Full-voltage class bearing capacity analysis method for energy access power distribution network

Abstract

The invention discloses a full-voltage class bearing capacity analysis method for an energy access power distribution network, and relates to the field of power systems. Comprising the following steps: S1, taking the power supply range of a 220-kilovolt transformer substation as a unit, S2, calculating the openable capacity of all 110-kilovolt or 35-kilovolt main transformers in the 220-kilovolt power supply range, and obtaining the allowable photovoltaic maximum output of the main transformers; s3, calculating the photovoltaic output reverse transmission load of the 110-kilovolt or 35-kilovolt transformer substation directly supplied within the power supply range of the 220-kilovolt transformer substation; S4, calculating the openable capacity of all 10-kilovolt lines within the power supply range of 220 kilovolt; and S5, verifying the openable capacity of the 10-kilovolt line, and completing the verification. During work, mutual influence and mutual restriction relations of bearing capacity between different voltage grades are fully considered, the openable capacity of 110 (35) kilovolt substations and 10 kilovolt lines is calculated, the bearing capacity of equipment of each voltage grade is obtained through analysis, accurate guidance is provided for distributed photovoltaic access to a power distribution network, the accuracy of an analysis result is improved, and the method is suitable for popularization and application. Safe operation of a power grid is ensured.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and in particular to a method for analyzing the full voltage level carrying capacity of energy access distribution networks. Background Art

[0002] With the rapid development of renewable energy, such as wind power and solar energy, their share in the power system has gradually increased. However, the instability and intermittency of these energy sources have brought challenges to the stable operation of the power system. Therefore, how to effectively connect new energy to the distribution network and improve the carrying capacity of the distribution network has become a current research hotspot. At present, the carrying capacity analysis of energy access to the distribution network mainly adopts traditional static or dynamic methods.

[0003] For example, the publication number of the National Intellectual Property Administration on May 23, 2023 is CN116154849A, and its name is the evaluation method of the carrying capacity of distributed power sources in power grids. This method is based on system model data, operation data, etc., and fully considers the stability, short-circuit current, voltage deviation and harmonics of the distribution network. The numerical results of the distributed power carrying capacity of the busbars at all levels of the distribution network are obtained, and the carrying capacity levels are divided by color, which can provide an effective basis for the government, power grid companies, and investors to make decisions. However, this method only considers the carrying capacity of different voltage levels, and ignores the mutual influence of the carrying capacity between different voltage levels, resulting in inaccurate analysis results. In this way, it is easy to cause too much photovoltaic access to a certain voltage (such as the lower level, 10kV), causing the carrying capacity of the upper-level power grid to exceed the carrying range, posing a hidden danger to the safe operation of the power grid. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0005] The technical solution of the present invention is: a method for analyzing the full voltage level carrying capacity of energy access distribution network, comprising the following steps:

[0006] S1. Taking the power supply range of 220 kV substation as the unit, 13:00 on the annual minimum load day of 220 kV substation within the range is selected as the typical time for analysis;

[0007] S2. Calculate the open capacity of all 110 kV or 35 kV main transformers within the 220 power supply range to obtain the maximum photovoltaic output allowed by the main transformers;

[0008] S3. Calculate the photovoltaic output reverse load of the 110 kV or 35 kV substation directly supplied within the power supply range of the 220 kV substation. The sum of the photovoltaic output reverse load of the 220 kV substation directly supplied to the lower-level power grid shall not be greater than the typical daily load of the 220 kV substation; when the sum of the photovoltaic output reverse load directly supplied to the lower-level power grid exceeds the typical daily load of the 220 kV substation, the photovoltaic output reverse load of the 110 kV or 35 kV substation of the lower-level power grid shall be reduced in proportion to the total typical daily load of the 220 kV substation;

[0009] S4. Calculate the available capacity of all 10 kV lines within the 220 power supply range;

[0010] S5. Verify the open capacity of the 10 kV line. Complete.

[0011] In step S2, the open capacity assessment of the 110 kV or 35 kV main transformer takes into account three factors: equipment carrying capacity, short-circuit current, and voltage deviation;

[0012] Among them, the equipment carrying capacity capability evaluates the transformer carrying capacity;

[0013] The short-circuit current evaluates the short-circuit current margin of the low-voltage side bus and the high-voltage side bus without exceeding the limit, thereby calculating the distributed photovoltaic output;

[0014] The voltage deviation evaluates the voltage deviation margin of the low-voltage side bus and the high-voltage side bus without exceeding the limit, thereby calculating the distributed photovoltaic output;

[0015] The calculation results of the upper limit of distributed photovoltaic output considering the three factors are compared, and the minimum value is selected as the maximum photovoltaic output allowed by the main transformer.

[0016] The main transformer carrying capacity takes into account that when the photovoltaic load is reversed, the main transformer is not overloaded;

[0017] Using the calculation formula: main transformer carrying capacity = main transformer load at typical time + main transformer capacity × 0.8, the allowable photovoltaic output of 110 kV or 35 kV main transformer without overload in reverse direction is obtained.

[0018] Considering the bus short-circuit current, the upper limit of the distributed photovoltaic output allowed by the high and low voltage side bus is evaluated, and the calculation is as follows:

[0019]

[0020] Where P m I is the upper limit of the distributed photovoltaic output on the bus side; xz is the current value of busbar short-circuit current under the maximum operation mode of the system; U N I is the rated voltage of each busbar; m is the allowable short-circuit current limit.

[0021] Considering the bus voltage deviation, the active power of the high- and low-voltage bus distributed photovoltaic output is evaluated and calculated as follows:

[0022]

[0023] Where P is the distributed photovoltaic output return active value; ΔQ is the photovoltaic system reactive power increment, is the distributed photovoltaic power factor;

[0024] The obtained distributed photovoltaic output returned active power value is superimposed on the load carried by the high and low voltage side bus, and the active power value allowed by the high and low voltage side bus for distributed photovoltaic access is calculated.

[0025] In step S4,

[0026] The calculation formula for the open capacity of distributed photovoltaic power generation on a 10 kV line is as follows:

[0027]

[0028] in:

[0029] S xl_pv Open capacity for distributed photovoltaics on medium voltage lines;

[0030] P xl_max is the net load of the medium voltage line in a typical scenario;

[0031] U xl is the rated voltage of the medium voltage line;

[0032] I xl is the rated current of the medium voltage line;

[0033] T xl It is the maximum reverse load rate allowed for the medium voltage line;

[0034] η xl is the power factor of the medium voltage line;

[0035] τ is the distributed photovoltaic output coefficient of the 220 kV station area to which the medium voltage line belongs;

[0036] S xl_bbzt Report the in-transit capacity of distributed photovoltaics within the power supply range of medium voltage lines.

[0037] In step S4, the 10 kV line includes:

[0038] 10 kV lines directly supplied by 110 kV or 35 kV substations within the power supply range of 220 kV substations,

[0039] Or a 10 kV line directly supplied by a 220 kV substation.

[0040] Based on the open capacity of a 110 kV or 35 kV substation, the sum of the open capacity of the 110 kV or 35 kV substation directly supplying the lower-level power grid shall not be greater than the open capacity of the substation;

[0041] When the sum of the open capacities of the directly supplied lower-level power grids is greater than the open capacities of the substations, the open capacities of the 10 kV lines of the lower-level power grids shall be reduced in proportion to the total open capacities of the 110 kV or 35 kV substations.

[0042] For a 220 kV substation with a voltage transformation ratio of 220 / 110 / 10, the sum of the photovoltaic output reverse load directly supplied to the lower-level power grid by the 220 kV substation shall not exceed the typical daily load of the 220 kV substation;

[0043] When the sum of the photovoltaic output reverse load of the direct-supply lower-level power grid exceeds the typical daily load of a 220 kV substation, the photovoltaic output reverse load of the lower-level power grid's 110 kV substation and 10 kV direct-supply line will be reduced in proportion to the total typical daily load of the 220 kV substation.

[0044] In operation, the present invention fully considers the mutual influence and mutual restriction relationship between the carrying capacities of different voltage levels, calculates the open capacity of 110 (35) kV substations and 10 kV lines, analyzes and obtains the carrying capacity of equipment at each voltage level, provides precise guidance for the access of distributed photovoltaic power generation to the distribution network, improves the accuracy of the analysis results, and ensures the safe operation of the power grid. DETAILED DESCRIPTION

[0045] The present invention is further described below in conjunction with embodiments.

[0046] The present invention provides a method for analyzing the carrying capacity of energy access distribution network at all voltage levels, wherein the voltage levels include 220-10 kV, and the mutual influence between the voltage levels is taken into account, specifically:

[0047] The sum of the photovoltaic output reverse load directly supplied to the lower-level power grid by the 220 kV substation shall not exceed the typical daily load of the 220 kV substation;

[0048] The sum of the open capacity of the 110 or 35 kV substation directly supplying the lower-level power grid shall not be greater than the open capacity of the substation;

[0049] The open capacity of the 10 kV line needs to be adjusted according to the open capacity limit of the superior substation.

[0050] Among them, the open capacity of 110(35) kV substation is conveniently calculated through the solidified substation open capacity calculation auxiliary tool. At the same time, the open capacity of 10 kV line is calculated to improve the analysis efficiency and accuracy of the analysis results.

[0051] Specifically, the present invention comprises the following steps:

[0052] (1) Taking the power supply range of 220 kV substation as the unit, 13:00 on the annual minimum load day (non-holiday and sunny day) of the 220 kV substation within the range is selected as the typical time for analysis. The present invention mainly considers photovoltaic power generation. The minimum load day is the day with the maximum photovoltaic output, and the maximum photovoltaic output time is usually noon, so 13:00 is selected as the typical time.

[0053] (2) Calculate the available capacity of all 110(35kV) main transformers within the 220 power supply range;

[0054] The evaluation of the open capacity of 110(35) kV main transformer mainly considers three factors: equipment carrying capacity, short-circuit current and voltage deviation. The equipment carrying capacity evaluates the transformer carrying capacity; the short-circuit current evaluates the short-circuit current margin of the low-voltage bus and the high-voltage bus when the short-circuit current does not exceed the limit, so as to calculate the distributed photovoltaic output; the voltage deviation evaluates the voltage deviation margin of the low-voltage bus and the high-voltage bus when the voltage deviation does not exceed the limit, so as to calculate the distributed photovoltaic output.

[0055] (3) The main transformer carrying capacity takes into account that the main transformer is not overloaded when the photovoltaic load is reversed. Using the calculation formula: main transformer carrying capacity = main transformer load at typical time + main transformer capacity × 0.8, the 110 (35) kV main transformer is not overloaded when reversed to allow photovoltaic output.

[0056] (4) Considering the bus short-circuit current, the upper limit of the distributed photovoltaic output allowed by the high and low voltage bus is evaluated, and the

[0057] Perform calculations.

[0058] Where P m I is the upper limit of the distributed photovoltaic output on the bus side; xz U is the current value of the busbar short-circuit current under the maximum operation mode of the system, which can be determined according to the busbar maximum mode short-circuit capacity; N is the rated voltage of each busbar; the short-circuit current generated by distributed photovoltaics usually does not exceed 1.5 times its rated current; I m For the allowable short-circuit current limit, select the minimum value of the breaking current limit of the corresponding circuit breaker connected to the busbar.

[0059] (5) Considering the bus voltage deviation, the distributed photovoltaic output on the high and low voltage bus is evaluated to reverse the active power.

[0060] Perform calculations.

[0061] Where P is the distributed photovoltaic output return active value; ΔQ is the photovoltaic system reactive power increment, is the distributed photovoltaic power factor;

[0062] Where ΔQ = S sc *δU / 100, δU is the upper limit of bus voltage margin, S sc It is the small mode short-circuit capacity of the busbar.

[0063] The obtained distributed photovoltaic output returned active power value is superimposed with the load carried by the high and low voltage side bus (high and low voltage side bus load on the minimum load day), and the active power value allowed by the high and low voltage side bus to access the distributed photovoltaic power is calculated.

[0064] (6) Compare the three calculation results of the upper limit of distributed photovoltaic output obtained in steps (3), (4), and (5), and select the minimum value as the maximum photovoltaic output allowed by the main transformer.

[0065] (7) Using steps (3)-(6), calculate the photovoltaic output reverse load of the 110(35) kV substation directly supplied within the power supply range of the 220 kV substation (here only the voltage ratio of 220 / 110 / 35 is considered). The sum of the photovoltaic output reverse load of the 220 kV substation directly supplied to the lower-level power grid is not greater than the typical daily load of the 220 kV substation. When the sum of the photovoltaic output reverse load directly supplied to the lower-level power grid exceeds the typical daily load of the 220 kV substation, the photovoltaic output reverse load of the lower-level power grid (110(35) kV substation) is proportionally reduced according to the sum of the typical daily load of the 220 kV substation.

[0066] After the reduction, it is specifically: the proportion of the photovoltaic output reverse load of the lower-level power grid to the sum of all reverse loads * the typical daily load of the 220 kV substation.

[0067] (8) Calculate the available capacity of all 10 kV lines within the 220 power supply area;

[0068] The evaluation of the open capacity of a 10 kV line mainly considers boundary and constraint conditions such as voltage deviation, line thermal stability, short-circuit current, and reverse load rate taking into account "N-1" safety.

[0069] 1) Voltage deviation constraint:

[0070]

[0071] Where V n Indicates the voltage rated value; ε indicates the voltage deviation operating range. According to the "Power Quality Supply Voltage Deviation" (GB / T 12325), the sum of the absolute values ​​of the positive and negative deviations of the 110-35 kV power supply voltage shall not exceed 10% of the nominal voltage; the allowable deviation of the three-phase power supply voltage of 10 kV and below is ±7% of the nominal voltage; the allowable deviation of the 220 V single-phase power supply voltage is +7% and -10% of the nominal voltage.

[0072] 2) Line thermal stability constraints:

[0073]

[0074] In the formula, represents the current flowing through the line at time t in scenario m; I ij,max Indicates the maximum current carrying capacity of the line.

[0075] 3) Short-circuit current constraint:

[0076]

[0077] In the formula, represents the system bus short-circuit current at time t in scenario m; I SCL,max Indicates the maximum allowable short-circuit current limit. The minimum value of the breaking current limit of all devices connected to the busbar and the corresponding circuit breakers on the feeder should be selected.

[0078] The short-circuit current of the photovoltaic power station access system is calculated as follows

[0079] Short-circuit current at common connection point:

[0080] I' PCC =I PCC +1.5I n

[0081] Short-circuit current at the grid connection point:

[0082]

[0083] In the formula, I PCC It is the short-circuit current of the public connection point before the photovoltaic power station is connected, provided by the local power supply company; U N1 , U N2 is the reference voltage of the common connection point and the grid connection point; X L I is the impedance of the line from the grid connection point to the public connection point; n It is the rated working current of the photovoltaic power station.

[0084] 4) “N-1” constraint:

[0085] According to the Technical Guidelines for Planning and Design of Distribution Networks (Q / GDW 10738-2020), 10kV lines in A+, A, B, and C power supply areas should meet the "N-1" principle. Therefore, the maximum load rate values ​​of 10kV lines in various wiring modes are shown in Table 1:

[0086] Table 1 Table of maximum load rate values ​​of 10kV lines in various wiring modes

[0087]

[0088] 5) Equipment reverse load rate constraints:

[0089]

[0090] In the formula, λ m (t) represents the reverse load rate at time t in scenario m; represents the photovoltaic output at time t in scenario m; S represents the equivalent power load at time t in scenario m, that is, the load minus the output of other power sources except distributed power sources; e Indicates the actual operating limit of the transformer or line; max Indicates the maximum allowable reverse load rate.

[0091] From the N-1 constraint, it can be seen that the device reverse load rate constraint is essentially the reverse load constraint considering N-1.

[0092] (9) Based on the boundary and constraint conditions analyzed in step (8), a simplified calculation process for the open capacity of 10 kV lines is proposed, as follows:

[0093] 1) Basic data collection

[0094] Collect 8760 data of load and photovoltaic throughout the year, as well as the voltage level of the line to be verified, voltage operating range, line model parameters, and photovoltaic access location.

[0095] 2) Typical day selection

[0096] The most difficult time for photovoltaic consumption is selected as the typical day by manual selection or clustering algorithm: that is, the time when photovoltaic output is the largest and load is the smallest.

[0097] 3) Time section selection

[0098] First, the typical daily load and photovoltaic output are processed into 24-hour shape data (per unit value); then the difference between the photovoltaic and load per unit output is calculated; the moment with the maximum difference is the time section to be calculated.

[0099] 4) Based on the results of constraint analysis, an empirical formula for calculating the open capacity of distributed photovoltaic power generation on 10 kV lines is proposed, as follows:

[0100]

[0101] in:

[0102] S xl_pv Open capacity for distributed photovoltaics on medium voltage lines;

[0103] P xl_max is the net load of the medium voltage line in a typical scenario;

[0104] U xl is the rated voltage of the medium voltage line;

[0105] I xl is the rated current of the medium voltage line;

[0106] T xl The maximum reverse load rate allowed for the medium voltage line is determined based on whether the feeder group where the medium voltage line is located meets the N-1 requirement, such as 50% for a single tie line, 66.67% for two tie lines, 75% for three tie lines, and 80% for a single radial line.

[0107] η xl is the power factor of the medium voltage line;

[0108] τ is the distributed photovoltaic output coefficient of the 220 kV station area to which the medium voltage line belongs (the value can be taken as 1.0);

[0109] S xl_bbzt Report the in-transit capacity of distributed photovoltaics within the power supply range of medium voltage lines.

[0110] (10) Using the calculation formula for the open capacity of 10 kV lines, complete the evaluation of the open capacity of 10 kV lines directly supplied by 110(35) kV substations and 10 kV lines directly supplied by 220 kV substations within the power supply range of 220 kV substations.

[0111] (11) Verification of the open capacity of 10 kV lines Case 1: Taking the open capacity of 110 (35) kV substation as the benchmark, the sum of the open capacity of the lower-level power grid directly supplied by the 110 (35) kV substation shall not be greater than the open capacity of the substation. When the sum of the open capacity of the lower-level power grid directly supplied is greater than the open capacity of the substation, the open capacity of the lower-level power grid (10 kV line) shall be reduced in proportion to the total open capacity of the 110 (35) kV substation.

[0112] (12) Case 2 of the open capacity verification of the 10 kV line: For a 220 kV substation with a voltage transformation ratio of 220 / 110 / 10, the sum of the photovoltaic output reverse load directly supplied to the lower-level power grid by the 220 kV substation is not greater than the typical daily load of the 220 kV substation. When the sum of the photovoltaic output reverse load directly supplied to the lower-level power grid exceeds the typical daily load of the 220 kV substation, the photovoltaic output reverse load of the lower-level power grid (110 kV substation, 10 kV direct supply line) is proportionally reduced according to the sum of the typical daily load of the 220 kV substation. Please refer to the description of the embodiment.

[0113] Example:

[0114] The substations and lines in the power supply area of ​​220 kV Weiyang Substation in Yangzhou City were selected for analysis. The voltage transformation ratio of 220 kV Weiyang Substation is 220 / 110 / 10 kV, of which 110 kV Wenhui Substation #2 and #4 main transformers, West Lake Substation #1 and #2 main transformers, Shita Substation #3 main transformer are directly supplied, and 28 10 kV lines are directly supplied. According to the above steps (3)-(6), the maximum photovoltaic output allowed by the 110 kV main transformer and the maximum photovoltaic capacity that can be installed by the main transformer are obtained, as shown in Table 2. According to the above steps (9)-(12), the maximum photovoltaic output allowed by the 28 10 kV lines directly supplied by the 220 kV Weiyang Substation and the open capacity of the lines are obtained, as shown in Table 3.

[0115] Table 2 Maximum photovoltaic output allowed by 110 kV main transformers in the 220 kV Weiyang transformer power supply area in Yangzhou City and maximum photovoltaic capacity that can be installed on the main transformers

[0116]

[0117] Table 3 Maximum photovoltaic output allowed by the 220 kV Weiyang transformer direct supply 10 kV line in Yangzhou city and the open capacity of the line

[0118]

[0119] Since the typical daily load of the 220 kV Weiyang transformer is 57.7 MW, the maximum photovoltaic output allowed by the direct-supply 110 kV main transformer is 202 MW, and the maximum photovoltaic output allowed by the direct-supply 10 kV line is 218.88 MW in total. If the sum of the photovoltaic output reverse load of the lower-level power grid directly supplied by the 220 kV Weiyang transformer exceeds the typical daily load of the 220 kV Weiyang transformer, the photovoltaic output reverse load of the lower-level power grid (110 kV substation, 10 kV direct supply line) will be reduced in proportion to the total typical daily load of the 220 kV substation. As shown in Table 4.

[0120] Table 4 The maximum photovoltaic output and maximum photovoltaic capacity that can be installed in Yangzhou City, which is directly supplied by 220 kV Weiyang transformer and 110 kV main transformer and 10 kV line

[0121]

[0122] The present invention provides a method for analyzing the carrying capacity of all voltage levels of energy access distribution networks. The method can comprehensively consider the mutual influence between different voltage levels, quickly calculate the actual carrying capacity (openable capacity) of existing 110 (35) kV substations or 10 kV lines, and provide an accurate reference for the access of 110 (35) kV substations or 10 kV lines to distributed photovoltaic capacity.

Claims

1. A method for analyzing the full voltage level carrying capacity of energy access distribution network, characterized in that: The following steps are involved: S1. Taking the power supply range of 220 kV substation as the unit, 13:00 on the annual minimum load day of 220 kV substation within the range is selected as the typical time for analysis; S2. Calculate the open capacity of all 110 kV or 35 kV main transformers within the 220 power supply range to obtain the maximum photovoltaic output allowed by the main transformers; S3. Calculate the photovoltaic output reverse load of the 110 kV or 35 kV substation directly supplied within the power supply range of the 220 kV substation. The sum of the photovoltaic output reverse load of the 220 kV substation directly supplied to the lower-level power grid shall not be greater than the typical daily load of the 220 kV substation; when the sum of the photovoltaic output reverse load directly supplied to the lower-level power grid exceeds the typical daily load of the 220 kV substation, the photovoltaic output reverse load of the 110 kV or 35 kV substation of the lower-level power grid shall be reduced in proportion to the total typical daily load of the 220 kV substation; S4. Calculate the available capacity of all 10 kV lines within the 220 power supply range; S5. Verify the open capacity of the 10 kV line. Complete.

2. A method for analyzing the full voltage level carrying capacity of energy access distribution network according to claim 1, characterized in that: In step S2, the open capacity assessment of the 110 kV or 35 kV main transformer takes into account three factors: equipment carrying capacity, short-circuit current, and voltage deviation; Among them, the equipment carrying capacity capability evaluates the transformer carrying capacity; The short-circuit current evaluates the short-circuit current margin of the low-voltage side bus and the high-voltage side bus without exceeding the limit, thereby calculating the distributed photovoltaic output; The voltage deviation evaluates the voltage deviation margin of the low-voltage side bus and the high-voltage side bus without exceeding the limit, thereby calculating the distributed photovoltaic output; The calculation results of the upper limit of distributed photovoltaic output considering the three factors are compared, and the minimum value is selected as the maximum photovoltaic output allowed by the main transformer.

3. A method for analyzing the full voltage level carrying capacity of energy access distribution network according to claim 2, characterized in that: The main transformer carrying capacity takes into account that when the photovoltaic load is reversed, the main transformer is not overloaded; Using the calculation formula: main transformer carrying capacity = main transformer load at typical time + main transformer capacity × 0.8, the allowable photovoltaic output of 110 kV or 35 kV main transformer without overload in reverse direction is obtained.

4. The method for analyzing the full voltage level carrying capacity of energy access distribution network according to claim 2 is characterized in that: Considering the bus short-circuit current, the upper limit of the distributed photovoltaic output allowed by the high and low voltage side bus is evaluated, and the calculation is as follows: Where P m The upper limit of the distributed photovoltaic output on the bus side; I xz is the current value of busbar short-circuit current under the maximum operation mode of the system; U N I is the rated voltage of each busbar; m is the allowable short-circuit current limit.

5. A method for analyzing the full voltage level carrying capacity of energy access distribution network according to claim 2, characterized in that: Considering the bus voltage deviation, the active power of the high- and low-voltage bus distributed photovoltaic output is evaluated and calculated as follows: Where P is the distributed photovoltaic output return active value; ΔQ is the photovoltaic system reactive power increment, is the distributed photovoltaic power factor; The obtained distributed photovoltaic output returned active power value is superimposed on the load carried by the high and low voltage side bus, and the active power value allowed by the high and low voltage side bus for distributed photovoltaic access is calculated.

6. A method for analyzing the full voltage level carrying capacity of energy access distribution network according to claim 1, characterized in that: In step S4, The calculation formula for the open capacity of distributed photovoltaic power generation on a 10 kV line is as follows: in: S xl_pv Open capacity for distributed photovoltaics on medium voltage lines; P xl_max is the net load of the medium voltage line in a typical scenario; U xl is the rated voltage of the medium voltage line; I xl is the rated current of the medium voltage line; T xl The maximum reverse load rate allowed for the medium voltage line; η xl is the power factor of the medium voltage line; τ is the distributed photovoltaic output coefficient of the 220 kV station area to which the medium voltage line belongs; S xl_bbzt Report the in-transit capacity of distributed photovoltaics within the power supply range of medium voltage lines.

7. The method for analyzing the full voltage level carrying capacity of energy access distribution network according to claim 1 is characterized in that: In step S4, the 10 kV line includes: 10 kV lines directly supplied by 110 kV or 35 kV substations within the power supply range of 220 kV substations, Or a 10 kV line directly supplied by a 220 kV substation.

8. A method for analyzing the full voltage level carrying capacity of energy access distribution network according to claim 7, characterized in that: Based on the open capacity of a 110 kV or 35 kV substation, the sum of the open capacity of the 110 kV or 35 kV substation directly supplying the lower-level power grid shall not be greater than the open capacity of the substation; When the sum of the open capacities of the directly supplied lower-level power grids is greater than the open capacities of the substations, the open capacities of the 10 kV lines of the lower-level power grids shall be reduced in proportion to the total open capacities of the 110 kV or 35 kV substations.

9. A method for analyzing the full voltage level carrying capacity of energy access distribution network according to claim 7, characterized in that: For a 220 kV substation with a voltage transformation ratio of 220 / 110 / 10, the sum of the photovoltaic output reverse load directly supplied to the lower-level power grid by the 220 kV substation shall not exceed the typical daily load of the 220 kV substation; When the sum of the photovoltaic output reverse load of the direct-supply lower-level power grid exceeds the typical daily load of a 220 kV substation, the photovoltaic output reverse load of the lower-level power grid's 110 kV substation and 10 kV direct-supply line will be reduced in proportion to the total typical daily load of the 220 kV substation.

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