Method and related device for acquiring multiple sending-out short circuit ratios of sending-end power grid

Abstract

The invention belongs to the technical field of stability analysis of an alternating-current and direct-current power grid of a power system, and discloses a method and a related device for acquiring multiple sending-out short circuit ratios of a sending-end power grid. The acquisition method comprises the following steps: calculating and obtaining an initial multi-output short-circuit ratio by combining the own transmission power of each single-circuit direct current, the equivalent power influence of all other direct currents and the short-circuit capacity of a converter station bus corresponding to each single-circuit direct current in a to-be-evaluated power system; correcting the initial multi-sending-out short-circuit ratio by combining the short-circuit capacity correction of the bus of the converter station before and after the new energy grid connection to obtain the multi-sending-out short-circuit ratio of the sending-end power grid in the to-be-evaluated power system; the converter station bus short-circuit capacity correction is calculated according to the influence on the converter station bus equivalent potential before and after new energy grid connection. According to the technical scheme disclosed by the invention, correction is carried out on the basis of considering new energy coupling, and the accuracy and reliability of power grid short-circuit current calculation are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of AC-DC power grid stability analysis in power systems, and particularly relates to a method for obtaining the multi-outfeed short-circuit ratio of a sending-end power grid and related devices. Background Art

[0002] With the transformation of the global energy structure and the rapid development of new energy technologies, the penetration rate of new energy (such as wind power, photovoltaic power, etc.) in the power system has been continuously increasing, which poses new challenges to the stable operation of the power grid; further explanatory, in the sending-end power grid, the large-scale access of new energy not only changes the traditional power source structure, but also brings complexity and uncontrollable factors to the short-circuit current calculation and stability analysis of the power grid due to the intermittency and uncertainty of its output.

[0003] Currently, in order to reflect the influence of AC-DC coupling on the sending-end power of the power system, researchers usually use the short-circuit ratio as an evaluation index. In existing methods, the short-circuit ratio calculation of the sending-end power grid mainly focuses on the case where synchronous generators are the main power sources, and evaluates the strength of the power grid by calculating the ratio of the short-circuit current to the system rated current under short-circuit faults. For the multi-outfeed short-circuit ratio, the Thevenin equivalent method is mainly used to establish a simplified model of the AC-DC system, so as to consider the influence brought by DC coupling to the traditional short-circuit ratio. However, the coupling effect between new energy sources connected to the grid through power electronic devices has significantly changed the characteristics of the short-circuit current, and these changes include but are not limited to: waveform distortion of the short-circuit current, fast response characteristics, and dynamic behavior of new energy generation units during faults. In existing methods, the influence of new energy power stations on the multi-outfeed short-circuit ratio is often ignored, resulting in inaccurate calculation results and difficulty in comprehensively reflecting the true situation of the power grid under short-circuit faults, which not only affects the safety and stability assessment of the power grid, but also may mislead the design of subsequent power grid planning, protection, and control measures. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for obtaining the multi-outfeed short-circuit ratio of a sending-end power grid and related devices to solve one or more of the above-mentioned technical problems. The technical solution disclosed by the present invention is specifically a calculation scheme for the multi-outfeed short-circuit ratio of a sending-end power grid considering new energy coupling. For the calculation of the multi-outfeed short-circuit ratio, it is corrected on the basis of considering new energy coupling, overcomes the deficiencies of the existing technology, improves the accuracy and reliability of the power grid short-circuit current calculation, and provides strong support for the safe and stable operation of the power grid.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In the first aspect of the present invention, a method for obtaining the multi-outfeed short-circuit ratio of a sending-end power grid is provided, including the following steps: Obtain a simplified model of the multi-outfeed HVDC transmission system of the power system to be evaluated; Based on the simplified model of the multi-outfeed HVDC transmission system, considering the interaction between the two HVDC lines, calculate the equivalent power impact generated in the other HVDC line when the active and reactive powers of each single HVDC line are disturbed; based on the equivalent power impact generated in the other HVDC line when the active and reactive powers of each single HVDC line are disturbed, use the superposition principle to calculate the equivalent power impact of each single HVDC line affected by all the other HVDC lines. Combined with the transmission power of each single HVDC line itself and the equivalent power impact affected by all the other HVDC lines, as well as the short-circuit capacity of the converter station bus corresponding to each single HVDC line in the power system to be evaluated, calculate the initial multi-outfeed short-circuit ratio. Combined with the correction amount of the short-circuit capacity of the converter station bus before and after the new energy grid connection, correct the initial multi-outfeed short-circuit ratio to obtain the multi-outfeed short-circuit ratio of the sending-end grid in the power system to be evaluated; wherein, the correction amount of the short-circuit capacity of the converter station bus is calculated based on the impact on the equivalent potential of the converter station bus before and after the new energy grid connection.

[0006] A further improvement of the technical solution of the present invention lies in that the step of obtaining the simplified model of the multi-outfeed HVDC transmission system of the power system to be evaluated specifically includes: Obtain the grid operation data of the power system to be evaluated; wherein, the grid operation data includes unit output, node voltage, HVDC transmission power, and grid structure information. Based on the grid operation data, establish a simplified model of the multi-outfeed HVDC transmission system. Among them, in the simplified model of the multi-outfeed HVDC transmission system, the coupling effect of the HVDC is represented by the equivalent current method, and the expression is: ; In the formula, represents the equivalent current reflecting the influence of the injected current at the bus node on the bus node . represents the mutual impedance between the bus node and the bus node . represents the self-impedance of the bus node .

[0007] A further improvement of the technical solution of the present invention lies in that the power system to be evaluated includes thermal power units and new energy units, and the new energy units at least include wind power generation and photovoltaic power generation.

[0008] A further improvement of the technical solution of the present invention lies in that, in the step of calculating the equivalent power influence generated in another DC line when the active and reactive powers of each individual DC line are disturbed, based on the simplified model of the multi-outfeed HVDC system and considering the mutual coupling effect between the two DC lines, the calculation expression is as follows: ; In the formula, represents the influence of the voltage disturbance at bus node on the active power of bus node ; represents the operation of taking the real part; represents the voltage phasor of bus node ; represents 's conjugate phasor, represents the equivalent current reflecting the influence of the injected current at bus node on bus node ; , represent the voltage values of bus node , bus node ; , represent the active and reactive powers of bus node ; represents the phase angle difference between bus node , bus node .

[0009] A further improvement of the technical solution of the present invention lies in that, in the step of calculating the equivalent power influence of each individual DC line affected by all the other DC lines by using the superposition principle based on the equivalent power influence generated in another DC line when the active and reactive powers of each individual DC line are disturbed, the calculation expression is as follows: ; In the formula, represents the equivalent power applied by the other DC lines on the -th DC line, and the converter station bus of the -th DC line is bus node ; is the number of DC lines.

[0010] A further improvement of the technical solution of the present invention lies in that, in the step of calculating the initial multi-outfeed short-circuit ratio by combining the transmission power of each individual DC line itself and the equivalent power influence of all the other DC lines, as well as the short-circuit capacity of the converter station bus corresponding to each individual DC line in the power system to be evaluated, the calculation expression is as follows: ; In the formula, Indicates the multi - sending short - circuit ratio of the nth DC loop; Indicates the AC short - circuit capacity of the converter station bus; Indicates the active power of the nth DC loop.

[0011] A further improvement of the technical solution of the present invention lies in that in the step of correcting the initial multi - sending short - circuit ratio by using the correction amount of the short - circuit capacity of the converter station bus before and after the new energy is connected to the grid to obtain the multi - sending short - circuit ratio of the sending - end power grid in the power system to be evaluated, the calculation expression is: ; In the formula, represents the multi - sending short - circuit ratio of the sending - end power grid in the power system to be evaluated, which is the DC - corrected multi - sending short - circuit ratio considering the influence of new - energy coupling; represents the AC short - circuit capacity of the converter station bus; is the short - circuit capacity correction amount of the converter station bus node ; Indicates the active power of the nth DC loop; represents the equivalent power applied by the remaining DCs on the nth DC loop; ; ; ; In the formula, represents the number of new - energy power stations; represents the change amount of the equivalent potential of the power station before and after the new energy is connected to the grid; Indicates the th new - energy power station and the Thevenin equivalent impedance between the bus node ; represents the voltage value of the bus node ; represents the equivalent potential of the power station before the new energy is connected to the grid, represents the equivalent potential of the power station after the new energy is connected to the grid.

[0012] In the second aspect of the present invention, a system for obtaining the multi - sending short - circuit ratio of the sending - end power grid is provided, including: A model acquisition module, configured to acquire a simplified model of the multi - sending DC power transmission system of the power system to be evaluated; The equivalent power acquisition module is configured to calculate the equivalent power impact generated in another DC line when the active and reactive powers of each single DC line are disturbed, based on the simplified model of the multi - outgoing HVDC transmission system and considering the mutual coupling effect between the two DC lines; and calculate the equivalent power impact of each single DC line from all the other DC lines by using the superposition principle based on the equivalent power impact generated in another DC line when the active and reactive powers of each single DC line are disturbed. The calculation module is configured to calculate the initial multi - outgoing short - circuit ratio by combining the transmission power of each single DC line itself, the equivalent power impact from all the other DC lines, and the short - circuit capacity of the converter station bus corresponding to each single DC line in the power system to be evaluated. The correction module is configured to correct the initial multi - outgoing short - circuit ratio by combining the correction amount of the converter station bus short - circuit capacity before and after the new energy grid connection, so as to obtain the multi - outgoing short - circuit ratio of the sending - end power grid in the power system to be evaluated; wherein, the correction amount of the converter station bus short - circuit capacity is calculated based on the impact on the equivalent potential of the converter station bus before and after the new energy grid connection.

[0013] In the third aspect of the present invention, there is provided an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the method for obtaining the multi - outgoing short - circuit ratio of the sending - end power grid as described in any one of the first aspects of the present invention is implemented.

[0014] In the fourth aspect of the present invention, there is provided a non - transitory computer - readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the method for obtaining the multi - outgoing short - circuit ratio of the sending - end power grid as described in any one of the first aspects of the present invention is implemented.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention specifically provides a calculation scheme for the multi - outgoing short - circuit ratio of the sending - end power grid considering new - energy coupling. It establishes a simplified model of the multi - DC outgoing system, evaluates the impact of DC coupling on the short - circuit ratio, and considers the impact of adjacent new - energy power stations, which can improve the accuracy of power - grid short - circuit current calculation and adapt to the current situation of large - scale access of new energy. Further specifically, the present invention evaluates the impact of new - energy coupling based on power - grid operation data and corrects the initial multi - outgoing short - circuit ratio to obtain the DC multi - outgoing short - circuit ratio considering the impact of adjacent new - energy power stations. The technical solution of the present invention takes into account the impact of new - energy coupling on the AC - DC system and improves the accuracy of power - grid short - circuit current calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art; obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a schematic flowchart of a method for obtaining the multi-outfeed short-circuit ratio of a sending-end power grid in an embodiment of the present invention; Figure 2 It is a schematic flowchart of a method for obtaining the multi-outfeed short-circuit ratio of a sending-end power grid in a specific embodiment of the present invention; Figure 3 It is an equivalent schematic diagram for calculating the mutual coupling effect between direct currents in a simplified model of a multi-outfeed HVDC transmission system in an embodiment of the present invention; Figure 4 It is a schematic diagram of a system for obtaining the multi-outfeed short-circuit ratio of a sending-end power grid in an embodiment of the present invention. Detailed implementation manners

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the drawings in the embodiments of the present invention; obviously, the described embodiments of the technical solutions are some, but not all, embodiments of the present invention.

[0019] Based on the technical solutions disclosed in the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0020] Please refer to Figure 1 , a method for obtaining the multi-outfeed short-circuit ratio of a sending-end power grid provided by an embodiment of the present invention includes the following steps: Step 1, obtain a simplified model of the multi-outfeed HVDC transmission system of the power system to be evaluated; Step 2: Based on the simplified model of the multi-outfeed HVDC system, considering the interaction between the two HVDC lines, calculate the equivalent power impact generated on the other HVDC line when the active and reactive power of each single HVDC line is disturbed; Based on the equivalent power impact generated on the other HVDC line when the active and reactive power of each single HVDC line is disturbed, use the superposition principle to calculate the equivalent power impact of each single HVDC line by the rest of all HVDC lines. Step 3: Combine the transmission power of each single HVDC line itself, the equivalent power impact by the rest of all HVDC lines, and the short-circuit capacity of the converter station bus corresponding to each single HVDC line in the power system to be evaluated, and calculate the initial multi-outfeed short-circuit ratio. Step 4: Combine the correction amount of the short-circuit capacity of the converter station bus before and after the new energy grid connection, and correct the initial multi-outfeed short-circuit ratio to obtain the multi-outfeed short-circuit ratio of the sending-end grid in the power system to be evaluated; wherein, the correction amount of the short-circuit capacity of the converter station bus is calculated based on the impact on the equivalent potential of the converter station bus before and after the new energy grid connection.

[0021] Aiming at the problem that the existing method ignores the impact of new energy power stations on the multi-outfeed short-circuit ratio, the technical solution of the embodiment of the present invention combines the correction amount of the short-circuit capacity of the converter station bus before and after the new energy grid connection when calculating the multi-outfeed short-circuit ratio; by calculating the correction amount of the short-circuit capacity of the converter station bus based on the impact on the equivalent potential of the converter station bus before and after the new energy grid connection, and using this correction amount to correct the initial multi-outfeed short-circuit ratio, the multi-outfeed short-circuit ratio of the sending-end grid in the power system to be evaluated is obtained. Explanatory principle: The grid connection of new energy power stations will change the electrical characteristics of the grid, especially the equivalent potential and short-circuit capacity of the converter station bus; by accurately calculating the correction amount of the short-circuit capacity of the converter station bus brought by the new energy grid connection and incorporating it into the calculation of the multi-outfeed short-circuit ratio, the impact of new energy power stations on the grid can be considered more comprehensively, and the calculation result can more accurately reflect the true situation of the grid under short-circuit faults.

[0022] Aiming at the problems that the calculation results of the existing methods are inaccurate and it is difficult to comprehensively reflect the real situation of the power grid, the technical solution of the embodiment of the present invention adopts a more refined calculation step. Specifically, first, a simplified model of the multi-outfeed HVDC transmission system of the power system to be evaluated is obtained. Then, based on this model, considering the mutual coupling effect between two HVDC lines, the equivalent power influence generated in the other HVDC line when the active and reactive powers of each single HVDC line are disturbed is calculated. Next, the superposition principle is used to calculate the equivalent power influence of each single HVDC line by the rest of all HVDC lines, and combined with the transmission power of each single HVDC line itself and the equivalent power influence by the rest of all HVDC lines, as well as the short-circuit capacity of the converter station bus corresponding to each single HVDC line in the power system to be evaluated, the initial multi-outfeed short-circuit ratio is calculated. Explanation of the principle: In a multi-outfeed HVDC transmission system, there is a mutual coupling effect between each HVDC line. When the power of one HVDC line is disturbed, an equivalent power influence will be generated in other HVDC lines. By considering this mutual coupling effect and using the superposition principle for calculation, the mutual influence relationship between each HVDC line can be more accurately reflected. At the same time, by combining the transmission power of each single HVDC line itself and the short-circuit capacity of the converter station bus, the calculation results are more comprehensive and accurate, and can better reflect the real situation of the power grid under short-circuit faults.

[0023] In summary, the technical solution of the embodiment of the present invention considers the mutual coupling effect between HVDC lines: when calculating the multi-outfeed short-circuit ratio, the mutual coupling effect between two HVDC lines is fully considered. By calculating the equivalent power influence generated in the other HVDC line when the active and reactive powers of each single HVDC line are disturbed, and using the superposition principle to calculate the equivalent power influence of each single HVDC line by the rest of all HVDC lines. It combines the influence of new energy grid connection: The initial multi-outfeed short-circuit ratio is corrected by combining the correction amount of the short-circuit capacity of the converter station bus before and after new energy grid connection, where the correction amount of the short-circuit capacity of the converter station bus is calculated based on the influence on the equivalent potential of the converter station bus before and after new energy grid connection. The core effects that the technical solution of the embodiment of the present invention can achieve include: by considering the mutual coupling effect between HVDC lines and the influence of new energy grid connection, the calculated multi-outfeed short-circuit ratio is more accurate and can more comprehensively reflect the real situation of the power grid under short-circuit faults; the accurate calculation results provide a more reliable basis for the safety and stability assessment of the power grid, helping to improve the accuracy and reliability of the assessment, and thus better ensuring the safe and stable operation of the power grid; based on the more accurate calculation results of the multi-outfeed short-circuit ratio, the subsequent power grid planning, protection and control measures will be designed more reasonably and effectively, can better adapt to the actual operation situation of the power grid, and improve the overall performance and reliability of the power grid.

[0024] Please refer to Figure 2 and Figure 3 , the embodiment of the present invention proposes a calculation method for the multi-outfeed short-circuit ratio of the sending-end power grid considering new energy coupling, Figure 2The flow of the method is shown, and the method includes the following steps: Step S1: Obtain the relevant historical data of the unit output, DC transmission power, and grid operation within the power system to be calculated; among them, the relevant historical data of the power system to be calculated refers to various parameters during the operation of the power system, including but not limited to the output of new energy units, the output of thermal power units, the DC transmission power of each circuit, the bus voltage of the converter station, the phase angle difference of the converter station bus, the short-circuit capacity of the converter station bus, the installed capacity of new energy, and the impedance distribution of each line. In a specific exemplary technical solution, the actual operation data of the Northwest Power Grid in 2024 is selected, and the data set is divided, and key data such as the output of new energy units, the output of thermal power units, the DC transmission power of each circuit, the bus voltage of the converter station, the phase angle difference of the converter station bus, the short-circuit capacity of the converter station bus, the installed capacity of new energy, and the impedance distribution of each line are screened. In a specific exemplary technical solution, the above grid operation data can be obtained by using the power system analysis software PSASP. PSASP, full name "Power System Analysis Software Package", is a comprehensive power system analysis program, a software package developed by the Power System Technology Branch of the China Electric Power Research Institute for power system analysis and calculation.

[0025] Step S2: Based on the grid operation data and the system grid structure information composed of the DC and the AC system it feeds, establish a simplified model of the multi-out DC transmission system; among them, the simplified model of the multi-out DC transmission system can be constructed in the following way: Assume that for the sending-end AC system, consider two DCs among them and , calculate the voltage change caused by injecting a certain amount of current at the bus node according to the node voltage equation, and then inject current at the bus node , calculate the magnitude of the current required to cause the same voltage change, obtain the equivalent current of the injection node , and then use the equivalent current method to calculate the AC bus power caused by the DC in the DC , thereby establishing a simplified model of the multi-out DC transmission system, and its calculation expression is: ; ; In the formula, represents the injection current of node , represents the mutual impedance between the bus node and the bus node , represents the self-impedance of the bus node , represents reflecting the node Injected current The equivalent current affecting the node

[0026] Step S3: According to the simplified model of the multi - HVDC system, considering the mutual coupling effect between two HVDC lines, calculate the equivalent power generated in the other HVDC line when the active and reactive powers of a single HVDC line are disturbed; among them, the calculation expression for the influence of the disturbance of the converter bus of the th HVDC line on the active power of the converter bus of the th HVDC line is: ; In the formula, represents the influence of the disturbance of the converter bus of the th HVDC line on the active power of the converter bus of the th HVDC line, represents the equivalent current reflecting the influence of the injected current at node on node , represents the mutual impedance between bus node and bus node ; represents the self - impedance of bus node ; , represent the voltages of the converter station buses, represents the phase - angle difference of the converter station buses, , represent the active and reactive powers of the th HVDC line, represents the equivalent current reflecting the influence of the injected current at node on node ;

[0027] Step S4: Calculate the multi - HVDC coupling effect, and superimpose it with the transmission power of the HVDC itself to obtain the total equivalent power of this HVDC line; among them, as Figure 3 shown, Figure 3 in which HVDC stands for "High Voltage Direct Current", translated as "High - Voltage Direct - Current Transmission"; on the basis of the two - HVDC coupling effect, extend it to calculate the multi - HVDC coupling effect, and then calculate the multi - sending short - circuit ratio: ; ; In the formula, represents the multi - sending short - circuit ratio of the th HVDC line, ​​​Represents the AC short-circuit capacity of the commutation bus, Represents the active power of the th DC circuit, represents the equivalent power applied by the remaining DCs to the th DC circuit; Explanatorily, the superposition of each item in the multi-outlet short-circuit ratio fully considers the coupling effect of multiple DC circuits.

[0028] Step S5: Evaluate the coupling effect of new energy based on grid operation data, mainly considering the new energy supporting the DC. According to the change in the equivalent internal potential of the substation caused by the grid connection of new energy, calculate the correction amount of the system short-circuit capacity, including: ; ; In the formula, represents the change amount of the equivalent potential of the substation before and after the grid connection of new energy, represents the equivalent potential of the substation before the grid connection of new energy, represents the equivalent potential of the substation after the grid connection of new energy, is the correction amount of the short-circuit capacity of the commutation bus node , represents the number of new energy substations, represents the th new energy substation and the Thevenin equivalent impedance between the commutation bus node , represents the commutation bus voltage.

[0029] Specifically and exemplarily, the calculation of the correction amount of the short-circuit capacity is completed in Table 1. On this basis, it is necessary to correct the multi-outlet short-circuit ratio to obtain the DC multi-outlet short-circuit ratio considering the influence of adjacent new energy substations.

[0030] Table 1. Calculation of short-circuit capacity and its correction amount

[0031] Step S6: Combine the correction amount of the short-circuit capacity to correct the multi-outlet short-circuit ratio to obtain the DC multi-outlet short-circuit ratio considering the influence of adjacent new energy substations; among them, in the calculation of the traditional multi-outlet short-circuit ratio, the multi-outlet short-circuit ratio is obtained by the ratio of the short-circuit capacity of the commutation bus to the actual DC transmission power after equivalence. After considering the influence of new energy coupling, it is necessary to subtract the correction amount from the short-circuit capacity of the commutation bus to obtain the actual short-circuit capacity of the new energy AC-DC system, and then calculate the corrected multi-outlet short-circuit ratio: ; In the formula, represents the corrected multi-outlet short-circuit ratio considering the influence of new energy coupling, represents the AC short-circuit capacity of the commutation bus, is the short-circuit capacity correction of the commutation station bus node .

[0032] In a specific exemplary technical solution, according to the actual operation data of a certain power grid in 2024, under the conditions of large-scale new energy generation and small thermal power generation and full connection mode, the multi-outlet short-circuit ratio of three HVDCs and the multi-outlet short-circuit ratio considering the influence of new energy power stations are calculated, and the calculation results before and after are compared, as shown in Table 2. Compared with the short-circuit ratio calculation of the traditional method, the result obtained after correction by the new energy power station potential and equivalent impedance in the embodiment of the present invention is more accurate.

[0033] Table 2. Calculation of multi-outlet short-circuit ratio considering new energy coupling

[0034] In summary, the embodiment of the present invention provides a method for calculating the multi-outlet short-circuit ratio of a sending-end power grid considering new energy coupling. The method includes the steps of: obtaining the output of conventional units and new energy units, DC transmission power and relevant historical data of the power grid operation of the power system to be calculated; establishing a simplified model of the multi-outlet DC transmission system based on the power grid structure composed of the DC and the AC system it feeds; considering the influence of AC-DC coupling, when a disturbance occurs in the commutation station, the output power fluctuations of this DC and the remaining DCs are caused, and then the influence on the AC system is calculated to obtain the DC multi-outlet short-circuit ratio index; considering the influence of adjacent new energy power stations, the DC multi-outlet short-circuit ratio is corrected to obtain the multi-outlet short-circuit ratio index considering new energy coupling. The technical solution provided by the present invention combines the actual operation state of the power system and proposes a multi-outlet short-circuit ratio index considering the influence of new energy coupling, which can be applied to the calculation of the multi-outlet short-circuit ratio of a high-proportion new energy power grid.

[0035] The following is the device embodiment of the present invention, which can be used to execute the method embodiment of the present invention. For the details not disclosed in the device embodiment, please refer to the method embodiment of the present invention.

[0036] Please refer to Figure 4 , in the embodiment of the present invention, a system for obtaining the multi-outlet short-circuit ratio of a sending-end power grid is provided, including: a model acquisition module, configured to acquire a simplified model of the multi-outlet DC transmission system of the power system to be evaluated; The equivalent power acquisition module is configured to calculate the equivalent power influence generated on another DC line when the active and reactive powers of each single DC line are disturbed, based on the simplified model of the multi-outfeed HVDC system and considering the mutual coupling effect between the two DC lines; and calculate the equivalent power influence of each single DC line affected by all the other DC lines by using the superposition principle based on the equivalent power influence generated on another DC line when the active and reactive powers of each single DC line are disturbed. The calculation module is configured to calculate the initial multi-outfeed short-circuit ratio by combining the transmission power of each single DC line itself and the equivalent power influence of all the other DC lines, and the short-circuit capacity of the converter station bus corresponding to each single DC line in the power system to be evaluated. The correction module is configured to correct the initial multi-outfeed short-circuit ratio by combining the correction amount of the short-circuit capacity of the converter station bus before and after the integration of new energy, so as to obtain the multi-outfeed short-circuit ratio of the sending-end power grid in the power system to be evaluated; wherein, the correction amount of the short-circuit capacity of the converter station bus is calculated based on the influence on the equivalent potential of the converter station bus before and after the integration of new energy.

[0037] In an embodiment of the present invention, a computer device is provided. The computer device includes a processor and a memory. The memory is used to store a computer program. The computer program includes program instructions. The processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may also be 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. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used to execute the operations of the method for obtaining the multi-outfeed short-circuit ratio of the sending-end power grid.

[0038] In one embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in a computer device and is used to store programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and, of course, the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, and the operating system of the terminal is stored in this storage space. Moreover, one or more instructions suitable for being loaded and executed by the processor are stored in this storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM (Random Access Memory) or a non-volatile memory, such as at least one disk memory. One or more instructions stored in the computer-readable storage medium can be loaded and executed by the processor to implement the corresponding steps of the method for obtaining the multi-injection short-circuit ratio of the sending-end power grid in the above embodiment.

[0039] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, optical memories, etc.) containing computer-usable program codes.

[0040] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0041] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured product including an instruction device, and the instruction device implements the process in Figure 1One process or multiple processes and / or boxes Figure 1 The functions specified in one box or multiple boxes.

[0042] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one process or multiple processes and / or boxes Figure 1 One process or multiple processes and / or boxes Figure 1 The steps of the functions specified in one box or multiple boxes.

[0043] It should be understood that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of one or more embodiments of the present invention as described above, which are not provided in detail for the sake of brevity. The above specific embodiments of the present invention are only used for exemplary illustration or explanation of the principle of the present invention, and do not constitute a limitation to the present invention. Therefore, any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and scope of the present invention shall be included within the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for obtaining the multi-outgoing short-circuit ratio of a sending-end power grid, characterized in that Including the following steps: Obtain a simplified model of the multi-outfeed HVDC transmission system of the power system to be evaluated; Based on the simplified model of the multi-outfeed HVDC transmission system, considering the mutual coupling effect between two HVDC lines, calculate the equivalent power impact generated in the other HVDC line when the active and reactive power of each single HVDC line is disturbed; based on the equivalent power impact generated in the other HVDC line when the active and reactive power of each single HVDC line is disturbed, use the superposition principle to calculate the equivalent power impact of each single HVDC line affected by all the other HVDC lines; Combined with the transmission power of each single HVDC line itself and the equivalent power impact affected by all the other HVDC lines, as well as the short-circuit capacity of the converter station bus corresponding to each single HVDC line in the power system to be evaluated, calculate the initial multi-outfeed short-circuit ratio; Combined with the correction amount of the short-circuit capacity of the converter station bus before and after the new energy grid connection, correct the initial multi-outfeed short-circuit ratio to obtain the multi-outfeed short-circuit ratio of the sending-end grid in the power system to be evaluated; wherein, the correction amount of the short-circuit capacity of the converter station bus is calculated based on the impact on the equivalent potential of the converter station bus before and after the new energy grid connection.

2. The method for obtaining the multi-outgoing short-circuit ratio of a sending-end power grid according to claim 1, wherein The step of obtaining a simplified model of the multi-outfeed HVDC transmission system of the power system to be evaluated specifically includes: Obtain the grid operation data of the power system to be evaluated; wherein, the grid operation data includes unit output, node voltage, HVDC transmission power, and grid structure information; Based on the grid operation data, establish a simplified model of the multi-outfeed HVDC transmission system; Wherein, in the simplified model of the multi-outfeed HVDC transmission system, the coupling effect of HVDC is represented by the equivalent current method, and the expression is: ； In the formula, represents the equivalent current reflecting the injected current at the bus node and affecting the bus node; represents the mutual impedance between the bus node and the bus node; represents the self-impedance of the bus node.

3. The method for obtaining the multi-outgoing short-circuit ratio of a sending-end power grid according to claim 2, wherein The power system to be evaluated includes thermal power units and new energy units, and the new energy units at least include wind power generation and photovoltaic power generation.

4. The method for obtaining the multi-outgoing short-circuit ratio of a sending-end power grid according to claim 2, wherein In the step of calculating the equivalent power impact generated in the other HVDC line when the active and reactive power of each single HVDC line is disturbed based on the simplified model of the multi-outfeed HVDC transmission system and considering the mutual coupling effect between two HVDC lines, the calculation expression is: ； Wherein, represents the bus node the influence of voltage disturbance on the active power of the bus node ; represents the operation of taking the real part; represents the bus node voltage phasor of; represents conjugate phasor of, represents the equivalent current reflecting the influence of the injected current of the bus node on the bus node ; , represent the voltage values of the bus node , the bus node ; , represent the active and reactive powers of the bus node ; represent the phase angle difference between the bus node , the bus node .

5. The method for obtaining the multi-outgoing short-circuit ratio of a sending-end power grid according to claim 4, wherein In the step of calculating the equivalent power impact of each single HVDC line affected by all the other HVDC lines using the superposition principle based on the equivalent power impact generated in the other HVDC line when the active and reactive power of each single HVDC line is disturbed, the calculation expression is: ； In the formula, represents the equivalent power applied by the remaining DC on the th DC loop. The converter station bus of the th DC loop is the bus node ; is the number of DC loops.

6. The method for obtaining the multi-outgoing short-circuit ratio of a sending-end power grid according to claim 5, wherein, In the step of calculating the initial multi-outfeed short-circuit ratio by combining the transmission power of each single HVDC line itself and the equivalent power impact affected by all the other HVDC lines, as well as the short-circuit capacity of the converter station bus corresponding to each single HVDC line in the power system to be evaluated, the calculation expression is: ； In the formula, represents the multi-outflow short-circuit ratio of the th DC; represents the AC short-circuit capacity of the converter station bus; represents the th active power of the DC.

7. The method for obtaining the multi-outgoing short-circuit ratio of a sending-end power grid according to claim 1, wherein In the step of correcting the initial multi-outfeed short-circuit ratio by combining the correction amount of the short-circuit capacity of the converter station bus before and after the new energy grid connection to obtain the multi-outfeed short-circuit ratio of the sending-end grid in the power system to be evaluated, the calculation expression is: ； Wherein, represents the multi-outfeed short-circuit ratio of the sending-end power grid in the power system to be evaluated, which is the DC-corrected multi-outfeed short-circuit ratio considering the influence of new energy coupling; represents the AC short-circuit capacity of the converter station bus; is the short-circuit capacity correction amount of the converter station bus node ; represents the active power of the th DC line; represents the equivalent power applied by the remaining DC lines to the th DC line; ； ； Wherein, represents the number of new energy power stations; represents the change in the equivalent potential of the power station before and after the new energy is connected to the grid; represents the th new energy power station and the bus node The Thevenin equivalent impedance between; represents the voltage value of the bus node ; represents the equivalent potential of the power station before the new energy is connected to the grid, represents the equivalent potential of the power station after the new energy is connected to the grid.

8. A system for obtaining the multi-outgoing short-circuit ratio of a sending-end power grid, characterized in that, Including: A model acquisition module for obtaining a simplified model of the multi-outfeed HVDC transmission system of the power system to be evaluated; The equivalent power acquisition module is used to calculate the equivalent power impact generated on the other DC line when the active and reactive powers of each single DC line are disturbed, based on the simplified model of the multi-outfeed HVDC transmission system and considering the mutual coupling effect between the two DC lines; and calculate the equivalent power impact of each single DC line affected by all the other DC lines by using the superposition principle based on the equivalent power impact generated on the other DC line when the active and reactive powers of each single DC line are disturbed. The calculation module is used to calculate the initial multi-outfeed short-circuit ratio by combining the transmission power of each single DC line itself and the equivalent power impact affected by all the other DC lines, as well as the short-circuit capacity of the converter station bus corresponding to each single DC line in the power system to be evaluated. The correction module is used to correct the initial multi-outfeed short-circuit ratio by combining the correction amount of the short-circuit capacity of the converter station bus before and after the new energy grid connection, so as to obtain the multi-outfeed short-circuit ratio of the sending-end grid in the power system to be evaluated; wherein, the correction amount of the short-circuit capacity of the converter station bus is calculated based on the impact on the equivalent potential of the converter station bus before and after the new energy grid connection.

9. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the method for obtaining the multi-outfeed short-circuit ratio of the sending-end grid as described in any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method for obtaining the multi-outfeed short-circuit ratio of the sending-end grid as described in any one of claims 1 to 7.

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