Method and system for improving short-circuit calculation convergence of new energy access power system

Abstract

This invention provides a method and system for improving the convergence of short-circuit calculations in power systems connected to renewable energy sources. The method includes aggregating equivalent values ​​of renewable energy sources in the renewable energy power plants connected to the power system to generate first and second renewable energy equivalent models; performing initial short-circuit calculations to determine the initial voltages of all nodes in the power system without considering the output of the second renewable energy equivalent model; after a short-circuit fault occurs, dividing the power system into a fault near-zone and a fault far-zone based on the initial voltages; treating the second renewable energy equivalent model in the fault far-zone as an open circuit and the second renewable energy equivalent model in the fault near-zone as a voltage-controlled current source model, and performing iterative short-circuit calculations to determine the system's short-circuit convergence. This method and system effectively solve the problem of balancing short-circuit calculation convergence and accuracy when renewable energy is connected, laying the foundation for relay protection setting calculations and correct protection operation in new power systems.

Description

Technical Field

[0001] This invention relates to the field of relay protection setting technology, and more specifically, to a method and system for improving the convergence of short-circuit calculations in new energy power systems. Background Technology

[0002] Relay protection (referred to as protection) is the "first line of defense" for the safe and stable operation of a power system. It bears the heavy responsibility of quickly, reliably, sensitively, and selectively isolating faulty electrical components and ensuring the safe operation of the power system. The circuit breaker's opening is determined by judging whether electrical characteristic quantities reach the operating settings; therefore, the setting of relay protection operating settings directly affects the protection's fault isolation performance. Setting calculation is the process of modeling power system fault scenarios, calculating the distribution of short-circuit current in the system after a fault, and setting the protection operating settings accordingly.

[0003] Compared to conventional power sources, new power systems with an increasing proportion of renewable energy exhibit strong controllability during fault processes. Traditional methods of equating renewable energy with linear components such as constant current sources cannot guarantee the accuracy of short-circuit calculations. Therefore, nonlinear models such as voltage-controlled current sources are gradually being used in main grid protection setting calculation software to equate renewable energy, and short-circuit calculations are performed iteratively. In this process, the iterative convergence of the short-circuit calculation results means that almost all conditions, including KCL, KVL, Ohm's law, and renewable energy control constraints, are met simultaneously. As the number of renewable energy nodes increases, the convergence of the calculation gradually decreases, leading to situations where the system fails to converge and short-circuit current results cannot be obtained once the renewable energy integration scale is slightly higher. Summary of the Invention

[0004] To address the technical problem that the convergence of short-circuit calculations using nonlinear models to approximate new energy sources gradually decreases as the scale of new energy integration increases, this invention provides a method and system for improving the convergence of short-circuit calculations in power systems with new energy integration, thereby enhancing the convergence of calculations without reducing the accuracy of short-circuit calculations in power systems containing new energy sources.

[0005] According to one aspect of the present invention, the present invention provides a method for improving the convergence of short-circuit calculations for new energy sources integrated into a power system, the method comprising: For new energy generating units with the same control strategy in new energy power stations connected to the power system, the grid-connected capacity of the new energy generating units is aggregated and equivalent to generate the first new energy equivalent model. The first new energy equivalent model with different control strategies and connected to a common node is aggregated and equivalent to generate the second new energy equivalent model. Initial short-circuit calculations are performed without considering the output of the second new energy equivalent model to determine the initial voltage of all nodes in the power system; After a short-circuit fault occurs, the power system is divided into a fault near zone and a fault far zone based on the initial voltage. The equivalent model of the second new energy source in the far-fault area is regarded as an open circuit, and the equivalent model of the second new energy source in the near-fault area is regarded as a voltage-controlled current source model. Short-circuit iterative calculation is performed to determine the fault components of all node voltages in each iteration. The short-circuit iteration calculation ends when the number of iterations is not greater than the set iteration limit and the fault components of all node voltages meet the set iteration convergence criterion.

[0006] According to another aspect of the present invention, the present invention provides a system for improving the short-circuit calculation convergence of new energy access to the power system, the system comprising: The first model unit is used to aggregate and equate new energy generating units with the same control strategy in new energy power stations connected to the power system according to the grid-connected capacity of the new energy generating units to generate the first new energy equivalent model. The second model unit is used to aggregate and equate the first new energy equivalent models with different control strategies and connected to a common node to generate the second new energy equivalent model. The initial voltage unit is used to perform initial short-circuit calculations without considering the output of the second new energy equivalent model, and to determine the initial voltage of all nodes in the power system. A region division unit is used to divide the power system into a fault near zone and a fault far zone based on the initial voltage after a short-circuit fault occurs. The iterative calculation unit is used to treat the equivalent model of the second new energy source in the far-fault area as an open circuit and the equivalent model of the second new energy source in the near-fault area as a voltage-controlled current source model, and to perform short-circuit iterative calculation to determine the fault components of all node voltages in each iteration. The iteration termination unit is used to terminate the short-circuit iteration calculation when the number of iterations is not greater than the set iteration limit and the fault components of all node voltages meet the set iteration convergence criterion.

[0007] According to another aspect of the present invention, a computer-readable storage medium is provided, the storage medium storing a computer program that, when executed by a processor, implements the methods described in any of the above aspects of the present invention.

[0008] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising: a processor; a memory for storing executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the method described in any of the preceding aspects of the present invention.

[0009] The present invention discloses a method and system for improving the convergence of short-circuit calculations for renewable energy units connected to a power system. The method includes: for renewable energy units with the same control strategy in renewable energy power plants connected to the power system, performing aggregated equivalent calculations based on the grid-connected capacity of the renewable energy units to generate a first renewable energy equivalent model; performing aggregated equivalent calculations on the first renewable energy equivalent models with different control strategies but connected to a common node to generate a second renewable energy equivalent model; performing initial short-circuit calculations without considering the output of the second renewable energy equivalent model to determine the initial voltage of all nodes in the power system; after a short-circuit fault occurs, dividing the power system into a fault near zone and a fault far zone based on the initial voltage; treating the second renewable energy equivalent model in the fault far zone as an open circuit and the second renewable energy equivalent model in the fault near zone as a voltage-controlled current source model, performing iterative short-circuit calculations to determine the fault components of all node voltages in each iteration; and ending the iterative short-circuit calculation when the number of iterations is not greater than a set iteration limit and the fault components of all node voltages meet the set iterative convergence criteria. The method and system described above can significantly reduce the short-circuit calculation complexity of new energy sources while ensuring equivalent accuracy. When the calculation convergence cannot be met, it can ensure short-circuit calculation convergence by sacrificing a certain amount of calculation accuracy. This can effectively solve the problem that the convergence and accuracy of short-circuit calculation cannot be simultaneously achieved when large-scale new energy sources are connected, which makes iterative short-circuit calculation methods impractical in power systems containing new energy sources. This lays the foundation for relay protection setting calculation and correct protection operation in new power systems. Attached Figure Description

[0010] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures: Figure 1 A flowchart of a method for improving the short-circuit calculation convergence of a renewable energy access power system according to a preferred embodiment of the present invention; Figure 2 A schematic diagram of generating a first new energy equivalent model according to a preferred embodiment of the present invention; Figure 3 This is a schematic diagram comparing the terminal voltage of the new energy unit generating the first new energy equivalent model with the terminal voltage of the first new energy equivalent model according to a preferred embodiment of the present invention. Figure 4 A schematic diagram illustrating the generation of a second new energy equivalent model according to a preferred embodiment of the present invention; Figure 5 A flowchart of a method for improving the short-circuit calculation convergence of a renewable energy access power system according to another preferred embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of a system for improving the short-circuit calculation convergence of a new energy access power system according to a preferred embodiment of the present invention; Figure 7This is a schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention. Detailed Implementation

[0011] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0012] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0013] Exemplary methods Figure 1 This is a flowchart illustrating a method for improving the short-circuit calculation convergence of a renewable energy source integrated into a power system according to a preferred embodiment of the present invention. Figure 1 As shown, the method for improving the short-circuit calculation convergence of new energy access to the power system according to this preferred embodiment starts from step 101.

[0014] In step 101, for new energy generating units with the same control strategy in the new energy power stations connected to the power system, the grid-connected capacity of the new energy generating units is aggregated and equivalent to generate the first new energy equivalent model.

[0015] Preferably, generating the first new energy equivalent model by aggregating and equivalencing the grid-connected capacity of the new energy units refers to generating the first new energy equivalent model by weighted multiplication of the grid-connected capacity of the new energy units, wherein: The output current and terminal voltage of the first new energy equivalent model are expressed as follows: In the formula, When '+' is used, it represents a positive order; when '-' is used, it represents a negative order. This indicates the number of new energy generating units with the same control strategy in a new energy power station; and Indicating the first in the new energy power station Unit Sequence current and The sequence terminal voltage is a per-unit value; and These represent the first new energy equivalent model. Sequence current and Sequence terminal voltage; If the output currents of all new energy units with the same control strategy in a new energy power station are considered to be in phase, then the relationship between the output current and the terminal voltage of the first new energy equivalent model is as follows: In the formula, This indicates the output of the first new energy equivalent model. Sequence current about A function of the sequence terminal voltage.

[0016] In this preferred embodiment, since the collection lines in the new energy power station are short and the voltage drop along the line is negligible, any new energy unit with the same control strategy in any new energy power station can be equivalently multiplied by weighted multiplication based on the grid-connected capacity of the new energy unit, thereby generating the first new energy equivalent model.

[0017] Figure 2 A schematic diagram illustrating the generation of a first new energy equivalent model according to a preferred embodiment of the present invention. (See diagram below.) Figure 2 As shown, for the 14 wind turbines in the new energy power station, they can be weighted and multiplied by their grid-connected capacity in ADPSS to be equivalent to one wind turbine. Under steady-state conditions, the per-unit value of the equivalent turbine's terminal voltage is close to the average value of the terminal voltages of the 14 wind turbines before the equivalent. Its terminal voltage is as follows: Figure 3 As shown, the voltage difference between different terminals does not exceed 2%.

[0018] In step 102, the first new energy equivalent model with different control strategies and connected to a common node is aggregated and equivalent to generate the second new energy equivalent model.

[0019] Preferably, the first new energy equivalent model with different control strategies and connected to a common node is aggregated and equivalent to generate a second new energy equivalent model, including: Suppose that the common node connected to the first new energy equivalent model with different control strategies is... Sequence terminal voltage and The sequence currents are respectively and ,and ,in, for Sequence voltage amplitude; make By consistently taking per-unit values ​​within the range (0,1), each common node is determined using an iterative method. The output current corresponding to the sequence voltage, where the expression for calculating the output current is: In the formula, This indicates the number of first new energy equivalent models with different control strategies; This represents the aggregation region of the public node. Order node admittance matrix; , and These represent the first new energy equivalent models of the j-th control strategy in the aggregation region of the common node. Sequence output current, The sequence terminal voltage and its relationship as a function; According to each public node The terminal voltage of the sequence machine and its corresponding output current are aggregated and equivalent to generate the second new energy equivalent model. The order model, wherein the output characteristic expression of the second new energy equivalent model is: In the formula, The first new energy equivalent model represents the aggregation to a common node. Sequence output current about A function of the sequence terminal voltage.

[0020] After aggregating and equipping the renewable energy units at the same renewable energy power station, several renewable energy nodes with different control strategies will be formed. When these renewable energy nodes with different control strategies are connected to a common node after passing through different transformers and lines, they can be regarded as a single-port network to the outside world, and thus further aggregated into a whole. Figure 4 This is a schematic diagram illustrating the generation of a second new energy equivalent model according to a preferred embodiment of the present invention. In this preferred embodiment, three different types of new energy sources with different control strategies (denoted as power stations 1, 2, and 3) are used as examples in engineering projects. Figure 4 As shown. By first generating a first equivalent model for each power station, and then iteratively calculating the voltage and current relationship curves of the common node connecting the three new energy power stations, the feasibility of generating a second equivalent model for the new energy power station is proven. In this preferred embodiment, the expression for the output current is obtained by substituting different... Common iterative methods such as forward and backward substitution, and the Newton-Raphson method, are used to obtain each voltage. corresponding current This allows for the aggregation of various new energy sources with different control strategies into a whole, and the output characteristics of the aggregated second new energy equivalent model are obtained.

[0021] In step 103, initial short-circuit calculations are performed without considering the output of the second new energy equivalent model to determine the initial voltage of all nodes in the power system.

[0022] In step 104, after a short-circuit fault occurs, the power system is divided into a fault near zone and a fault far zone based on the initial voltage.

[0023] Preferably, after a short-circuit fault occurs, dividing the power system into a fault near zone and a fault far zone based on the initial voltage includes: The area where the initial voltage is not less than the set voltage per-unit threshold is classified as the fault far zone, and the area where the initial voltage is less than the set voltage per-unit threshold is classified as the fault near zone.

[0024] In this preferred embodiment, after the renewable energy sources in the power system are aggregated and modeled using the above steps, if the power system contains N nodes, of which M nodes are renewable energy nodes, then, without considering the output of the renewable energy nodes (i.e., assuming that the renewable energy nodes are disconnected from the grid), the initial voltage matrix of each node in the system can be obtained by performing initial short-circuit calculations. The expression for this matrix is: In the formula, to All represent non-new energy nodes in the initial short-circuit calculation. Sequence voltage, to All represent the new energy nodes in the initial short-circuit calculation. Sequence voltage.

[0025] The voltage drop in the system after a short-circuit fault will cause the renewable energy nodes to output according to the low-voltage ride-through control requirements. Sequential reactive current, thereby increasing the renewable energy node's Sequence voltage. Therefore, after considering the output of the new energy node, the short-circuit calculation yields the new energy node's... The sequence voltages will all be higher than those calculated during short circuits without considering the output of new energy nodes. The corresponding value in the table.

[0026] Based on this, renewable energy nodes are included in the calculation. According to the short-circuit calculation results of the first calculation without considering the output of renewable energy nodes, renewable energy nodes in the near-field of the fault with significant voltage drop are regarded as voltage-controlled current source models, and renewable energy nodes in the far-field of the fault with small voltage drop that have not entered the low-voltage breakdown control stage are regarded as open circuits. Specifically: In the formula, This represents the k-th new energy node among the M new energy nodes in the first short-circuit calculation result. Sequence voltage, Indicates its amplitude; Indicates according to The output of the kth new energy node is set Sequence current; This indicates the voltage amplitude at which new energy sources can enter low-voltage ride-through, which is the set voltage per-unit threshold. According to the standard, it can be set to a per-unit value of 0.85~0.90. This represents the output of the second new energy equivalent model. Sequence current about the machine terminal The zero-sequence voltage is a function of the sequence voltage. Since new energy sources are connected to the power system through transformers with at least one side ungrounded, the zero-sequence voltage is considered to be an open circuit.

[0027] In step 105, the equivalent model of the second new energy source in the far-fault area is regarded as an open circuit, and the equivalent model of the second new energy source in the near-fault area is regarded as a voltage-controlled current source model. Short-circuit iterative calculation is performed to determine the fault components of all node voltages in each iteration.

[0028] Preferably, the equivalent model of the second new energy source in the far-fault region is treated as an open circuit, and the equivalent model of the second new energy source in the near-fault region is treated as a voltage-controlled current source model. Short-circuit iterative calculations are performed to determine the fault components of all node voltages in each iteration, including: The fault components of the positive-sequence, negative-sequence, and zero-sequence voltages of all nodes in the t-th iteration are calculated using the following expression: in, N is the set iteration limit. , and These represent the positive-sequence, negative-sequence, and zero-sequence node admittance matrices of the power system, respectively. , and Let represent the positive-sequence, negative-sequence, and zero-sequence current matrices injected by all nodes in the t-th iteration, including three types of nodes: new energy nodes, fault nodes, and other nodes. When t=1, the positive-sequence current injected by the new energy node is the rated current of the new energy connected to the node, and the negative-sequence and zero-sequence currents injected by the new energy node are both 0. The positive-sequence, negative-sequence, and zero-sequence currents injected by the fault node are the fault node currents calculated without considering the short circuit when the new energy is connected. The positive-sequence, negative-sequence, and zero-sequence currents injected by the other nodes in each iteration are all zero. , and Let f(x) represent the fault component matrices of all node positive-sequence, negative-sequence, and zero-sequence voltages calculated in the t-th iteration, respectively. The expression for calculating the positive-sequence, negative-sequence, and zero-sequence voltage matrices of all nodes after the t-th iteration correction is as follows:

[0029] In the formula, , and Let these represent the positive, negative, and zero-sequence voltage matrices of all nodes after the t-th iteration correction, respectively. This is the positive sequence voltage matrix of all nodes in normal operation before the fault occurred; Based on the output characteristics of the second new energy equivalent model, the positive, negative, and zero sequence currents injected into the new energy nodes in the (t+1)th iteration are updated by extracting the positive, negative, and zero sequence voltages of the new energy nodes from the positive, negative, and zero sequence voltage matrices of all nodes after the t-th iteration correction. The positive, negative, and zero sequence currents injected into the fault nodes in the (t+1)th iteration are updated based on the positive, negative, and zero sequence voltages of the fault nodes extracted from the positive, negative, and zero sequence voltage matrices of each node after the t-th iteration correction. The expression is as follows: In the formula, These represent the positive-sequence, negative-sequence, and zero-sequence voltages of the fault node after the t-th iteration correction, respectively, and their values ​​are taken from the matrix. , and The faulty node in; These represent the positive-sequence, negative-sequence, and zero-sequence currents injected into the faulty node in the (t+1)th iteration, respectively. This represents a function used in short-circuit calculations to determine the sequence current based on boundary conditions, sequence voltage, and system impedance.

[0030] Based on the positive-sequence, negative-sequence, and zero-sequence currents injected by the new energy nodes in the (t+1)th iteration, and the positive-sequence, negative-sequence, and zero-sequence currents injected by the fault nodes, a matrix of positive-sequence, negative-sequence, and zero-sequence currents injected by each node in the (t+1)th iteration is constructed.

[0031] In step 106, the short-circuit iteration calculation ends when the number of iterations is not greater than the set iteration limit and the fault components of all node voltages meet the set iteration convergence criterion.

[0032] Preferably, the short-circuit iteration calculation ends when the number of iterations is not greater than the set iteration limit and the fault components of all node voltages satisfy the set iteration convergence criterion, wherein the expression of the iteration convergence criterion is: In the formula, when t=1, It is a matrix in which all elements are 0; This represents the maximum deviation of the fault component of the node voltage determined in two consecutive iterations.

[0033] Preferably, the method further includes treating the second new energy equivalent model of the fault near zone as a linear model and re-executing the short-circuit iterative calculation when the number of iterations is greater than the set number of iterations and the fault components of all node voltages do not meet the set iterative convergence criteria.

[0034] Figure 5 This is a flowchart illustrating a method for improving the short-circuit calculation convergence of a renewable energy-integrated power system according to another preferred embodiment of the present invention. Figure 5 As shown, in another preferred embodiment, after performing modeling and computational dimensionality reduction in steps 101 to 106, if the number of iterations reaches the set iteration limit and the fault components of all node voltages do not meet the set iteration convergence criteria, forced convergence is performed. The faulty near-field renewable energy node is switched to a linear model, and the short-circuit calculation is re-executed. The positive-sequence linear model of the renewable energy includes a constant voltage source model and a constant current source model. The negative-sequence linear model is a fixed impedance determined by its control characteristics.

[0035] In this preferred embodiment, a test model is established based on a certain actual power grid topology to analyze the feasibility and differences of simplifying equivalent new energy sources through constant voltage and constant current sources during the forced convergence phase. The short-circuit calculation results are shown in Table 1 below.

[0036] Table 1

[0037] As shown in Table 1, the constant current source model is close to the actual value in calculating the short-circuit current amplitude of the renewable energy transmission line, but the phase and voltage amplitudes differ significantly, resulting in large deviations in the current at the system side and fault point. The constant voltage source model has a larger deviation in calculating the short-circuit current amplitude of the renewable energy transmission line, but other parts are relatively accurate. Therefore, forced convergence ensures a solution for the short-circuit calculation, providing a basis for operation and maintenance settings, but it increases the calculation error. The constant current source model is advantageous in simulating the amplitude of the renewable energy output current, but it introduces certain deviations in the phase of the renewable energy output current, terminal voltage, and system-side current. The constant voltage source model has the advantage of smaller calculation deviations at the system side, but it has some deviations in calculating the renewable energy output current. Therefore, the constant current source model should only be used for renewable energy at the end of the transmission line when the fault occurs at the transmission line; the constant voltage source model should be used for renewable energy at other nodes or in other scenarios.

[0038] The method for improving the short-circuit calculation convergence of new energy access to the power system described in this preferred embodiment can significantly reduce the short-circuit calculation complexity of new energy while ensuring equivalent accuracy. When the calculation convergence cannot be satisfied, it ensures short-circuit calculation convergence by sacrificing a certain amount of calculation accuracy. This can effectively solve the problem that the convergence and accuracy of short-circuit calculation cannot be simultaneously achieved when large-scale new energy access is implemented, which makes iterative short-circuit calculation methods impractical in power systems containing new energy. This lays the foundation for relay protection setting calculation and correct protection operation in new power systems.

[0039] Exemplary System Figure 6 This is a schematic diagram of the system for improving the short-circuit calculation convergence of a renewable energy power system according to a preferred embodiment of the present invention. Figure 6 As shown, the system 200 for improving the short-circuit calculation convergence of the new energy access power system according to this preferred embodiment includes: The first model unit 201 is used to aggregate and equate new energy generating units with the same control strategy in new energy power stations connected to the power system according to the grid-connected capacity of the new energy generating units to generate a first new energy equivalent model. The second model unit 202 is used to aggregate and equate the first new energy equivalent models with different control strategies and connected to a common node to generate the second new energy equivalent model. The initial voltage unit 203 is used to perform initial short-circuit calculations without considering the output of the second new energy equivalent model, and to determine the initial voltage of all nodes in the power system. The area division unit 204 is used to divide the power system into a fault near zone and a fault far zone according to the initial voltage after a short circuit fault occurs. The iterative calculation unit 205 is used to treat the equivalent model of the second new energy source in the far-field fault as an open circuit and the equivalent model of the second new energy source in the near-field fault as a voltage-controlled current source model, and to perform short-circuit iterative calculation to determine the fault components of all node voltages in each iteration. The iteration termination unit 206 is used to terminate the short-circuit iteration calculation when the number of iterations is not greater than the set iteration limit and the fault components of all node voltages meet the set iteration convergence criterion.

[0040] The system for improving the short-circuit calculation convergence of the renewable energy access power system described in this preferred embodiment and the method for improving the short-circuit calculation convergence of the renewable energy access power system have the same steps for modeling and dimensionality reduction of renewable energy power plants and calculation and maintenance to calculate the short-circuit convergence of the system, and achieve the same technical effect, so they will not be described again here.

[0041] Exemplary electronic devices Figure 7 This is a schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention. Figure 7 As shown, the electronic device includes one or more processors 301 and memory 302.

[0042] The processor 301 may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0043] The memory 302 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 301 may execute the program instructions to implement the methods for improving the short-circuit calculation convergence of new energy access to the power system as described in the various embodiments disclosed above, and / or other desired functions. In one example, the electronic device may also include an input device 303 and an output device 304, these components being interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0044] In addition, the input device 303 may also include, for example, a keyboard, a mouse, etc.

[0045] The output device 304 can output various information to the outside. The output device 304 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0046] Of course, for the sake of simplicity, Figure 7 Only some of the components of the electronic device relevant to this disclosure are shown, omitting components such as buses, input / output interfaces, etc. In addition, the electronic device may include any other suitable components depending on the specific application.

[0047] Exemplary computer program products and computer-readable storage media In addition to the methods and apparatus described above, embodiments of this disclosure may also be computer program products, including computer program instructions that, when executed by a processor, cause the processor to perform the steps in the methods for improving the short-circuit calculation convergence of new energy access power systems according to various embodiments of this disclosure as described in the "Exemplary Methods" section above.

[0048] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of this disclosure. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on a user's computing device, partially on a user's computing device, as a standalone software package, partially on a user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0049] Furthermore, embodiments of this disclosure may also be computer-readable storage media storing computer program instructions that, when executed by a processor, cause the processor to perform the steps of the methods for improving the short-circuit calculation convergence of new energy access to the power system according to various embodiments of this disclosure as described in the "Exemplary Methods" section above.

[0050] The computer-readable storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof.

[0051] The basic principles of this disclosure have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0052] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For system embodiments, since they largely correspond to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0053] The block diagrams of devices, apparatuses, devices, and systems disclosed herein are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0054] The apparatus and methods of this disclosure may be implemented in many ways. For example, they may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order of steps for the methods is for illustrative purposes only, and the steps of the methods of this disclosure are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, this disclosure may also be implemented as a program recorded on a recording medium, the program including machine-readable instructions for implementing the methods according to this disclosure. Thus, this disclosure also covers recording media storing programs for performing the methods according to this disclosure.

[0055] It should also be noted that in the apparatus, devices, and methods of this disclosure, the components or steps are decomposable and / or recombinable. Such decomposition and / or recombination should be considered equivalent to the present disclosure. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0056] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this disclosure to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A method for improving short-circuit calculation convergence of new energy access to a power system, characterized in that, The method includes: For new energy generating units with the same control strategy in new energy power stations connected to the power system, the grid-connected capacity of the new energy generating units is aggregated and equivalent to generate the first new energy equivalent model. Aggregate and equate the first new energy equivalent models with different control strategies and connected to a common node to generate a second new energy equivalent model, including: Suppose that the common node connected to the first new energy equivalent model with different control strategies is... Sequence terminal voltage and The sequence currents are respectively and ,and ,in, for Sequence voltage amplitude; make By consistently taking per-unit values ​​within the range (0,1), each common node is determined using an iterative method. The output current corresponding to the sequence voltage, where the expression for calculating the output current is: In the formula, When '+' is used, it represents a positive order; when '-' is used, it represents a negative order. This indicates the number of first new energy equivalent models with different control strategies; This represents the aggregation region of the public node. Order node admittance matrix; , and These represent the first new energy equivalent models of the j-th control strategy in the aggregation region of the common node. Sequence output current, The sequence terminal voltage and its relationship as a function; According to each public node The terminal voltage of the sequence machine and its corresponding output current are aggregated and equivalent to generate the second new energy equivalent model. The order model, wherein the output characteristic expression of the second new energy equivalent model is: In the formula, The first new energy equivalent model represents the aggregation to a common node. Sequence output current about A function of the sequence terminal voltage; Initial short-circuit calculations are performed without considering the output of the second new energy equivalent model to determine the initial voltage of all nodes in the power system; After a short-circuit fault occurs, the power system is divided into a fault near zone and a fault far zone based on the initial voltage. The equivalent model of the second new energy source in the far-fault area is regarded as an open circuit, and the equivalent model of the second new energy source in the near-fault area is regarded as a voltage-controlled current source model. Short-circuit iterative calculation is performed to determine the fault components of all node voltages in each iteration. The short-circuit iteration calculation ends when the number of iterations is not greater than the set iteration limit and the fault components of all node voltages meet the set iteration convergence criterion.

2. The method of claim 1, wherein, The generation of the first new energy equivalent model involves aggregating and equating the grid-connected capacity of new energy units. This means generating the first new energy equivalent model by weighted multiplication of the grid-connected capacity of new energy units. The output current and terminal voltage of the first new energy equivalent model are expressed as follows: In the formula, This indicates the number of new energy generating units with the same control strategy in a new energy power station; and Indicating the first in the new energy power station Unit Sequence current and The sequence terminal voltage is a per-unit value; and These represent the first new energy equivalent model. Sequence current and Sequence terminal voltage; If the output currents of all new energy units with the same control strategy in a new energy power station are considered to be in phase, then the relationship between the output current and the terminal voltage of the first new energy equivalent model is as follows: In the formula, represents the output of the first new energy equivalent model The sequence current is a function of The sequence machine terminal voltage.

3. The method of claim 1, wherein, After a short-circuit fault occurs, the power system is divided into a fault near zone and a fault far zone based on the initial voltage, including: The area where the initial voltage is not less than the set voltage per-unit threshold is classified as the fault far zone, and the area where the initial voltage is less than the set voltage per-unit threshold is classified as the fault near zone.

4. The method of claim 1, wherein, The equivalent model of the second new energy source in the far-fault region is treated as an open circuit, and the equivalent model of the second new energy source in the near-fault region is treated as a voltage-controlled current source model. Short-circuit iterative calculations are performed to determine the fault components of all node voltages in each iteration, including: The fault components of the positive-sequence, negative-sequence, and zero-sequence voltages of all nodes in the t-th iteration are calculated using the following expression: in, N is the set iteration limit. , and These represent the positive-sequence, negative-sequence, and zero-sequence node admittance matrices of the power system, respectively. , and Let represent the positive-sequence, negative-sequence, and zero-sequence current matrices injected by all nodes in the t-th iteration, including three types of nodes: new energy nodes, fault nodes, and other nodes. When t=1, the positive-sequence current injected by the new energy node is the rated current of the new energy connected to the node, and the negative-sequence and zero-sequence currents injected by the new energy node are both 0. The positive-sequence, negative-sequence, and zero-sequence currents injected by the fault node are the fault node currents calculated without considering the short circuit when the new energy is connected. The positive-sequence, negative-sequence, and zero-sequence currents injected by the other nodes in each iteration are all zero. , and Let f(x) represent the fault component matrices of all node positive-sequence, negative-sequence, and zero-sequence voltages calculated in the t-th iteration, respectively. The expression for calculating the positive-sequence, negative-sequence, and zero-sequence voltage matrices of all nodes after the t-th iteration correction is as follows: In the formula, , and Let these represent the positive, negative, and zero-sequence voltage matrices of all nodes after the t-th iteration correction, respectively. This is the positive sequence voltage matrix of all nodes in normal operation before the fault occurred; Based on the output characteristics of the second new energy equivalent model, the positive, negative, and zero sequence currents injected into the new energy nodes in the (t+1)th iteration are updated by extracting the positive, negative, and zero sequence voltages of the new energy nodes from the positive, negative, and zero sequence voltage matrices of all nodes after the t-th iteration correction. The positive, negative, and zero sequence currents injected into the fault nodes in the (t+1)th iteration are updated based on the positive, negative, and zero sequence voltages of the fault nodes extracted from the positive, negative, and zero sequence voltage matrices of each node after the t-th iteration correction. The expression is as follows: In the formula, These represent the positive-sequence, negative-sequence, and zero-sequence voltages of the fault node after the t-th iteration correction, respectively, and their values ​​are taken from the matrix. , and The faulty node in; These represent the positive-sequence, negative-sequence, and zero-sequence currents injected into the faulty node in the (t+1)th iteration, respectively. This represents a function used in short-circuit calculations to determine the sequence current based on boundary conditions, sequence voltage, and system impedance. Based on the positive-sequence, negative-sequence, and zero-sequence currents injected by the new energy nodes in the (t+1)th iteration, and the positive-sequence, negative-sequence, and zero-sequence currents injected by the fault nodes, a matrix of positive-sequence, negative-sequence, and zero-sequence currents injected by each node in the (t+1)th iteration is constructed.

5. The method of claim 4, wherein, The short-circuit iteration calculation ends when the number of iterations is not greater than the set iteration limit, and the fault components of all node voltages satisfy the set iteration convergence criterion. The expression for the iteration convergence criterion is: where t = 1, is a matrix of all zeros; denotes the maximum deviation of the fault component of the node voltage determined by the two successive iteration calculations.

6. The method of claim 1, wherein, The method further includes treating the second new energy equivalent model of the fault near zone as a linear model and re-executing the short-circuit iterative calculation when the number of iterations is greater than the set iteration limit and the fault components of all node voltages do not meet the set iteration convergence criteria.

7. A system for improving short-circuit calculation convergence of new energy access to a power system, characterized in that, The system includes: The first model unit is used to aggregate and equate new energy generating units with the same control strategy in new energy power stations connected to the power system according to the grid-connected capacity of the new energy generating units to generate the first new energy equivalent model. The second model unit is used to aggregate and equate the first new energy equivalent models with different control strategies and connected to a common node, generating a second new energy equivalent model, including: Suppose that the common node connected to the first new energy equivalent model with different control strategies is... Sequence terminal voltage and The sequence currents are respectively and ,and ,in, for Sequence voltage amplitude; make By consistently taking per-unit values ​​within the range (0,1), each common node is determined using an iterative method. The output current corresponding to the sequence voltage, where the expression for calculating the output current is: In the formula, When '+' is used, it represents a positive order; when '-' is used, it represents a negative order. This indicates the number of first new energy equivalent models with different control strategies; This represents the aggregation region of the public node. Order node admittance matrix; , and These represent the first new energy equivalent models of the j-th control strategy in the aggregation region of the common node. Sequence output current, The sequence terminal voltage and its relationship as a function; According to each of the public nodes The sequence machine terminal voltage and its corresponding output current are aggregated and equivalent to generate the output characteristic expression of the second new energy equivalent model The sequence model, wherein the output characteristic expression of the second new energy equivalent model is In the formula, represents the first new energy equivalent model aggregated to the common node The sequence output current is a function of The sequence machine end voltage The initial voltage unit is used to perform initial short-circuit calculations without considering the output of the second new energy equivalent model, and to determine the initial voltage of all nodes in the power system. A region division unit is used to divide the power system into a fault near zone and a fault far zone based on the initial voltage after a short-circuit fault occurs. The iterative calculation unit is used to treat the equivalent model of the second new energy source in the far-fault area as an open circuit and the equivalent model of the second new energy source in the near-fault area as a voltage-controlled current source model, and to perform short-circuit iterative calculation to determine the fault components of all node voltages in each iteration. The iteration termination unit is used to terminate the short-circuit iteration calculation when the number of iterations is not greater than the set iteration limit and the fault components of all node voltages meet the set iteration convergence criterion.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method as described in any one of claims 1-6.

9. An electronic device, comprising: include: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the executable instructions to implement the steps of the method according to any one of claims 1-6.

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