Method and system for calculating maximum short-circuit current of new energy grid-connected system

Abstract

The application discloses a method and system for calculating maximum short-circuit current of a new energy grid-connected system, comprising: determining a fault point short-circuit current expression, a node voltage expression and a new energy reactive current increment expression corresponding to a system operation mode of a fault point maximum short-circuit current; initializing a new energy grid-connected system network, generating a network impedance matrix, and initializing the fault point maximum short-circuit current, the node voltage and the new energy reactive current increment based on the fault point short-circuit current expression, the node voltage expression and the new energy reactive current increment expression; performing iterative calculation based on the current fault point maximum short-circuit current, the node voltage and the new energy reactive current increment, and performing convergence judgment based on the node voltage after each iteration and the node voltage after the last iteration to obtain a judgment result; and outputting the current fault point maximum short-circuit current as the maximum short-circuit current of the new energy grid-connected system when the judgment result indicates that the convergence condition is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of short-circuit current calculation of power electronic power system, and more particularly, to a method and system for calculating maximum short-circuit current of new energy grid-connected system. BACKGROUND

[0002] Short-circuit current calculation is a basic calculation of power system, mainly used for switch device capacity parameter selection, protection device setting value setting and operation mode arrangement, etc., and its accuracy and reliability are directly related to the safe and economic operation of the system. With the construction of new-type power system and the access of new energy equipment, the power supply structure of the power grid has changed. In the early stage of new energy development, the scale is small, and the short-circuit current provided to the grid-connected point is much smaller than the short-circuit level of the grid-connected point, and has less influence on the accuracy of short-circuit current calculation. Therefore, how to take into account and evaluate the short-circuit current of the new energy contribution to the system is crucial. The key to short-circuit current calculation is to determine the maximum and minimum short-circuit currents of the system. For a new energy grid-connected system, the minimum short-circuit current can be considered as the shutdown of the new energy, at this time the new energy branch is open circuit, and the traditional model and algorithm can still be used for calculation. Therefore, the most important thing is to determine the maximum short-circuit current level of the new energy grid-connected system.

[0003] At present, in the case that the operation mode corresponding to the maximum short-circuit current is unknown, the existing method for evaluating the maximum short-circuit current level is based only on the connection mode of the system, which either equivalent the new energy as a fixed current source outputting the maximum current, or uses amplitude addition instead of phasor addition to adjust the output current of the new energy with the most serious node voltage, both of which have large calculation errors. Therefore, a new method for calculating the maximum short-circuit current of the new energy grid-connected system is needed. SUMMARY

[0004] The present application provides a method and system for calculating the maximum short-circuit current of a new energy grid-connected system to solve the problem of how to efficiently and accurately determine the maximum short-circuit current of a new energy grid-connected system.

[0005] In order to solve the above problems, according to one aspect of the present application, a method for calculating the maximum short-circuit current of a new energy grid-connected system is provided, the method comprising:

[0006] determining the short-circuit current expression, the node voltage expression and the new energy reactive current increment expression of the system in the operation mode corresponding to the maximum short-circuit current of the fault point;

[0007] initializing the network of the new energy grid-connected system, generating the network impedance matrix, and initializing the maximum short-circuit current of the fault point, the node voltage and the new energy reactive current increment based on the short-circuit current expression, the node voltage expression and the new energy reactive current increment expression of the fault point;

[0008] Iterative calculations are performed based on the current maximum short-circuit current at the fault point, node voltage, and the incremental reactive current of new energy sources. Convergence is judged based on the node voltage after each iteration and the node voltage after the previous iteration, and the judgment result is obtained.

[0009] When the judgment result indicates that the convergence condition is met, the current maximum short-circuit current of the fault point is output as the maximum short-circuit current of the new energy grid-connected system.

[0010] Preferably, the system operation mode corresponding to the maximum short-circuit current at the fault point is: the extreme operating condition of zero power at the initial start-up of all new energy vehicles, while the voltage coefficient is taken as the maximum value corresponding to the highest operating voltage of the system.

[0011] Preferably, the expression for the short-circuit current at the fault point is:

[0012] ,

[0013] The expression for node voltage is:

[0014] ,

[0015] The expression for the incremental reactive current of new energy sources is:

[0016] ,

[0017] in, This represents the maximum short-circuit current at the fault point. This represents the maximum value of the voltage coefficient. The system's nominal voltage; The magnitude of the system's self-impedance at the fault point; The system impedance matrix is ​​the first i Line number j The magnitude of the column element; For nodes j The incremental reactive current from new energy sources injected into the system; R A set of nodes representing new energy sources; For nodes j The voltage; The system impedance matrix is ​​the first k Line number j The magnitude of the column element; For nodes k The incremental reactive current from new energy sources injected into the system; For nodes j Low voltage ride-through threshold; For nodes j The rated current of new energy sources; For nodes j The maximum current that a new energy source can generate; For nodesj The reactive power compensation coefficient of new energy.

[0018] Preferably, the iterative calculation based on the current maximum short-circuit current at the fault point, node voltage, and reactive current increment of the new energy source includes:

[0019] ,

[0020] ,

[0021] ,

[0022] in, The node after the m-th iteration j The incremental reactive current from new energy sources injected into the system; The maximum short-circuit current at the fault point after the m-th iteration; This represents the maximum value of the voltage coefficient. The system's nominal voltage; The magnitude of the system's self-impedance at the fault point; The system impedance matrix is ​​the first i Line number j The magnitude of the column element; R A set of nodes representing new energy sources; The node after the m-th iteration j The voltage; The node after the (m-1)th iteration j The voltage; The system impedance matrix is ​​the first k Line number j The magnitude of the column element; The node after the m-th iteration k The incremental reactive current from new energy sources injected into the system; For nodes j Low voltage ride-through threshold; For nodes j The rated current of new energy sources; For nodes j The maximum current that a new energy source can generate; For nodes j The reactive power compensation coefficient of new energy.

[0023] Preferably, the convergence determination is based on the node voltage after each iteration and the node voltage after the previous iteration, and the determination result is obtained, including:

[0024] If satisfied If the condition is met, the result is determined to be that the convergence condition is satisfied; otherwise, the result is determined to be that the convergence condition is not satisfied.

[0025] wherein, is the voltage of the node after the mth iteration; j is the voltage of the node after the m-1th iteration; is the voltage of the node after the m-1th iteration; j is the voltage of the node after the m-1th iteration; is a preset threshold value; j is a node number; R represents a node set composed of new energy.

[0026] According to another aspect of the present application, a system for calculating the maximum short-circuit current of a new energy grid-connected system is provided, and the system comprises:

[0027] an expression determination unit configured to determine a fault point short-circuit current expression, a node voltage expression and a new energy reactive current increment expression corresponding to a system operating mode of a fault point maximum short-circuit current;

[0028] an initialization unit configured to initialize a new energy grid-connected system network, generate a network impedance matrix, and initialize the fault point maximum short-circuit current, the node voltage and the new energy reactive current increment based on the fault point short-circuit current expression, the node voltage expression and the new energy reactive current increment expression;

[0029] an iterative calculation unit configured to perform iterative calculation based on the current fault point maximum short-circuit current, the node voltage and the new energy reactive current increment, and perform convergence judgment based on the node voltage after each iteration and the node voltage after the last iteration, and obtain a judgment result;

[0030] a maximum short-circuit current determination unit configured to output the current fault point maximum short-circuit current as the new energy grid-connected system maximum short-circuit current when the judgment result indicates that the convergence condition is met.

[0031] Preferably, the system operating mode corresponding to the fault point maximum short-circuit current is a limit operating condition of new energy full start-up initial zero power, and the voltage coefficient takes the maximum value corresponding to the highest operating voltage of the system.

[0032] Preferably, the fault point short-circuit current expression is:

[0033] ,

[0034] the node voltage expression is:

[0035] ,

[0036] the new energy reactive current increment expression is:

[0037] ,

[0038] wherein, maximum short-circuit current at the fault point; maximum voltage coefficient; nominal voltage of the system; system self-impedance amplitude at the fault point; amplitude of the element in the system impedance matrix at the i row and the j column; new energy reactive current increment injected by the node j into the system; R node set composed of new energy; voltage of the node j ; amplitude of the element in the system impedance matrix at the k row and the j column; new energy reactive current increment injected by the node k into the system; low voltage ride-through action threshold of the node j ; rated current of the new energy of the node j ; maximum current that the new energy of the node j can generate; new energy reactive compensation coefficient of the node j .

[0039] Preferably, wherein the iterative calculation unit performs iterative calculation based on the current maximum short-circuit current at the fault point, the node voltage and the new energy reactive current increment, comprising:

[0040] ,

[0041] ,

[0042] ,

[0043] wherein, new energy reactive current increment injected by the node j into the system after the mth iteration; maximum short-circuit current at the fault point after the mth iteration; maximum voltage coefficient; nominal voltage of the system; system self-impedance amplitude at the fault point; amplitude of the element in the system impedance matrix at the i row and the j column; R node set composed of new energy; voltage of the node j after the mth iteration; The node after the (m-1)th iteration j The voltage; The system impedance matrix is ​​the first k Line number j The magnitude of the column element; The node after the m-th iteration k The incremental reactive current from new energy sources injected into the system; For nodes j Low voltage ride-through threshold; For nodes j The rated current of new energy sources; For nodes j The maximum current that a new energy source can generate; For nodes j The reactive power compensation coefficient of new energy.

[0044] Preferably, the iterative calculation unit performs a convergence judgment based on the node voltage after each iteration and the node voltage after the previous iteration, and obtains the judgment result, including:

[0045] If satisfied If the condition is met, the result is determined to be that the convergence condition is satisfied; otherwise, the result is determined to be that the convergence condition is not satisfied.

[0046] in, The node after the m-th iteration j The voltage; The node after the (m-1)th iteration j The voltage; The preset threshold; j Number the nodes; R A set of nodes representing new energy sources.

[0047] Based on another aspect of the present invention, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any one of the steps of a method for calculating the maximum short-circuit current of a new energy grid-connected system.

[0048] According to another aspect of the present invention, the present invention provides an electronic device, comprising:

[0049] The aforementioned computer-readable storage medium; and

[0050] One or more processors for executing a program in the computer-readable storage medium.

[0051] The application provides a method and system for calculating maximum short-circuit current of a new energy grid-connected system, comprising: determining a fault point short-circuit current expression, a node voltage expression and a new energy reactive current increment expression corresponding to a system operation mode of a fault point maximum short-circuit current; initializing a new energy grid-connected system network, generating a network impedance matrix, and initializing the fault point maximum short-circuit current, the node voltage and the new energy reactive current increment based on the fault point short-circuit current expression, the node voltage expression and the new energy reactive current increment expression; performing iterative calculation based on the current fault point maximum short-circuit current, the node voltage and the new energy reactive current increment, and performing convergence judgment based on the node voltage after each iteration and the node voltage after the last iteration to obtain a judgment result; and outputting the current fault point maximum short-circuit current as the maximum short-circuit current of the new energy grid-connected system when the judgment result indicates that the convergence condition is met. The application finds an operation mode corresponding to the maximum short-circuit current, thereby calculating the short-circuit current scheme under the mode, and can solve the problem of conservative treatment of new energy in the existing algorithm, and improve the accuracy and reliability of short-circuit current calculation. BRIEF DESCRIPTION OF DRAWINGS

[0052] The exemplary embodiments of the application can be more completely understood in reference to the following drawings:

[0053] Figure 1 A flowchart of the method 100 for calculating the maximum short-circuit current of the new energy grid-connected system according to the embodiments of the application;

[0054] Figure 2 A schematic diagram of the influence of the initial active current of the new energy on the fault point current according to the embodiments of the application;

[0055] Figure 3 A general flowchart of the method for calculating the maximum short-circuit current of the new energy grid-connected system according to the embodiments of the application;

[0056] Figure 4 An example diagram of a 36-node system according to the embodiments of the application;

[0057] Figure 5 A structural schematic diagram of the system 500 for calculating the maximum short-circuit current of the new energy grid-connected system according to the embodiments of the application. DETAILED DESCRIPTION

[0058] Reference will now be made to the drawings to describe the exemplary embodiments of the present application in greater detail. The present application can be variously embodied and is not limited to the embodiments described herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art. The terminology used in the description of the exemplary embodiments herein is not intended to be limiting of the present application. Same reference numerals in different drawings denote the same elements.

[0059] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0060] Figure 1 A flowchart of a method 100 for calculating maximum short-circuit current of a new energy grid-connected system according to an embodiment of the present application is shown in FIG. 1. As shown in FIG. 1, the method for calculating maximum short-circuit current of a new energy grid-connected system according to an embodiment of the present application finds the system operating mode corresponding to the maximum short-circuit current, and then calculates the short-circuit current scheme under this mode, thereby solving the problem of conservative treatment of new energy in the prior art and improving the accuracy and reliability of short-circuit current calculation. The method 100 for calculating maximum short-circuit current of a new energy grid-connected system according to an embodiment of the present application starts from step 101, in which the short-circuit current expression, the node voltage expression, and the new energy reactive current increment expression under the system operating mode corresponding to the fault point maximum short-circuit current are determined. Figure 1

[0061] Preferably, the system operating mode corresponding to the fault point maximum short-circuit current is the limit condition of full startup of the new energy and initial zero power, and the voltage coefficient is the maximum value corresponding to the highest operating voltage of the system.

[0062] Preferably, the short-circuit current expression is

[0063]

[0064] The node voltage expression is

[0065]

[0066] The new energy reactive current increment expression is

[0067]

[0068] wherein, is the fault point maximum short-circuit current; is the maximum value of the voltage coefficient.​​​​ is the nominal voltage of the system; is the amplitude of the system self-impedance at the fault point; is the amplitude of the element in the system impedance matrix at the i th row and the j th column; is the voltage of the j th node; R is the set of nodes that the new energy is composed of; is the voltage of the j th node; is the amplitude of the element in the system impedance matrix at the k th row and the j th column; is the new energy reactive current increment injected into the system by the k th node; is the low voltage ride through action threshold of the j th node; is the new energy rated current of the j th node; is the maximum current that the new energy of the j th node can generate; is the new energy reactive compensation coefficient of the j th node.

[0069] The short-circuit current at the fault point can be expressed as:

[0070] ,

[0071] wherein: is the current generated by the t th synchronous generator; is the current generated by the i th new energy device before the fault; is the value of the element in the system impedance matrix at the i th row and the j th column; and G is the set of nodes that all synchronous generators are connected to. represents the open-circuit voltage at the fault node i when the system is in normal operation, i.e., the equivalent voltage source voltage

[0072] ,

[0073] wherein, is the phase angle of the open-circuit voltage at the fault point.

[0074] The short-circuit current at the fault point is:

[0075]

[0076] The corresponding voltage of each node during the fault is expressed as:

[0077] 。

[0078] In the present application, the maximum short-circuit current at the fault point is the maximum value of the short-circuit current that the fault point can reach under the condition of change of system operation mode. As can be known from the formula of short-circuit current at the fault point, under the condition of determined network equivalent impedance, the maximum short-circuit current at the fault point is influenced by the difference value of new energy output current and the operation voltage coefficient c . For a fault at a certain bus node, when the node voltage drop is determined, the only uncertain factor with the change of mode is the initial current , which corresponds to the initial active power .

[0079] (1) Influence of initial power of new energy before fault.

[0080] Ignoring the influence of network resistance, the node impedance matrix can be approximated as the node reactance matrix, i.e. . Considering , the short-circuit current increment contribution of new energy to the fault point before and after fault can be expressed as:

[0081] ,

[0082] wherein is the active current increment contributed by new energy; is the reactive current increment contributed by new energy.

[0083] The active current increment thereof can be further expressed as:

[0084] ,

[0085] wherein is the active current component contributed by new energy to the fault point during fault, is the active current component contributed by new energy to the fault point during normal operation, and the expressions thereof are as follows

[0086] ,

[0087] Considering that the synchronous generator only sends reactive current during fault, the current component contributed by the synchronous generator to the fault point is:

[0088] ,

[0089] The current component generated by the normal operation network is:

[0090] ,

[0091] For the fault occurring at the same node, the superposition process of each component of the fault point short-circuit current under different new energy initial active power is shown in Figure 2 Figure 2 From (a) in , when the new energy initial active current , the current component produced by the normal operation network before the fault is , When the increment of the new energy is superimposed, the smaller the initial active current is, the larger the superimposed short-circuit current is, that is Figure 2 . From (b) in , the smaller the active current difference is, the larger the superimposed short-circuit current is, and if , there is . Considering the case that the initial active current and the active current difference are both zero, that is Figure 2 , when the new energy is fully on before the fault and the initial zero power, the fault point short-circuit current reaches the maximum amplitude, corresponding to in (b) in . Since the influence of the active current difference on the difference before and after the fault of the new energy is far less than the influence of the initial active power on , the smaller the initial active power of the new energy is, the larger the fault point short-circuit current is.

[0092]

[0093] ,

[0094] The corresponding node voltage can be represented as:

[0095] .

[0096] (2) Influence of operating voltage coefficient

[0097] Further simplify the node voltage formula. Approximate the node voltage without considering the influence of new energy reactive support as the judgment condition of whether the new energy enters the low voltage ride-through mode, let I REqk =0, then the node voltage is approximately represented as:

[0098] ,

[0099] Among them, the superscript “~” of the variable represents the approximate value, the same below. ​

[0100] The node voltage approximation result in the above formula will be slightly lower than the actual situation, and the purpose is to screen out new energy stations entering low voltage ride through mode during fault. When , the station enters low voltage ride through mode, and the new energy station meeting the condition will be recorded as set L , which belongs to set L The node determination condition is: .

[0101] The approximate expression based on the above formula is:

[0102] ,

[0103] The maximum short-circuit current at the fault point can be approximately expressed as:

[0104] ,

[0105] Taking the derivative of the voltage coefficient c in the above formula can get:

[0106] ,

[0107] From the above formula, the short-circuit current and the voltage coefficient c present a monotonic increasing / monotonic decreasing relationship. But in fact, the scenario that makes almost impossible. Assuming that all new energy stations have the same reactive power compensation coefficient, , since , The minimum value of ,

[0108] If the above formula can meet , then , and the total capacity of new energy entering low voltage ride through mode during fault meets . For a 220kV voltage level, the node short-circuit current is 20kA, the fault point self-impedance , the reactive power compensation coefficient is , and the new energy entering low voltage ride through mode is at least , then , which is obviously impossible.

[0109] Therefore, for the current power system, the higher the operating voltage at the fault point, the greater the short-circuit current during fault, and it increases linearly with the voltage coefficient. When calculating the maximum short-circuit current, c , .

[0110] In summary, the system operation mode corresponding to the maximum short-circuit current at the fault point in this invention is: the extreme operating condition of zero power at the initial start-up of all new energy sources, while the voltage coefficient is taken as the maximum value corresponding to the highest operating voltage of the system.

[0111] The maximum short-circuit current at the fault point can be expressed as:

[0112] ,

[0113] The expression for node voltage is:

[0114] ,

[0115] The expression for the incremental reactive current of new energy sources is:

[0116] ,

[0117] in, This represents the maximum short-circuit current at the fault point. This represents the maximum value of the voltage coefficient. The system's nominal voltage; The magnitude of the system's self-impedance at the fault point; The system impedance matrix is ​​the first i Line number j The magnitude of the column element; For nodes j The incremental reactive current from new energy sources injected into the system; R A set of nodes representing new energy sources; For nodes j The voltage; The system impedance matrix is ​​the first k Line number j The magnitude of the column element; For nodes k The incremental reactive current from new energy sources injected into the system; For nodes j Low voltage ride-through threshold; For nodes j The rated current of new energy sources; For nodes j The maximum current that a new energy source can generate; For nodes j The reactive power compensation coefficient of new energy.

[0118] In step 102, the new energy grid-connected system network is initialized, the network impedance matrix is ​​generated, and the maximum short-circuit current at the fault point, the node voltage expression, and the new energy reactive current increment are initialized based on the fault point short-circuit current expression, the node voltage expression, and the new energy reactive current increment expression.

[0119] In step 103, iterative calculations are performed based on the current maximum short-circuit current at the fault point, node voltage, and incremental reactive current of new energy sources. Convergence is then determined based on the node voltage after each iteration and the node voltage after the previous iteration, and the determination result is obtained.

[0120] Preferably, the iterative calculation based on the current maximum short-circuit current at the fault point, node voltage, and reactive current increment of the new energy source includes:

[0121] ,

[0122] ,

[0123] ,

[0124] in, The node after the m-th iteration j The incremental reactive current from new energy sources injected into the system; The maximum short-circuit current at the fault point after the m-th iteration; This represents the maximum value of the voltage coefficient. The system's nominal voltage; The magnitude of the system's self-impedance at the fault point; The system impedance matrix is ​​the first i Line number j The magnitude of the column element; R A set of nodes representing new energy sources; The node after the m-th iteration j The voltage; The node after the (m-1)th iteration j The voltage; The system impedance matrix is ​​the first k Line number j The magnitude of the column element; The node after the m-th iteration k The incremental reactive current from new energy sources injected into the system; For nodes j Low voltage ride-through threshold; For nodes j The rated current of new energy sources; For nodes j The maximum current that a new energy source can generate; For nodes j The reactive power compensation coefficient of new energy.

[0125] Preferably, the convergence determination is based on the node voltage after each iteration and the node voltage after the previous iteration, and the determination result is obtained, including:

[0126] If satisfied If the condition is met, the result is determined to be that the convergence condition is satisfied; otherwise, the result is determined to be that the convergence condition is not satisfied.

[0127] in, The node after the m-th iteration j The voltage; The node after the (m-1)th iteration j The voltage; The preset threshold; j Number the nodes; R A set of nodes representing new energy sources.

[0128] In step 104, when the judgment result indicates that the convergence condition is met, the current maximum short-circuit current of the fault point is output as the maximum short-circuit current of the new energy grid-connected system.

[0129] In this invention, considering the voltage-current coupling relationship between the short-circuit current expression at the fault point, the node voltage expression, and the incremental reactive current expression of new energy sources, an iterative correction method is adopted during calculation.

[0130] Specifically, such as Figure 3 As shown, the calculation process for the maximum short-circuit current of new energy sources connected to the power system includes:

[0131] (1) Initialize the network. Generate the network impedance matrix. Initialize variables , .

[0132] (2) Perform the first m The next iteration. m The node voltage obtained from the -1st iteration Calculate the first m Variables after the second iteration , , The value of, that is:

[0133] ,

[0134] ,

[0135] ,

[0136] (3) Convergence determination. The determination criterion is that the convergence of each new energy power station is... m The node voltage after the second iteration and the first iteration m The node voltage after -1 iteration satisfies If the convergence condition is met, the iteration will converge; otherwise, proceed to step (2) until the convergence condition is met, at which point the iteration ends and step (4) is performed.

[0137] (4) Output the maximum short-circuit current and node voltage at the fault point, and use the current maximum short-circuit current at the fault point as the maximum short-circuit current of the new energy grid-connected system.

[0138] This invention, based on actual control strategies for renewable energy sources, establishes a refined nonlinear model of node voltage-output current increments. All model parameters are fundamental, exhibiting low dependence on manufacturers. By acquiring the influence of parameter changes related to operating modes on short-circuit current, the operating mode corresponding to the maximum short-circuit current at the fault point is selected. Based on this operating mode, the maximum short-circuit current level can be directly calculated. At the fault point, the phase angle superposition between the current increment generated by renewable energy sources and the current component generated by the equivalent voltage source is considered, effectively reducing the conservatism of amplitude superposition in existing methods. An iterative framework for short-circuit current calculation is designed to address the characteristics of the renewable energy model. Finally, an implementation scheme for calculating the maximum short-circuit current when renewable energy is integrated into the power system is derived.

[0139] The comparison between the proposed solution of this invention and the prior art is shown in Table 1.

[0140] Table 1 Comparison of various short-circuit current calculation methods

[0141]

[0142] To compare with existing technologies and demonstrate the superiority of the method proposed in this invention, the following approach is adopted: Figure 4 The 36-node example shown is used for verification. Seven new energy power stations are connected to nodes 1, 4, 12, 13, 32, 34, and 36, respectively, and four synchronous generators are connected to nodes 14, 23, 24, and 27.

[0143] The comparison results are shown in Table 2, with electromagnetic transient simulation results used as the benchmark. Table 2 shows that the result obtained using the first method (IEC 60909-2016 / GBT 15544-2023) is the most conservative, with an error of 22.14%. The second method (GBT 44659-2024) can obtain the maximum short-circuit current under different renewable energy simultaneous rates. Selecting the maximum short-circuit current, the error is 12.64%, a reduction of 9.5% compared to the first method. Using the method proposed in this invention, the calculation error is 3.64%, a further reduction of 9% compared to the first method. It can be seen that the proposed solution significantly reduces the conservatism of the results and improves the accuracy and reliability of the calculation results.

[0144] Table 2 Comparison of results from different calculation methods for maximum short-circuit current.

[0145]

[0146] Figure 5 This is a schematic diagram of the structure of a system 500 for calculating the maximum short-circuit current of a renewable energy grid-connected system according to an embodiment of the present invention. Figure 5 As shown, the system 500 for calculating the maximum short-circuit current of a new energy grid-connected system provided by the embodiments of the present invention includes: an expression determination unit 501, an initialization unit 502, an iterative calculation unit 503, and a maximum short-circuit current determination unit 504.

[0147] Preferably, the expression determination unit 501 is used to determine the expression for the short-circuit current at the fault point, the expression for the node voltage, and the expression for the incremental reactive current of the new energy source under the system operation mode corresponding to the maximum short-circuit current at the fault point.

[0148] Preferably, the system operation mode corresponding to the maximum short-circuit current at the fault point is: the extreme operating condition of zero power at the initial start-up of all new energy vehicles, while the voltage coefficient is taken as the maximum value corresponding to the highest operating voltage of the system.

[0149] Preferably, the expression for the short-circuit current at the fault point is:

[0150] ,

[0151] The expression for node voltage is:

[0152] ,

[0153] The expression for the incremental reactive current of new energy sources is:

[0154] ,

[0155] in, This represents the maximum short-circuit current at the fault point. This represents the maximum value of the voltage coefficient. The system's nominal voltage; The magnitude of the system's self-impedance at the fault point; The system impedance matrix is ​​the first i Line number j The magnitude of the column element; For nodes j The incremental reactive current from new energy sources injected into the system; R A set of nodes representing new energy sources; For nodes j The voltage; The system impedance matrix is ​​the first k Line number j The magnitude of the column element; For nodes k The incremental reactive current from new energy sources injected into the system; For nodes j Low voltage ride-through threshold; For nodes j The rated current of new energy sources; For nodes j The maximum current that a new energy source can generate; For nodes j The reactive power compensation coefficient of new energy.

[0156] Preferably, the initialization unit 502 is used to initialize the new energy grid-connected system network, generate a network impedance matrix, and initialize the maximum short-circuit current at the fault point, the node voltage, and the new energy reactive current increment based on the fault point short-circuit current expression, the node voltage expression, and the new energy reactive current increment expression.

[0157] Preferably, the iterative calculation unit 503 is used to perform iterative calculations based on the current maximum short-circuit current at the fault point, the node voltage, and the incremental reactive current of the new energy source, and to perform convergence judgment based on the node voltage after each iteration and the node voltage after the previous iteration, and to obtain the judgment result.

[0158] Preferably, the iterative calculation unit 503 performs iterative calculations based on the current maximum short-circuit current at the fault point, node voltage, and reactive current increment of the new energy source, including:

[0159] ,

[0160] ,

[0161] ,

[0162] in, The node after the m-th iteration j The incremental reactive current from new energy sources injected into the system; The maximum short-circuit current at the fault point after the m-th iteration; This represents the maximum value of the voltage coefficient. The system's nominal voltage; The magnitude of the system's self-impedance at the fault point; The system impedance matrix is ​​the first i Line number j The magnitude of the column element; R A set of nodes representing new energy sources; The node after the m-th iteration j The voltage; The node after the (m-1)th iteration j The voltage; The system impedance matrix is ​​the first k Line number j The magnitude of the column element; The node after the m-th iteration kNew energy reactive current increment injected into the system; a low voltage ride through action threshold of the node j ; a new energy rated current of the node j ; a maximum current capable of being generated by the new energy of the node j ; a new energy reactive compensation coefficient of the node j .

[0163] Preferably, the maximum short-circuit current determination unit 504 is configured to output the current fault point maximum short-circuit current as the new energy grid-connected system maximum short-circuit current when the determination result indicates that the convergence condition is met.

[0164] Preferably, the iterative calculation unit 503 is configured to perform a convergence judgment based on the node voltage after each iteration and the node voltage after the last iteration, and obtain a determination result, including:

[0165] If the following condition is met: , it is determined that the determination result meets the convergence condition; otherwise, it is determined that the convergence result does not meet the convergence condition.

[0166] Wherein, is the voltage of the node j after the mth iteration; is the voltage of the node j after the (m-1)th iteration; is a preset threshold; j is a node number; R represents a node set composed of new energy.

[0167] The system 500 for calculating the new energy grid-connected system maximum short-circuit current of the embodiment of the present application corresponds to the method 100 for calculating the new energy grid-connected system maximum short-circuit current of another embodiment of the present application, and will not be described here.

[0168] Based on another aspect of the present application, the present application provides a computer readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the steps of any one of the methods for calculating the new energy grid-connected system maximum short-circuit current.

[0169] Based on another aspect of the present application, the present application provides an electronic device, comprising:

[0170] The computer readable storage medium described above; and

[0171] One or more processors for executing the program in the computer readable storage medium.

[0172] The application has been described by reference to several embodiments. However, other embodiments, which are within the scope of the application, will be apparent to those skilled in the art from this disclosure. For instance, the steps of any of the methods disclosed herein do not have to be performed in the precise order described.

[0173] In general, all terms used herein are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined herein otherwise. All references to "a" or "an" means "at least one" or "one or more" unless otherwise indicated by the context of the specification. Any method disclosed herein does not necessarily imply the combination of all recipients of the individual steps of the method, unless explicitly stated.

[0174] As will be appreciated by one skilled in the art, embodiments of the present application can be comprised of a method, a system, or a computer program product. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer readable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0175] The present application is described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processing system or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart Figure 1 one or more functions specified in the flowchart block or blocks. Figure 1 one or more functions specified in the flowchart block or blocks.

[0176] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart block or blocks. Figure 1 one or more functions specified in the flowchart block or blocks. Figure 1 one or more functions specified in the flowchart block or blocks.

[0177] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks.Figure 1 one or more processes and / or functions specified in one or more blocks Figure 1 one or more blocks or any combination thereof.

[0178] It should be noted that the above-mentioned embodiments are only used to illustrate the technical solutions of the present application, but not limit the technical solutions of the present application. Although the present application has been described in detail with reference to the above-mentioned embodiments, it should be understood by those skilled in the art that the specific embodiments of the present application can be modified or equivalent replaced without departing from the spirit and scope of the present application, and any modification or equivalent replacement should be covered in the protection scope of the present application.

Claims

1. A method for calculating maximum short-circuit current of a new energy grid-connected system, characterized in that, The method comprises: determining a fault point short-circuit current expression, a node voltage expression and a new energy reactive current increment expression under a system operation mode corresponding to the fault point maximum short-circuit current; initializing a network of the new energy grid-connected system, generating a network impedance matrix, and initializing the fault point maximum short-circuit current, the node voltage and the new energy reactive current increment based on the fault point short-circuit current expression, the node voltage expression and the new energy reactive current increment expression; performing iterative calculation based on the current fault point maximum short-circuit current, the node voltage and the new energy reactive current increment, and performing convergence judgment based on the node voltage after each iteration and the node voltage after the last iteration to obtain a judgment result; when the judgment result indicates that the convergence condition is met, outputting the current fault point maximum short-circuit current as the maximum short-circuit current of the new energy grid-connected system; wherein the system operation mode corresponding to the fault point maximum short-circuit current is a limit working condition of new energy full on-machine initial zero power, and a voltage coefficient takes a maximum value corresponding to a highest running voltage of the system; wherein the fault point short-circuit current expression is: ， the node voltage expression is: ， and the new energy reactive current increment expression is: ， wherein, is the maximum short circuit current at the fault point; is the maximum value of the voltage coefficient; is the nominal voltage of the system; is the amplitude of the system self-impedance at the fault point; is the amplitude of the element of the system impedance matrix in the i-th row and j-th column; is the incremental reactive power current of the new energy injected into the system by node j; R represents the set of nodes composed of new energy; is the voltage of node j; is the amplitude of the element of the system impedance matrix in the k-th row and j-th column; is the incremental reactive power current of the new energy injected into the system by node k; is the low voltage ride through action threshold value of node j; is the rated current of the new energy of node j; is the maximum current that the new energy of node j can generate; is the new energy reactive power compensation coefficient of node j.

2. The method of claim 1, wherein, performing iterative calculation based on the current fault point maximum short-circuit current, the node voltage and the new energy reactive current increment, comprising: ， ， ， wherein, is the new energy reactive current increment injected by node j to the system after the mth iteration; is the maximum short-circuit current at the fault point after the mth iteration; is the maximum value of the voltage coefficient; is the nominal voltage of the system; is the amplitude of the system self-impedance at the fault point; is the amplitude of the i-th row and j-th column element of the system impedance matrix; R represents the set of nodes composed of new energy; is the voltage of node j after the mth iteration; is the voltage of node j after the (m-1)th iteration; is the amplitude of the k-th row and j-th column element of the system impedance matrix; is the new energy reactive current increment injected by node k to the system after the mth iteration; is the low voltage ride through action threshold of node j; is the rated current of the new energy of node j; is the maximum current that the new energy of node j can generate; is the new energy reactive compensation coefficient of node j.

3. The method of claim 1, wherein, performing convergence judgment based on the node voltage after each iteration and the node voltage after the last iteration to obtain a judgment result, comprising: If the following condition is satisfied then the determination result is determined as satisfying the convergence condition; otherwise, the convergence result is determined as not satisfying the convergence condition; wherein, Vj(m) is the voltage of node j after the mth iteration; Vj(m-1) is the voltage of node j after the (m-1)th iteration; Vth is a preset threshold; j is a node number; and R represents a node set composed of new energy sources.

4. A system for calculating maximum short-circuit current of a new energy grid-connected system, characterized in that, The system comprises: an expression determination unit configured to determine a fault point short-circuit current expression, a node voltage expression and a new energy reactive current increment expression under a system operation mode corresponding to the fault point maximum short-circuit current; an initialization unit configured to initialize a network of the new energy grid-connected system, generate a network impedance matrix, and initialize the fault point maximum short-circuit current, the node voltage and the new energy reactive current increment based on the fault point short-circuit current expression, the node voltage expression and the new energy reactive current increment expression; an iterative calculation unit configured to perform iterative calculation based on the current fault point maximum short-circuit current, the node voltage and the new energy reactive current increment, and perform convergence judgment based on the node voltage after each iteration and the node voltage after the last iteration to obtain a judgment result; a maximum short-circuit current determination unit configured to, when the judgment result indicates that the convergence condition is met, output the current fault point maximum short-circuit current as the maximum short-circuit current of the new energy grid-connected system; wherein the system operation mode corresponding to the fault point maximum short-circuit current is a limit working condition of new energy full on-machine initial zero power, and a voltage coefficient takes a maximum value corresponding to a highest running voltage of the system; wherein the fault point short-circuit current expression is: ， the node voltage expression is: ， and the new energy reactive current increment expression is: ， wherein, is the maximum short circuit current at the fault point; is the maximum voltage coefficient; is the nominal voltage of the system; is the amplitude of the system self-impedance at the fault point; is the amplitude of the element in the i-th row and j-th column of the system impedance matrix; is the incremental reactive power current of the new energy injected into the system by node j; R represents the set of nodes composed of new energy; is the voltage of node j; is the amplitude of the element in the k-th row and j-th column of the system impedance matrix; is the incremental reactive power current of the new energy injected into the system by node k; is the low voltage ride through action threshold of node j; is the rated current of the new energy of node j; is the maximum current that the new energy of node j can generate; is the reactive power compensation coefficient of the new energy of node j.

5. The system of claim 4, wherein, the iterative calculation unit performs iterative calculation based on the current fault point maximum short-circuit current, the node voltage and the new energy reactive current increment, comprising: ， ， ， wherein, is the new energy reactive current increment injected by node j to the system after the mth iteration; is the maximum short-circuit current at the fault point after the mth iteration; is the maximum value of the voltage coefficient; is the nominal voltage of the system; is the amplitude of the system self-impedance at the fault point; is the amplitude of the i-th row and j-th column element of the system impedance matrix; R represents the set of nodes composed of new energy; is the voltage of node j after the mth iteration; is the voltage of node j after the m-1th iteration; is the amplitude of the k-th row and j-th column element of the system impedance matrix; is the new energy reactive current increment injected by node k to the system after the mth iteration; is the low voltage ride through action threshold of node j; is the rated current of the new energy of node j; is the maximum current that the new energy of node j can generate; is the new energy reactive compensation coefficient of node j.

6. The system of claim 4, wherein, the iterative calculation unit performs convergence judgment based on the node voltage after each iteration and the node voltage after the last iteration to obtain a judgment result, comprising: If the following condition is satisfied the determination result is determined to satisfy the convergence condition; otherwise, the convergence result is determined to not satisfy the convergence condition; wherein, Vj(m) is the voltage of node j after the mth iteration; Vj(m-1) is the voltage of node j after the (m-1)th iteration; Vth is a preset threshold; j is a node number; and R represents a node set composed of new energy sources.

7. A computer-readable storage medium having stored thereon a computer program, characterized in that The program is executed by the processor to implement the steps of the method in any one of claims 1-3.

8. An electronic device, comprising: comprising: the computer readable storage medium recited in claim 7; and one or more processors for executing a program in the computer readable storage medium.

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