A power system short-circuit current calculation method, system, device and medium

Abstract

The application discloses a kind of power system short-circuit current calculation method, system, equipment and medium.The method of the application includes: by the low voltage crossing strategy of converter and current limiter, the steady-state short-circuit current calculation model of converter is established, and the short-circuit current-voltage curve of non-synchronous machine power supply is obtained;Short-circuit current not containing non-synchronous machine power supply is calculated;According to the mutual impedance of short-circuit current not containing non-synchronous machine power supply and node impedance matrix, the residual voltage of each node is calculated;According to residual voltage and the short-circuit current-voltage curve of non-synchronous machine power supply, the short-circuit current injected by non-synchronous machine power supply is obtained;Using the mutual impedance of node impedance matrix, the influence of short-circuit current injected by non-synchronous machine power supply on fault point voltage is obtained, which forms a new boundary condition in combination with the boundary condition that fault point voltage is zero, and the short-circuit current of fault point is recalculated.The application can effectively evaluate the contribution of flexible HVDC transmission technology and new energy to power grid short-circuit current.

Description

Technical Field

[0001] This invention belongs to the field of power system technology, specifically a method, system, equipment, and medium for calculating short-circuit current in power systems including flexible DC and new energy sources. Background Technology

[0002] As the scale of new energy integration continues to expand globally, especially with the increasing proportion of renewable energy sources such as wind power and photovoltaics, new challenges are being brought to the power system.

[0003] The integration of renewable energy sources into power systems has not only accelerated the green transformation of the power grid but has also raised unique challenges in short-circuit current calculation compared to traditional power systems. In particular, with the widespread application of power electronic equipment in the power grid, the short-circuit current contribution of these devices has become an increasingly significant factor. Compared to traditional synchronous machines, the short-circuit current contribution mechanism of power electronic equipment differs. Existing short-circuit current calculation methods mainly focus on calculations for single devices or small-scale systems, lacking a universal calculation model applicable to power grids containing flexible DC transmission and large-scale renewable energy sources. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this invention proposes a method, system, device, and medium for calculating short-circuit current in large-scale power systems containing flexible DC transmission and new energy sources. It combines different low-voltage ride-through strategies to construct a short-circuit current calculation model applicable to power grids containing flexible DC transmission and large-scale new energy sources. This model takes into account that the short-circuit current has rapidly entered a steady state before the circuit breaker operates, so as to effectively evaluate the contribution of flexible DC transmission technology and new energy sources to the short-circuit current of the power grid.

[0005] Therefore, the present invention adopts the following technical solution.

[0006] In a first aspect, the present invention provides a method for calculating short-circuit current in a power system, comprising:

[0007] A calculation model for the steady-state short-circuit current of the converter is established by using the converter's low-voltage ride-through strategy and current limiter.

[0008] Based on the converter steady-state short-circuit current calculation model, the short-circuit current-voltage curve of the asynchronous power supply is obtained through simulation.

[0009] Calculate the short-circuit current excluding the asynchronous machine power supply;

[0010] The residual voltage of each node is calculated based on the short-circuit current excluding the asynchronous power supply and the mutual impedance of the node impedance matrix.

[0011] Based on the residual voltage at the asynchronous power supply access node and the short-circuit current-voltage curve of the asynchronous power supply, the short-circuit current injected by the asynchronous power supply is obtained.

[0012] By utilizing the mutual impedance of the node impedance matrix, the effect of the short-circuit current injected by the asynchronous machine power supply on the fault point voltage is determined. This effect, combined with the boundary condition that the fault point voltage is zero, forms a new boundary condition, and the fault point short-circuit current is recalculated.

[0013] This invention first obtains the short-circuit current-voltage curve of asynchronous power sources (new energy power plants and flexible DC power), and then uses a short-circuit current calculation model to calculate the short-circuit current.

[0014] Furthermore, when the low voltage ride-through strategy is a reactive power priority limiting strategy, the asynchronous power supply prioritizes the generation of reactive current to support the system voltage, and the remaining capacity generates active current; when the command value of reactive current exceeds the limit value, the current limiter limits it to the limit value, at which time the active current command is 0; when the command value of reactive current does not exceed the limit value, the current limiter does not operate, and the remaining capacity generates active current.

[0015] Furthermore, when the low voltage ride-through strategy is an active power priority limiting strategy, the asynchronous machine power supply prioritizes the generation of active current, and the remaining capacity generates reactive current; when the command value of the active current exceeds the limit value, the current limiter limits it to the limit value, at which time the reactive current command is 0; when the command value of the active current does not exceed the limit value, the current limiter does not operate, and the remaining capacity generates reactive current.

[0016] Furthermore, when the low voltage ride-through strategy is a proportional limiting strategy, the asynchronous power supply issues active and reactive currents according to a fixed power factor. When the current command value exceeds the limit value, the active and reactive current command values ​​are issued according to the fixed power factor; when the active current command value does not exceed the limit value, the current limiter does not operate.

[0017] Furthermore, the specific steps for calculating the short-circuit current excluding asynchronous power supplies are as follows: obtain the node admittance matrix based on the power flow data, and inverse the node admittance matrix to obtain the node impedance matrix; and write the short-circuit current calculation formula based on the boundary condition that the fault point voltage is zero, and obtain the short-circuit current from the calculation formula.

[0018] Furthermore, the formula for calculating the residual pressure at each node is as follows:

[0019] ,

[0020] in, For nodes i Residual pressure, For nodes i The voltage before the fault, Represents the nodes in the nodal impedance matrix i and the point of failure fmutual impedance between This indicates that the short-circuit current does not include the power supply of the asynchronous machine.

[0021] Furthermore, the specific steps to obtain the short-circuit current injected by the asynchronous power supply are as follows: For the asynchronous power supply access node, substitute the residual voltage into the short-circuit current-voltage curve of the asynchronous power supply to obtain the short-circuit current injected by the asynchronous power supply, and calculate the active and reactive components separately.

[0022] In a second aspect, the present invention provides a power system short-circuit current calculation system, comprising:

[0023] Current Calculation Model Establishment Unit: Used to establish a steady-state short-circuit current calculation model for the converter;

[0024] Short-circuit current-voltage curve acquisition unit: used to obtain the short-circuit current-voltage curve of the asynchronous power supply through simulation based on the converter steady-state short-circuit current calculation model;

[0025] First short-circuit current acquisition unit: used to calculate the short-circuit current excluding asynchronous machine power supply;

[0026] Node residual voltage calculation unit: used to calculate the residual voltage of each node based on the short-circuit current excluding the asynchronous machine power supply and the mutual impedance of the node impedance matrix.

[0027] The second short-circuit current acquisition unit is used to obtain the short-circuit current injected by the asynchronous power supply based on the residual voltage of the asynchronous power supply access node and the short-circuit current-voltage curve of the asynchronous power supply.

[0028] The third short-circuit current acquisition unit: using the mutual impedance of the node impedance matrix, the influence of the short-circuit current injected by the asynchronous machine power supply on the fault point voltage is obtained. This influence, combined with the boundary condition that the fault point voltage is zero, forms a new boundary condition, and the fault point short-circuit current is re-obtained.

[0029] Thirdly, the present invention provides a computer device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method.

[0030] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described method.

[0031] This invention addresses the problem of short-circuit current calculation for asynchronous power sources, constructing a short-circuit current calculation model applicable to power grids containing flexible DC and large-scale renewable energy. The calculation results obtained from this model effectively assess the contribution of flexible DC and renewable energy to the short-circuit current of the power system. This not only provides theoretical support for power system planning and design, relay protection settings, and electrical equipment selection and verification, but is also particularly suitable for modern power systems containing large-scale renewable energy, helping to improve the security and stability of the power grid. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a flowchart of a method for calculating short-circuit current in a power system according to the present invention;

[0034] Figure 2 This is a short-circuit current-voltage curve diagram when the power factor PF=0 in a specific embodiment of the present invention;

[0035] Figure 3 This is a short-circuit current-voltage curve diagram when the power factor PF = 0.33 in a specific embodiment of the present invention;

[0036] Figure 4 This is a short-circuit current-voltage curve diagram when the power factor PF = 0.67 in a specific embodiment of the present invention;

[0037] Figure 5 This is a short-circuit current-voltage curve diagram when the power factor PF=1 in a specific embodiment of the present invention;

[0038] Figure 6 This is a diagram illustrating the composition of a power system short-circuit current calculation system according to the present invention.

[0039] Figure 7 This is a schematic diagram of the logical structure of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] This embodiment provides a method for calculating short-circuit current in a power system, such as... Figure 1 As shown, the steps are as follows:

[0043] Step (1): Establish a calculation model for the steady-state short-circuit current of the converter through the low-voltage ride-through strategy and current limiter of the converter;

[0044] Step (2): Based on the converter steady-state short-circuit current calculation model, the short-circuit current-voltage curve of the asynchronous power supply is obtained through simulation.

[0045] Step (3): Calculate the short-circuit current excluding the asynchronous machine power supply;

[0046] Step (4): Based on the short-circuit current excluding the asynchronous power supply and the mutual impedance of the node impedance matrix, the residual voltage of each node is calculated.

[0047] Step (5): Based on the residual voltage of the asynchronous machine power supply access node and the short-circuit current-voltage curve of the asynchronous machine power supply, the short-circuit current injected by the asynchronous machine power supply is obtained.

[0048] Step (6): Using the mutual impedance of the node impedance matrix, the effect of the short-circuit current injected by the asynchronous machine power supply on the fault point voltage is obtained. This effect, combined with the boundary condition that the fault point voltage is zero, forms a new boundary condition, and the fault point short-circuit current is re-observed.

[0049] Step (1) establishes a steady-state short-circuit current calculation model for the converter using the converter's low-voltage ride-through strategy and current limiter. The specific details are as follows:

[0050] Synchronous power supplies typically employ PV or PQ control in steady state. When an AC fault occurs, the PCC voltage drops. If the voltage drop is significant, PV or PQ control can cause the current command value to exceed the IGBT device's rated value. Therefore, a current limiting circuit is usually introduced into the control system. The current command value calculated by the outer loop is passed through the limiting circuit and then transmitted to the inner current loop for control. In this case, the asynchronous machine can be considered a current source. Different low-voltage ride-through strategies determine the output current characteristics of asynchronous power supplies (new energy power plants and flexible DC power). Common low-voltage ride-through strategies include reactive power priority limiting strategy, active power priority limiting strategy, and proportional limiting strategy.

[0051] a. Reactive power priority constraint strategy

[0052] In this situation, the asynchronous power supply prioritizes reactive current to support the system voltage, and the remaining capacity generates active current. The active and reactive current command values ​​are:

[0053] (1)

[0054] In the formula, I lim This is the converter current limiting value; i vd and i vq These are the command values ​​for the d-axis and q-axis current components of the inner-loop current controller that have not passed through the current limiter. i vd * and i vq * These are the command values ​​for the d-axis and q-axis current components of the inner loop current controller after passing through the current limiter.

[0055] When the reactive current command value exceeds the limit value, the current limiter limits it to the limit value, at which point the active current command is 0; when the reactive current command value does not exceed the limit value, the current limiter does not operate, and the remaining capacity generates active current.

[0056] b. Active power priority restriction strategy

[0057] In this situation, the asynchronous power supply prioritizes generating active current to avoid a significant active current surge on the system, while the remaining capacity generates reactive current. The active and reactive current command values ​​are:

[0058] (2)

[0059] When the active current command value exceeds the limit value, the current limiter limits it to the limit value, at which point the reactive current command is 0; when the active current command value does not exceed the limit value, the current limiter does not operate, and the remaining capacity outputs reactive current.

[0060] c. Proportional Limitation Strategy

[0061] In this case, the asynchronous power supply generates active and reactive currents according to a fixed power factor, and the active and reactive current command values ​​are:

[0062] (3)

[0063] In the formula, The power factor during low-level wear; i v The amplitude of the current command value before limiting is equal to the arithmetic square root of the sum of the squares of the active current command value and the reactive current command value.

[0064] When the command value of the current exceeds the limit, the command values ​​of the active and reactive currents are issued according to the fixed power factor; when the command value of the active current does not exceed the limit, the current limiter does not operate.

[0065] Step (2): Based on the converter steady-state short-circuit current calculation model (Equations (1) to (3)), the short-circuit current-voltage curves of asynchronous power supplies (new energy power plants and flexible DC power) are obtained through simulation. The specific details are as follows:

[0066] Unlike renewable energy power plants, UHV flexible DC transmission systems do not contain a large number of asynchronous power sources, meaning their short-circuit current-voltage curves can be directly determined by the low-voltage drive-through strategy. However, for renewable energy power plants composed of numerous asynchronous power sources, a simulation strategy is set based on the converter steady-state short-circuit current calculation model. The short-circuit current-voltage curves of the asynchronous power sources (renewable energy power plants and flexible DC transmission systems) are obtained based on the simulation results. I d = f ( U ), I q = f ( U ), I d Indicates active current. I q This represents reactive current.

[0067] Step (3) calculates the short-circuit current excluding asynchronous power supplies. Specifically, the node admittance matrix is ​​obtained from the power flow data, and the node impedance matrix is ​​obtained by inverting the node admittance matrix. The node voltage equations of the fault component network are written, and the short-circuit current calculation formula is written based on the boundary condition that the fault point voltage is zero. The short-circuit current is obtained from the calculation formula.

[0068] The nodal voltage equations of the fault component network are as follows:

[0069] (4)

[0070] In the formula, (i, j = 1, 2, ..., n and i ≠ j) are the nodes in the nodal impedance matrix. i and j Mutual impedance between them; For nodes i Self-impedance; for i Voltage deviation; To inject current at the fault point; This indicates that the short-circuit current does not include the power supply of the asynchronous machine.

[0071] Based on the boundary condition that the voltage at the fault point is zero, the short-circuit current calculation formula is as follows:

[0072]

[0073] In the formula, The voltage at the fault point;

[0074] The short-circuit current (initial subtransient current) at the fault point can be obtained as follows:

[0075]

[0076] In the formula, The voltage at the fault point before the fault can be selected based on the power flow calculation method, depending on the short-circuit current calculation method.

[0077] Step (4): The residual voltage of each node is calculated based on the short-circuit current excluding the asynchronous power supply and the mutual impedance of the node impedance matrix.

[0078] The residual voltage at each node can be calculated based on the node impedance matrix and short-circuit current, as follows:

[0079]

[0080] In the formula, For nodes i Residual pressure, For nodes i The voltage before the fault, Represents the nodes in the nodal impedance matrix i and the point of failure f The mutual impedance between them.

[0081] Step (5): Based on the residual voltage of the asynchronous power supply access node and the short-circuit current-voltage curve of the asynchronous power supply, the short-circuit current injected by the asynchronous power supply is obtained.

[0082] For the asynchronous machine power supply access node, substitute the node residual voltage into the short-circuit current-voltage curve of the asynchronous machine power supply to obtain the short-circuit current injected by the asynchronous machine power supply. The active and reactive components are calculated separately.

[0083]

[0084] In the formula, , These are the active current and reactive current injected into the asynchronous machine power supply node, respectively. f This is the short-circuit current-voltage curve.

[0085] Step (6): Using the mutual impedance of the node impedance matrix, the effect of the short-circuit current injected by the asynchronous machine power supply on the fault point voltage is obtained (it will increase the fault component of the fault point voltage). This effect, combined with the boundary condition that the fault point voltage is zero, forms a new boundary condition, and the fault point short-circuit current is re-observed.

[0086]

[0087] In the formula, Represents the fault point in the nodal impedance matrix f Mutual impedance between the asynchronous machine power supply node i; This represents the short-circuit current injected into the power node i of the asynchronous machine.

[0088]

[0089] The short-circuit current (initial subtransient current) at the fault point of the asynchronous power supply can be considered as follows:

[0090]

[0091] Thus, the short-circuit current considering the asynchronous power supply is obtained. By setting the convergence accuracy and iterating through steps (4)-(6), the short-circuit current at the specified accuracy can be obtained.

[0092] A case study was conducted on a specific power grid to verify the effectiveness of the short-circuit current calculation method of this invention. The short-circuit current-voltage curves of the aforementioned renewable energy power plants were used as the port characteristics of all renewable energy power plants, such as... Figures 2 to 5 As shown. Both new energy sources and flexible DC transmission employ the same low-voltage ride-through strategy, using a proportional current-limiting strategy. That is, during low-voltage ride-through, active and reactive power are generated at a fixed ratio, PF=0 respectively (see...). Figure 2 ), 0.33 (see) Figure 3 ), 0.67 (see) Figure 4 ), 1 (see Figure 5 ).

[0093] The ASCC short-circuit current calculation results in PSS\E were compared with the calculation results of the Python program without asynchronous power supply. The two were used with the same boundary conditions and the results were found to be completely consistent, which proved the correctness of the node impedance matrix obtained by the program.

[0094] Next, the contribution of asynchronous power supplies to the short-circuit currents of 525kV and 230kV buses under different low-voltage strategies was analyzed. The results are shown in Table 1. As the power factor increases, the active component of the short-circuit current gradually increases, while the reactive component gradually decreases, which is consistent with the theory. The calculation results for the four power factors mostly converged after one iteration, proving the convergence of the method of this invention.

[0095] Table 1 Calculation results of short-circuit current of a power grid

[0096]

[0097] The method of this invention can evaluate the contribution of flexible DC and new energy sources to the short-circuit current of the power system and has good engineering applicability.

[0098] Example 2

[0099] This embodiment provides a power system short-circuit current calculation system to implement the power system short-circuit current calculation method described in Embodiment 1, such as... Figure 6 As shown, it consists of a current calculation model establishment unit, a short-circuit current-voltage curve acquisition unit, a first short-circuit current acquisition unit, a node residual voltage calculation unit, a second short-circuit current acquisition unit, and a third short-circuit current acquisition unit.

[0100] Current calculation model establishment unit: used to establish the steady-state short-circuit current calculation model of the converter.

[0101] Short-circuit current-voltage curve acquisition unit: used to obtain the short-circuit current-voltage curve of the asynchronous power supply through simulation based on the converter steady-state short-circuit current calculation model.

[0102] First short-circuit current acquisition unit: used to calculate the short-circuit current excluding asynchronous power supplies.

[0103] Node residual voltage calculation unit: used to calculate the residual voltage of each node based on the short-circuit current excluding the asynchronous power supply and the mutual impedance of the node impedance matrix.

[0104] The second short-circuit current acquisition unit is used to obtain the short-circuit current injected by the asynchronous power supply based on the residual voltage of the asynchronous power supply access node and the short-circuit current-voltage curve of the asynchronous power supply.

[0105] The third short-circuit current acquisition unit: using the mutual impedance of the node impedance matrix, the influence of the short-circuit current injected by the asynchronous machine power supply on the fault point voltage is obtained. This influence, combined with the boundary condition that the fault point voltage is zero, forms a new boundary condition, and the fault point short-circuit current is re-obtained.

[0106] It should be noted that each unit in the aforementioned power system short-circuit current calculation system can be implemented entirely or partially through software, hardware, or a combination thereof. These units can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each unit. For specific limitations regarding the power system short-circuit current calculation system, please refer to the limitations of the power system short-circuit current calculation method (i.e., Embodiment 1) above; both have the same function and role, and will not be repeated here.

[0107] Example 3

[0108] This embodiment provides a computer device, including: at least one processor; and a memory communicatively connected to the at least one processor. The memory stores a computer program executable by the at least one processor, which, when executed by the at least one processor, causes the electronic device to perform the method according to Embodiment 1 of the present invention.

[0109] Example 4

[0110] This embodiment provides a non-transitory computer-readable storage medium storing a computer program, wherein the computer program, when executed by a computer's processor, is used to cause the computer to perform the method according to Embodiment 1 of the present invention.

[0111] refer to Figure 7 The present invention will now be described in the form of a structural block diagram of an electronic device 400 that can serve as a server or client of the present invention, which is an example of a hardware device that can be applied to various aspects of the present invention. The electronic device is intended to represent various forms of digital electronic computer devices, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the invention described and / or claimed herein.

[0112] like Figure 7 As shown, the electronic device 400 includes a computing unit 401, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 402 or a computer program loaded from a storage unit 408 into a random access memory (RAM) 403. The RAM 403 may also store various programs and data required for the operation of the electronic device 400. The computing unit 401, ROM 402, and RAM 403 are interconnected via a bus 404. An input / output (I / O) interface 405 is also connected to the bus 404.

[0113] Multiple components in electronic device 400 are connected to I / O interface 405, including: input unit 406, output unit 407, storage unit 408, and communication unit 409. Input unit 406 can be any type of device capable of inputting information to electronic device 400. Input unit 406 can receive input digital or character information and generate key signal inputs related to user settings and / or function control of electronic device. Output unit 407 can be any type of device capable of presenting information and may include, but is not limited to, a display, speaker, video / audio output terminal, vibrator, and / or printer. Storage unit 408 may include, but is not limited to, disks and optical discs. Communication unit 409 allows electronic device 400 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks, and may include, but is not limited to, modems, network cards, infrared communication devices, wireless communication transceivers, and / or chipsets, such as Bluetooth™ devices, WiFi devices, WiMax devices, cellular communication devices, and / or the like.

[0114] The computing unit 401 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the computing unit 401 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, a digital signal processor (DSP), and any suitable processor, controller, microcontroller, etc. The computing unit 401 performs the various methods and processes described above. For example, in some embodiments, the aforementioned power system short-circuit current calculation method can be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as storage unit 408. In some embodiments, part or all of the computer program can be loaded and / or installed on the electronic device 400 via ROM 402 and / or communication unit 409. In some embodiments, the computing unit 401 can be configured to perform the aforementioned power system short-circuit current calculation method by any other suitable means (e.g., by means of firmware).

[0115] The program code used to implement the methods of the present invention can be written in any combination of one or more programming languages. This program code can be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing device, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a standalone software package partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0116] In the context of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0117] As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any computer program product, device, and / or apparatus (e.g., disk, optical disk, memory, programmable logic device (PLD)) for providing machine instructions and / or data to a programmable processor, including machine-readable media that receive machine instructions as machine-readable signals. The term "machine-readable signal" refers to any signal for providing machine instructions and / or data to a programmable processor.

[0118] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device for displaying information to the user (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor); and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the computer. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0119] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as a data server), or computing systems that include middleware components (e.g., an application server), or computing systems that include frontend components (e.g., a user computer with a graphical user interface or web browser through which a user can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., a communication network). Examples of communication networks include local area networks (LANs), wide area networks (WANs), and the Internet.

[0120] Computer systems can include clients and servers. Clients and servers are generally located far apart and typically interact through communication networks. Client-server relationships are created by computer programs running on the respective computers and having a client-server relationship with each other.

[0121] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to the above embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A method for calculating short-circuit current in a power system, characterized in that, include: A calculation model for the steady-state short-circuit current of the converter is established by using the converter's low-voltage ride-through strategy and current limiter. Based on the converter steady-state short-circuit current calculation model, the short-circuit current-voltage curve of the asynchronous power supply is obtained through simulation. Calculate the short-circuit current excluding the asynchronous machine power supply; The residual voltage of each node is calculated based on the short-circuit current excluding the asynchronous power supply and the mutual impedance of the node impedance matrix. Based on the residual voltage at the asynchronous power supply access node and the short-circuit current-voltage curve of the asynchronous power supply, the short-circuit current injected by the asynchronous power supply is obtained. By utilizing the mutual impedance of the node impedance matrix, the effect of the short-circuit current injected by the asynchronous machine power supply on the fault point voltage is determined. This effect, combined with the boundary condition that the fault point voltage is zero, forms a new boundary condition, and the fault point short-circuit current is recalculated.

2. The method for calculating short-circuit current in a power system according to claim 1, characterized in that, When the low voltage ride-through strategy is a reactive power priority limiting strategy, the asynchronous power supply prioritizes the generation of reactive current to support the system voltage, and the remaining capacity generates active current. When the command value of reactive current exceeds the limit value, the current limiter limits it to the limit value, at which time the active current command is 0. When the command value of reactive current does not exceed the limit value, the current limiter does not operate, and the remaining capacity generates active current.

3. The method for calculating short-circuit current in a power system according to claim 1, characterized in that, When the low voltage ride-through strategy is an active power priority limiting strategy, the asynchronous machine power supply prioritizes the generation of active current, and the remaining capacity generates reactive current. When the command value of the active current exceeds the limit value, the current limiter limits it to the limit value, at which time the reactive current command is 0. When the command value of the active current does not exceed the limit value, the current limiter does not operate, and the remaining capacity generates reactive current.

4. The method for calculating short-circuit current in a power system according to claim 1, characterized in that, When the low voltage ride-through strategy is a proportional limiting strategy, the asynchronous power supply issues active and reactive currents according to a fixed power factor. When the current command value exceeds the limit value, the active and reactive current command values ​​are issued according to the fixed power factor; when the active current command value does not exceed the limit value, the current limiter does not operate.

5. The method for calculating short-circuit current in a power system according to claim 1, characterized in that, The specific steps for calculating the short-circuit current excluding asynchronous power supplies are as follows: obtain the node admittance matrix based on the power flow data, and inverse the node admittance matrix to obtain the node impedance matrix; write the short-circuit current calculation formula based on the boundary condition that the fault point voltage is zero, and obtain the short-circuit current from the calculation formula.

6. The method for calculating short-circuit current in a power system according to claim 1, characterized in that, The formulas for calculating the residual pressure at each node are as follows: ， in, For nodes i Residual pressure, For nodes i The voltage before the fault, Represents the nodes in the nodal impedance matrix i and the point of failure f mutual impedance between This indicates that the short-circuit current does not include the power supply of the asynchronous machine.

7. The method for calculating short-circuit current in a power system according to claim 1, characterized in that, The specific steps to obtain the short-circuit current injected by the asynchronous power supply are as follows: For the asynchronous power supply access node, substitute the residual voltage into the short-circuit current-voltage curve of the asynchronous power supply to obtain the short-circuit current injected by the asynchronous power supply, and calculate the active and reactive components separately.

8. A power system short-circuit current calculation system, characterized in that, include: Current Calculation Model Establishment Unit: Used to establish a steady-state short-circuit current calculation model for the converter; Short-circuit current-voltage curve acquisition unit: used to obtain the short-circuit current-voltage curve of the asynchronous power supply through simulation based on the converter steady-state short-circuit current calculation model; First short-circuit current acquisition unit: used to calculate the short-circuit current excluding asynchronous machine power supply; Node residual voltage calculation unit: used to calculate the residual voltage of each node based on the short-circuit current excluding the asynchronous machine power supply and the mutual impedance of the node impedance matrix. The second short-circuit current acquisition unit is used to obtain the short-circuit current injected by the asynchronous power supply based on the residual voltage of the asynchronous power supply access node and the short-circuit current-voltage curve of the asynchronous power supply. The third short-circuit current acquisition unit: using the mutual impedance of the node impedance matrix, the influence of the short-circuit current injected by the asynchronous machine power supply on the fault point voltage is obtained. This influence, combined with the boundary condition that the fault point voltage is zero, forms a new boundary condition, and the fault point short-circuit current is re-obtained.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

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