Short-circuit current suppression method and device, terminal equipment and storage medium

Abstract

The invention discloses a short-circuit current suppression method, device and equipment and a storage medium, and belongs to the technical field of power systems and power electronics, and the method comprises the steps: building an equivalent model of a target power grid, and carrying out the load flow calculation of the equivalent model, and obtaining an initial state; when the initial state accords with an operable state, calculating an admittance matrix based on line parameters and equipment parameters of each line in the equivalent model; the line comprises a bus and a branch line; calculating according to the admittance matrix to obtain an impedance matrix, and obtaining transfer impedance between corresponding buses according to the impedance matrix; establishing a short-circuit current sensitivity index according to the transfer impedance, and determining a target AC line based on the short-circuit current sensitivity index; and replacing the target alternating-current line with a flexible direct-current transmission line so as to suppress the short-circuit current. Therefore, by implementing the method, the problem of low stability caused by non-uniform power flow distribution on the line in the prior art can be solved.

Description

Technical Field

[0001] This invention relates to the fields of power systems and power electronics, and in particular to a short-circuit current suppression method, apparatus, terminal equipment, and storage medium. Background Technology

[0002] To ensure the steady development of the national economy and meet electricity demand, especially the needs of emerging technologies such as artificial intelligence in recent years, the electricity supply in some regions has gradually shifted from a slight surplus to a tight supply. The integration of new power sources is urgent; however, there is a mismatch between the level of power source construction and the development of regional loads. This further increases the transmission power on the lines, causing the system's short-circuit current level to rise continuously. This not only approaches the breaking capacity limit of circuit breakers but also triggers thermal and dynamic stability problems in electrical equipment, leading to serious safety hazards. The magnitude of the short-circuit current has become an important reference indicator for assessing the stability of the power grid.

[0003] Existing short-circuit current suppression measures mainly include connecting reactors in series in the power grid or configuring fault current limiters. However, these devices generally suffer from drawbacks such as high investment costs, large operating losses, large footprint, and insufficient flexibility. In addition, the traditional approach to short-circuit current suppression involves opening a loop at appropriate locations, which can exacerbate uneven power flow distribution on some lines and significantly reduce stability. Summary of the Invention

[0004] This invention provides a short-circuit current suppression method, device, terminal equipment, and storage medium, which can solve the technical problem of low stability caused by uneven power flow distribution on the line in the prior art.

[0005] This invention provides a short-circuit current suppression method, comprising: An equivalent model of the target power grid is established, and power flow calculations are performed on the equivalent model to obtain the initial state; When the initial state meets the operational requirements, the admittance matrix is ​​calculated based on the line parameters and equipment parameters of each line in the equivalent model; wherein, the line includes: busbars and branch lines; The impedance matrix is ​​calculated based on the admittance matrix, and the transfer impedance between the corresponding buses is obtained based on the impedance matrix. Based on the transfer impedance, a short-circuit current sensitivity index is established, and based on the short-circuit current sensitivity index, the target AC line is determined. The target AC line is replaced with a flexible DC transmission line to suppress short-circuit current.

[0006] As a preferred option, after replacing the target AC line with a flexible DC transmission line, the following is also included: The equivalent model is updated, and the new admittance matrix is ​​recalculated, thereby obtaining the new impedance matrix; Short-circuit calculations are performed based on the new impedance matrix to obtain the short-circuit current of each busbar. Determine whether the short-circuit current of all buses is within the preset current threshold range for the circuit breaker to perform interruption; If so, then current suppression is completed; If at least one busbar is not within the preset current threshold range, a new transfer impedance between the corresponding buses is obtained based on the current impedance matrix. Based on the transfer impedance, a new target AC line is determined and replaced with a flexible DC transmission line until the short-circuit current of all replaced buses is within the preset current threshold range.

[0007] As a preferred embodiment, the calculation of the admittance matrix based on the equipment parameters of each bus and its branches in the equivalent model specifically includes: Based on the line parameters of each bus and its branch in the equivalent model, and the equipment parameters on each bus and its branch, the admittance of each bus and its branch is calculated. The admittance matrix is ​​obtained based on the admittance of each busbar and its branch; wherein the equipment parameters include: reactor parameters and transformer parameters.

[0008] As a preferred embodiment, the step of calculating the impedance matrix based on the admittance matrix specifically includes: The impedance matrix is ​​obtained by inverting the admittance matrix; wherein the impedance matrix characterizes the coupling strength between the buses by describing the relationship between the bus voltage and the injected current.

[0009] As a preferred embodiment, obtaining the transfer impedance between corresponding buses based on the impedance matrix specifically includes: Based on the impedance matrix, the busbars in which the short-circuit current exceeds the preset current threshold range are identified as target busbars. The target bus is subjected to transfer impedance analysis to obtain the power supply bus. The power supply bus is taken as the starting point and the other target buses are taken as the ending point. Thus, the bus corresponding to the line through which the fault current flows from the starting point to the ending point is taken as the bus subset. The ring structure existing in the bus sub-unit is processed into an open-loop structure, and the bus after the open-loop processing is used as a candidate bus. The transfer impedance of the candidate bus is calculated.

[0010] As a preferred embodiment, the step of establishing a short-circuit current sensitivity index based on the transfer impedance, and determining the target AC line based on the short-circuit current sensitivity index, includes: Based on the transfer impedance, the change in short-circuit current is determined, and the relationship between the open-loop processing position and the short-circuit current is evaluated based on the change in short-circuit current. Based on the relationship between the open-loop processing position and the short-circuit current, the priority order of the candidate buses is rearranged. Based on the change in short-circuit current, the sensitivity index of the arranged candidate busbars is calculated to obtain the short-circuit current sensitivity index. Based on the short-circuit current sensitivity index, the optimal unlooping point position of the candidate bus is obtained, and the candidate bus corresponding to the unlooping point position is taken as the target AC line.

[0011] As a preferred embodiment, replacing the target AC line with a flexible DC transmission line includes: At the unloop point of the target AC line, a flexible DC line is connected to suppress the short-circuit current of the bus.

[0012] Another embodiment of the present invention provides a short-circuit current suppression device, comprising: a power flow module, an admittance module, an impedance module, a sensitivity module, and a replacement module; The power flow module is used to establish an equivalent model of the target power grid and perform power flow calculations on the equivalent model to obtain the initial state. The admittance module is used to calculate the admittance matrix based on the line parameters and equipment parameters of each line in the equivalent model when the initial state meets the operable state; wherein, the line includes: bus and branch line; The impedance module is used to calculate the impedance matrix based on the admittance matrix, and to obtain the transfer impedance between the corresponding buses based on the impedance matrix. The sensitivity module is used to establish a short-circuit current sensitivity index based on the transfer impedance, and to determine the target AC line based on the short-circuit current sensitivity index. The replacement module is used to replace the target AC line with a flexible DC transmission line, thereby suppressing short-circuit current.

[0013] Another embodiment of the present invention provides a terminal device, including: a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements the steps of the short-circuit current suppression method provided by the present invention.

[0014] Another embodiment of the present invention provides a computer-readable storage medium item, including: a stored computer program, which, when the computer program is running, controls the device where the computer-readable storage medium is located to perform steps of the short-circuit current suppression method provided by the present invention.

[0015] By implementing this invention, the following beneficial effects are achieved: This invention establishes an equivalent model of the target power grid, performs power flow calculations to determine the initial state, and then calculates the admittance matrix based on the equipment parameters of each bus and its branches, determining the corresponding impedance matrix to calculate the transfer impedance. By establishing a short-circuit sensitivity index, the target AC line is identified, and finally, the target AC line is replaced with a flexible DC transmission line, thereby suppressing short-circuit current without significantly affecting power flow and maintaining the overall stability of the target power grid system. Furthermore, by selecting the corresponding line through transfer impedance, compared to the traditional method of relying on experience and historical data to select loop-breaking locations, this method can adapt to the current dynamically changing power grid environment, improving the overall stability of the power grid system in the short-circuit current suppression process. It can provide more effective solutions for new problems or fault modes in power grid development. Attached Figure Description

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

[0017] Figure 1 This is a schematic flowchart of a short-circuit current suppression method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a demonstration model provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a short-circuit current suppression device provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0020] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0021] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0023] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0024] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0025] See Figure 1 To address the technical problem of low stability caused by uneven power flow distribution on lines in existing technologies, an embodiment of the present invention provides a short-circuit current suppression method, comprising the following steps S101-S104: Step S101: Establish an equivalent model of the target power grid, and perform power flow calculations on the equivalent model to obtain the initial state; In this embodiment, an equivalent model of the target power grid is established to perform power flow calculations, providing a data foundation for subsequent analysis. To perform subsequent short-circuit current calculations, power flow calculations must first be performed on the equivalent model corresponding to the target power grid to obtain the initial state of the target power grid system. Ensuring the convergence of power flow in the target power grid system is fundamental to all subsequent steps. If the power flow in the equivalent model is correct, meaning the corresponding initial state conforms to an operational state, it indicates that the topology of the target power grid system matches the actual situation.

[0026] Step S102: When the initial state meets the operable state, the admittance matrix is ​​calculated based on the line parameters and equipment parameters of each line in the equivalent model; wherein, the line includes: bus and branch line; As a preferred embodiment, the calculation of the admittance matrix based on the line parameters and equipment parameters of each line in the equivalent model specifically includes: Based on the line parameters of each bus and its branch in the equivalent model, and the equipment parameters on each bus and its branch, the admittance of each bus and its branch is calculated. The admittance matrix is ​​obtained based on the admittance of each busbar and its branch; wherein the equipment parameters include: reactor parameters and transformer parameters.

[0027] As a preferred embodiment, the step of calculating the impedance matrix based on the admittance matrix specifically includes: The impedance matrix is ​​obtained by inverting the admittance matrix; wherein the impedance matrix characterizes the coupling strength between the buses by describing the relationship between the bus voltage and the injected current.

[0028] In this embodiment, after performing power flow calculations on the equivalent model of the target power grid, the admittance matrix Y between the corresponding system buses is calculated. bus By analyzing Y bus Inverse Z can be obtained by taking the inverse. bus The elements on the diagonal of the impedance matrix represent the equivalent impedance of the bus, while the elements off-diagonal represent the transfer impedance between the buses, thus visualizing the coupling strength between the buses. If the system is complex and has a large number of buses, it is not necessary to obtain all the elements in the matrix.

[0029] It should be noted that, in order to calculate the impedance matrix Z bus In engineering, the incremental method is commonly used to obtain the impedance matrix. However, the incremental method requires continuously adding buses and gradually updating the matrix, which is complex to derive and cumbersome to program. Therefore, it is more common to obtain the impedance matrix by inverting the admittance matrix. The calculation formula is shown below; (1) In the formula, Represents the impedance matrix. This represents the admittance matrix. Each element originates from the network topology and branch parameters. Knowing the parameters of the lines, reactors, and transformers makes it very easy to obtain... .

[0030] (2) In the formula, the diagonal element Equal to the sum of the admittances of all branches connected to this bus, and the off-diagonal element. It equals the negative value of the branch admittance between bus i and j. Functions such as power flow calculation and steady-state operating point analysis are all based on... Most simulation software, such as PSS®E, supports direct generation. .

[0031] The coupling strength between two points is reflected by describing the relationship between the bus voltage and the injected current.

[0032] (3) In the formula, the diagonal element This reflects the coupling strength of the busbar itself; off-diagonal elements It reflects the coupling strength between bus i and j, that is, the degree of voltage change at bus j when current is injected at bus i.

[0033] Step S103: Calculate the impedance matrix based on the admittance matrix, and obtain the transfer impedance between the corresponding buses based on the impedance matrix; As a preferred embodiment, the step of obtaining the transfer impedance between corresponding buses based on the impedance matrix specifically includes: Based on the impedance matrix, the busbars in which the short-circuit current exceeds the preset current threshold range are identified as target busbars. The target bus is subjected to transfer impedance analysis to obtain the power bus. The power bus is taken as the starting point and the other target buses are taken as the ending point. Thus, the bus corresponding to the line through which the fault current flows from the starting point to the ending point is taken as the bus subset. The ring structure existing in the bus sub-unit is processed into an open-loop structure, and the bus after the open-loop processing is used as a candidate bus to calculate the transfer impedance of the candidate bus.

[0034] In this embodiment, the location for flexible DC replacement is determined based on the transfer impedance, and the transfer impedance between each bus is calculated according to the obtained bus impedance matrix. A short-circuit current sensitivity index is then established to characterize the influence of different AC lines on the short-circuit current. Based on the magnitude of the sensitivity index, the AC line that contributes the most to the short-circuit current is identified, and this line is replaced with a flexible DC transmission line to effectively suppress the short-circuit current.

[0035] In this embodiment, it is necessary to first identify the set of busbars where the short-circuit current has exceeded the limit or has a potential for exceeding the limit, and then perform transfer impedance analysis on the target busbars. For a three-phase short circuit occurring at busbar k, the current is approximately: (4) In the formula, This represents the bus electromotive force, preferably taken as 1.0 pu in practical power grid systems. This is what was obtained in step S102 above. The diagonal elements. Through the impedance matrix. By short-circuiting the ports between the two nodes, the transfer impedance of each candidate bus can be determined. If the transfer impedance between the bus connected to an AC line and the faulty bus is relatively small, it indicates that the line forms a low-impedance path, allowing fault current to pass easily, and this bus contributes relatively more to the fault current at the short-circuit point. If the transfer impedance is large, the line's effect on short-circuit current transmission is weak. Therefore, by calculating and comparing the transfer impedance, the influence of different lines on the short-circuit current level can be quantitatively assessed, providing a basis for determining the replacement location of flexible DC lines.

[0036] By using transfer impedance analysis, the power supply bus that has the greatest impact on the short-circuit current of the target bus can be identified. Starting from this power supply bus and ending at the target bus, the bus corresponding to the line through which the fault current flows from the starting point to the ending point is taken as a subset of bus. The ring structure existing in this subset of bus is then processed by opening the loop.

[0037] Step S104: Based on the transfer impedance, establish a short-circuit current sensitivity index, and based on the short-circuit current sensitivity index, determine the target AC line; As a preferred embodiment, the step of establishing a short-circuit current sensitivity index based on the transfer impedance and determining the target AC line based on the short-circuit current sensitivity index includes: Based on the transfer impedance, the change in short-circuit current is determined, and the relationship between the open-loop processing position and the short-circuit current is evaluated based on the change in short-circuit current. Based on the relationship between the open-loop processing position and the short-circuit current, the priority order of the candidate buses is rearranged. Based on the change in short-circuit current, the sensitivity index of the arranged candidate busbars is calculated to obtain the short-circuit current sensitivity index. Based on the short-circuit current sensitivity index, the optimal unlooping point position of the candidate bus is obtained, and the candidate bus corresponding to the unlooping point position is taken as the target AC line.

[0038] In this embodiment, the transfer impedance of the candidate bus is determined by short-circuiting the ports between the two nodes. This allows for the determination of the change in transfer impedance from the power bus to the target bus before and after the short circuit. It is assumed that when this line is replaced, the change in short-circuit current can be approximated by the effect of the change in the line's transfer impedance on the current. This allows for the determination of the change in short-circuit current, and thus, the impact of the open-loop position on the short-circuit current can be evaluated. Specifically, a large change in short-circuit current indicates a significant impact of the open-loop processing position of the candidate bus on the short-circuit current. Therefore, by measuring the change in short-circuit current, the priority order of the candidate buses can be determined based on the magnitude of the change in short-circuit current.

[0039] In this embodiment, a bus line with an open-loop design on the ring is selected as the candidate bus. It is assumed that when this line is replaced, the change in short-circuit current can be approximated by the effect of the change in the transfer impedance of that line on the current. According to the principles of power system analysis, the short-circuit current of the candidate bus line is inversely proportional to the transfer impedance. (5) in busbar Self-impedance, transfer impedance The impact on short-circuit current can usually be estimated using a ratio: (6) In the formula, It is the change in short-circuit current before and after the replacement line. It is the change in the transfer impedance from the power supply bus to the target bus before and after the replacement line. This is the self-impedance of bus i. Based on this, it is not necessary to recalculate the entire short-circuit current each time; instead, the change in short-circuit current can be approximately estimated by the change in transfer impedance.

[0040] By determining the change in short-circuit current through the change in transfer impedance, the influence of open-loop location on short-circuit current is evaluated based on the change in short-circuit current. Candidate bus sets are obtained by sorting the candidates from largest to smallest influence, and sensitivity indices are calculated for these candidate bus sets. (7) In the formula, For sensitivity indicators, It is the target bus set. and Let K be the short-circuit current of bus k before and after the open loop. This is a weighting coefficient, related to factors such as the importance of the busbar, voltage level, and load size. Preferably, it can be set according to the specific project. The optimal loop-breaking point can be obtained through the sensitivity index, at which the flexible DC line is connected. The optimal loop-breaking point is unique on each busbar in the target busbar set and can be set manually or empirically. The sensitivity index can also be used to obtain the optimal candidate busbar in the target busbar set, which can then be used as the target AC line and thus the busbar for the flexible DC transmission line connection.

[0041] Step S105: Replace the target AC line with a flexible DC transmission line to suppress short-circuit current.

[0042] As a preferred embodiment, replacing the target AC line with a flexible DC transmission line includes: At the unloop point of the target AC line, a flexible DC line is connected to suppress the short-circuit current of the bus.

[0043] In this embodiment, after determining the location of the flexible DC replacement and completing the replacement, it should be confirmed that its equivalent connection parameters can be consistent with the power transmission capacity of the original AC line, and that excessive power loss or instability factors will not be introduced into the power grid after the replacement.

[0044] As a preferred option, after replacing the target AC line with a flexible DC transmission line, steps S106-S110 are also included: S106: Update the equivalent model and recalculate the new admittance matrix to obtain the new impedance matrix; S107: Perform short-circuit calculations based on the new impedance matrix to obtain the short-circuit current of each busbar; S108: Determine whether the short-circuit current of all busbars is within the preset current threshold range for the circuit breaker to perform interruption. S109: If so, then current suppression is completed; S110: If at least one busbar is not within the preset current threshold range, then according to the current impedance matrix, a new transfer impedance between the corresponding buses is obtained, and according to the transfer impedance, a new target AC line is determined, and the new target AC line is replaced with a flexible DC transmission line until the short-circuit current of all replaced buses is within the preset current threshold range.

[0045] In this embodiment, after updating the equivalent model topology of the target power grid, power flow calculations and short-circuit calculations are required. The short-circuit currents of all critical buses in the replaced power grid are calculated, and these calculated short-circuit currents are compared with the breaking capacity of the system's circuit breakers to confirm whether the short-circuit currents on all critical buses are within acceptable limits. If the short-circuit current of any bus exceeds the breaking capacity of the circuit breaker, the above steps need to be iterated again to find a new replacement point. If a single flexible straight line replacement cannot meet the short-circuit current requirements, the topology is updated based on the existence of a flexible straight line, and the above steps are repeated to select a second replacement point and perform the replacement. This iterative process continues until all short-circuit currents in the target power grid system meet the breaking capacity requirements of the circuit breakers.

[0046] It is understandable that the technical advantages of this invention are mainly reflected in efficient short-circuit current suppression, the scientific and precise selection of alternative lines through impedance transfer, and the fact that it does not significantly affect the stability of the power grid. Traditional short-circuit current suppression methods involve opening a loop at a suitable location, which can exacerbate uneven power flow distribution on certain lines and significantly reduce stability. However, replacing the traditional loop-breaking approach with the addition of flexible DC lines does not significantly impact power flow and maintains system stability. Furthermore, selecting lines based on impedance transfer, compared to the traditional method of relying on experience and historical data to choose loop-breaking locations, is more adaptable to the dynamic power grid environment and can provide more effective solutions to new problems or fault modes in power grid development.

[0047] Please see Figure 2 This is a demonstration model provided in the embodiments of the present invention, which constructs an equivalent topology model of the target power grid. Figure 2 The power distribution system shown is explained and analyzed. First, the Y... bus Because the number of nodes in a power grid system is usually large, we choose not to calculate the entire Z-axis. bus We only selected the key rows and columns of the calculation matrix. Assuming the short-circuit current of bus 3006 exceeds the limit, we sorted the transfer impedances from each power source (excluding the balancing bus) to bus 3006, and the results are shown in Table 1. It can be seen that the transfer impedance between 3006 and 3018 is the smallest, indicating that their coupling is the strongest. For now, we will consider limiting 3018.

[0048] Table 1 Transfer impedance between busbars The approximate calculation of the change in short-circuit current before and after the alternative line was performed, and the results are shown in Table 2.

[0049] Table 2 shows the candidate routes. Since there is no weighting coefficient in this description, de-looping between bus 3002 and bus 3004 is the most effective way to suppress short-circuit current. Therefore, the flexible DC transmission line is replaced here. The short-circuit current before replacement was 8336.4A, and the short-circuit current after replacement was 8040.5A. After verification, the short-circuit current decreased to an acceptable range and the power flow converged.

[0050] like Figure 3 As shown, based on the above method embodiments, corresponding apparatus embodiments are provided; One embodiment of the present invention provides a short-circuit current suppression device, including: a power flow module 201, an admittance module 202, an impedance module 203, a sensitivity module 204, and a replacement module 205; The power flow module 201 is used to establish an equivalent model of the target power grid and perform power flow calculations on the equivalent model to obtain the initial state. The admittance module 202 is used to calculate the admittance matrix based on the line parameters and equipment parameters of each line in the equivalent model when the initial state meets the operable state; wherein, the line includes: bus and branch line; The impedance module 203 is used to calculate the impedance matrix based on the admittance matrix, and to obtain the transfer impedance between the corresponding buses based on the impedance matrix. The sensitivity module 204 is used to establish a short-circuit current sensitivity index based on the transfer impedance, and to determine the target AC line based on the short-circuit current sensitivity index. The replacement module 205 is used to replace the target AC line with a flexible DC transmission line, thereby suppressing short-circuit current.

[0051] As a preferred option, after replacing the target AC line with a flexible DC transmission line, the following is also included: The equivalent model is updated, and the new admittance matrix is ​​recalculated, thereby obtaining the new impedance matrix; Short-circuit calculations are performed based on the new impedance matrix to obtain the short-circuit current of each busbar. Determine whether the short-circuit current of all buses is within the preset current threshold range for the circuit breaker to perform interruption; If so, then current suppression is completed; If at least one busbar is not within the preset current threshold range, a new transfer impedance between the corresponding buses is obtained based on the current impedance matrix. Based on the transfer impedance, a new target AC line is determined and replaced with a flexible DC transmission line until the short-circuit current of all replaced buses is within the preset current threshold range.

[0052] As a preferred embodiment, the calculation of the admittance matrix based on the line parameters and equipment parameters of each line in the equivalent model specifically includes: Based on the line parameters of each bus and its branch in the equivalent model, and the equipment parameters on each bus and its branch, the admittance of each bus and its branch is calculated. The admittance matrix is ​​obtained based on the admittance of each busbar and its branch; wherein the equipment parameters include: reactor parameters and transformer parameters.

[0053] As a preferred embodiment, the step of calculating the impedance matrix based on the admittance matrix specifically includes: The impedance matrix is ​​obtained by inverting the admittance matrix; wherein the impedance matrix characterizes the coupling strength between the buses by describing the relationship between the bus voltage and the injected current.

[0054] As a preferred embodiment, obtaining the transfer impedance between corresponding buses based on the impedance matrix specifically includes: Based on the impedance matrix, the busbars in which the short-circuit current exceeds the preset current threshold range are identified as target busbars. The target bus is subjected to transfer impedance analysis to obtain the power supply bus. The power supply bus is taken as the starting point and the other target buses are taken as the ending point. Thus, the bus corresponding to the line through which the fault current flows from the starting point to the ending point is taken as the bus subset. The ring structure existing in the bus sub-unit is processed into an open-loop structure, and the bus after the open-loop processing is used as a candidate bus to calculate the transfer impedance of the candidate bus.

[0055] As a preferred embodiment, the step of establishing a short-circuit current sensitivity index based on the transfer impedance, and determining the target AC line based on the short-circuit current sensitivity index, includes: Based on the transfer impedance, the change in short-circuit current is determined, and the relationship between the open-loop processing position and the short-circuit current is evaluated based on the change in short-circuit current. Based on the relationship between the open-loop processing position and the short-circuit current, the priority order of the candidate buses is rearranged. Based on the change in short-circuit current, the sensitivity index of the arranged candidate busbars is calculated to obtain the short-circuit current sensitivity index. Based on the short-circuit current sensitivity index, the optimal unlooping point position of the candidate bus is obtained, and the candidate bus corresponding to the unlooping point position is taken as the target AC line.

[0056] As a preferred embodiment, replacing the target AC line with a flexible DC transmission line includes: At the unloop point of the target AC line, a flexible DC line is connected to suppress the short-circuit current of the bus.

[0057] It is understood that the above-described device embodiments correspond to the method embodiments of the present invention, and can implement the short-circuit current suppression method provided by any of the above-described method embodiments of the present invention.

[0058] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can specifically be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0059] Based on the above embodiments of the short-circuit current suppression method, another embodiment of the present invention provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the short-circuit current suppression method of any embodiment of the present invention.

[0060] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the terminal device.

[0061] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0062] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0063] Based on the above-described method embodiments, another embodiment of the present invention provides a computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute the short-circuit current suppression method described in any of the above-described method embodiments of the present invention.

[0064] The modules / units integrated in the device / terminal equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0065] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A short-circuit current suppression method characterized by, include: An equivalent model of the target power grid is established, and power flow calculations are performed on the equivalent model to obtain the initial state; When the initial state meets the operational requirements, the admittance matrix is ​​calculated based on the line parameters and equipment parameters of each line in the equivalent model; wherein, the line includes: busbars and branch lines; The impedance matrix is ​​calculated based on the admittance matrix, and the transfer impedance between the corresponding buses is obtained based on the impedance matrix. Based on the transfer impedance, a short-circuit current sensitivity index is established, and based on the short-circuit current sensitivity index, the target AC line is determined. The target AC line is replaced with a flexible DC transmission line to suppress short-circuit current.

2. The short-circuit current suppression method according to claim 1, characterized by, After replacing the target AC line with a flexible DC transmission line, the method further includes: The equivalent model is updated, and the new admittance matrix is ​​recalculated, thereby obtaining the new impedance matrix; Short-circuit calculations are performed based on the new impedance matrix to obtain the short-circuit current of each busbar. Determine whether the short-circuit current of all busbars is within the preset current threshold range for the circuit breaker to perform interruption; If so, then current suppression is completed; If at least one busbar is not within the preset current threshold range, a new transfer impedance between the corresponding buses is obtained based on the current impedance matrix. Based on the transfer impedance, a new target AC line is determined and replaced with a flexible DC transmission line until the short-circuit current of all replaced buses is within the preset current threshold range.

3. The short-circuit current suppression method as described in claim 2, characterized in that, The admittance matrix is ​​calculated based on the line parameters and equipment parameters of each line in the equivalent model, specifically including: Based on the line parameters of each bus and its branch in the equivalent model, and the equipment parameters on each bus and its branch, the admittance of each bus and its branch is calculated. The admittance matrix is ​​obtained based on the admittance of each busbar and its branch; wherein the equipment parameters include: reactor parameters and transformer parameters.

4. The short-circuit current suppression method as described in claim 3, characterized in that, The calculation of the impedance matrix based on the admittance matrix specifically includes: The impedance matrix is ​​obtained by inverting the admittance matrix; wherein the impedance matrix characterizes the coupling strength between the buses by describing the relationship between the bus voltage and the injected current.

5. The short-circuit current suppression method as described in claim 4, characterized in that, The step of obtaining the transfer impedance between the corresponding buses based on the impedance matrix specifically includes: Based on the impedance matrix, the busbars in which the short-circuit current exceeds the preset current threshold range are identified as target busbars. The target bus is subjected to transfer impedance analysis to obtain the power bus. The power bus is taken as the starting point and the other target buses are taken as the ending point. The bus corresponding to the line through which the fault current flows from the starting point to the ending point is taken as the bus subset. The ring structure existing in the bus sub-unit is processed into an open-loop structure, and the bus after the open-loop processing is used as a candidate bus. The transfer impedance of the candidate bus is calculated.

6. The short-circuit current suppression method as described in claim 5, characterized in that, The step of establishing a short-circuit current sensitivity index based on the transfer impedance, and determining the target AC line based on the short-circuit current sensitivity index, includes: Based on the transfer impedance, the change in short-circuit current is determined, and the relationship between the open-loop processing position and the short-circuit current is evaluated based on the change in short-circuit current. Based on the relationship between the open-loop processing position and the short-circuit current, the priority order of the candidate buses is rearranged. Based on the change in short-circuit current, the sensitivity index of the arranged candidate busbars is calculated to obtain the short-circuit current sensitivity index. Based on the short-circuit current sensitivity index, the optimal unlooping point position of the candidate bus is obtained, and the candidate bus corresponding to the unlooping point position is taken as the target AC line.

7. The short-circuit current suppression method as described in claim 6, characterized in that, The replacement of the target AC line with a flexible DC transmission line includes: At the unloop point of the target AC line, a flexible DC line is connected to suppress the short-circuit current of the bus.

8. A short-circuit current suppression device, characterized in that, include: Power flow module, admittance module, impedance module, sensitivity module, and replacement module; The power flow module is used to establish an equivalent model of the target power grid and perform power flow calculations on the equivalent model to obtain the initial state. The admittance module is used to calculate the admittance matrix based on the line parameters and equipment parameters of each line in the equivalent model when the initial state meets the operable state; wherein, the line includes: bus and branch line; The impedance module is used to calculate the impedance matrix based on the admittance matrix, and to obtain the transfer impedance between the corresponding buses based on the impedance matrix. The sensitivity module is used to establish a short-circuit current sensitivity index based on the transfer impedance, and to determine the target AC line based on the short-circuit current sensitivity index. The replacement module is used to replace the target AC line with a flexible DC transmission line, thereby suppressing short-circuit current.

9. A terminal device, characterized in that, The device includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements the short-circuit current suppression method as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, include: A stored computer program, wherein, when the computer program is executed, it controls the device containing the computer-readable storage medium to perform the short-circuit current suppression method as described in any one of claims 1-7.

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