Short-circuit current calculation method and system for distributed photovoltaic power distribution network

Abstract

The invention discloses a short-circuit current calculation method and system for a distributed photovoltaic power distribution network, and relates to the technical field of power distribution networks, and the method comprises the steps: obtaining the power parameters of each port of a distributed power supply in the distributed photovoltaic power distribution network, and constructing a distributed power supply fault calculation model according to the power parameters of each port; according to the electric power parameters of the distributed power supply in the initial state and a distributed power supply fault calculation model, the output current of the distributed power supply is calculated; calculating column elements of IBDG in an equivalent Norton impedance matrix of the nodes under a sequence component calculation model; according to the output current and the column element of the distributed power supply, calculating the voltage of the photovoltaic inverter in the fault distribution network; and under the sequence component calculation model, calculating to obtain the fault current of the fault port. According to the method, the fault nodes are equivalently removed from the network through a negative branch parallel connection method, only very few element parameters need to be corrected for different fault types, and the solving method is simpler and more convenient.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution network, and in particular to a short-circuit current calculation method and system for a distributed photovoltaic power distribution network. Background Art

[0002] With the continuous growth of global energy demand and the emphasis on renewable energy, photovoltaic power generation, as a clean and renewable energy form, has been widely used and developed in recent years. As an important form of photovoltaic power generation, distributed photovoltaic power generation systems have the characteristics of decentralized layout, small scale, and wide geographical coverage, and are widely used in residential areas, commercial buildings and rural areas. However, with the large-scale access of distributed photovoltaic systems to the distribution network, traditional short-circuit current calculation methods face new challenges.

[0003] The traditional short-circuit current calculation method is mainly based on the single power network theory. However, after the introduction of distributed photovoltaic power sources, the distribution network changes from a single power network to a multi-power network. This change will affect the normal operation and abnormal operation of the distribution network. The existence of multiple power sources will cause many different types of faults, making the calculation of short-circuit current more complicated. Especially when a short-circuit fault occurs, some existing distributed power distribution network fault calculation methods are generally established for similar or identical fault types, and many different types of faults will occur, making it difficult to solve the problem of calculating different types of fault currents in the distribution network. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the problem to be solved by the present invention is: how to solve the problem of calculating the current of different types of faults in the distribution network when a short circuit fault occurs. Some existing distributed power distribution network fault calculation methods are generally established for similar or identical fault types, and many different types of faults may occur, making it difficult to solve the problem of calculating the current of different types of faults in the distribution network.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: a method for calculating short-circuit current of a distributed photovoltaic distribution network, comprising: obtaining power parameters of each port of a distributed power source in the distributed photovoltaic distribution network, and constructing a distributed power source fault calculation model according to the power parameters of each port; obtaining power parameters of the distributed power source in the distributed photovoltaic distribution network in an initial state, and calculating the output current of the distributed power source according to the power parameters of the distributed power source in the initial state and the distributed power source fault calculation model; calculating the column elements of IBDG in an equivalent Norton impedance matrix of a node under a sequence component calculation model; calculating the voltage of a photovoltaic inverter when the distribution network is faulty according to the output current and column elements of the distributed power source; under the sequence component calculation model, calculating the fault current of the fault port according to the voltage of the photovoltaic inverter when the distribution network is faulty and the equivalent Norton admittance matrix of the node.

[0007] As a preferred solution of the short-circuit current calculation method of a distributed photovoltaic distribution network described in the present invention, wherein: the distributed power supply fault calculation model includes that according to the low voltage ride-through characteristics of the distributed power supply, when a fault occurs in the distribution network, the output state of the photovoltaic inverter can be divided into a constant power output state and a voltage support output state by the voltage of the grid-connected node; the constant power output state includes a judgment condition that the voltage of the inverter grid-connected node exceeds 90% of the rated voltage of the inverter during normal operation, the inverter control strategy remains unchanged, and the original output state is maintained. In the constant power output state, the inverter-type distributed power supply is connected to the distribution network node i, and the voltage and current calculation model of the inverter output is expressed as:

[0008]

[0009] in, is the positive and negative zero-sequence voltage component of the voltage at port i, is the phase voltage at port i of the inverter-type grid-connected distributed power source, iI 1.i is the positive sequence current of the distributed generation grid-connected port i, is the current at the input port i of the distributed power supply, is the conjugate of the output power of the distributed generation grid-connected port i, is the conjugate of the positive sequence voltage at the input port i of the distributed power supply, S is the symmetric component matrix, is the zero-sequence voltage component of port i, is the positive sequence voltage component of the voltage at port i, is the negative sequence voltage component of the voltage at port i, is the phase a voltage at port i of the inverter-type grid-connected distributed power source, is the phase b voltage at port i of the inverter-type grid-connected distributed power source, is the c-phase voltage at port i of the inverter-type grid-connected distributed power source.

[0010] As a preferred solution of the short-circuit current calculation method of a distributed photovoltaic distribution network described in the present invention, the voltage support output state includes the judgment condition that the voltage of the inverter grid-connected node is less than 90% of the rated voltage of the inverter during normal operation, the inverter working state is the voltage support output state, and the active current, reactive current and output current of the distributed power source are calculated as follows:

[0011]

[0012] Among them, I q.i and I p.i are the active current and reactive current injected into the IBDG grid-connected port i, I N.i is the rated current output by the IBDG inverter at the grid-connected port i, P N.i is the active power output by the IBDG inverter at the grid-connected port i, is the positive sequence current output by the IBDG inverter, θ is the angle between the voltage phasor at the IBDG access point and the reference coordinate axis in the coordinate system, U 1.i It is the positive sequence voltage output by the inverter.

[0013] As a preferred solution of the short-circuit current calculation method of a distributed photovoltaic distribution network described in the present invention, the output current of the distributed power source is expressed as:

[0014]

[0015] I' DG2 =F(U' d )

[0016] in, is the output current of the distributed generation before the fault, is the conjugate of the rated power of the distributed generation connected to node i, is the conjugate of the voltage at node i, F(U' d ) is the piecewise nonlinear function of the distributed power supply fault calculation model, U' d =U' (0) is the voltage of the distributed power supply in the initial state, I' DG2 is the output current of the distributed power supply.

[0017] As a preferred solution of the short-circuit current calculation method of a distributed photovoltaic distribution network described in the present invention, wherein: the equivalent Norton impedance matrix includes a node impedance matrix calculated by using the Thevenin equivalent under the sequence component calculation model, and there are two fault ports α=(i,j) and β=(p,q) in the power grid, α=(i,j) is a longitudinal fault port, β=(p,q) is a transverse fault port, i,p,q are nodes in the power grid, j is a reference node ground node, then the impedance matrix Z eq It is expressed as:

[0018]

[0019] Among them, M α is a matrix with the element at the i-th node being 1 and all other elements being 0. β is a matrix whose elements on the i-th node are 1 and -1, and other elements are all 0; the association matrix M of each node F Substituting in, it is expressed as:

[0020]

[0021] The elements are all elements in the node impedance matrix. According to the node impedance matrix Z eq Get the column element Z of IBDG DG2 .

[0022] As a preferred solution of the short-circuit current calculation method of a distributed photovoltaic distribution network described in the present invention, the voltage of the photovoltaic inverter during a fault distribution network is expressed as:

[0023]

[0024] in, It is the voltage of the PV inverter when the fault occurs.

[0025] As a preferred solution of the short-circuit current calculation method of a distributed photovoltaic distribution network described in the present invention, the fault current of the fault port is expressed as:

[0026]

[0027] Y F =Z eq -1

[0028] in, is the fault current of the fault port, I is the unit matrix, is the Thevenin equivalent voltage column vector, is the voltage phasor at point β, Y F Node equivalent Norton admittance matrix, U' FIt is the voltage of the PV inverter when the fault occurs.

[0029] Another object of the present invention is to provide a system for a short-circuit current calculation method of a distributed photovoltaic distribution network, which can solve the short-circuit current calculation problem of a distributed photovoltaic distribution network by constructing a short-circuit current calculation system of the distributed photovoltaic distribution network.

[0030] To solve the above technical problems, the present invention provides the following technical solutions: a short-circuit current calculation system for a distributed photovoltaic distribution network, comprising a model construction module, an output current calculation module, a column element calculation module, a voltage calculation module and a fault current calculation module; the model construction module is used to obtain the power parameters of each port of a distributed power source in the distributed photovoltaic distribution network, and to construct a distributed power source fault calculation model according to the power parameters of each port; the output current calculation module is used to obtain the power parameters of the distributed power source in the distributed photovoltaic distribution network in the initial state, and to calculate the output current of the distributed power source according to the power parameters of the distributed power source in the initial state and the distributed power source fault calculation model; the column element calculation module is used to calculate the column elements of IBDG in the equivalent Norton impedance matrix of the node under the sequence component calculation model; the voltage calculation module calculates the voltage of the photovoltaic inverter when the fault distribution network is in operation according to the output current and column elements of the distributed power source; the fault current calculation module is used to calculate the fault current of the fault port according to the voltage of the photovoltaic inverter when the fault distribution network is in operation and the node equivalent Norton admittance matrix under the sequence component calculation model.

[0031] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the above-mentioned method for calculating short-circuit current of a distributed photovoltaic distribution network are implemented.

[0032] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the short-circuit current calculation method of a distributed photovoltaic distribution network as described above.

[0033] The beneficial effects of the present invention are as follows: a short-circuit current calculation method for a distributed photovoltaic distribution network provided by the present invention performs Norton equivalence on the original network except for the faulty node, and then establishes calculation models for the grid connection of inverter-type distributed power sources under the sequence component calculation model, and utilizes the Norton Thevenin equivalence to remove the faulty node equivalently from the network by connecting a negative branch in parallel, so that only a very small number of component parameters need to be corrected for different fault types, and the solution method is simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0035] Figure 1 A flow chart of a method for calculating short-circuit current of a distributed photovoltaic distribution network provided in the first embodiment of the present invention.

[0036] Figure 2 A schematic diagram of a distributed photovoltaic distribution network and a distributed power source grid connection diagram of a short-circuit current calculation method of a distributed photovoltaic distribution network provided by a first embodiment of the present invention.

[0037] Figure 3 A structural diagram of a short-circuit current calculation system for a distributed photovoltaic distribution network provided in accordance with a second embodiment of the present invention.

[0038] Figure 4 An inverter grid-connected distributed power supply diagram of a short-circuit current calculation method for a distributed photovoltaic distribution network provided in a third embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0040] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] Example 1, reference Figure 1-2, which is the first embodiment of the present invention, and the embodiment provides a short-circuit current calculation method for a distributed photovoltaic distribution network, including: obtaining power parameters of each port of a distributed power source in the distributed photovoltaic distribution network, and constructing a distributed power source fault calculation model according to the power parameters of each port; obtaining power parameters of the distributed power source in the distributed photovoltaic distribution network in an initial state, and calculating the output current of the distributed power source according to the power parameters of the distributed power source in the initial state and the distributed power source fault calculation model; calculating the column elements of IBDG in the equivalent Norton impedance matrix of the node under the sequence component calculation model; calculating the voltage of the photovoltaic inverter when the fault distribution network is in operation according to the output current and column elements of the distributed power source; under the sequence component calculation model, calculating the fault current of the fault port according to the voltage of the photovoltaic inverter when the fault distribution network is in operation and the node equivalent Norton admittance matrix.

[0042] S1. Obtain the power parameters of each port of the distributed power source in the distributed photovoltaic distribution network, and build a distributed power source fault calculation model based on the power parameters of each port.

[0043] According to the low voltage ride-through characteristics of distributed power sources, when a distribution network failure occurs, the output state of the photovoltaic inverter can be divided into the following states according to the voltage of the grid-connected node:

[0044] S1.1, constant power output state.

[0045] The condition for determining the constant power output state is that the voltage of the inverter grid-connected node exceeds 90% of the rated voltage during normal operation of the inverter. At this time, the control strategy of the inverter device remains unchanged and the original output state is maintained.

[0046] In the constant power output state, it is assumed that the inverter distributed power supply is connected to the distribution network node i, as follows Figure 2 As shown, the voltage and current calculation model of the inverter output is as follows:

[0047]

[0048] in, is the positive and negative zero-sequence voltage component of the voltage at port i, is the phase voltage at port i of the inverter-type grid-connected distributed power source, is the positive sequence current of the distributed generation grid-connected port i, is the current at the input port i of the distributed power supply, is the conjugate of the output power of the distributed generation grid-connected port i, is the conjugate of the positive sequence voltage at the input port i of the distributed power supply, S is the symmetric component matrix, is the zero-sequence voltage component of port i, is the positive sequence voltage component of the voltage at port i, is the negative sequence voltage component of the voltage at port i, is the phase a voltage at port i of the inverter-type grid-connected distributed power source, is the phase b voltage at port i of the inverter-type grid-connected distributed power source, is the c-phase voltage at port i of the inverter-type grid-connected distributed power source.

[0049] S1.2, voltage support output status.

[0050] The condition for determining the voltage support output state is that the voltage of the inverter grid-connected node is less than 90% of the rated voltage when the inverter is in normal operation. At this time, the inverter working state is the voltage support output state. At this time, the active current, reactive current and output current of the distributed power source are calculated as follows:

[0051]

[0052] Among them, I q.i and I p.i are the active current and reactive current injected into the IBDG grid-connected port i, I N.i is the rated current output by the IBDG inverter at the grid-connected port i, P N.i is the active power output by the IBDG inverter at the grid-connected port i, iI 1.i is the positive sequence current output by the IBDG inverter, θ is the angle between the voltage phasor at the IBDG access point and the reference coordinate axis in the coordinate system, U 1.i It is the positive sequence voltage output by the inverter.

[0053] S2. Obtain the power parameters of the distributed power source in the distributed photovoltaic distribution network in the initial state. According to the power parameters of the distributed power source in the initial state and the distributed power source fault calculation model, calculate the output current of the distributed power source, which is expressed as:

[0054]

[0055] I' DG2 =F(U' d )

[0056] in, is the output current of the distributed power source before the fault; is the conjugate of the rated power of the distributed generation connected to node i; is the conjugate of the voltage at node i; F(U' d ) is the piecewise nonlinear function of the distributed power supply fault calculation model; U' d =U' (0) is the voltage of the distributed power source in the initial state (the voltage before the fault), I' DG2 is the output current of the distributed power supply.

[0057] S3, according to the equivalent Norton impedance matrix Z of the node calculated under the sequence component calculation model eq The column element Z of IBDG DG2 .

[0058] The sequence component calculation model is an existing voltage or current calculation model that combines the positive sequence, negative sequence and zero sequence components to simplify the calculation process and improve the calculation accuracy.

[0059] Under the sequence component calculation model, the Thevenin equivalent is used to calculate the node impedance matrix; assuming that there are two fault ports α=(i,j) and β=(p,q) in the power grid, α=(i,j) is the longitudinal fault port, β=(p,q) is the transverse fault port; i,p,q are nodes in the power grid, and j is the reference node. Then the Thevenin equivalent impedance Z eq (The node impedance matrix in the network) can be expressed as:

[0060]

[0061] Among them, M α is a matrix with the element at the i-th node being 1 and all other elements being 0; M β It is a matrix whose elements at the i-th node are 1 and -1, and all other elements are 0.

[0062] The association matrix M of each node F Substituting into the above formula, we can get the following formula:

[0063]

[0064] It should be noted that the elements in the above formula are all elements in the node impedance matrix; according to the node impedance matrix Z eq Get the column element Z of IBDG DG2 .

[0065] S4, according to the output current I' of the distributed power supply DG2 and column element Z DG2 , calculate the voltage U' of the PV inverter when the fault distribution network is D ' G2 .

[0066] The impact of the output current of the photovoltaic inverter on the voltage of the fault distribution network can be expressed as:

[0067]

[0068] S5. Under the sequence component model, the fault current of the fault port is calculated based on the voltage of the PV inverter at the time of fault distribution and the node equivalent Norton admittance matrix (the node equivalent Norton admittance matrix is ​​obtained from the equivalent Norton impedance matrix). It is expressed as:

[0069]

[0070] Y F =Z eq -1

[0071] Where I is the identity matrix, is the Thevenin equivalent voltage column vector; is the voltage phasor at point β; Y F Node equivalent Norton admittance matrix, U' F It is the voltage of the PV inverter when the fault distribution network occurs (fault voltage of the fault port).

[0072] Example 2, reference Figure 3 , which is the second embodiment of the present invention, is different from the previous embodiment in that it provides a short-circuit current calculation system for a distributed photovoltaic distribution network, including: a model building module 100, an output current calculation module 200, a column element calculation module 300, a voltage calculation module 400 and a fault current calculation module 500.

[0073] The model building module 100 is used to obtain power parameters of each port of a distributed power source in a distributed photovoltaic distribution network, and to build a distributed power source fault calculation model according to the power parameters of each port.

[0074] The output current calculation module 200 is used to obtain the power parameters of the distributed power source in the distributed photovoltaic distribution network in the initial state, and calculate the output current of the distributed power source according to the power parameters of the distributed power source in the initial state and the distributed power source fault calculation model.

[0075] The column element calculation module 300 is used to calculate the column elements of the IBDG in the equivalent Norton impedance matrix of the node under the sequence component calculation model.

[0076] The voltage calculation module 400 calculates the voltage of the photovoltaic inverter when the fault distribution network occurs according to the output current and column elements of the distributed power source.

[0077] The fault current calculation module 500 is used to calculate the fault current of the fault port according to the voltage of the photovoltaic inverter and the node equivalent Norton admittance matrix when the fault distribution network is in the sequence component calculation model.

[0078] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0079] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0080] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0081] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0082] Example 3, reference Figure 4 , which is the third embodiment of the present invention, and which is different from the first two embodiments in that it is used to verify and illustrate the technical effects adopted in the present invention, so as to verify the real effects of this method.

[0083] as follows Figure 4 As shown in the figure, there are 10 nodes in total. Nodes 5 and 8 are connected to the first type of distributed power distribution network and the second type of distributed power distribution network respectively. Both are inverter grid-connected distributed power sources. (1)...(9) are line impedances, (i) represents the branch number, and Arabic numerals represent the node number. The fault node is set at node 8, and the short-circuit components when different types of short-circuit faults occur at node 8 are calculated and analyzed.

[0084] In order to verify the practicality of the algorithm proposed in this paper, the convergence performance of the fault current calculation algorithm under two different access positions and different rated capacities is obtained under the same convergence accuracy. The initial data of distributed power supply and the algorithm iteration results are shown in Tables 1 and 2. Comparing the number of iterations of two-phase short circuit and three-phase short circuit in Table 1 and Table 2, it can be seen that for two-phase short circuit, the larger the capacity of distributed power supply and the farther the distributed power supply is from the upper power supply, the more iterations there are. Therefore, the short-circuit current calculation algorithm for the distribution network containing distributed power supply proposed in this paper has high accuracy, good applicability, good convergence for different types of faults, and is universal and effective.

[0085] Table 1 Initial data of distributed generation distribution network

[0086]

[0087]

[0088] Table 2 Calculation iterations for different fault types

[0089]

[0090] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for calculating short-circuit current of a distributed photovoltaic distribution network, characterized in that: include, Obtain the power parameters of each port of the distributed power source in the distributed photovoltaic distribution network, and build a distributed power source fault calculation model based on the power parameters of each port; Obtaining power parameters of the distributed power source in the distributed photovoltaic distribution network in the initial state, and calculating the output current of the distributed power source according to the power parameters of the distributed power source in the initial state and the distributed power source fault calculation model; According to the column elements of IBDG in the equivalent Norton impedance matrix of the node calculated under the sequence component calculation model; According to the output current and column elements of the distributed power source, the voltage of the photovoltaic inverter when the fault distribution network is in failure is calculated; Under the sequence component calculation model, the fault current of the fault port is calculated according to the voltage of the photovoltaic inverter during the fault distribution network and the node equivalent Norton admittance matrix.

2. A method for calculating short-circuit current of a distributed photovoltaic distribution network as claimed in claim 1, characterized in that: The distributed power supply fault calculation model includes that according to the low voltage ride-through characteristics of the distributed power supply, when a distribution network fault occurs, the output state of the photovoltaic inverter can be divided into a constant power output state and a voltage support output state according to the voltage of the grid-connected node; The constant power output state includes a judgment condition that the voltage of the inverter grid-connected node exceeds 90% of the rated voltage when the inverter is in normal operation, the control strategy of the inverter device remains unchanged, and the original output state is maintained. In the constant power output state, the inverter-type distributed power supply is connected to the distribution network node i, and the voltage and current calculation model of the inverter output is expressed as: in, is the positive and negative zero-sequence voltage component of the voltage at port i, is the phase voltage at port i of the inverter-type grid-connected distributed power source, is the positive sequence current of the distributed generation grid-connected port i, is the current at the input port i of the distributed power supply, is the conjugate of the output power of the distributed generation grid-connected port i, is the conjugate of the positive sequence voltage at the input port i of the distributed power supply, S is the symmetric component matrix, is the zero-sequence voltage component of port i, is the positive sequence voltage component of the voltage at port i, is the negative sequence voltage component of the voltage at port i, is the phase a voltage at port i of the inverter-type grid-connected distributed power source, is the phase b voltage at port i of the inverter-type grid-connected distributed power source, is the c-phase voltage at port i of the inverter-type grid-connected distributed power source.

3. A method for calculating short-circuit current of a distributed photovoltaic power distribution network as claimed in claim 2, characterized in that: The voltage support output state includes the judgment condition that the voltage of the inverter grid-connected node is less than 90% of the rated voltage when the inverter is in normal operation, the inverter working state is the voltage support output state, and the active current, reactive current and output current of the distributed power source are calculated and expressed as follows: Among them, I q.i and I p.i are the active current and reactive current injected into the IBDG grid-connected port i, I N.i is the rated current output by the IBDG inverter at the grid-connected port i, P N.i is the active power output by the IBDG inverter at the grid-connected port i, is the positive sequence current output by the IBDG inverter, θ is the angle between the voltage phasor at the IBDG access point and the reference coordinate axis in the coordinate system, U 1.i It is the positive sequence voltage output by the inverter.

4. A method for calculating short-circuit current of a distributed photovoltaic power distribution network as claimed in claim 3, characterized in that: The output current of the distributed power supply is expressed as, I′ DG2 =F(U′ d ) in, is the output current of the distributed generation before the fault, is the conjugate of the rated power of the distributed generation connected to node i, is the conjugate of the voltage at node i, F(U' d ) is the piecewise nonlinear function of the distributed power supply fault calculation model, U' d =U' (0) is the voltage of the distributed power supply in the initial state, I' DG2 is the output current of the distributed power supply.

5. A method for calculating short-circuit current of a distributed photovoltaic power distribution network as claimed in claim 4, characterized in that: The equivalent Norton impedance matrix includes a node impedance matrix calculated by using the Thevenin equivalent under the sequence component calculation model. There are two fault ports α=(i,j) and β=(p,q) in the power grid, α=(i,j) is a longitudinal fault port, β=(p,q) is a transverse fault port, i,p,q are nodes in the power grid, j is a reference node ground node, then the impedance matrix Z eq It is expressed as, Among them, M α is a matrix with the element at the i-th node being 1 and all other elements being 0. β It is a matrix whose elements at the i-th node are 1 and -1, and all other elements are 0; The association matrix M of each node F Substituting, it is expressed as, The elements are all elements in the node impedance matrix. According to the node impedance matrix Z eq Get the column element Z of IBDG DG2 .

6. A method for calculating short-circuit current of a distributed photovoltaic power distribution network as claimed in claim 5, characterized in that: The voltage of the photovoltaic inverter during fault distribution is expressed as: in, It is the voltage of the PV inverter when the fault occurs.

7. A method for calculating short-circuit current of a distributed photovoltaic power distribution network as claimed in claim 6, characterized in that: The fault current of the fault port is expressed as, Y F =Z eq -1 in, is the fault current of the fault port, I is the unit matrix, is the Thevenin equivalent voltage column vector, is the voltage phasor at point β, Y F Node equivalent Norton admittance matrix, U' F It is the voltage of the PV inverter when the fault occurs.

8. A system using a short-circuit current calculation method for a distributed photovoltaic distribution network as claimed in any one of claims 1 to 7, characterized in that: It comprises a model building module (100), an output current calculation module (200), a column element calculation module (300), a voltage calculation module (400) and a fault current calculation module (500); The model building module (100) is used to obtain power parameters of each port of a distributed power source in a distributed photovoltaic power distribution network, and to build a distributed power source fault calculation model according to the power parameters of each port; The output current calculation module (200) is used to obtain the power parameters of the distributed power source in the distributed photovoltaic power distribution network in the initial state, and calculate the output current of the distributed power source according to the power parameters of the distributed power source in the initial state and the distributed power source fault calculation model; The column element calculation module (300) is used to calculate the column elements of IBDG in the equivalent Norton impedance matrix of the node under the sequence component calculation model; The voltage calculation module (400) calculates the voltage of the photovoltaic inverter when the distribution network fails according to the output current and column elements of the distributed power source; The fault current calculation module (500) is used to calculate the fault current of the fault port according to the voltage of the photovoltaic inverter during the fault distribution network and the node equivalent Norton admittance matrix under the sequence component calculation model.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of a method for calculating short-circuit current of a distributed photovoltaic distribution network according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of a method for calculating short-circuit current of a distributed photovoltaic distribution network according to any one of claims 1 to 7 are implemented.

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