A method and system for evaluating the carrying capacity of distributed photovoltaic power in a medium voltage distribution network

Abstract

A method for evaluating the distributed photovoltaic carrying capacity of a medium-voltage distribution network first calculates the maximum distributed photovoltaic carrying capacity of the distribution network to be evaluated under different operating conditions, initializes the access capacity of all photovoltaic access nodes under the current operating condition, increases the access capacity of each photovoltaic access node, verifies whether the access capacity of each photovoltaic access node after the increase meets the safety operation constraint condition through simulation calculation, and if so, continues to increase and iterates the calculation, and if not, takes the sum of the access capacities of all photovoltaic access nodes when the safety operation constraint condition is met for the last time as the maximum distributed photovoltaic carrying capacity under the current operating condition; then selects the operating condition with the smallest distributed photovoltaic maximum carrying capacity, and the distributed photovoltaic maximum carrying capacity under the operating condition is the final distributed photovoltaic carrying capacity evaluation result of the distribution network to be evaluated; the result can adapt to the operating condition of the distribution network throughout the year, and has good safety and stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of distribution network planning, and in particular relates to a method and system for evaluating the distributed photovoltaic carrying capacity of a medium-voltage distribution network. Background Art

[0002] The access of a large number of distributed photovoltaics changes the distribution network from a simple radial network to a multi-terminal active network, which will inevitably bring about changes in the planning and operation of the distribution network, such as changes in the size and direction of the power flow of the distribution network, causing current and voltage distortion, and causing the original protection setting scheme to fail. In order to achieve the full carrying capacity and efficient utilization of distributed photovoltaics, the impact of high-proportion distributed photovoltaic access on the distribution network is generally quantified as the calculation of the grid carrying capacity or acceptance capacity. The existing grid carrying capacity assessment method has the following shortcomings:

[0003] (1) Due to the rapid change of various types of information in the distribution network and the obvious randomness of distributed photovoltaic output, the previous distributed photovoltaic carrying capacity assessment theory of the distribution network is generally based on specific time sections for calculation and analysis, which cannot adapt to the distribution network's annual timing operation curve.

[0004] (2) The evaluation of the distributed photovoltaic capacity of the distribution network is generally based on the topology and operation data of the power grid, and then the ideal result is obtained by using the optimization algorithm. However, the actual distribution and growth of distributed photovoltaics are generally determined by the market and will not evolve according to the calculation results of the optimization algorithm. Summary of the invention

[0005] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and to provide a method and system for evaluating the distributed photovoltaic carrying capacity of a medium-voltage distribution network that can adapt to the annual timing operation curve of the distribution network and has good safety and stability.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for evaluating the carrying capacity of distributed photovoltaic power in a medium voltage distribution network, the method comprising:

[0008] S1. Calculate the maximum carrying capacity of distributed photovoltaic power generation under different operating conditions of the distribution network to be evaluated, including:

[0009] S11, initializing the distributed photovoltaic access capacity of all photovoltaic access nodes in the current operation state, and starting iterative calculation;

[0010] S12. Increase the distributed photovoltaic access capacity of each photovoltaic access node;

[0011] S13, verifying through simulation calculation whether the distributed photovoltaic access capacity of each photovoltaic access node after the increase meets the safety operation constraint condition; if so, return to S12 and continue iteration; if not, calculate the sum of the distributed photovoltaic access capacities of all photovoltaic access nodes when the safety operation constraint condition was met for the last time, and use the calculated result as the maximum carrying capacity of the distributed photovoltaic under this operation state;

[0012] S2. Select the operating state with the smallest distributed photovoltaic maximum carrying capacity. The distributed photovoltaic maximum carrying capacity under this operating state is the final distributed photovoltaic carrying capacity assessment result of the distribution network to be assessed.

[0013] In S12, the growth range of the distributed photovoltaic access capacity of the photovoltaic access node is the product of the growth step of the distributed photovoltaic capacity and the distributed photovoltaic development coefficient of the photovoltaic access node. The method for obtaining the distributed photovoltaic development coefficient of the photovoltaic access node is:

[0014] Obtain GIS satellite images around the photovoltaic access nodes, randomly sample the GIS satellite images, and use the number of times the sampling result is a roof as the initial distributed photovoltaic potential coefficient of the photovoltaic access node; select the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes, and calculate the distributed photovoltaic development coefficient of each photovoltaic access node according to the following formula:

[0015] β=α / α max ;

[0016] In the above formula, β is the distributed photovoltaic development coefficient of the photovoltaic access node; α is the initial distributed photovoltaic potential coefficient of the photovoltaic access node; α max It is the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes.

[0017] In S13, the safety operation constraints include:

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] In the above formula, Ω N represents the set of all nodes in the distribution network to be evaluated; S i (k) is the distributed photovoltaic access capacity of node i under operating state k. For photovoltaic access nodes, Si (k) is the increased distributed photovoltaic access capacity obtained by S12; for non-photovoltaic access nodes, S i (k) Always 0; are the maximum active power and reactive power injected by distributed photovoltaic at node i under operating state k respectively; are the effective values ​​of the voltage at node i and node j respectively; G ij , B ij are the conductance and susceptance between node i and node j respectively; node j is the node adjacent to node i in the system; I ij，max U is the long-term allowable current carrying capacity of the branch connecting node i and node j; i，N is the rated voltage of node i; ε H , ε L They are the upper and lower limits of voltage deviation respectively; are respectively the active power and reactive power of the load at node i in operating state k; is the phase angle difference between node i and node j in operating state k.

[0024] The random sampling is specifically as follows: based on the same level of the GIS satellite map, a GIS satellite image tile map within a nine-square grid range centered on the photovoltaic access node is obtained, and random sampling is performed within the GIS satellite image tile map.

[0025] In a second aspect, the present invention provides a system for evaluating the carrying capacity of distributed photovoltaic power in a medium voltage distribution network, the evaluation system comprising a simulation calculation module and an evaluation module;

[0026] The simulation calculation module is used to calculate the maximum carrying capacity of distributed photovoltaics in different distribution networks under operating conditions. The simulation calculation module includes an initialization module and a simulation verification module;

[0027] The initialization module is used to initialize the distributed photovoltaic access capacity of all photovoltaic access nodes in the current operation state;

[0028] The simulation verification module is used to first increase the distributed photovoltaic access capacity of each photovoltaic access node; then verify through simulation calculation whether the distributed photovoltaic access capacity of each photovoltaic access node after the increase meets the safe operation constraint condition; if it does, then continue to increase the distributed photovoltaic access capacity of each photovoltaic access node; if it does not meet the requirements, then calculate the sum of the distributed photovoltaic access capacities of all photovoltaic access nodes when the safe operation constraint condition was met for the last time, and use the calculated result as the maximum carrying capacity of the distributed photovoltaic under this operation state;

[0029] The evaluation module is used to select the operating state with the smallest distributed photovoltaic maximum carrying capacity, and the distributed photovoltaic maximum carrying capacity under this operating state is the final distributed photovoltaic carrying capacity evaluation result of the distribution network to be evaluated.

[0030] The growth range of the distributed photovoltaic access capacity of the photovoltaic access node is the product of the growth step of the distributed photovoltaic capacity and the distributed photovoltaic development coefficient of the photovoltaic access node;

[0031] The evaluation system also includes a distributed photovoltaic development coefficient acquisition module, which is used to acquire GIS satellite images around photovoltaic access nodes, randomly sample the GIS satellite images, and use the number of times the sampling result is a roof as the initial distributed photovoltaic potential coefficient of the photovoltaic access node; select the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes, and calculate the distributed photovoltaic development coefficient of each photovoltaic access node according to the following formula:

[0032] β=α / α max ;

[0033] In the above formula, β is the distributed photovoltaic development coefficient of the photovoltaic access node; α is the initial distributed photovoltaic potential coefficient of the photovoltaic access node; α max It is the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes.

[0034] The safety operation constraints include:

[0035]

[0036]

[0037]

[0038]

[0039]

[0040] In the above formula, Ω N Represents the set of all nodes in the distribution network to be evaluated; is the distributed photovoltaic access capacity of node i under operating state k. For photovoltaic access nodes, S i (k) The distributed photovoltaic access capacity after the increase obtained by S12, for non-photovoltaic access nodes, S i (k) Always 0; are the maximum active power and reactive power injected by distributed photovoltaic at node i under operating state k respectively; are the effective values ​​of the voltage at node i and node j respectively; G ij , B ij are the conductance and susceptance between node i and node j respectively; node j is the adjacent node of node i in the system; I ij，max U is the long-term allowable current carrying capacity of the branch connecting node i and node j; i，N is the rated voltage of node i; ε H , ε L They are the upper and lower limits of voltage deviation respectively; are respectively the active power and reactive power of the load at node i in operating state k; is the phase angle difference between node i and node j in operating state k.

[0041] The random sampling is specifically as follows: based on the same level of the GIS satellite map, a GIS satellite image tile map within a nine-square grid range centered on the photovoltaic access node is obtained, and random sampling is performed within the GIS satellite image tile map.

[0042] In a third aspect, the present invention provides a medium voltage distribution network distributed photovoltaic carrying capacity evaluation device, the evaluation device comprising a memory and a processor;

[0043] The memory is used to store computer program code and transmit the computer program code to the processor;

[0044] The processor is used to execute the aforementioned method according to the instructions in the computer program code.

[0045] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the aforementioned method when executed by a processor.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. A method for evaluating the distributed photovoltaic carrying capacity of a medium-voltage distribution network of the present invention first calculates the maximum distributed photovoltaic carrying capacity of the distribution network to be evaluated under different operating conditions. When calculating the maximum distributed photovoltaic carrying capacity under a certain operating condition, the distributed photovoltaic access capacity of all photovoltaic access nodes under the current operating condition is first initialized, and then the distributed photovoltaic access capacity of each photovoltaic access node is increased. The distributed photovoltaic access capacity of each photovoltaic access node after the increase is verified by simulation calculation to see whether it meets the safety operation constraint condition. If it meets the condition, it continues to increase and iteratively calculates. If it does not meet the condition, the sum of the distributed photovoltaic access capacities of all photovoltaic access nodes when the safety operation constraint condition is met for the last time is calculated. The calculation result obtained is the maximum distributed photovoltaic carrying capacity under the current operating condition. The maximum distributed photovoltaic carrying capacity obtained at this time is the maximum distributed photovoltaic capacity that the distribution network can accommodate under the condition that any device in the distribution network is continuously not overloaded and the voltage and current of any node do not exceed the standard. Then, the operating state with the smallest distributed photovoltaic maximum carrying capacity is selected, and the distributed photovoltaic maximum carrying capacity under the operating state is used as the final distributed photovoltaic carrying capacity evaluation result of the distribution network to be evaluated. The distributed photovoltaic carrying capacity under the operating state can adapt to the operating state of the distribution network throughout the year and ensure the safety and stability of the distribution network. Therefore, the photovoltaic carrying capacity assessment result obtained by the present invention can adapt to the operation status of the distribution network throughout the year and ensure the safety and stability of the distribution network.

[0048] 2. In a method for evaluating the distributed photovoltaic carrying capacity of a medium-voltage distribution network of the present invention, the growth rate of the distributed photovoltaic access capacity of the photovoltaic access node is the product of the growth step of the distributed photovoltaic capacity and the distributed photovoltaic development coefficient of the photovoltaic access node; the method for obtaining the distributed photovoltaic development coefficient is to obtain the GIS satellite image around the photovoltaic access node, randomly sample the GIS satellite image, and use the number of times the sampling result is a roof as the initial distributed photovoltaic potential coefficient of the photovoltaic access node; select the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes, and the maximum value of the initial distributed photovoltaic potential coefficient of the photovoltaic access node / the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes is the distributed photovoltaic development coefficient of the photovoltaic access node; in this design, the growth of distributed photovoltaic is simulated based on the distribution of roofs in the GIS satellite image, which is more in line with the development law of distributed photovoltaics in the actual market. Therefore, the photovoltaic carrying capacity evaluation result obtained by the present invention is more in line with reality. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a flow chart of the evaluation method described in Example 1.

[0050] Figure 2 This is a flow chart of Example 1 for calculating the maximum carrying capacity of distributed photovoltaics under any operating state.

[0051] Figure 3This is the GIS satellite image tile map obtained in Example 1.

[0052] Figure 4 This is a schematic diagram of the structure of the evaluation system described in Example 2.

[0053] Figure 5 This is a schematic diagram of the structure of the evaluation device described in Example 3. DETAILED DESCRIPTION

[0054] The present invention is further described in detail below in conjunction with specific implementations and drawings.

[0055] Embodiment 1:

[0056] This embodiment uses a medium-voltage distribution network in a certain province as an example to carry out calculations.

[0057] See also Figure 1 , a method for evaluating the carrying capacity of distributed photovoltaic power in a medium voltage distribution network is performed in the following steps:

[0058] 1. Obtain the distributed photovoltaic development coefficient of each photovoltaic access node in the medium voltage distribution network. The acquisition method is:

[0059] Based on the same level of the GIS satellite map, the GIS satellite image tile map within the nine-square grid range centered on the photovoltaic access node is obtained. The obtained GIS satellite image tile map is as follows: Figure 3 As shown in the figure, random sampling is performed in the GIS satellite image tile map, and the number of times the sampling result is a roof is used as the initial distributed photovoltaic potential coefficient of the photovoltaic access node; the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes is selected, and the distributed photovoltaic development coefficient of each photovoltaic access node is calculated according to the following formula:

[0060] β=α / α max ;

[0061] In the above formula, β is the distributed photovoltaic development coefficient of the photovoltaic access node; α is the initial distributed photovoltaic potential coefficient of the photovoltaic access node; α max is the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes;

[0062] The preliminary distributed photovoltaic potential coefficient of photovoltaic access node A1 in the medium voltage distribution network is the largest, and the calculation results are shown in Table 1:

[0063] Table 1 Distributed photovoltaic development coefficient of each photovoltaic access node

[0064] Access Point A1 A6 A10 A14 A18 A21 B7 β 1 0.07696 0.17042 0.29912 0.25174 0.5733 0.97027

[0065] 2. Calculate the maximum carrying capacity of distributed photovoltaic power under different operating conditions of the medium-voltage distribution network during the evaluation period. The evaluation period of the medium-voltage distribution network is one year, and there are 12 operating conditions in total, such as Figure 2 As shown, the specific calculation steps are:

[0066] S11, initializing the distributed photovoltaic access capacity of all photovoltaic access nodes in this operation state, and setting the initial distributed photovoltaic access capacity of each photovoltaic access node to 0;

[0067] S12, increase the distributed photovoltaic access capacity of each photovoltaic access node, the increase range is the product of the distributed photovoltaic capacity growth step and the distributed photovoltaic development coefficient of the photovoltaic access node, and the growth step is set to 0.1MW;

[0068] S13, using the increased distributed photovoltaic access capacity of each photovoltaic access node, combined with the collected distribution network operating parameters under this operation state (distribution network topology, voltage phase angle of each node, head-end voltage, load active and reactive power, line distribution transformer parameters, etc.), verify whether the safe operation constraint conditions are met through simulation calculation; if satisfied, return to S12, continue to increase the distributed photovoltaic access capacity of each photovoltaic access node, iterative calculation, if not satisfied, calculate the sum of the distributed photovoltaic access capacities of all photovoltaic access nodes when the safe operation constraint conditions were met for the last time, and use the calculated result as the maximum carrying capacity of distributed photovoltaic under this operation state; wherein, the safe operation constraint conditions include:

[0069]

[0070]

[0071]

[0072]

[0073]

[0074] In the above formula, Ω N represents the set of all nodes in the distribution network to be evaluated; S i (k) is the distributed photovoltaic access capacity of node i under operating state k. For photovoltaic access nodes, S i (k) The distributed photovoltaic access capacity after the increase obtained by S12, for non-photovoltaic access nodes, S i (k) It is always 0; are the maximum active power and reactive power injected by distributed photovoltaic at node i under operating state k respectively; are the effective values ​​of the voltage at node i and node j respectively; G ij , B ij are the conductance and susceptance between node i and node j respectively; node j is the node adjacent to node i in the system; I ij，max U is the long-term allowable current carrying capacity of the branch connecting node i and node j; i，N is the rated voltage of node i; ε H , ε L They are the upper and lower limits of voltage deviation respectively; are respectively the active power and reactive power of the load at node i in operating state k; is the phase angle difference between node i and node j in operating state k;

[0075] S2. Select the operating state with the smallest distributed photovoltaic maximum carrying capacity. The distributed photovoltaic maximum carrying capacity under this operating state is the final distributed photovoltaic carrying capacity evaluation result S of the distribution network to be evaluated. The expression is:

[0076]

[0077] In the above formula, K is the total number of operating states, represents the sum of the distributed photovoltaic access capacities of all photovoltaic access nodes when the safety operation constraint conditions are met for the last time under the operating state k; Ω DG Represents the set of all photovoltaic access nodes in the distribution network to be evaluated.

[0078] The final distributed photovoltaic carrying capacity assessment result S of the medium-voltage distribution network is finally calculated to be 47.3MW.

[0079] Embodiment 2:

[0080] See also Figure 3 , a distributed photovoltaic carrying capacity assessment system for a medium-voltage distribution network, comprising an assessment area selection module, a distributed photovoltaic development coefficient acquisition module, a simulation calculation module, an assessment module, and a report output module; the assessment area selection module is used by a user to select the distribution network range for which distributed photovoltaic carrying capacity assessment is to be performed and to set distributed photovoltaic access nodes; the distributed photovoltaic development coefficient acquisition module is used to obtain a GIS satellite image tile map within a nine-square grid range centered on a photovoltaic access node based on the same level of a GIS satellite map, perform random sampling in the GIS satellite image tile map, and use the number of times the sampling result is a roof as the initial distributed photovoltaic potential coefficient of the photovoltaic access node; select the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes, and calculate the distributed photovoltaic development coefficient of each photovoltaic access node according to the following formula:

[0081] β=α / α max ;

[0082] In the above formula, β is the distributed photovoltaic development coefficient of the photovoltaic access node; α is the initial distributed photovoltaic potential coefficient of the photovoltaic access node; α max is the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes;

[0083] The simulation calculation module is used to calculate the maximum carrying capacity of distributed photovoltaic under different distribution networks in operation, and the simulation calculation module includes an initialization module and a simulation verification module; the initialization module is used to initialize the distributed photovoltaic access capacity of all photovoltaic access nodes under this operation state; the simulation verification module is used to first increase the distributed photovoltaic access capacity of each photovoltaic access node, and the increase range is the product of the distributed photovoltaic capacity growth step and the distributed photovoltaic development coefficient of the photovoltaic access node; then the distributed photovoltaic access capacity of each photovoltaic access node after the increase is verified by simulation calculation to see whether it meets the safe operation constraint condition; if it does, the distributed photovoltaic access capacity of each photovoltaic access node continues to increase; if it does not, the sum of the distributed photovoltaic access capacities of all photovoltaic access nodes when the safe operation constraint condition is met for the last time is calculated, and the calculated result is used as the maximum carrying capacity of distributed photovoltaic under this operation state; wherein, the safe operation constraint condition includes:

[0084]

[0085]

[0086]

[0087]

[0088]

[0089] In the above formula, Ω N Represents the set of all nodes in the distribution network to be evaluated; is the distributed photovoltaic access capacity of node i under operating state k. For photovoltaic access nodes, S i (k) The distributed photovoltaic access capacity after the increase obtained by S12, for non-photovoltaic access nodes, S i (k) Always 0; are the maximum active power and reactive power injected by distributed photovoltaic at node i under operating state k respectively; are the effective values ​​of the voltage at node i and node j respectively; G ij , B ij are the conductance and susceptance between node i and node j respectively; node j is the node adjacent to node i in the system; I ij，maxU is the long-term allowable current carrying capacity of the branch connecting node i and node j; i，N is the rated voltage of node i; ε H , ε L They are the upper and lower limits of voltage deviation respectively; are respectively the active power and reactive power of the load at node i in operating state k; is the phase angle difference between node i and node j in operating state k;

[0090] The evaluation module is used to select the operating state with the smallest distributed photovoltaic maximum carrying capacity, and the distributed photovoltaic maximum carrying capacity under this operating state is the final distributed photovoltaic carrying capacity evaluation result of the distribution network to be evaluated; the report output module is used to display the maximum distributed photovoltaic carrying capacity of the distribution network during the evaluation period and the distributed photovoltaic capacity configuration of each photovoltaic access node, the city (county) to which it belongs, the power supply zone, the power supply grid, the power supply unit and the line, etc. in the form of a table.

[0091] The above-mentioned medium-voltage distribution network distributed photovoltaic carrying capacity assessment system has human-computer interaction and interface display functions, and is simple to operate, adapting to the grid management needs of the distribution network.

[0092] Embodiment 3:

[0093] See also Figure 4 , a medium-voltage distribution network distributed photovoltaic carrying capacity assessment device, comprising a memory and a processor; the memory is used to store computer program code and transmit the computer program code to the processor; the processor is used to execute the method described in Example 1 according to the instructions in the computer program code.

[0094] Embodiment 4:

[0095] A computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the method described in Example 1 when executed by a processor.

[0096] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0097] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0098] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0099] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0100] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for evaluating the carrying capacity of distributed photovoltaic power in a medium voltage distribution network, characterized in that: The evaluation methods include: S1. Calculate the maximum carrying capacity of distributed photovoltaic power generation under different operating conditions of the distribution network to be evaluated, including: S11, initializing the distributed photovoltaic access capacity of all photovoltaic access nodes in the current operation state, and starting iterative calculation; S12. Increase the distributed photovoltaic access capacity of each photovoltaic access node; S13, verifying through simulation calculation whether the distributed photovoltaic access capacity of each photovoltaic access node after the increase meets the safety operation constraint condition; if so, return to S12 and continue iteration; if not, calculate the sum of the distributed photovoltaic access capacities of all photovoltaic access nodes when the safety operation constraint condition was met for the last time, and use the calculated result as the maximum carrying capacity of the distributed photovoltaic under this operation state; S2. Select the operating state with the smallest distributed photovoltaic maximum carrying capacity. The distributed photovoltaic maximum carrying capacity under this operating state is the final distributed photovoltaic carrying capacity assessment result of the distribution network to be assessed. In S12, the growth amplitude of the distributed photovoltaic access capacity of the photovoltaic access node is equal to the product of the growth step of the distributed photovoltaic capacity and the distributed photovoltaic development coefficient of the photovoltaic access node. The method for obtaining the distributed photovoltaic development coefficient of the photovoltaic access node is: Obtain GIS satellite images around the photovoltaic access nodes, randomly sample the GIS satellite images, and use the number of times the sampling result is a roof as the preliminary distributed photovoltaic potential coefficient of the photovoltaic access node; select the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes, and calculate the distributed photovoltaic development coefficient of each photovoltaic access node according to the following formula: β＝α / α max ； In the above formula, β is the distributed photovoltaic development coefficient of the photovoltaic access node; α is the initial distributed photovoltaic potential coefficient of the photovoltaic access node; α max It is the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes.

2. A method for evaluating the distributed photovoltaic carrying capacity of a medium voltage distribution network according to claim 1, characterized in that: In S13, the safety operation constraints include: In the above formula, Ω N represents the set of all nodes in the distribution network to be evaluated; S i (k) is the distributed photovoltaic access capacity of node i under operating state k. For photovoltaic access nodes, S i (k) is the increased distributed photovoltaic access capacity obtained by S12; for non-photovoltaic access nodes, S i (k) Always 0; are the maximum active power and reactive power injected by distributed photovoltaic at node i under operating state k respectively; are the effective values ​​of the voltage at node i and node j respectively; G ij , B ij are the conductance and susceptance between node i and node j respectively; node j is the node adjacent to node i in the system; I ij，max U is the long-term allowable current carrying capacity of the branch connecting node i and node j; i，N is the rated voltage of node i; ε H , ε L They are the upper and lower limits of voltage deviation respectively; are respectively the active power and reactive power of the load at node i in operating state k; is the phase angle difference between node i and node j in operating state k.

3. A method for evaluating the distributed photovoltaic carrying capacity of a medium voltage distribution network according to claim 1, characterized in that: The random sampling is specifically as follows: based on the same level of the GIS satellite map, a GIS satellite image tile map within a nine-square grid range centered on the photovoltaic access node is obtained, and random sampling is performed within the GIS satellite image tile map.

4. A medium voltage distribution network distributed photovoltaic carrying capacity assessment system, characterized by: The evaluation system includes a simulation calculation module and an evaluation module; The simulation calculation module is used to calculate the maximum carrying capacity of distributed photovoltaics in different distribution networks under operating conditions. The simulation calculation module includes an initialization module and a simulation verification module; The initialization module is used to initialize the distributed photovoltaic access capacity of all photovoltaic access nodes in the current operation state; The simulation verification module is used to first increase the distributed photovoltaic access capacity of each photovoltaic access node; then verify through simulation calculation whether the distributed photovoltaic access capacity of each photovoltaic access node after the increase meets the safe operation constraint condition; if it does, then continue to increase the distributed photovoltaic access capacity of each photovoltaic access node; if it does not meet the requirements, then calculate the sum of the distributed photovoltaic access capacities of all photovoltaic access nodes when the safe operation constraint condition was met for the last time, and use the calculated result as the maximum carrying capacity of the distributed photovoltaic under this operation state; The evaluation module is used to select the operating state with the smallest distributed photovoltaic maximum carrying capacity, and the distributed photovoltaic maximum carrying capacity under this operating state is the final distributed photovoltaic carrying capacity evaluation result of the distribution network to be evaluated; The growth rate of the distributed photovoltaic access capacity of the photovoltaic access node is equal to the product of the growth step of the distributed photovoltaic capacity and the distributed photovoltaic development coefficient of the photovoltaic access node; The evaluation system also includes a distributed photovoltaic development coefficient acquisition module, which is used to acquire GIS satellite images around photovoltaic access nodes, randomly sample the GIS satellite images, and use the number of times the sampling result is a roof as the preliminary distributed photovoltaic potential coefficient of the photovoltaic access node; select the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes, and calculate the distributed photovoltaic development coefficient of each photovoltaic access node according to the following formula: β＝α / α max ； In the above formula, β is the distributed photovoltaic development coefficient of the photovoltaic access node; α is the initial distributed photovoltaic potential coefficient of the photovoltaic access node; α max It is the maximum value of the preliminary distributed photovoltaic potential coefficients of all photovoltaic access nodes.

5. A medium voltage distribution network distributed photovoltaic carrying capacity assessment system according to claim 4, characterized in that: The safety operation constraints include: In the above formula, Ω N represents the set of all nodes in the distribution network to be evaluated; S i (k) is the distributed photovoltaic access capacity of node i under operating state k. For photovoltaic access nodes, S i (k) is the increased distributed photovoltaic access capacity obtained by S12; for non-photovoltaic access nodes, S i (k) Always 0; are the maximum active power and reactive power injected by the distributed photovoltaic in the node under the operating state k; are the effective values ​​of the voltage at node i and node j respectively; G ij , B ij are the conductance and susceptance between node i and node j respectively; node j is the node adjacent to node i in the system; I ij，max U is the long-term allowable current carrying capacity of the branch connecting node i and node j; i，N is the rated voltage of node i; ε H , ε L They are the upper and lower limits of voltage deviation respectively; are respectively the active power and reactive power of the load at node i in operating state k; is the phase angle difference between node i and node j in operating state k.

6. A medium voltage distribution network distributed photovoltaic carrying capacity assessment system according to claim 4, characterized in that: The random sampling is specifically as follows: based on the same level of the GIS satellite map, a GIS satellite image tile map within a nine-square grid range centered on the photovoltaic access node is obtained, and random sampling is performed within the GIS satellite image tile map.

7. A medium voltage distribution network distributed photovoltaic carrying capacity assessment device, characterized in that: The evaluation device includes a memory and a processor; The memory is used to store computer program code and transmit the computer program code to the processor; The processor is configured to execute the method according to any one of claims 1 to 3 according to instructions in the computer program code.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 3 is implemented.

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