Fault clearing method and device of direct-current power transmission system, electronic equipment and medium

Abstract

The invention discloses a fault clearing method and device for a direct-current power transmission system, electronic equipment and a medium, which are used for solving the technical problems that the calculation efficiency is low and the system fault clearing is influenced due to large calculation amount when the number of full-bridge and half-bridge sub-modules needs to be calculated in the current related technology. Wherein the MMC converter in the direct current power transmission system comprises a sub-module with a full-bridge and half-bridge structure; when it is detected that the direct-current power transmission system breaks down, the maximum overvoltage between bridge arm ends of the MMC converter after the fault is obtained; based on the maximum overvoltage after the fault, constructing a full-bridge and half-bridge sub-module quantity model considering the commutation safety; solving the full-half-bridge sub-module quantity model to obtain the minimum quantity of the full-half-bridge sub-modules; and updating the input number of the full-bridge and half-bridge sub-modules of the MMC converter to the minimum number so as to carry out fault clearing on the direct-current power transmission system.

Description

Technical Field

[0001] This invention relates to the field of flexible DC transmission system technology, and in particular to a fault clearing method, apparatus, electronic device and medium for DC transmission systems. Background Technology

[0002] Currently, flexible DC transmission has become the preferred topology for large-scale, ultra-long-distance transmission of new energy. Ultra-long-distance transmission often utilizes overhead lines, primarily due to their relatively low cost. However, the use of overhead lines cannot completely prevent faults such as wildfires and lightning strikes, leading to frequent DC line failures. To ensure the safe and stable operation of AC / DC systems, it is essential to ensure that the DC transmission system possesses robust overhead line fault clearing capabilities. Therefore, the number of power submodules deployed by the MMC converter during fault clearing needs to be carefully considered.

[0003] Taking a hybrid MMC converter as an example, its DC fault clearing capability and buck operation capability are related to the proportion of full-bridge power modules. The higher the proportion of full-bridge power modules, the better the DC fault clearing capability and the stronger the buck operation capability.

[0004] Previously, the number of modules was mainly determined by the requirements of steady-state operation. During the operation of MMC converters, electromagnetic transient simulation is usually used to simulate the overvoltage between the converter valve terminals under different operating conditions to obtain the number of modules. However, this method involves a large amount of computation, often requiring multiple iterations, resulting in low computational efficiency and making it unsuitable for practical fault clearing scenarios. Summary of the Invention

[0005] This invention provides a fault clearing method, apparatus, electronic device, and medium for DC transmission systems, which solves or partially solves the technical problem in current related technologies where the large amount of computation required to calculate the number of full and half bridge submodules leads to low computational efficiency and affects the fault clearing of the system.

[0006] This invention provides a fault clearing method for a DC transmission system, wherein the MMC converter in the DC transmission system contains a sub-module with a full-half-bridge structure; the method includes:

[0007] When a fault is detected in the DC transmission system, the maximum overvoltage after the fault between the bridge arms of the MMC converter is obtained;

[0008] Based on the maximum overvoltage after the fault, a model for the number of full-half-bridge submodules considering commutation safety is constructed.

[0009] Solve the full-half-bridge submodule quantity model to obtain the minimum number of full-half-bridge submodules;

[0010] The number of full and half bridge sub-modules of the MMC converter is updated to the minimum number to clear faults in the DC transmission system.

[0011] Optionally, the step of constructing a full-half-bridge submodule quantity model considering commutation safety based on the maximum overvoltage after the fault includes:

[0012] Obtain the withstand voltage thresholds of various devices in the MMC converter, and determine the commutation safety voltage based on the withstand voltage thresholds of various devices;

[0013] Based on the maximum overvoltage after the fault and the commutation safety voltage, and taking into account the module voltage parameters and device aging parameters of the MMC converter, a full half-bridge sub-module quantity model considering commutation safety is constructed.

[0014] Optionally, the device types in the MMC converter include IGBT elements, capacitors, and bypass thyristors; determining the commutation safety voltage based on the withstand voltage thresholds of the various devices includes:

[0015] The minimum withstand voltage threshold value is selected from the withstand voltage threshold values ​​corresponding to the IGBT element, the capacitor, and the bypass thyristor, and used as the commutation safety voltage of the MMC converter.

[0016] Optionally, the device types in the MMC converter include IGBT elements and capacitors; determining the commutation safety voltage based on the withstand voltage thresholds of the various types of devices includes:

[0017] The minimum withstand voltage threshold value is selected from the withstand voltage threshold values ​​corresponding to the IGBT element and the capacitor, and is used as the commutation safety voltage of the MMC converter.

[0018] Optionally, the module voltage parameters include the average module voltage and the peak module voltage; the device aging parameters include capacitor manufacturing and aging deviations, and surge arrester aging factors; the construction of a full-half-bridge sub-module quantity model considering commutation safety, based on the maximum overvoltage after the fault and the commutation safety voltage, while considering the module voltage parameters and device aging parameters of the MMC converter, includes:

[0019] Based on the maximum overvoltage after the fault, the commutation safety voltage, the average module voltage, the peak module voltage, the manufacturing and aging deviation of the capacitor, and the aging factor of the surge arrester, combined with the safety factor, a full-half-bridge sub-module quantity model considering commutation safety is constructed.

[0020] Optionally, the expression for the number of full-half-bridge submodules is as follows:

[0021]

[0022] in, Indicates the safety factor; This represents the average module voltage. Indicates the peak voltage of the module; This indicates manufacturing and aging deviations in capacitors; Indicates the aging factor of the surge arrester; Indicates the maximum overvoltage after the fault; Indicates the number of full and half bridge sub-modules; This indicates the commutation safety voltage.

[0023] Optionally, the number of full-and-half bridge submodules is calculated using the following formula:

[0024]

[0025] After calculating the result on the right side of the equation, the minimum number of full and half bridge sub-modules is obtained by rounding the result up.

[0026] in, Indicates the number of full and half bridge sub-modules; Indicates the aging factor of the surge arrester; Indicates the maximum overvoltage after the fault; This indicates manufacturing and aging deviations in capacitors; Indicates the commutation safety voltage Indicates the safety factor; This represents the average module voltage. This indicates the peak voltage of the module.

[0027] The present invention also provides a fault clearing device for a DC transmission system, wherein the MMC converter in the DC transmission system contains a sub-module with a full half-bridge structure; the device includes:

[0028] The data acquisition unit is used to acquire the maximum overvoltage after the fault between the bridge arms of the MMC converter when a fault is detected in the DC transmission system.

[0029] The model building unit is used to build a model of the number of full-half-bridge sub-modules that takes into account commutation safety based on the maximum overvoltage after the fault.

[0030] The model solving unit is used to solve the full-half-bridge submodule quantity model to obtain the minimum number of full-half-bridge submodules;

[0031] The fault clearing unit is used to update the number of full and half bridge sub-modules of the MMC converter to the minimum number in order to clear faults in the DC transmission system.

[0032] The present invention also provides an electronic device, the device comprising a processor and a memory:

[0033] The memory is used to store program code and transmit the program code to the processor;

[0034] The processor is configured to execute the fault clearing method for a DC transmission system as described above, according to the instructions in the program code.

[0035] The present invention also provides a computer-readable storage medium for storing program code for performing the fault clearing method for a DC transmission system as described in any of the preceding claims.

[0036] As can be seen from the above technical solutions, the present invention has the following advantages:

[0037] A fault clearing method for DC transmission systems is proposed. The MMC converter in the DC transmission system contains sub-modules with a full-half-bridge structure. When a fault is detected in the DC transmission system, the maximum overvoltage after the fault between the bridge arms of the MMC converter is obtained. Based on the maximum overvoltage after the fault, a model for the number of full-half-bridge sub-modules considering converter safety is constructed. The model is solved to obtain the minimum number of full-half-bridge sub-modules. The number of full-half-bridge sub-modules deployed in the MMC converter is updated to the minimum number to clear the fault in the DC transmission system. The technical solution of this invention fully considers the maximum overvoltage after a fault between the bridge arms of the MMC converter, which is a decisive factor in the number of modules when a system failure occurs. Combined with the sub-module number calculation model designed in this invention, the calculation efficiency of the number of sub-modules can be improved, and the minimum number of full-half-bridge structure sub-modules required by the system when a fault occurs can be quickly estimated. Under the premise of meeting the requirements of system voltage support, rapid fault clearing capability, modulation accuracy, dynamic performance and reliability, the number of sub-modules can be reduced as much as possible, and the corresponding number of sub-modules can be put into fault clearing as soon as possible to achieve rapid fault clearing and enable the system to quickly restore stable and normal operation. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a typical structure of a multi-terminal flexible DC transmission system.

[0040] Figure 2(a) is a schematic diagram of the topology of a hybrid MMC converter;

[0041] Figure 2(b) is an equivalent circuit diagram of a full-bridge MMC converter under forward arm current;

[0042] Figure 2(c) is an equivalent circuit diagram of a full-bridge MMC converter under negative arm current.

[0043] Figure 3 A flowchart illustrating the steps of a fault clearing method for a DC transmission system;

[0044] Figure 4 This is a schematic diagram of the overall process of a fault clearing method for a DC transmission system;

[0045] Figure 5 This is a structural block diagram of a fault clearing device for a DC transmission system. Detailed Implementation

[0046] This invention provides a fault clearing method, apparatus, electronic device, and medium for a DC transmission system, which solves or partially solves the technical problem in the current related technology where the large amount of calculation required to calculate the number of full and half bridge submodules leads to low calculation efficiency and affects the fault clearing of the system.

[0047] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0048] As an example, to ensure the safe and stable operation of AC / DC systems, it is essential to ensure that DC transmission systems have good overhead line fault clearing capabilities. In this case, the number of power submodules deployed by the MMC converter during fault clearing needs to be carefully considered.

[0049] Taking a hybrid MMC converter as an example, its DC fault clearing capability and buck operation capability are related to the proportion of full-bridge power modules. The higher the proportion of full-bridge power modules, the better the DC fault clearing capability and the stronger the buck operation capability.

[0050] Figure 1 A typical structural diagram of a multi-terminal flexible DC transmission system is shown. The MMC converters are mostly of a hybrid full-bridge / half-bridge structure.

[0051] The hybrid MMC converter also follows the topology of the MMC converter. The power modules of each arm are composed of a portion of half-bridge power modules and a portion of full-bridge power modules, as shown in Figure 2(a).

[0052] The topology of the full-bridge MMC converter can also be seen in Figure 2(a). Compared with the half-bridge power module, its biggest advantage is its greater operational flexibility and ability to output negative voltage levels. The full-bridge MMC has a wider DC voltage regulation range, enabling continuous and smooth rise and fall of the DC voltage between negative and positive rated values. This characteristic meets the requirements for 70%, 80%, or even lower voltage reduction operation in long-distance DC transmission and rapid voltage reduction restart after DC faults.

[0053] In the locked-out state, the equivalent circuit of the full-bridge MMC converter is shown in Figure 2(b) and Figure 2(c). Figure 2(b) shows the equivalent circuit of the full-bridge MMC converter under positive arm current. Figure 2(c) shows the equivalent circuit of the full-bridge MMC converter under negative arm current.

[0054] Taking phases A and C as an example, the voltage applied across the anode and cathode of diodes D1~D4 is as follows, regardless of whether the current is in the forward or reverse bridge arm direction:

[0055]

[0056] In the above formula This represents the peak value of the AC line voltage. This represents the sum of the capacitor voltages of all power modules in each arm of a full-bridge MMC. During the main circuit parameter design phase of the converter station, this generally meets the following requirements. Less than Therefore, diodes D2 and D3 will be cut off due to reverse voltage. It is precisely because of this characteristic that the full-bridge MMC has the ability to self-clear DC faults.

[0057] The full-bridge MMC utilizes its own blocking characteristic to provide a back EMF with the opposite polarity to the AC power supply voltage in the blocked state, promoting rapid decay of DC fault current. The entire process does not require tripping the AC circuit breaker and involves no mechanical switching operations, thus enabling rapid fault clearing. During the DC system restart phase, the converter is unlocked again to gradually build up the DC voltage; this process also requires no mechanical switching operations, thus achieving rapid restart.

[0058] The DC voltage rating of the power module must match the voltage rating of the selected IGBT, which in turn determines the required number of power modules. The formula for calculating the number of power modules in series in a single bridge arm is:

[0059]

[0060] In the formula, It is a rounding function; This is the maximum DC voltage under no-load operation; and The amplitude of the DC voltage and the AC phase voltage output by the flexible DC converter valve under different operating conditions.

[0061] As can be seen, the module count has traditionally been determined primarily based on steady-state operating requirements. During MMC converter operation, electromagnetic transient simulation is typically used to simulate overvoltages between converter valve terminals under different operating conditions to determine the module count. However, this method involves a large computational load, often requiring multiple iterations, resulting in low computational efficiency and making it unsuitable for practical fault clearing scenarios.

[0062] Therefore, one of the core inventive points of this invention is to propose a fault clearing method for DC transmission systems, addressing the shortcomings of current technologies. Specifically, it proposes a rapid calculation method for the number of full-half-bridge sub-modules required in an MMC converter when a fault occurs in a DC transmission system. This invention fully considers the maximum overvoltage after a fault between the bridge arms of the MMC converter, a decisive factor in determining the number of modules. Combined with the sub-module number calculation model designed in this invention, the calculation efficiency of the number of sub-modules can be improved, quickly estimating the minimum number of full-half-bridge sub-modules required when a system fault occurs. This minimizes the number of sub-modules while meeting the requirements for system voltage support, rapid fault clearing capability, modulation accuracy, dynamic performance, and reliability, and simultaneously deploys the corresponding number of sub-modules for fault clearing as quickly as possible, thereby achieving rapid fault clearing and enabling the system to quickly return to stable and normal operation.

[0063] Reference Figure 3 This diagram illustrates a flowchart of a fault clearing method for a DC transmission system according to an embodiment of the present invention. The MMC converter in the DC transmission system contains a sub-module with a full-half-bridge structure. The method specifically includes the following steps:

[0064] Step 301: When a fault is detected in the DC transmission system, obtain the maximum overvoltage after the fault between the bridge arms of the MMC converter.

[0065] Compared to full-bridge MMC converters, half-bridge MMC converters offer significant advantages in terms of submodule structure, cost, efficiency, control complexity, dynamic response, and modular expansion, making them more suitable for DC transmission systems requiring efficient, reliable, and flexible control. How to quickly determine the number of modules in a half-bridge is a critical issue that urgently needs to be addressed, and it is also the key problem that this invention aims to solve.

[0066] In this embodiment of the invention, a fast method for estimating the number of submodules is designed for the submodule topology of the full-half-bridge structure in a hybrid MMC converter, so as to quickly determine the number of full-half-bridge submodules that the MMC converter needs to put into use when a system failure occurs.

[0067] In practical implementation, when a fault is detected in the DC transmission system, the maximum overvoltage after the fault between the MMC converter arms can be obtained, which can be used for subsequent calculation of the number of full and half bridge sub-modules.

[0068] Step 302: Based on the maximum overvoltage after the fault, construct a full-half-bridge submodule quantity model that considers commutation safety;

[0069] Based on the maximum overvoltage following an inter-arm fault in an MMC converter, this invention proposes a model for the number of full-half-bridge submodules that considers converter safety, in order to quickly estimate the number of full-half-bridge submodules to be deployed. This reduces computational load, increases computational efficiency, buys time for fault clearing, minimizes the impact of faults on the system, and enables the system to quickly return to a stable and safe operating state.

[0070] In some embodiments, the execution flow of constructing a full-half-bridge submodule quantity model considering commutation safety based on the maximum overvoltage after a fault may include: obtaining the withstand voltage thresholds of various devices in the MMC converter, and determining the commutation safety voltage based on the withstand voltage thresholds of various devices; and constructing a full-half-bridge submodule quantity model considering commutation safety based on the maximum overvoltage after a fault and the commutation safety voltage, while also considering the module voltage parameters and device aging parameters of the MMC converter.

[0071] In one optional embodiment, the device types in the MMC converter mainly include IGBT elements, capacitors, and bypass thyristors (i.e., in addition to the necessary IGBT elements and capacitors, bypass thyristors are also provided). In this case, determining the commutation safety voltage based on the withstand voltage thresholds of each type of device can include: selecting the lowest withstand voltage threshold from the respective withstand voltage thresholds of the IGBT elements, capacitors, and bypass thyristors as the commutation safety voltage of the MMC converter. In this case, the expression for determining the commutation safety voltage is as follows:

[0072]

[0073] in, For commutation safety voltage; This refers to the maximum withstand voltage of the IGBT element; This is the maximum withstand voltage of the capacitor; This is the maximum withstand voltage of the bypass thyristor.

[0074] In another alternative embodiment, the device types in the MMC converter mainly include IGBT elements and capacitors (i.e., only the necessary IGBT elements and capacitors are set in the MMC converter line). In this case, determining the commutation safety voltage based on the withstand voltage thresholds of various devices can include: selecting the lowest withstand voltage threshold from the respective withstand voltage thresholds of the IGBT elements and capacitors as the commutation safety voltage of the MMC converter. In this case, the expression for determining the commutation safety voltage is as follows:

[0075]

[0076] Furthermore, the module voltage parameters in this embodiment of the invention mainly include the average module voltage and the peak module voltage. Device aging parameters mainly include capacitor manufacturing and aging deviations, and surge arrester aging factors. In a specific implementation, the process of constructing a full-half-bridge sub-module quantity model considering commutation safety, based on the maximum overvoltage after a fault and the commutation safety voltage, while considering the module voltage parameters and device aging parameters of the MMC converter, can include: constructing a full-half-bridge sub-module quantity model considering commutation safety based on the maximum overvoltage after a fault, the commutation safety voltage, the average module voltage, the peak module voltage, capacitor manufacturing and aging deviations, the surge arrester aging factor, and the safety factor.

[0077] More specifically, the expression for the full-half-bridge submodule quantity model provided in this embodiment of the invention is as follows:

[0078]

[0079] in, This represents the safety factor, which takes into account unforeseen or unsimulable influencing factors, and is typically set to 1.1 to 1.15. This represents the average voltage of the module, typically 50% of the highest voltage of the IGBT element. This represents the peak voltage of the module, i.e., the maximum peak value of the module voltage, which can be considered as 10% of the average module voltage. This indicates manufacturing and aging deviations in capacitors, which can be considered according to 1.1; This indicates the aging factor of the surge arrester, which can be considered as 1.03. This represents the maximum overvoltage after a fault, i.e., the simulated maximum overvoltage between bridge arm terminals after a fault. In this embodiment of the invention, it is represented as the protection level of the configured surge arrester between the converter valve terminals. Indicates the number of full and half bridge sub-modules; This indicates the safe voltage for commutation, i.e., the safe voltage of the commutation valve.

[0080] Step 303: Solve the full-half-bridge submodule quantity model to obtain the minimum number of full-half-bridge submodules;

[0081] Based on the preceding discussion, the number of full-and-half bridge submodules can be calculated using the following formula:

[0082]

[0083] After calculating the result on the right side of the equation, the minimum number of full-half-bridge submodules is obtained by rounding the result up. For example, if the right side of the equation yields a value of 3.5, rounding it up gives a value of 4. This value of 4 is the minimum number of full-half-bridge submodules found in this calculation.

[0084] in, Indicates the number of full and half bridge sub-modules; Indicates the aging factor of the surge arrester; Indicates the maximum overvoltage after the fault; This indicates manufacturing and aging deviations in capacitors; Indicates the commutation safety voltage Indicates the safety factor; This represents the average module voltage. This indicates the peak voltage of the module.

[0085] Understandably, the goal of calculating the minimum number of full-half-bridge submodules is to minimize the number of submodules while meeting the requirements for system voltage support, rapid fault clearing capability, modulation accuracy, dynamic performance, and reliability, thereby optimizing the system's economy, efficiency, and complexity.

[0086] Step 304: Update the number of full and half bridge sub-modules of the MMC converter to the minimum number to clear faults in the DC transmission system.

[0087] Once the minimum number of full-half-bridge submodules is quickly calculated through the preceding steps, the number of full-half-bridge submodules in the MMC converter can be updated to the minimum number to clear faults in the DC transmission system.

[0088] This invention proposes a fault clearing method for DC transmission systems. Specifically, it presents a rapid calculation method for the number of full-half-bridge submodules required in an MMC converter when a DC transmission system fault occurs. This invention fully considers the maximum overvoltage between the MMC converter bridge arms after a fault, a crucial factor determining the number of submodules required. Combined with the submodule number calculation model designed in this invention, the calculation efficiency of the submodule number can be improved, quickly estimating the minimum number of full-half-bridge submodules required when a system fault occurs. This minimizes the number of submodules while meeting the requirements for system voltage support, rapid fault clearing capability, modulation accuracy, dynamic performance, and reliability, and allows for the rapid deployment of the corresponding number of submodules for fault clearing, enabling the system to quickly return to stable and normal operation.

[0089] For better explanation, refer to Figure 4 This diagram illustrates the overall flow of a fault clearing method for a DC transmission system according to an embodiment of the present invention. It should be noted that this embodiment only provides a brief description of the general flow of fault clearing in a DC transmission system. The specific implementation process of each step can be understood by referring to the relevant content in the foregoing embodiments, and will not be elaborated upon here. It is understood that the present invention does not impose any limitations on this.

[0090] Step 401: When a fault is detected in the DC transmission system, obtain the withstand voltage threshold of various devices in the MMC converter, as well as the maximum overvoltage after the fault between the bridge arm terminals;

[0091] Step 402: Determine the commutation safety voltage based on the withstand voltage thresholds of various devices;

[0092] Step 403: Based on the maximum overvoltage after a fault and the commutation safety voltage, and considering the module voltage parameters and device aging parameters of the MMC converter, construct a full half-bridge sub-module quantity model that considers commutation safety.

[0093] Step 404: Solve the full-half-bridge submodule quantity model to obtain the minimum number of full-half-bridge submodules;

[0094] Step 405: Update the number of full and half bridge sub-modules of the MMC converter to the minimum number to clear faults in the DC transmission system.

[0095] Reference Figure 5 This diagram illustrates a structural block diagram of a fault clearing device for a DC transmission system according to an embodiment of the present invention. The MMC converter in the DC transmission system contains a sub-module with a full-half-bridge structure. Specifically, the device may include:

[0096] Data acquisition unit 501 is used to acquire the maximum overvoltage after the fault between the bridge arms of the MMC converter when a fault is detected in the DC transmission system.

[0097] Model building unit 502 is used to build a model of the number of full-half-bridge sub-modules considering commutation safety based on the maximum overvoltage after the fault.

[0098] The model solving unit 503 is used to solve the full-half-bridge submodule quantity model to obtain the minimum number of full-half-bridge submodules;

[0099] The fault clearing unit 504 is used to update the number of full and half bridge sub-modules of the MMC converter to the minimum number in order to clear faults in the DC transmission system.

[0100] In one alternative embodiment, the model building unit 502 includes:

[0101] The commutation safety voltage determination unit is used to obtain the withstand voltage thresholds of various devices in the MMC converter, and determine the commutation safety voltage based on the withstand voltage thresholds of various devices.

[0102] The model building subunit is used to construct a full-half-bridge submodule quantity model that considers commutation safety, based on the maximum overvoltage after the fault and the commutation safety voltage, while also considering the module voltage parameters and device aging parameters of the MMC converter.

[0103] In one optional embodiment, the device types in the MMC converter include IGBT elements, capacitors, and bypass thyristors; the commutation safety voltage determination unit is specifically used for:

[0104] The minimum withstand voltage threshold value is selected from the withstand voltage threshold values ​​corresponding to the IGBT element, the capacitor, and the bypass thyristor, and used as the commutation safety voltage of the MMC converter.

[0105] In one optional embodiment, the device types in the MMC converter include IGBT elements and capacitors; the commutation safety voltage determination unit is specifically used for:

[0106] The minimum withstand voltage threshold value is selected from the withstand voltage threshold values ​​corresponding to the IGBT element and the capacitor, and is used as the commutation safety voltage of the MMC converter.

[0107] In one optional embodiment, the module voltage parameters include the average module voltage and the peak module voltage; the device aging parameters include capacitor manufacturing and aging deviations, and surge arrester aging factor; the model construction subunit is specifically used for:

[0108] Based on the maximum overvoltage after the fault, the commutation safety voltage, the average module voltage, the peak module voltage, the manufacturing and aging deviation of the capacitor, and the aging factor of the surge arrester, combined with the safety factor, a full-half-bridge sub-module quantity model considering commutation safety is constructed.

[0109] In one alternative embodiment, the expression for the number of full-half-bridge submodules is as follows:

[0110]

[0111] in, Indicates the safety factor; This represents the average module voltage. Indicates the peak voltage of the module; This indicates manufacturing and aging deviations in capacitors; Indicates the aging factor of the surge arrester; Indicates the maximum overvoltage after the fault; Indicates the number of full and half bridge sub-modules; This indicates the commutation safety voltage.

[0112] In one alternative embodiment, the number of full-half-bridge submodules is calculated using the following formula:

[0113]

[0114] After calculating the result on the right side of the equation, the minimum number of full and half bridge sub-modules is obtained by rounding the result up.

[0115] in, Indicates the number of full and half bridge sub-modules; Indicates the aging factor of the surge arrester; Indicates the maximum overvoltage after the fault; This indicates manufacturing and aging deviations in capacitors; Indicates the commutation safety voltage Indicates the safety factor; This represents the average module voltage. This indicates the peak voltage of the module.

[0116] As the device embodiment is basically similar to the method embodiment, it is described in a relatively simple way. For relevant details, please refer to the description of the method embodiment above.

[0117] This invention also provides an electronic device, which includes a processor and a memory:

[0118] The memory is used to store program code and transfer the program code to the processor;

[0119] The processor is used to execute the fault clearing method of the DC transmission system according to the instructions in the program code of any embodiment of the present invention.

[0120] This invention also provides a computer-readable storage medium for storing program code for executing the fault clearing method for a DC transmission system according to any embodiment of this invention.

[0121] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0122] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this invention are all information and data authorized by the user or fully authorized by all parties. Furthermore, the collection, use and processing of related data must comply with the relevant laws, regulations and standards of the relevant countries and regions, and corresponding operation entry points are provided for users to choose to authorize or refuse.

[0123] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between devices or units through some interfaces, and may be electrical, mechanical, or other forms.

[0124] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0125] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0126] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0127] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of clearing a fault in a direct current power transmission system, characterized by, The MMC converter in the direct current transmission system contains sub-modules of full-bridge and half-bridge structures; the method comprises: When detecting that the direct current transmission system fails, obtaining the maximum overvoltage after the failure of the MMC converter bridge arm end; Based on the maximum overvoltage after the failure, a full-bridge and half-bridge sub-module quantity model considering the commutation safety is constructed; Solving the full-bridge and half-bridge sub-module quantity model to obtain the minimum quantity of full-bridge and half-bridge sub-modules; The quantity of full-bridge and half-bridge sub-modules of the MMC converter is updated to the minimum quantity to clear the fault of the direct current transmission system.

2. The method of claim 1, wherein, The full-bridge and half-bridge sub-module quantity model considering the commutation safety is constructed based on the maximum overvoltage after the failure, comprising: Obtaining the withstand voltage threshold of each type of device in the MMC converter, and determining the commutation safety voltage based on the withstand voltage threshold of each type of device; Based on the maximum overvoltage after the failure and the commutation safety voltage, and considering the module voltage parameters and device aging parameters of the MMC converter, a full-bridge and half-bridge sub-module quantity model considering the commutation safety is constructed.

3. The method of claim 2, wherein, The types of devices in the MMC converter include IGBT elements, capacitors and bypass thyristors; the commutation safety voltage is determined based on the withstand voltage threshold of each type of device, comprising: From the withstand voltage threshold corresponding to each of the IGBT elements, the capacitors and the bypass thyristors, the minimum withstand voltage threshold is selected as the commutation safety voltage of the MMC converter.

4. The method of claim 2, wherein, The types of devices in the MMC converter include IGBT elements and capacitors; the commutation safety voltage is determined based on the withstand voltage threshold of each type of device, comprising: From the withstand voltage threshold corresponding to each of the IGBT elements and the capacitors, the minimum withstand voltage threshold is selected as the commutation safety voltage of the MMC converter.

5. The method of claim 2 to 4, wherein The module voltage parameters include the module voltage average and the module voltage peak; the device aging parameters include the capacitor manufacturing and aging deviation and the arrester aging factor; based on the maximum overvoltage after the failure and the commutation safety voltage, and considering the module voltage parameters and device aging parameters of the MMC converter, a full-bridge and half-bridge sub-module quantity model considering the commutation safety is constructed, comprising: Based on the maximum overvoltage after the failure, the commutation safety voltage, the module voltage average, the module voltage peak, the capacitor manufacturing and aging deviation, the arrester aging factor, and the safety factor, a full-bridge and half-bridge sub-module quantity model considering the commutation safety is constructed.

6. The method of claim 5, wherein, The expression of the full-bridge and half-bridge sub-module quantity model is as follows: wherein, represents a safety factor; represents a module voltage average; represents a module voltage peak; represents a capacitor manufacturing and aging deviation; represents a surge arrester aging factor; represents a maximum overvoltage after a fault; represents a full half-bridge sub-module number; represents a commutation safety voltage.

7. The method of claim 1, wherein, The quantity of full-bridge and half-bridge sub-modules is calculated by the following formula: After calculating the result on the right side of the formula, the minimum quantity of full-bridge and half-bridge sub-modules is obtained by rounding up the calculation result; wherein, represents the number of full and half bridge submodules; represents the arrester aging factor; represents the maximum overvoltage after a fault; represents the capacitor manufacturing and aging deviation; represents the commutation safety voltage represents the safety factor; represents the average value of the module voltage; represents the peak value of the module voltage.

8. A fault clearing device for a direct current power transmission system, characterized in that The MMC converter in the direct current transmission system contains sub-modules of full-bridge and half-bridge structures; the device comprises: A data acquisition unit is configured to obtain the maximum overvoltage after the failure of the MMC converter bridge arm end when detecting that the direct current transmission system fails; A model construction unit is configured to construct, based on the maximum overvoltage after the fault, a full-half bridge submodule quantity model considering commutation safety. A model solution unit is configured to solve the full-half bridge submodule quantity model to obtain a minimum quantity of full-half bridge submodules. A fault clearing unit is configured to update the quantity of full-half bridge submodules of the MMC converter to the minimum quantity to clear the fault of the DC power transmission system.

9. An electronic device, comprising: The device comprises a processor and a memory: The memory is configured to store program code and transmit the program code to the processor; The processor is configured to execute the fault clearing method of the DC power transmission system according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium is configured to store program code for executing the fault clearing method of the DC power transmission system.

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