion threshold of the second converter station. For example, the conversion threshold may include information such as conversion time and conversion parameters.

[0078] See Figure 5 , step S230 in the grounding conversion method 2000 includes step S231 and step S232.

[0079] In step S231, it is determined that the first current value satisfies the first preset condition, and a second instruction is determined according to the conversion threshold of the second converter station.

[0080] According to an exemplary embodiment, the second instruction may also be instruction information for closing the grounding switch of the third converter station generated according to the conversion threshold information of the second converter station. For example, in step S231, see Figure 2 , the computer system determines that the first current value is less than the protection value of the first switch, and the computer system determines the second instruction according to the conversion time and conversion parameters in the conversion threshold of the second converter station 12.

[0081] In step S232, the second instruction is sent to the third converter station so that the third converter station closes the grounding switch of the third converter station in response to the second instruction.

[0082] According to an exemplary embodiment, the computer system generates the second instruction according to the conversion threshold, which can make the third converter station more clearly close the grounding switch of the third converter station.

[0083] For example, in step S232, see Figure 2 , the computer system sends the second instruction to the third converter station 21 so that the third converter station 21 closes the grounding switch 22 of the third converter station 21 in response to the second instruction.

[0084] Optionally, the grounding switch of the third converter station includes a first grounding switch and a second grounding switch. See Figure 6 , step S230 in the grounding conversion method 2000 further includes step S233.

[0085] In step S233, if it is determined that the first current value satisfies the first preset condition, a second instruction is sent to the third converter station to cause the third converter station to close the first grounding switch or the second grounding switch in response to the second instruction.

[0086] According to the exemplary embodiment, refer to Figure 2 , the grounding switch 22 of the third converter station 21 includes a first grounding switch 23 and a second grounding switch 24, and the first grounding switch 23 and the second grounding switch 24 are in parallel.

[0087] For example, in step S233, refer to Figure 2 , the computer system determines that the first current value is less than the protection value of the first transfer switch. Then the computer system sends a second instruction to the third converter station 21 to cause the third converter station 21 to close the first grounding switch 23 of the third converter station 21 in response to the second instruction. The DC current flows into the grounding device of the second converter station 12 through the grounding device of the first grounding switch 23.

[0088] For another example, the computer system sends a second instruction to the third converter station 21 to cause the third converter 21 station to close the second grounding switch 24 of the third converter station 21 in response to the second instruction. The DC current flows into the grounding device of the second converter station 12 through the grounding device of the second grounding switch 24. Setting two grounding switches can improve the stability of the grounding conversion method 2000.

[0089] Optionally, the grounding device of the first grounding switch is arranged within the area of the third converter station. Refer to Figure 7 , step S230 in the grounding conversion method 2000 further includes steps S231a and S232a, where step S231 includes step S231a and step S232 includes step S232a.

[0090] In step S231a, if it is determined that the first current value satisfies the first preset condition and it is determined that the conversion threshold satisfies the first conversion threshold condition, the second instruction is determined according to the conversion threshold.

[0091] According to the exemplary embodiment, the first conversion threshold condition may be that the conversion time in the conversion threshold is less than or equal to 3 seconds.

[0092] Refer to Figure 2 , the grounding device of the first grounding switch 23 is arranged within the area of the third converter station 21, and the time during the closing process of the first grounding switch 23 is relatively fast, generally in milliseconds, so that the first grounding switch 23 can be closed quickly.

[0093] For example, in step S231a, refer to Figure 2, if the computer system determines that the first current value is less than the protection value of the first switching switch 14 and determines that the conversion time in the conversion threshold is 3 seconds, then the computer system determines a second instruction according to the conversion time and conversion parameters in the conversion threshold of the second converter station 12. The second instruction may further include instruction information for closing the first grounding switch 23 of the third converter station 21 within 3 seconds.

[0094] In step S232a, a second instruction is sent to the third converter station to cause the third converter station to close the first grounding switch in response to the second instruction.

[0095] According to the exemplary embodiment, if the computer system determines the second instruction for quickly closing the first grounding switch, then the second instruction is sent to the third converter station. For example, in step S232a, refer to Figure 2 , the computer system sends a second instruction to the third converter station 21 to close the first grounding switch 23 within 3 seconds, so that the third converter station 21 closes the first grounding switch 23 within 3 seconds in response to the second instruction. Thus, the computer system can quickly complete the conversion process of the second converter station 12 from grounding through the grounding electrode line on its own side to grounding through the grounding electrode line of the first converter station 11.

[0096] Optionally, the grounding device of the second grounding switch is arranged outside the area of the third converter station. Refer to Figure 8 , step S230 in the grounding conversion method 2000 further includes steps S231b and S232b, where step S231 further includes step S231b, and step S232 further includes step S232b.

[0097] In step S231b, if it is determined that the first current value meets the first preset condition and it is determined that the conversion threshold meets the second conversion threshold condition, then a second instruction is determined according to the conversion threshold.

[0098] According to the exemplary embodiment, the second conversion threshold condition may be that the conversion time in the conversion threshold is greater than 3 seconds.

[0099] Refer to Figure 2 , the grounding device of the second grounding switch 24 is arranged outside the area of the third converter station 21. Generally, two disconnecting switches (not shown in the figure) are respectively arranged on both sides of the second grounding switch 24. During the process of closing the second grounding switch 24, it is necessary to first close the two disconnecting switches on both sides of the second grounding switch 24 and then close the second grounding switch 24, resulting in a slower closing process of the second grounding switch 24, generally at the ten-second level.

[0100] For example, in step S231b, refer to Figure 2, the computer system determines that the first current value is less than the protection value of the first switch, and determines that the conversion time in the conversion threshold is 60 seconds. Then, the computer system determines a second instruction according to the conversion time and conversion parameters in the conversion threshold of the second converter station 12. The second instruction may further include instruction information for closing the second grounding switch 24 of the third converter station 21 within 60 seconds.

[0101] In step S232b, a second instruction is sent to the third converter station to cause the third converter station to close the second grounding switch in response to the second instruction.

[0102] According to the exemplary embodiment, when the computer system determines the second instruction for closing the second grounding switch, it sends the second instruction to the third converter station. For example, in step S232b, refer to Figure 2 , the computer system sends a second instruction to the third converter station 21 to close the second grounding switch 24 within 60 seconds, so that the third converter station 21 closes the second grounding switch 24 within 60 seconds in response to the second instruction. Thus, the computer system can complete the conversion process of the second converter station 12 from grounding through the local grounding electrode line to grounding through the grounding electrode line of the first converter station 11 in a relatively long time.

[0103] Optionally, refer to Figure 9 , step S260 in the grounding conversion method 2000 further includes step S261.

[0104] In step S261, a fifth instruction is sent to the third converter station to cause the third converter station to open the first grounding switch or the second grounding switch in response to the fifth instruction.

[0105] According to the exemplary embodiment, the grounding device of the first grounding switch is arranged within the area of the third converter station. According to the overcurrent protection requirement of the station grounding switch, the closing time of the first grounding switch is less than or equal to 3 seconds. To avoid the situation that the grounding device within the area of the third converter station has a large current flowing through it for a long time. The computer system can set the first closing time of the first grounding switch to 1 second.

[0106] The grounding device of the second grounding switch is arranged outside the area of the third converter station. According to the dispatching requirement of the DC power transmission system, the closing time of the second grounding switch can be maintained for a certain period of time. For example, the time can be on the order of hours. However, it should not exceed several hours to avoid the situation that the grounding device outside the area of the third converter station has a large current flowing through it for a long time. The computer system can set the second closing time of the second grounding switch to 2 minutes.

[0107] For example, in step S261, refer to Figure 2, the computer system sends a fifth instruction to the third converter station 21, so that the third converter station 21 disconnects the first grounding switch 23 within the first closing time in response to the fifth instruction. Alternatively, in step S261, the computer system sends a fifth instruction to the third converter station 21, so that the third converter station 21 disconnects the second grounding switch 24 within the second closing time in response to the fifth instruction.

[0108] Optionally, the present application also provides a grounding conversion method 3000 for a multi-site cascaded HVDC transmission system. Refer to Figure 10 , the grounding conversion method 3000 includes steps S310 - S380. Exemplarily, the grounding conversion method 3000 can be executed by a computer system, and the computer system can be a client device with data processing capabilities (such as a host, etc.).

[0109] According to an exemplary embodiment, the grounding switches of the third converter station include a first grounding switch and a second grounding switch. The grounding device of the first grounding switch is arranged within the area of the third converter station, and the grounding device of the second grounding switch is arranged outside the area of the third converter station.

[0110] The closing times of the first grounding switch and the second grounding switch will not be elaborated here.

[0111] In step S310, the third current value of the converter of the second converter station is collected.

[0112] According to an exemplary embodiment, the computer system can collect the third current value passing through the converter of the second converter station periodically or in real time through an electronic current transformer or an optical current transformer.

[0113] For example, in step S310, refer to Figure 2 , the computer system can collect the third current value of the high-voltage converter 19 passing through the second converter station 12 as 5000 amperes in real time through an electronic current transformer.

[0114] In step S320, according to the third current value, the first current value of the first conversion switch of the second converter station is determined.

[0115] According to an exemplary embodiment, the third current value can be the current value of the main circuit in a parallel circuit, and the first current value can be the current value of a branch in the parallel circuit. The computer system can determine the first current value according to the relationship between the main circuit current and the branch current in the parallel circuit based on the third current value.

[0116] For example, refer to Figure 2, the computer system can calculate the first current value flowing through the first switch 14 and the fourth current value of the second switch 15 according to the third current value, the resistance value of the first grounding electrode line 16, the resistance value of the second grounding electrode line 17, the resistance value of the second DC line 13, and the resistance value between the second switch 15 and the high-voltage converter 19. The calculation formula can be:

[0117]

[0118] I4 = I3 - I1;

[0119] where, I3 is the third current value, R 16 is the resistance value of the first grounding electrode line 16, R 17 is the resistance value of the second grounding electrode line 17, R 13 is the resistance value of the second DC line 13, R 15 is the resistance value between the second switch 15 and the high-voltage converter 19, I1 is the first current value, and I4 is the fourth current value.

[0120] For example, in step S320, referring to Figure 2 , the third current value is 5000 amperes. The computer system determines that the first current value is 10 amperes according to the third current value.

[0121] In step S330, receive the first instruction from the first converter station.

[0122] According to the exemplary embodiment, the first instruction may also be instruction information that the valve group of the first converter station is about to start operating within the first time.

[0123] The first time can be in seconds, minutes, or hours.

[0124] For example, in step S330, referring to Figure 2 , the computer system receives the first instruction from the first converter station 11. The grounding method of the second converter station 12 needs to be switched from grounding through the grounding electrode line on its own side to grounding through the grounding electrode line of the first converter station 11 within the first time.

[0125] In step S340, if it is determined according to the first instruction that the first current value meets the first preset condition, then send a second instruction to the third converter station so that the third converter station closes the second grounding switch in response to the second instruction.

[0126] According to the exemplary embodiment, since the first time can be in seconds, minutes, or hours, the second grounding switch of the third converter station can be closed in advance to wait for the conversion of the grounding method of the second converter station.

[0127] For example, in step S340, referring toFigure 2 After receiving the first instruction, the computer system determines that the first current value is less than the protection value of the first switch. Then the computer system sends a second instruction to the third converter station 21, so that the third converter station 21 closes the second grounding switch 24 in response to the second instruction. The first DC line 32 of the second pole is short-circuited. The DC current flows into the grounding device of the second converter station 12 through the grounding device of the third converter station 21.

[0128] In step S350, in response to the third instruction from the third converter station, a sixth instruction is sent to the second converter station, so that the second converter station closes the first switch in response to the sixth instruction.

[0129] According to the exemplary embodiment, the third instruction may be feedback instruction information generated after the third converter station closes the grounding switch.

[0130] The sixth instruction may be generated after the computer system receives the third instruction. The sixth instruction may include instruction information for closing the first switch of the second converter station. Thus, the computer system establishes a grounding transfer branch of the second converter station, that is, a branch for the second converter station to be grounded through the grounding electrode line of the first converter station.

[0131] For example, in step S350, refer to Figure 2 , after the computer system receives the third instruction, in response to the third instruction, it generates a sixth instruction. The computer system sends the sixth instruction to the second converter station 12, so that the second converter station 12 closes the first switch 14 in response to the sixth instruction.

[0132] In step S360, the second current value of the first switch is collected.

[0133] According to the exemplary embodiment, after the first switch is closed, the computer system can collect the current value flowing through the first switch by means of an electronic current transformer or an optical current transformer. For example, in step S232, refer to Figure 2 , the computer system can collect the second current value of the first switch 14 by means of an electronic current transformer.

[0134] Refer to Figure 10 , step S370 in the grounding conversion method 3000 is the same as step S150 in the grounding conversion method 1000, and will not be elaborated here.

[0135] Through the above embodiments, the present application collects the second current value of the converter of the second converter station and determines the first current value of the first switch according to the second current value. Before switching the DC current grounding mode of the second converter station, the present application closes the second grounding switch of the third converter station, thereby waiting for the grounding conversion process of the second converter station, thereby reducing the time during the conversion process and achieving a fast conversion process between the second converter station grounding through the grounding pole line on its own side and grounding through the grounding pole line of the first converter station.

[0136] Optionally, referring to Figure 11 , the grounding conversion method 3000 may further include step S380.

[0137] In step S380, a fifth instruction is sent to the third converter station to cause the third converter station to disconnect the second grounding switch in response to the fifth instruction.

[0138] According to the exemplary embodiment, the fifth instruction may be generated after the computer system completes the conversion of the grounding pole line of the second converter station, and the fifth instruction may include instruction information for disconnecting the second grounding switch of the third converter station.

[0139] The grounding device of the second grounding switch is arranged outside the area of the third converter station. According to the dispatching requirements of the DC power transmission system, the closing time of the second grounding switch can be maintained for a certain period of time, for example, the time can be on the order of hours. However, it should not exceed several hours to avoid the situation that a large current flows through the grounding device outside the area of the third converter station for a long time. The computer system can set the second closing time of the second grounding switch to 2 minutes.

[0140] For example, in step S380, referring to Figure 2 , the computer system sends a fifth instruction to the third converter station 21 to cause the third converter station 21 to disconnect the second grounding switch 24 within the second closing time in response to the fifth instruction.

[0141] According to an aspect of the present application, there is also provided a grounding conversion system 4000 for a multi-site cascaded DC power transmission system. Referring to Figure 12 , the grounding conversion system 4000 includes a processing module 4100 and a collection module 4200.

[0142] According to the exemplary embodiment, the processing module 4100 receives a first instruction from the first converter station.

[0143] According to the exemplary embodiment, the first instruction may be instruction information for the first converter station to be put into operation. The first instruction may be generated and sent by the first converter station.

[0144] For example, the processing module 4100 receives a first instruction from the first converter station. The grounding method of the second converter station needs to be switched from grounding through the grounding electrode line on its own side to grounding through the grounding electrode line of the first converter station. For example, refer to Figure 2 , the grounding method of the second converter station 12 needs to be switched from being connected to the grounding device through the second transfer switch 15 - the second grounding electrode line 17 to being connected to the grounding device through the first transfer switch 14 - the second DC line 13 - the first converter station 11 - the first grounding electrode line 16.

[0145] According to the exemplary embodiment, after receiving the first instruction, the processing module 4100 closes the first transfer switch of the second converter station in response to the first instruction. After the first transfer switch is closed, the processing module 4100 establishes a grounding transfer branch for the second converter station, that is, establishes a branch for the second converter station to be grounded through the grounding electrode line of the first converter station.

[0146] According to the exemplary embodiment, the acquisition module 4200 receives the first instruction transmitted by the processing module 4100 and acquires the first current value of the first transfer switch of the second converter station according to the first instruction.

[0147] According to the first instruction, the acquisition module 4200 can acquire the first current value flowing through the first transfer switch by means of an electronic current transformer or an optical current transformer. For example, refer to Figure 2 , the acquisition module 4200 can acquire the first current value of the first transfer switch 14 as 10 amperes by means of an electronic current transformer.

[0148] According to the exemplary embodiment, the processing module 4100 also receives and determines the first current value. If it is determined that the first current value meets the first preset condition, a second instruction is sent to the third converter station to cause the third converter station to close the grounding switch of the third converter station in response to the second instruction.

[0149] According to the exemplary embodiment, the first preset condition may be that the first current value of the first transfer switch is less than the protection value of the first transfer switch. The protection value of the first transfer switch can be determined according to the zero drift value of the current measurement point beside the first transfer switch.

[0150] According to the exemplary embodiment, the second instruction may be instruction information for causing the grounding switch of the third converter station to close. After the third converter station closes the grounding switch of the third converter station in response to the second instruction, the DC current flows into the grounding device of the second converter station through the grounding device of the third converter station. Then, the DC current flows into the high-voltage converter of the second converter station through the grounding electrode line and the second transfer switch of the second converter station; the DC current also flows into the high-voltage converter of the second converter station through the grounding electrode line of the first converter station, the first converter station, the DC line between the first converter station and the second converter station, and the first transfer switch.

[0151] For example, refer to Figure 2 where the first current value is 10 amperes and the protection value of the first transfer switch 14 is 20 amperes. The processing module 4100 determines that the first current value is less than the protection value of the first transfer switch. Then, the processing module 4100 sends a second instruction to the third converter station to cause the third converter station to close the grounding switch of the third converter station in response to the second instruction.

[0152] Refer to Figure 2 where the third converter station 21 closes the grounding switch 22 of the third converter station 21 in response to the second instruction. After the DC current flows into the grounding device of the second converter station 12 through the grounding device of the third converter station 21, it flows into the high-voltage converter 19 of the second converter station 12 through the third branch: the second grounding electrode line 17 - the second transfer switch 15; the DC current also flows into the high-voltage converter 19 of the second converter station 12 through the fourth branch: the first grounding electrode line 16 - the first converter station 11 - the second DC line 13 - the first transfer switch 14.

[0153] Refer to Figure 2 where the third branch and the fourth branch are in parallel. Compared with the second branch, the fourth branch has an additional second grounding electrode line 17, which increases the resistance value of the fourth branch compared with the second branch. Compared with the first branch, the third branch has one less second grounding electrode line 17, which reduces the resistance value of the third branch compared with the first branch. As a result, the current value flowing through the first transfer switch 14 increases.

[0154] According to the exemplary embodiment, the processing module 4100 receives a third instruction from the third converter station. The acquisition module 4200 receives the third instruction transmitted by the processing module 4100 and acquires the second current value of the first transfer switch according to the third instruction.

[0155] For example, refer to Figure 2 where after the acquisition module 4200 receives the third instruction, according to the third instruction, the acquisition module 4200 can acquire the second current value of the first transfer switch 14 as 1500 amperes through an electronic current transformer or an optical current transformer.

[0156] According to the exemplary embodiment, if the processing module 4100 also determines that the second current value meets the second preset condition, it sends a fourth instruction to the second converter station to cause the second converter station to open the second transfer switch of the second converter station in response to the fourth instruction.

[0157] According to the exemplary embodiment, the second preset condition may be that the second current value of the first transfer switch is greater than or equal to the protection value of the first transfer switch.

[0158] The fourth instruction may be instruction information for the processing module 4100 to generate when determining that the second current value meets the second preset condition to disconnect the second switching switch. After the second switching switch is disconnected, the processing module 4100 disconnects the branch connected by the second converter station through the grounding electrode line on its own side, thereby completing the conversion process of the second converter station from grounding through the grounding electrode line on its own side to grounding through the grounding electrode line of the first converter station.

[0159] For example, referring to Figure 2 , the second current value is 1500 amperes, the protection value of the first switching switch 14 is 20 amperes, and the processing module 4100 determines that the second current value is greater than or equal to the protection value of the first switching switch. The processing module 4100 sends a fourth instruction to the second converter station 12 so that the second converter station 12 disconnects the second switching switch 15, thereby completing the conversion process of the second converter station 12 from being connected to the grounding device through the second switching switch 15 - the second grounding electrode line 17 to being connected to the grounding device through the first switching switch 14 - the second DC line 13 - the first converter station 11 - the first grounding electrode line 16.

[0160] Through the above embodiments, when the present application determines that the first current value of the first switching switch meets the first preset condition, by closing the grounding switch of the third converter station, the current value flowing through the first switching switch is increased, so that the computer system can effectively identify the effective establishment of the transfer branch.

[0161] The technical solution of the present application can avoid the problem that the computer system cannot identify whether the transfer branch is effectively established because the current value flowing through the first switching switch is less than the set protection value of the first switching switch, which may lead to the interruption of the grounding electrode line conversion.

[0162] Optionally, the processing module 4100 also sends a fifth instruction to the third converter station so that the third converter station disconnects the grounding switch in response to the fifth instruction.

[0163] According to the exemplary embodiment, the fifth instruction may be generated by the processing module 4100 after completing the conversion of the grounding electrode line of the second converter station, and the fifth instruction may include instruction information for disconnecting the grounding switch of the third converter station.

[0164] For example, referring to Figure 2 , the processing module 4100 sends a fifth instruction to the third converter station 21 so that the third converter station 21 disconnects the grounding switch in response to the fifth instruction, thereby avoiding the situation that a large current flows through the grounding device connected to the third converter station 21 for a long time.

[0165] Optionally, the first instruction includes the conversion threshold of the first converter station. For example, the conversion threshold may include information such as conversion time and conversion parameters.

[0166] According to an exemplary embodiment, the processing module 4100 further determines that the first current value meets a first preset condition, and determines a second instruction according to the conversion threshold of the first converter station.

[0167] According to an exemplary embodiment, the second instruction may also be instruction information for closing the earthing switch of the third converter station generated according to the conversion threshold information of the second converter station. For example, referring to Figure 2 , the processing module 4100 determines that the first current value is less than the protection value of the first switch 14, and the processing module 4100 determines a second instruction according to the conversion time and conversion parameters in the conversion threshold of the second converter station 12.

[0168] According to an exemplary embodiment, the processing module 4100 also sends the second instruction to the third converter station to cause the third converter station to close the earthing switch of the third converter station in response to the second instruction.

[0169] According to an exemplary embodiment, the processing module 4100 generates the second instruction according to the conversion threshold, which can cause the third converter station to more clearly close the earthing switch of the third converter station.

[0170] For example, referring to Figure 2 , the processing module 4100 sends the second instruction to the third converter station 21 to cause the third converter station 21 to close the earthing switch 22 of the third converter station 21 in response to the second instruction.

[0171] Optionally, the earthing switch of the third converter station includes a first earthing switch and a second earthing switch. For example, referring to Figure 2 , the first earthing switch 23 and the second earthing switch 24 are in parallel.

[0172] According to an exemplary embodiment, the processing module 4100 further determines that the first current value meets the first preset condition, and then sends the second instruction to the third converter station to cause the third converter station to close the first earthing switch or the second earthing switch in response to the second instruction.

[0173] For example, referring to Figure 2 , the processing module 4100 determines that the first current value is less than the protection value of the first switch. Then the computer system sends the second instruction to the third converter station 21 to cause the third converter station 21 to close the first earthing switch 23 of the third converter station 21 in response to the second instruction, and the DC current flows into the earthing device of the second converter station 12 through the earthing device of the first earthing switch 23.

[0174] For another example, the processing module 4100 sends a second instruction to the third converter station 21, so that the third converter station 21 closes the second grounding switch 24 of the third converter station 21 in response to the second instruction, and the DC current flows into the grounding device of the second converter station 12 through the grounding device of the second grounding switch 24. Setting two grounding switches can improve the stability of the grounding conversion system 4000.

[0175] Optionally, the grounding device of the first grounding switch is arranged within the area of the third converter station. Refer to Figure 2 , the grounding device of the first grounding switch 23 is arranged within the area of the third converter station 21. The time during the closing process of the first grounding switch 23 is relatively fast, generally in milliseconds, so that the first grounding switch can be closed quickly.

[0176] According to the exemplary embodiment, the processing module 4100 further determines that the first current value meets the first preset condition, and determines that the conversion threshold meets the second conversion threshold condition, and then determines the second instruction according to the conversion threshold.

[0177] According to the exemplary embodiment, the first conversion threshold condition may be that the conversion time in the conversion threshold is less than or equal to 3 seconds.

[0178] For example, refer to Figure 2 , the processing module 4100 determines that the first current value is less than the protection value of the first conversion switch 14, and determines that the conversion time in the conversion threshold is 3 seconds, then the processing module 4100 determines the second instruction according to the conversion time and conversion parameters in the conversion threshold of the second converter station 12. The second instruction may further include instruction information for closing the first grounding switch of the third converter station 21 within 3 seconds.

[0179] According to the exemplary embodiment, the processing module 4100 further sends a second instruction to the third converter station, so that the third converter station closes the second grounding switch in response to the second instruction.

[0180] According to the exemplary embodiment, when the processing module 4100 determines the second instruction for quickly closing the first grounding switch, it sends the second instruction to the third converter station. For example, refer to Figure 2 , the processing module 4100 sends a second instruction to the third converter station 21 to close the first grounding switch 23 within 3 seconds, so that the third converter station 21 closes the first grounding switch 23 within 3 seconds in response to the second instruction. Thus, the grounding conversion system 4000 can quickly complete the conversion process of the second converter station 12 from grounding through the grounding pole line on its own side to grounding through the grounding pole line of the first converter station 11.

[0181] Optionally, the grounding device of the second grounding switch is arranged outside the area of the third converter station. Refer to Figure 2, the grounding device of the second grounding switch 24 is arranged outside the area of the third converter station 21. Generally, two disconnect switches (not shown in the figure) are respectively arranged on both sides of the second grounding switch 24. During the process of closing the second grounding switch 24, it is necessary to first close the two disconnect switches on both sides of the second grounding switch 24, and then close the second grounding switch 24, resulting in a relatively slow closing process of the second grounding switch 24, which can generally be on the order of ten seconds).

[0182] According to the example embodiment, the processing module 4100 determines that the first current value satisfies the first preset condition, and determines that the conversion threshold satisfies the second conversion threshold condition, then determines the second instruction according to the conversion threshold.

[0183] According to the example embodiment, the second conversion threshold condition may be that the conversion time in the conversion threshold is greater than 3 seconds.

[0184] For example, referring to Figure 2 , the processing module 4100 determines that the first current value is less than the protection value of the first conversion switch 14, and determines that the conversion time in the conversion threshold is 4 seconds, then the processing module 4100 determines the second instruction according to the conversion time and conversion parameters in the conversion threshold of the second converter station 12. The second instruction may further include instruction information for causing the second grounding switch of the third converter station 21 to close within 60 seconds.

[0185] According to the example embodiment, the processing module 4100 sends the second instruction to the third converter station to cause the third converter station to close the second grounding switch in response to the second instruction.

[0186] According to the example embodiment, when the processing module 4100 determines the second instruction to close the second grounding switch, it sends the second instruction to the third converter station. For example, referring to Figure 2 , the processing module 4100 sends the second instruction to the third converter station 21 to close the second grounding switch 24 within 60 seconds, so that the third converter station 21 closes the second grounding switch 24 within 60 seconds in response to the second instruction. Thus, the grounding conversion system 4000 can complete the conversion process between the second converter station 12 grounding through the grounding electrode line on its own side and grounding through the grounding electrode line of the first converter station 11 through a relatively long time.

[0187] Optionally, the grounding switch of the third converter station includes a first grounding switch and a second grounding switch. The grounding device of the first grounding switch is arranged within the area of the third converter station, and the grounding device of the second grounding switch is arranged outside the area of the third converter station.

[0188] According to the example embodiment, the acquisition module 4200 also acquires the third current value of the converter of the second converter station.

[0189] According to the exemplary embodiment, the acquisition module 4200 may collect the third current value passing through the converter of the second converter station periodically or in real time by means of an electronic current transformer or an optical current transformer.

[0190] For example, referring to Figure 2 , the acquisition module 4200 may collect, in real time by means of an electronic current transformer, the third current value passing through the high-voltage converter 19 of the second converter station 12 as 5000 amperes.

[0191] According to the exemplary embodiment, the processing module 4100 further determines the first current value based on the third current value. If it is determined that the first current value meets the first preset condition, the processing module 4100 sends a second instruction to the third converter station so that the third converter station closes the second grounding switch in response to the second instruction.

[0192] According to the exemplary embodiment, the third current value may be the current value of the main circuit in a parallel circuit, and the first current value may be the current value of a branch circuit in the parallel circuit. The processing module 4100 may determine the first current value based on the relationship between the main circuit current and the branch circuit current in the parallel circuit according to the third current value.

[0193] For example, referring to Figure 2 , the processing module 4100 may calculate the first current value flowing through the first switch 14 and the fourth current value of the second switch 15 according to the third current value, the resistance value of the first grounding electrode line 16, the resistance value of the second grounding electrode line 17, the resistance value of the second DC line 13, and the resistance value between the second switch 15 and the high-voltage converter 19. The calculation formula may be:

[0194]

[0195] I4 = I3 - I1;

[0196] wherein, I3 is the third current value, R 16 is the resistance value of the first grounding electrode line 16, R 17 is the resistance value of the second grounding electrode line 17, R 13 is the resistance value of the second DC line 13, R 15 is the resistance value between the second switch 15 and the high-voltage converter 19, I1 is the first current value, and I4 is the fourth current value.

[0197] For example, referring to Figure 2 , the third current value is 5000 amperes. The processing module 4100 determines the first current value as 10 amperes according to the third current value.

[0198] According to an exemplary embodiment, the processing module 4100 receives a first instruction from the first converter station. The first instruction may also be instruction information indicating that the valve group of the first converter station is about to start operating within a first period of time.

[0199] The first period of time may be in seconds, minutes, or hours.

[0200] For example, referring to Figure 2 , the processing module 4100 receives a first instruction from the first converter station 11. The grounding method of the second converter station 12 needs to be switched from grounding through the grounding electrode line on its own side to grounding through the grounding electrode line of the first converter station 11 within the first period of time.

[0201] According to an exemplary embodiment, if the processing module 4100 determines that the first current value meets a first preset condition, it sends a second instruction to the third converter station, so that the third converter station closes a second grounding switch in response to the second instruction.

[0202] According to an exemplary embodiment, since the first period of time may be in seconds, minutes, or hours, the second grounding switch of the third converter station can be closed in advance to wait for the conversion of the grounding method of the second converter station. For example, referring to Figure 2 , the processing module 4100 determines that the first current value is less than the protection value of the first transfer switch 14. Then the processing module 4100 sends a second instruction to the third converter station 21, so that the third converter station 21 closes the second grounding switch 24 in response to the second instruction. The first DC line 32 of the second pole is short-circuited. The DC current flows into the grounding device of the second converter station 12 through the grounding device of the second grounding switch 24.

[0203] According to an exemplary embodiment, in response to a third instruction from the third converter station, the processing module 4100 sends a sixth instruction to the second converter station, so that the second converter station closes the first transfer switch in response to the sixth instruction;

[0204] According to an exemplary embodiment, the third instruction may be feedback instruction information generated after the third converter station closes the grounding switch. The sixth instruction may be generated by the processing module 4100 after receiving the third instruction. The sixth instruction may include instruction information for closing the first transfer switch of the second converter station. Thus, the processing module 4100 establishes a grounding transfer branch for the second converter station, that is, establishes a branch for the second converter station to ground through the grounding electrode line of the first converter station.

[0205] For example, referring to Figure 2 , after receiving the third instruction, the processing module 4100 generates a sixth instruction in response to the third instruction. The processing module 4100 sends the sixth instruction to the second converter station 12, so that the second converter station 12 closes the first transfer switch 14 in response to the sixth instruction.

[0206] According to an exemplary embodiment, the acquisition module 4200 also acquires a second current value of the first switching switch.

[0207] According to an exemplary embodiment, after the first switching switch is closed, for example, see Figure 2 , the acquisition module 4200 can acquire the second current value of the first switching switch 14 by means of an electronic current transformer or an optical current transformer.

[0208] Through the above embodiments, the present application acquires the second current value of the converter of the second converter station and determines the first current value of the first switching switch according to the second current value. Before switching the DC current grounding mode of the second converter station, the present application closes the second grounding switch of the third converter station, thereby waiting for the grounding conversion process of the second converter station, thereby reducing the time in the conversion process and achieving a fast completion of the conversion process of the second converter station from grounding through the grounding pole line on its own side to grounding through the grounding pole line of the first converter station.

[0209] Optionally, the processing module 4100 also sends a fifth instruction to the third converter station to cause the third converter station to disconnect the first grounding switch or the second grounding switch in response to the fifth instruction.

[0210] According to an exemplary embodiment, the grounding device of the first grounding switch is arranged within the area of the third converter station. According to the overcurrent protection requirement of the station grounding switch, the closing time of the first grounding switch is less than or equal to 3 seconds. To avoid the situation that the grounding device within the area of the third converter station carries a large current for a long time, the processing module 4100 can set the first closing time of the first grounding switch to 1 second.

[0211] The grounding device of the second grounding switch is arranged outside the area of the third converter station. According to the dispatching requirement of the DC power transmission system, the closing time of the second grounding switch can be maintained for a certain period of time. For example, the time can be on the order of hours. However, it should not exceed several hours to avoid the situation that the grounding device outside the area of the third converter station carries a large current for a long time. The processing module 4100 can set the second closing time of the second grounding switch to 2 minutes.

[0212] For example, see Figure 2 , the processing module 4100 sends a fifth instruction to the third converter station 21 to cause the third converter station 21 to disconnect the first grounding switch 23 within the first closing time in response to the fifth instruction. Or, the processing module 4100 sends a fifth instruction to the third converter station 21 to cause the third converter station 21 to disconnect the second grounding switch 24 within the second closing time in response to the fifth instruction.

[0213] According to one aspect of the present application, there is also provided a non-volatile computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it can implement the grounding conversion method of the address-divided cascaded HVDC transmission system as described above.

[0214] According to one aspect of the present application, there is also provided an electronic device, including: one or more processors; a storage device for storing one or more programs, and when the one or more programs are executed by the one or more processors, the one or more processors can implement the grounding conversion method of the address-divided cascaded HVDC transmission system as described above.

[0215] According to one aspect of the present application, there is also provided a computer program product, including: a computer program stored on a computer-readable storage medium; the computer program includes program instructions, and when the program instructions are executed by a computer, the computer is enabled to execute the grounding conversion method of the address-divided cascaded HVDC transmission system as described above.

[0216] According to one aspect of the present application, there is also provided a non-volatile computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it can implement the grounding conversion method of the address-divided cascaded HVDC transmission system as described above.

[0217] According to one aspect of the present application, there is also provided an electronic device, including: one or more processors; a storage device for storing one or more programs, and when the one or more programs are executed by the one or more processors, the one or more processors can implement the grounding conversion method of the address-divided cascaded HVDC transmission system as described above.

[0218] According to one aspect of the present application, there is also provided a computer program product, including: a computer program stored on a computer-readable storage medium; the computer program includes program instructions, and when the program instructions are executed by a computer, the computer is enabled to execute the grounding conversion method of the address-divided cascaded HVDC transmission system as described above.

[0219] Finally, it should be noted that the above are only the preferred embodiments of the present application and are not used to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions of the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A grounding conversion method for a multi-site cascaded HVDC transmission system, characterized in that, The grounding conversion method includes: Receiving a first instruction from a first converter station, where the first instruction includes a conversion threshold of a second converter station; Determining a first current value of a first conversion switch of the second converter station according to the first instruction; When it is determined that the first current value meets a first preset condition, sending a second instruction to a third converter station to cause the third converter station to close a grounding switch of the third converter station in response to the second instruction, including: When it is determined that the first current value meets the first preset condition, determining the second instruction according to the conversion threshold of the second converter station, where the first preset condition is that the first current value is less than a protection value of the first conversion switch; Sending the second instruction to the third converter station to cause the third converter station to close the grounding switch of the third converter station in response to the second instruction; In response to a third instruction from the third converter station, collecting a second current value of the first conversion switch; when it is determined that the second current value meets a second preset condition, sending a fourth instruction to the second converter station to cause the second converter station to open a second conversion switch of the second converter station in response to the fourth instruction; Wherein, the first conversion switch is connected to the first converter station through a DC line, and the second conversion switch is connected to the first converter station through a grounding electrode line and a grounding device.

2. The grounding conversion method according to claim 1, wherein After it is determined that the second current value meets the second preset condition and the fourth instruction is sent to the second converter station, the grounding conversion method further includes: Sending a fifth instruction to the third converter station to cause the third converter station to open the grounding switch in response to the fifth instruction.

3. The grounding conversion method according to claim 2, wherein The grounding switch of the third converter station includes a first grounding switch and a second grounding switch, the first grounding switch and the second grounding switch are in parallel, a grounding device of the first grounding switch is arranged within the area of the third converter station, and a grounding device of the second grounding switch is arranged outside the area of the third converter station; When it is determined that the first current value meets the first preset condition and a second instruction is sent to the third converter station to cause the third converter station to close the grounding switch of the third converter station in response to the second instruction, it includes: When it is determined that the first current value meets the first preset condition, sending a second instruction to the third converter station to cause the third converter station to close the first grounding switch or the second grounding switch in response to the second instruction.

4. The grounding conversion method according to claim 3, wherein The grounding device of the first grounding switch is arranged within the area of the third converter station; When it is determined that the first current value meets the first preset condition and the second instruction is determined according to the conversion threshold of the second converter station, it includes: When it is determined that the first current value meets the first preset condition and it is determined that the conversion threshold meets a first conversion threshold condition, determining the second instruction according to the conversion threshold; Sending the second instruction to the third converter station to cause the third converter station to close the grounding switch of the third converter station in response to the second instruction includes: Send the second instruction to the third converter station so that the third converter station closes the first grounding switch in response to the second instruction.

5. The grounding conversion method according to claim 4, wherein The grounding device of the second grounding switch is arranged outside the area of the third converter station; Determining that the first current value meets the first preset condition and determining the second instruction according to the conversion threshold of the second converter station includes: Determining that the first current value meets the first preset condition and determining that the conversion threshold meets the second conversion threshold condition, then determining the second instruction according to the conversion threshold; Sending the second instruction to the third converter station so that the third converter station closes the grounding switch of the third converter station in response to the second instruction includes: Send the second instruction to the third converter station so that the third converter station closes the second grounding switch in response to the second instruction.

6. The grounding conversion method according to claim 5, wherein Sending the fifth instruction to the third converter station so that the third converter station opens the grounding switch in response to the fifth instruction includes: Send the fifth instruction to the third converter station so that the third converter station opens the first grounding switch or the second grounding switch in response to the fifth instruction.

7. A grounding conversion method for a multi-site cascaded HVDC transmission system, characterized in that, The grounding switches of the third converter station include a first grounding switch and a second grounding switch. The grounding device of the first grounding switch is arranged within the area of the third converter station, and the grounding device of the second grounding switch is arranged outside the area of the third converter station; The grounding conversion method includes: Collect the third current value of the converter of the second converter station; Determine the first current value of the first transfer switch of the second converter station according to the third current value; Receive the first instruction from the first converter station; If it is determined that the first current value meets the first preset condition according to the first instruction, then send a second instruction to the third converter station so that the third converter station closes the second grounding switch in response to the second instruction; In response to the third instruction from the third converter station, send a sixth instruction to the second converter station so that the second converter station closes the first transfer switch in response to the sixth instruction; Collect the second current value of the first transfer switch; If it is determined that the second current value meets the second preset condition, then send a fourth instruction to the second converter station so that the second converter station opens the second transfer switch of the second converter station in response to the fourth instruction; Wherein, the first transfer switch is connected to the first converter station through a DC line, and the second transfer switch is connected to the first converter station through a grounding electrode line and a grounding device.

8. The grounding conversion method according to claim 7, characterized in that, After determining that the second current value meets the second preset condition and then sending a fourth instruction to the second converter station so that the second converter station opens the second transfer switch of the second converter station in response to the fourth instruction, the grounding conversion method further includes: Send a fifth instruction to the third converter station so that the third converter station opens the second grounding switch in response to the fifth instruction.

9. A grounding conversion system for a multi-terminal cascaded HVDC transmission system, characterized in that, The grounding conversion system includes: A processing module that receives a first instruction from a first converter station, where the first instruction includes a conversion threshold of a second converter station; An acquisition module that receives the first instruction transmitted by the processing module and acquires a first current value of a first switching device of the second converter station according to the first instruction; The processing module further receives and determines the first current value. If it is determined that the first current value meets a first preset condition, a second instruction is sent to a third converter station to cause the third converter station to close a grounding switch of the third converter station in response to the second instruction. The processing module receives a third instruction from the third converter station, including: the processing module further determines that the first current value meets the first preset condition, determines the second instruction according to the conversion threshold of the second converter station, and the processing module further sends the second instruction to the third converter station to cause the third converter station to close the grounding switch of the third converter station in response to the second instruction; The acquisition module receives the third instruction transmitted by the processing module and acquires a second current value of the first switching device according to the third instruction; If the processing module further determines that the second current value meets a second preset condition, a fourth instruction is sent to the second converter station to cause the second converter station to open a second switching device of the second converter station in response to the fourth instruction; Wherein the first switching device is connected to the first converter station through a DC line, and the second switching device is connected to the first converter station through a ground electrode line and a grounding device.

10. The grounding conversion system according to claim 9, wherein The processing module further sends a fifth instruction to the third converter station to cause the third converter station to open the grounding switch in response to the fifth instruction.

11. The grounding conversion system according to claim 10, wherein The grounding switch of the third converter station includes a first grounding switch and a second grounding switch. The first grounding switch and the second grounding switch are in parallel. The grounding device of the first grounding switch is arranged within the area of the third converter station, and the grounding device of the second grounding switch is arranged outside the area of the third converter station; If the processing module further determines that the first current value meets the first preset condition, a second instruction is sent to the third converter station to cause the third converter station to close the first grounding switch or the second grounding switch in response to the second instruction.

12. The grounding conversion system according to claim 11, wherein, The grounding device of the first grounding switch is arranged within the area of the third converter station; If the processing module further determines that the first current value meets the first preset condition and determines that the conversion threshold meets a first conversion threshold condition, the second instruction is determined according to the conversion threshold, and the processing module further sends the second instruction to the third converter station to cause the third converter station to close the first grounding switch in response to the second instruction.

13. The grounding conversion system according to claim 12, characterized in that, The grounding device of the second grounding switch is arranged outside the area of the third converter station; The processing module determines that the first current value meets the first preset condition and determines that the conversion threshold meets the second conversion threshold condition, and then determines the second instruction according to the conversion threshold. The processing module sends the second instruction to the third converter station so that the third converter station closes the second grounding switch in response to the second instruction.

14. The grounding conversion system according to claim 9, wherein The grounding switches of the third converter station include a first grounding switch and a second grounding switch. The grounding device of the first grounding switch is arranged within the area of the third converter station, and the grounding device of the second grounding switch is arranged outside the area of the third converter station. The acquisition module also acquires a third current value of the converter of the second converter station. The processing module also determines the first current value according to the third current value. When it is determined that the first current value meets the first preset condition, the processing module sends the second instruction to the third converter station so that the third converter station closes the second grounding switch in response to the second instruction. The processing module sends a sixth instruction to the second converter station in response to the third instruction from the third converter station so that the second converter station closes the first conversion switch in response to the sixth instruction. The acquisition module also acquires the second current value of the first conversion switch.

15. The grounding conversion system according to claim 14, wherein The processing module also sends a fifth instruction to the third converter station so that the third converter station disconnects the first grounding switch or the second grounding switch in response to the fifth instruction.

16. A non-volatile computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the grounding conversion method of the distributed cascaded HVDC transmission system according to any one of claims 1-6.

17. An electronic device, characterized in that, Comprising: One or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the grounding conversion method of the distributed cascaded HVDC transmission system according to any one of claims 1-6.

18. A computer program product, characterized in that, Comprising a computer program stored on a computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by a computer, the computer executes the grounding conversion method of the distributed cascaded HVDC transmission system according to any one of claims 1-6.

19. A non-volatile computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the grounding conversion method of the distributed cascaded HVDC transmission system according to any one of claims 7-8.

20. An electronic device, characterized in that, Comprising: One or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the grounding conversion method of the distributed cascaded HVDC transmission system according to any one of claims 7-8.

21. A computer program product, characterized in that, Comprising a computer program stored on a computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by a computer, the computer executes the grounding conversion method of the distributed cascaded HVDC transmission system according to any one of claims 7-8.

Images