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

Abstract

The invention discloses a method and system for calculating the maximum short-circuit current of a new energy grid-connected system. The method comprises the steps that a fault point short-circuit current expression, a node voltage expression and a new energy reactive current increment expression in a system operation mode corresponding to the maximum short-circuit current of a fault point are determined; initializing a new energy grid-connected system network, generating a network impedance matrix, and initializing the maximum short-circuit current, the node voltage and the new energy reactive current increment of the fault point based on the fault point short-circuit current expression, the node voltage expression and the new energy reactive current increment expression; iterative calculation is carried out based on the current fault point maximum short-circuit current, the node voltage and the new energy reactive current increment, convergence judgment is carried out based on the node voltage after each iteration and the node voltage after the last iteration, and a judgment result is obtained; and when the judgment result indicates that the convergence condition is met, outputting the current maximum short-circuit current of the fault point as the maximum short-circuit current of the new energy grid-connected system.

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 outage of 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: 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; 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; Iterative calculation is performed based on the current maximum short-circuit current at the fault point, node voltage, and renewable energy reactive current increment. Convergence is judged based on the node voltage after each iteration and the node voltage after the previous iteration to obtain the judgment result. When the judgment result indicates that the convergence condition is met, the maximum short-circuit current of the current fault point is output as the maximum short-circuit current of the new energy grid-connected system.

[0006] Preferably, the system operating mode corresponding to the maximum short-circuit current at the fault point is: the extreme operating condition of initial zero power when all new energy devices are fully powered on, and the voltage coefficient takes the maximum value corresponding to the highest operating voltage of the system.

[0007] Preferably, the short-circuit current expression at the fault point is: , The node voltage expression is: , The expression of the reactive current increment of new energy is: , in, is the maximum short-circuit current at the fault point; is the maximum value of the voltage coefficient; is the system nominal voltage; is the magnitude of the system self-impedance at the fault point; The system impedance matrix i Rank j the magnitude of the column elements; For nodes j The increase in reactive current from new energy injected into the system; R A collection of nodes representing new energy components; For nodes j voltage; The system impedance matrix k Rank j the magnitude of the column elements; For nodes k The increase in reactive current from new energy injected into the system; For nodes j Low voltage ride-through threshold; For nodes j Rated current of new energy; For nodes j The maximum current that can be generated by the new energy source; For nodes j The reactive power compensation coefficient of new energy.

[0008] Preferably, the iterative calculation is performed based on the current maximum short-circuit current at the fault point, the node voltage, and the reactive current increment of the new energy source, including: , , , in, The node after the mth iteration j The increase in reactive current from new energy injected into the system; is the maximum short-circuit current of the fault point after the mth iteration; is the maximum value of the voltage coefficient; is the system nominal voltage; is the magnitude of the system self-impedance at the fault point; The system impedance matrix i Rank j the magnitude of the column elements; R A collection of nodes representing new energy components; The node after the mth iteration j voltage; The node after the m-1th iteration j voltage; The system impedance matrix k Rank j the magnitude of the column elements; The node after the mth iteration k The increase in reactive current from new energy injected into the system; For nodes j Low voltage ride-through threshold; For nodes j Rated current of new energy; For nodes j The maximum current that can be generated by the new energy source; For nodes j The reactive power compensation coefficient of new energy.

[0009] Preferably, performing convergence judgment based on the node voltage after each iteration and the node voltage after the previous iteration to obtain the judgment result includes: If satisfied , then the judgment result is determined to meet the convergence condition; otherwise, the convergence result is determined to not meet the convergence condition; in, The node after the mth iteration j voltage; The node after the m-1th iteration j voltage; is the preset threshold; j Number the node;R a node set representing new energy.

[0010] According to another aspect of the present application, a system for calculating maximum short-circuit current of a new energy grid-connected system is provided, the system comprising: 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 operating 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, and obtain a judgment result; a maximum short-circuit current determination unit configured to output 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.

[0011] Preferably, the system operating mode corresponding to the fault point maximum short-circuit current is a limit operating condition of full startup of the new energy and initial zero power, and the voltage coefficient takes the maximum value corresponding to the highest operating voltage of the system.

[0012] Preferably, the fault point short-circuit current expression is: , the node voltage expression is: , the new energy reactive current increment expression is: , wherein, is the fault point maximum short-circuit current; is the maximum value of the voltage coefficient; is the system nominal voltage; is the fault point system self-impedance amplitude; is the amplitude of the element in the i row and the j column of the system impedance matrix; is the new energy reactive current increment injected into the system by the node j ; R a node set representing new energy; is the voltage of the node j ; is the element in thek Rank j the magnitude of the column elements; For nodes k The increase in reactive current from new energy injected into the system; For nodes j Low voltage ride-through threshold; For nodes j Rated current of new energy; For nodes j The maximum current that can be generated by the new energy source; For nodes j The reactive power compensation coefficient of new energy.

[0013] Preferably, the iterative calculation unit performs iterative calculation based on the current maximum short-circuit current of the fault point, the node voltage and the reactive current increment of the new energy source, including: , , , in, The node after the mth iteration j The increase in reactive current from new energy injected into the system; is the maximum short-circuit current of the fault point after the mth iteration; is the maximum value of the voltage coefficient; is the system nominal voltage; is the magnitude of the system self-impedance at the fault point; The system impedance matrix i Rank j the magnitude of the column elements; R A collection of nodes representing new energy components; The node after the mth iteration j voltage; The node after the m-1th iteration j voltage; The system impedance matrix k Rank j the magnitude of the column elements; The node after the mth iteration k The increase in reactive current from new energy injected into the system; For nodes j Low voltage ride-through threshold; For nodes j Rated current of new energy; For nodes j The maximum current that can be generated by the new energy source; For nodes j The reactive power compensation coefficient of new energy.

[0014] Preferably, the iteration calculation unit judges the convergence based on the node voltage after each iteration and the node voltage after the last iteration, and obtains a judgment result, including: If the following condition is met: the judgment result is determined to meet the convergence condition; otherwise, the convergence result is determined to not meet the convergence condition. wherein, is the voltage of the node after the mth iteration; j is the voltage of the node after the (m-1)th iteration; is a preset threshold value; j is a node number; represents a node set composed of new energy. j R 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 method for calculating the maximum short-circuit current of a new energy grid-connected system.

[0015] Based on another aspect of the present application, the present application provides an electronic device, including: the above-mentioned computer readable storage medium; and

[0016] one or more processors for executing the program in the computer readable storage medium. The present application provides a method and system for calculating the maximum short-circuit current of a new energy grid-connected system, including: determining the fault point short-circuit current expression, node voltage expression and new energy reactive current increment expression corresponding to the system operating mode of the fault point maximum short-circuit current; initializing the new energy grid-connected system network, generating the network impedance matrix, and initializing the fault point maximum short-circuit current, node voltage and new energy reactive current increment based on the fault point short-circuit current expression, node voltage expression and new energy reactive current increment expression; performing iterative calculation based on the current fault point maximum short-circuit current, node voltage and new energy reactive current increment, and judging the convergence based on the node voltage after each iteration and the node voltage after the last iteration, and obtaining 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. The present application finds the operating mode corresponding to the maximum short-circuit current, thereby calculating the short-circuit current scheme under this mode, and can solve the problem of conservative treatment of new energy by the existing algorithm, and improve the accuracy and reliability of short-circuit current calculation. BRIEF DESCRIPTION OF DRAWINGS

[0017] The exemplary embodiments of the present application can be more completely understood by reference to the following drawings:

[0018] The exemplary embodiments of the present application can be more completely understood by reference to the following drawings:​ Figure 1 A flow chart 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; Figure 2 A schematic diagram of influence of initial active current of a new energy on fault point current according to an embodiment of the present application; Figure 3 A general flow chart of a method for calculating maximum short-circuit current of a new energy grid-connected system according to an embodiment of the present application; Figure 4 An example diagram of a 36-node system according to an embodiment of the present application; Figure 5 A structural schematic diagram of a system 500 for calculating maximum short-circuit current of a new energy grid-connected system according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] Reference will now be made to the exemplary embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments of the present application can be embodied in many different forms, and are not limited to the embodiments described herein, which are provided as examples of the present application. The terminology used herein is for the purpose of describing the embodiments of the present application and is not intended to limit the present application. In the drawings, the same elements have the same reference numerals.

[0020] 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.

[0021] Figure 1 A flow chart 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. As shown in Figure 1 The method for calculating maximum short-circuit current of a new energy grid-connected system according to the embodiment of the present application can solve the problem of conservative treatment of new energy by existing algorithms by finding the operation mode corresponding to the maximum short-circuit current and calculating the short-circuit current scheme under the mode, and improve 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 the embodiment of the present application starts from step 101, in which the fault point short-circuit current expression, node voltage expression and new energy reactive current increment expression under the system operation mode corresponding to the fault point maximum short-circuit current are determined.

[0022] Preferably, the system operating mode corresponding to the maximum short-circuit current at the fault point is a limit operating condition of full-on initial zero power of new energy, and the voltage coefficient takes the maximum value corresponding to the highest operating voltage of the system.

[0023] Preferably, the short-circuit current expression at the fault point is: , The node voltage expression is: , 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 in the i th row and the j th column of the system impedance matrix; is the voltage of the node j injecting the new energy reactive current increment into the system; R represents a node set composed of new energy; is the voltage of the node j ; is the amplitude of the element in the k th row and the j th column of the system impedance matrix; is the new energy reactive current increment injected by the node k into the system; is the low-voltage ride-through action threshold of the node j ; is the rated current of the new energy of the node j ; is the maximum current that can be generated by the new energy of the node j ; is the new energy reactive compensation coefficient of the node j .

[0024] The short-circuit current at the fault point can be expressed as: , 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 element in the i th row and the j th column of the system impedance matrix.The value of the column; G is a set representing all synchronous generator access nodes. The open circuit voltage at the fault node i , i.e. the equivalent voltage source voltage , wherein, is the phase angle of the open circuit voltage at the fault point.

[0025] The short circuit current at the fault point is: The corresponding fault period voltage of each node is represented as: .

[0026] 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 system operation mode change. As can be seen from the formula of the short circuit current at the fault point, under the condition of network equivalent impedance being determined, the maximum short circuit current at the fault point is affected by the difference value of the output current of the new energy and the operation voltage coefficient c . For a certain bus node fault, when the node voltage drop is determined, the only uncertain factor with mode change is the initial current , and the corresponding initial active power .

[0027] (1) The influence of the initial power of the new energy before fault.

[0028] 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 contributed by the new energy to the fault point before and after the fault can be represented as: , wherein, is the active current increment contributed by the new energy; is the reactive current increment contributed by the new energy.

[0029] The active current increment thereof can be further represented as: , wherein, is the active current component contributed by the new energy to the fault point during the fault period, is the active current component contributed by the new energy to the fault point during normal operation, and the expressions thereof are as follows , Considering that the synchronous generator only generates reactive current during the fault period, the current component it contributes to the fault point is: , The current components generated by the normal operation network are: , For a fault occurring at the same node, the superposition process of the various components of the short-circuit current at the fault point under different initial active powers of renewable energy is as follows: Figure 2 As shown. Figure 2 As can be seen from (a) in the figure, when the initial active current of the new energy source is When the current component generated by the normal operation of the network before the fault Angle with the imaginary axis , Superimpose the incremental generation of new energy When the initial active current is smaller, the superimposed short-circuit current is larger, that is, .from Figure 2 As can be seen from (b), when the active current difference The smaller the value, the greater the short-circuit current after superposition. Sometimes, there are Consider the case where the initial active current and the active current difference are both zero, that is, , when the new energy source is fully powered on and initially at zero power before the fault, the short-circuit current at the fault point reaches its maximum amplitude, corresponding to Figure 2 (b) Since the influence of active current difference on the difference before and after the fault of new energy is far less than that of initial active power, Therefore, the smaller the initial active power of the new energy is, the greater the short-circuit current at the fault point is.

[0030] Therefore, when evaluating the maximum short-circuit current at the fault point, it can be considered that the initial zero power of the new energy fully started is the maximum operating mode, and the short-circuit current can be expressed as: , The corresponding node voltage can be expressed as: .

[0031] (2) Influence of operating voltage coefficient The node voltage formula is further simplified. The node voltage without considering the influence of reactive power support of new energy is used as the judgment condition for whether the new energy enters the low voltage ride-through mode. I REqk =0, then the node voltage is approximately expressed as: , Among them, the variable The superscript "~" in the formula above represents an approximate value, the same below.

[0032] The approximate result of the node voltage obtained 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 faults. When , the station enters low voltage ride-through mode, and the new energy station that meets the condition will be recorded as set L , which belongs to set L The node determination condition of set .

[0033] The approximate expression obtained based on the above formula is: , The maximum short-circuit current at the fault point can be approximately expressed as: , Taking the derivative of the voltage coefficient c in the above formula can obtain: , From the above formula, the short-circuit current and the voltage coefficient c present a monotonic increasing / monotonic decreasing relationship. However, in reality, the scenario that makes almost impossible. Assuming that all new energy stations have the same reactive power compensation coefficient, , since , The minimum value of can be expressed as: , If the above formula can satisfy , it is necessary , and the total capacity of new energy entering low voltage ride-through mode during faults satisfies . For a 220kV voltage level, the self-impedance of the fault point , the reactive power compensation coefficient is , and the new energy entering low voltage ride-through mode is at least , which is obviously impossible.

[0034] Therefore, for the current power system, the higher the operating voltage at the fault point, the larger the short-circuit current during faults, and it increases linearly with the voltage coefficient. When calculating the maximum short-circuit current, c , .

[0035] In summary, the system operating mode corresponding to the maximum short-circuit current at the fault point in the present invention is: the extreme operating condition of initial zero power when all new energy sources are fully turned on, and the voltage coefficient takes the maximum value corresponding to the highest operating voltage of the system.

[0036] The maximum short-circuit current at the fault point can be expressed as: , The node voltage expression is: , The expression of the reactive current increment of new energy is: , in, is the maximum short-circuit current at the fault point; is the maximum value of the voltage coefficient; is the system nominal voltage; is the magnitude of the system self-impedance at the fault point; The system impedance matrix i Rank j the magnitude of the column elements; For nodes j The increase in reactive current from new energy injected into the system; R A collection of nodes representing new energy components; For nodes j voltage; The system impedance matrix k Rank j the magnitude of the column elements; For nodes k The increase in reactive current from new energy injected into the system; For nodes j Low voltage ride-through threshold; For nodes j Rated current of new energy; For nodes j The maximum current that can be generated by the new energy source; For nodes j The reactive power compensation coefficient of new energy.

[0037] In step 102, the new energy grid-connected system network is initialized, a network impedance matrix is ​​generated, and the maximum short-circuit current at the fault point, the node voltage 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.

[0038] In step 103, an iterative calculation is performed based on the current maximum short-circuit current at the fault point, the node voltage, and the reactive current increment of the new energy source, and a convergence judgment is performed based on the node voltage after each iteration and the node voltage after the previous iteration to obtain a judgment result.

[0039] Preferably, the iterative calculation is performed based on the current maximum short-circuit current at the fault point, the node voltage, and the reactive current increment of the new energy source, including: , , , in, The node after the mth iteration j The increase in reactive current from new energy injected into the system; is the maximum short-circuit current of the fault point after the mth iteration; is the maximum value of the voltage coefficient; is the system nominal voltage; is the magnitude of the system self-impedance at the fault point; The system impedance matrix i Rank j the magnitude of the column elements; R A collection of nodes representing new energy components; The node after the mth iteration j voltage; The node after the m-1th iteration j voltage; The system impedance matrix k Rank j the magnitude of the column elements; The node after the mth iteration k The increase in reactive current from new energy injected into the system; For nodes j Low voltage ride-through threshold; For nodes j Rated current of new energy; For nodes j The maximum current that can be generated by the new energy source; For nodes j The reactive power compensation coefficient of new energy.

[0040] Preferably, performing convergence judgment based on the node voltage after each iteration and the node voltage after the previous iteration to obtain the judgment result includes: If satisfied , then the judgment result is determined to meet the convergence condition; otherwise, the convergence result is determined to not meet the convergence condition; in, The node after the mth iteration j voltage; The node after the m-1th iteration j voltage; is the preset threshold;j numbering the nodes; R representing a node set composed of new energy.

[0041] In step 104, when the judgment result indicates that the convergence condition is met, output the current fault point maximum short-circuit current as the new energy grid-connected system maximum short-circuit current.

[0042] In the present application, considering the voltage-current coupling relationship between the fault point short-circuit current expression, the node voltage expression and the new energy reactive power current increment expression, the iterative correction method is used in calculation.

[0043] Specifically, as shown in Figure 3 , the calculation process of the new energy access power system maximum short-circuit current includes: (1) initializing the network. Generating network impedance matrix , initializing variables , .

[0044] (2) the first iteration. According to the node voltage m obtained in the first-1 iteration, the values of variables m after the first iteration are calculated, i.e.: m , , , , , (3) convergence determination. The condition is that the node voltage after the first iteration of each new energy station meets m the node voltage after the first-1 iteration, then the iteration converges, otherwise step (2) is performed until the convergence condition is met, the iteration ends, and step (4) is performed. m (4) output the fault point maximum short-circuit current and the node voltage, and take the current fault point maximum short-circuit current as the new energy grid-connected system maximum short-circuit current.

[0045] (4) output the fault point maximum short-circuit current and the node voltage, and take the current fault point maximum short-circuit current as the new energy grid-connected system maximum short-circuit current.

[0046] ​​​​The present application is based on the actual control strategy of new energy, establishes a nonlinear refinement model of node voltage-output current increment, and the model parameters are all basic parameters, which has low dependence on manufacturers. By obtaining the influence law of parameter change related to the operation mode on short-circuit current, the operation mode corresponding to the maximum short-circuit current at the fault point is selected, and the maximum short-circuit current level can be directly calculated based on the operation mode. At the fault point, the phase angle superposition between the current increment generated by new energy and the current component generated by the equivalent voltage source is considered, which effectively reduces the conservatism of the amplitude superposition of the existing method. According to the characteristics of the new energy model, an iterative framework for short-circuit current calculation is designed. Finally, a new implementation scheme for calculating the maximum short-circuit current of a power system with new energy access is formed.

[0047] The comparison between the scheme and the prior art is shown in Table 1.

[0048] Table 1 Comparison of various short-circuit current calculation methods In order to compare with the results of the prior art and show the superiority of the method proposed in the present application, a 36-node example is used for verification. Seven new energy stations are connected to nodes 1, 4, 12, 13, 32, 34 and 36, and four synchronous generators are connected to nodes 14, 23, 24 and 27. Figure 4

[0049] The comparison results are shown in Table 2, and the electromagnetic transient simulation results are used as the comparison benchmark. As shown in Table 2, the results obtained by using the first technology IEC 60909-2016 / GBT 15544-2023 method are the most conservative, and the error will reach 22.14%. The second technology GBT 44659-2024 method can obtain the maximum short-circuit current results under different new energy simultaneous rates, and the maximum short-circuit current is selected, the error is 12.64%, which is reduced by 9.5% compared with the first technology. By using the method proposed in the present application, the calculation error is 3.64%, which is further reduced by 9% compared with the first technology. It can be seen that the scheme proposed in the present application greatly reduces the conservatism of the results, and improves the accuracy and reliability of the calculation results.

[0050] Table 2 Comparison of maximum short-circuit current results of different calculation methods Figure 5 A structural schematic diagram of a system 500 for calculating the maximum short-circuit current of a new energy grid-connected system according to an embodiment of the present application. As shown in Figure 5 ​As shown, the system 500 for calculating the maximum short-circuit current of the new energy grid-connected system provided by the embodiment of the present application comprises an expression determination unit 501, an initialization unit 502, an iterative calculation unit 503 and a maximum short-circuit current determination unit 504.

[0051] Preferably, the expression determination unit 501 is configured to determine the fault point short-circuit current expression, the node voltage expression and the new energy reactive current increment expression corresponding to the system operation mode of the fault point maximum short-circuit current.

[0052] Preferably, the system operation mode corresponding to the fault point maximum short-circuit current is the limit working condition of the 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.

[0053] Preferably, the fault point short-circuit current expression is: , The node voltage expression is: , The new energy reactive current increment expression is: , wherein, is the fault point maximum short-circuit current; is the maximum value of the voltage coefficient; is the system nominal voltage; is the fault point system self-impedance amplitude; is the amplitude of the element in the first row and the first column of the system impedance matrix; i is the new energy reactive current increment injected into the system by the node; j represents a node set composed of new energy; is the voltage of the node; j is the amplitude of the element in the first row and the first column of the system impedance matrix; R is the new energy reactive current increment injected into the system by the node; is the low voltage ride-through action threshold of the node; j is the rated current of the new energy of the node; is the maximum current that can be generated by the new energy of the node; k is the new energy reactive compensation coefficient of the node. j k j j j j

[0054] ​​​​​​​​​​​Preferably, the initialization unit 502 is configured to initialize a new energy grid-connected system network, generate a network impedance matrix, and initialize a fault point maximum short-circuit current, a node voltage, and a 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.

[0055] Preferably, the iterative calculation unit 503 is 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.

[0056] Preferably, the iterative calculation unit 503 performs iterative calculation based on the current fault point maximum short-circuit current, the node voltage, and the new energy reactive current increment, including: , , , wherein, is the voltage of the node j after the mth iteration; is the fault point maximum short-circuit current after the mth iteration; is the maximum value of the voltage coefficient; is the system nominal voltage; is the system self-impedance amplitude at the fault point; is the amplitude of the element in the mth row and the nth column of the system impedance matrix; i represents a node set composed of new energy; j is the voltage of the node R after the mth iteration; is the voltage of the node j after the (m-1)th iteration; is the amplitude of the element in the mth row and the nth column of the system impedance matrix; j is the new energy reactive current increment injected into the system by the node after the mth iteration; k is the low voltage ride through action threshold of the node j ; is the new energy rated current of the node k ; is the maximum current that can be generated by the new energy of the node j ; is the new energy reactive compensation coefficient of the node j . j j ​​​​

[0057] 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.

[0058] 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: If the following condition is met: the determination result is determined to meet the convergence condition; otherwise, the convergence result is determined to not meet the convergence condition. wherein, V m is the voltage of the node after the mth iteration; j V m-1 is the voltage of the node after the (m-1)th iteration; is a preset threshold value; j is a node number; represents a node set composed of new energy. j R 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.

[0059] 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 method for calculating the new energy grid-connected system maximum short-circuit current.

[0060] Based on another aspect of the present application, the present application provides an electronic device, including: the above-mentioned computer readable storage medium; and

[0061] one or more processors configured to execute the program in the computer readable storage medium. The present application has been described by referring to a small number of embodiments. However, it is well known to those skilled in the art that other embodiments, etc. within the scope of the present application are equivalent to the above disclosed embodiments.

[0062] Generally, all the terms used in the present application are interpreted according to their usual meanings in the technical field, unless otherwise explicitly defined therein. All references to "a / the / that [device, component, etc.]" are interpreted to be at least one example of the device, component, etc., unless otherwise explicitly stated. The steps of any method disclosed herein do not necessarily have to be run in the exact order disclosed, unless explicitly stated.

[0063] Generally, all the terms used in the present application are interpreted according to their usual meanings in the technical field, unless otherwise explicitly defined therein. All references to "a / the / that [device, component, etc.]" are interpreted to be at least one example of the device, component, etc., unless otherwise explicitly stated. The steps of any method disclosed herein do not necessarily have to be run in the exact order disclosed, unless explicitly stated.

[0064] ​Those skilled in the art will appreciate that embodiments of the application can be devised for a method, a system, or a computer program product. Accordingly, the present application can be embodied in 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-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0065] The present application is described in reference to the flowchart and / or block diagrams of the method, apparatus (system) and computer program product according to embodiments of the application. It will be understood that each block of the flowchart and / or block diagrams, and combinations of blocks in the flowchart 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 processor, 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 and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0066] 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 and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0067] These 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 and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0068] Finally, it should be noted that the above-mentioned embodiments are merely intended for describing the technical solutions of the present application, but not for limiting it. Although the present application is described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered in the protection scope of the present application.

Claims

1. A method for calculating the maximum short-circuit current of a new energy grid-connected system, characterized in that: The method comprises: Determine the short-circuit current expression at the fault point, the node voltage expression, and the incremental expression of the reactive current of new energy sources under the system operation mode corresponding to the maximum short-circuit current at the fault point; 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; Iterative calculation is performed based on the current maximum short-circuit current at the fault point, node voltage, and renewable energy reactive current increment. Convergence is judged based on the node voltage after each iteration and the node voltage after the previous iteration to obtain the judgment result. When the judgment result indicates that the convergence condition is met, the maximum short-circuit current of the current fault point is output as the maximum short-circuit current of the new energy grid-connected system.

2. The method according to claim 1, characterized in that The system operating mode corresponding to the maximum short-circuit current at the fault point is: the extreme operating condition of initial zero power when all new energy sources are fully turned on, and the voltage coefficient takes the maximum value corresponding to the highest operating voltage of the system.

3. The method according to claim 1, characterized in that The short-circuit current expression at the fault point is: ， The node voltage expression is: ， The expression of the reactive current increment of new energy is: ， in, is the maximum short-circuit current at the fault point; is the maximum value of the voltage coefficient; is the system nominal voltage; is the magnitude of the system self-impedance at the fault point; The system impedance matrix i Rank j the magnitude of the column elements; For nodes j The increase in reactive current from new energy injected into the system; R A collection of nodes representing new energy components; For nodes j voltage; The impedance matrix of the system k Rank j the magnitude of the column elements; For nodes k The increase in reactive current from new energy injected into the system; For nodes j Low voltage ride-through threshold; For nodes j Rated current of new energy; For nodes j The maximum current that can be generated by the new energy source; For nodes j The reactive power compensation coefficient of new energy.

4. The method according to claim 1, wherein Iterative calculation is performed based on the current maximum short-circuit current at the fault point, node voltage, and renewable energy reactive current increment, including: ， ， ， in, The node after the mth iteration j The increase in reactive current from new energy injected into the system; is the maximum short-circuit current of the fault point after the mth iteration; is the maximum value of the voltage coefficient; is the system nominal voltage; is the magnitude of the system self-impedance at the fault point; The system impedance matrix i Rank j the magnitude of the column elements; R A collection of nodes representing new energy components; The node after the mth iteration j voltage; The node after the m-1th iteration j voltage; The system impedance matrix k Rank j the magnitude of the column elements; The node after the mth iteration k The increase in reactive current from new energy injected into the system; For nodes j Low voltage ride-through threshold; For nodes j Rated current of new energy; For nodes j The maximum current that can be generated by the new energy source; For nodes j The reactive power compensation coefficient of new energy.

5. The method according to claim 1, wherein The convergence is judged based on the node voltage after each iteration and the node voltage after the previous iteration, and the judgment results are obtained, including: If satisfied , then the judgment result is determined to meet the convergence condition; otherwise, the convergence result is determined to not meet the convergence condition; in, The node after the mth iteration j voltage; The node after the m-1th iteration j voltage; is the preset threshold; j Number the node; R A collection of nodes representing new energy sources.

6. A system for calculating the maximum short-circuit current of a new energy grid-connected system, characterized in that: The system comprises: An expression determination unit, used to determine the short-circuit current expression of the fault point, the node voltage expression and the new energy reactive current increment expression under the system operation mode corresponding to the maximum short-circuit current of the fault point; An initialization unit 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; An iterative calculation unit is used to perform iterative calculation based on the current maximum short-circuit current of the fault point, the node voltage and the reactive current increment 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 to obtain a judgment result; The maximum short-circuit current determining unit is configured to output the current maximum short-circuit current of the fault point as the maximum short-circuit current of the new energy grid-connected system when the judgment result indicates that the convergence condition is met.

7. The system according to claim 6, characterized in that The system operating mode corresponding to the maximum short-circuit current at the fault point is: the extreme operating condition of initial zero power when all new energy sources are fully turned on, and the voltage coefficient takes the maximum value corresponding to the highest operating voltage of the system.

8. The system according to claim 6, wherein: The short-circuit current expression at the fault point is: ， The node voltage expression is: ， The expression of the reactive current increment of new energy is: ， in, is the maximum short-circuit current at the fault point; is the maximum value of the voltage coefficient; is the system nominal voltage; is the magnitude of the system self-impedance at the fault point; The impedance matrix of the system i Rank j the magnitude of the column elements; For nodes j The increase in reactive current from new energy injected into the system; R A collection of nodes representing new energy components; For nodes j voltage; The impedance matrix of the system k Rank j the magnitude of the column elements; For nodes k The increase in reactive current from new energy injected into the system; For nodes j Low voltage ride-through threshold; For nodes j Rated current of new energy; For nodes j The maximum current that can be generated by the new energy source; For nodes j The reactive power compensation coefficient of new energy.

9. The system according to claim 6, wherein: The iterative calculation unit performs iterative calculation based on the current maximum short-circuit current of the fault point, the node voltage and the reactive current increment of the new energy source, including: ， ， ， in, The node after the mth iteration j The increase in reactive current from new energy injected into the system; is the maximum short-circuit current of the fault point after the mth iteration; is the maximum value of the voltage coefficient; is the system nominal voltage; is the magnitude of the system self-impedance at the fault point; The impedance matrix of the system i Rank j the magnitude of the column elements; R A collection of nodes representing new energy components; The node after the mth iteration j voltage; The node after the m-1th iteration j voltage; The impedance matrix of the system k Rank j the magnitude of the column elements; The node after the mth iteration k The increase in reactive current from new energy injected into the system; For nodes j Low voltage ride-through threshold; For nodes j Rated current of new energy; For nodes j The maximum current that can be generated by the new energy source; For nodes j The reactive power compensation coefficient of new energy.

10. The system according to claim 6, wherein: The iterative calculation unit performs convergence judgment based on the node voltage after each iteration and the node voltage after the previous iteration to obtain a judgment result, including: If satisfied , then the judgment result is determined to meet the convergence condition; otherwise, the convergence result is determined to not meet the convergence condition; in, The node after the mth iteration j voltage; The node after the m-1th iteration j voltage; is the preset threshold; j Number the node; R A collection of nodes representing new energy sources.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

12. An electronic device, characterized in that: include: The computer-readable storage medium of claim 11; as well as One or more processors are configured to execute the program in the computer-readable storage medium.

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