10kV line and transformer area distributed photovoltaic bearing capacity assessment method

Abstract

A 10kV line and transformer area distributed photovoltaic bearing capacity assessment method comprises the steps of determining a line to be assessed and a transformer area to which the line to be assessed belongs and collecting and calculating required data on the premise that a superior power distribution network can be accessed to distributed photovoltaic; on the premise that line thermal stability evaluation is passed, distributed photovoltaic bearing capacity based on the reverse load rate and the voltage deviation is calculated and compared with the distributed photovoltaic bearing capacity of the corresponding bus, and a line distributed photovoltaic bearing capacity result is obtained; and on the premise that the thermal stability evaluation of the transformer area is passed, obtaining a transformer area distributed photovoltaic bearing capacity result based on the wire diameter, the power supply range and the power quality constraint condition of the transformer area. According to the method provided by the invention, the data information of the 10kV line and the transformer area is fully utilized, the algorithm is simple, the practical application is easy, the requirement of a power grid company for updating the openable capacity according to the quarterly can be met, and the orderly access and high-quality development of distributed photovoltaic are assisted.

Description

Technical Field

[0001] The present invention belongs to the technical field of distributed power supply and distribution network, and specifically relates to a method for evaluating the carrying capacity of distributed photovoltaic power generation in 10kV lines and substations. Background Art

[0002] On the one hand, the access of distributed photovoltaic to the distribution network has greatly changed the form of the traditional distribution network, making the traditional distribution network gradually transformed into an active distribution network; on the other hand, most distributed photovoltaics are connected to the grid at 220 / 380V and 10kV voltage levels. A large number of disorderly access will bring problems such as voltage over-limit, excessive line loss, and equipment overload operation to the distribution network, threatening the safety of distribution network equipment and the safety of users' electricity use. Therefore, in order to ensure the reasonable promotion of the "whole-county photovoltaic" policy, it is necessary to regularly carry out evaluation and calculation of the distributed photovoltaic carrying capacity of the distribution network, especially 10kV lines and substations. At present, there are two main methods for calculating the carrying capacity of distributed photovoltaics in 10kV lines and substations: one does not require an accurate topological map of the line or substation, but does not consider problems such as voltage over-limit and excessive line loss, and only calculates the distributed photovoltaic carrying capacity based on the reverse load rate; the other type considers problems such as voltage and line loss over-limit, but requires an accurate topological map of the line or substation, and the calculation process is complicated and not easy to use in practice.

[0003] The present invention proposes a rapid engineering calculation method for the distributed photovoltaic carrying capacity of 10kV lines and distribution networks in substations. The method comprehensively considers various constraint indicators of distribution equipment and distribution networks, maintains good calculation accuracy and efficiency while not requiring modeling and precise distribution network topology, and can meet the needs of power grid companies to update the open capacity on a quarterly basis. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a method for evaluating the carrying capacity of distributed photovoltaic power generation in 10kV lines and substations, so as to achieve effective evaluation of the carrying capacity of distributed photovoltaic power generation.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for evaluating the carrying capacity of distributed photovoltaic power generation in a 10 kV line and a substation, comprising the following steps:

[0007] Step S1: determine the assessment area, draw the power grid topology of the area to be assessed and collect data;

[0008] Step S2: Calculate and evaluate the distributed photovoltaic carrying capacity of the 10kV line;

[0009] Step S3: Calculate and evaluate the distributed photovoltaic carrying capacity of the low-voltage area connected to the above 10kV line;

[0010] Step S4: Repeat step 3 to calculate the distributed photovoltaic carrying capacity of other substations under the 10kV line in step 2.

[0011] As a further improvement of the present invention, step S1 includes the following steps:

[0012] S1.1 Determine the distribution network to which the 10kV line and low-voltage substation to be evaluated belong, draw the power grid topology map of the area, clearly identify each 10kV line and its connected substation, and collect the required historical operation data, equipment parameters, measured data and distribution network planning data;

[0013] S1.2 Use the existing method to evaluate the carrying capacity of the 10kV line to be evaluated and the upper-level distribution network to which the low-voltage substation belongs. If the evaluation result of the upper-level distribution network is that the distributed photovoltaic can be connected, then proceed to step S2; if the evaluation result is that the distributed photovoltaic cannot be connected, then the area cannot be connected to the distributed photovoltaic, and the distribution network carrying capacity evaluation of the area is terminated.

[0014] As a further improvement of the present invention, step S2 includes the following steps:

[0015] S2.1 evaluates the thermal stability of the 10kV line, selects the period when the grid acceptance level is the most saturated to calculate the distributed photovoltaic carrying capacity, and calculates the reverse load rate λ of the 10kV line during this period, where: P D is the distributed photovoltaic output within the power supply range of the 10kV line during this period, P L is the power load during this period, S e is the actual operation limit of the line;

[0016] S2.2 According to the reverse load rate λ, the distributed photovoltaic carrying capacity of 10kV lines can be divided into three levels: if λ≤0, it indicates that the distributed photovoltaics that have been connected can be consumed locally, and there is no reverse power flow in the power grid. It is recommended to connect distributed photovoltaics, and the carrying capacity of this line is evaluated as green; if 0≤λ≤80%, it indicates that the reverse power flow of the power grid does not exceed 80%. It is recommended to carry out special analysis for the projects to be connected, and the carrying capacity of this line is evaluated as yellow; if λ>80%, it indicates that the reverse power flow of the power grid exceeds 80% or there are hidden dangers in the operation of the power grid. It is recommended to suspend the connection of distributed photovoltaics before the carrying capacity of the power grid is improved, evaluate the carrying capacity of this line as red, and terminate the distribution network carrying capacity evaluation in this area; the above evaluation criteria are summarized in the following table.

[0017]

[0018]

[0019] S2.3 If λ≤80%, calculate the distributed photovoltaic carrying capacity P of the line based on the reverse load rate λ λ1 ,Right now

[0020] P λ1 =((1-λ)×S e )×k 1

[0021] Where k 1 Take 0.8;

[0022] S2.4 Calculate the distributed photovoltaic residual carrying capacity P of the 10kV line based on the voltage deviation condition u1 ,Right now

[0023]

[0024] In the formula, ΔU is usually taken as 0.07U N , r 1 、x 1 is the resistance and reactance per unit length of 10kV line, is the power factor, L is the length of the 10kV line, P G1 The installed capacity of distributed photovoltaic power generation connected to the current line;

[0025] S2.5 Comparison P λ1 With P u1 The smaller value of the two is temporarily set as the distributed photovoltaic carrying capacity P of the line. m1 ,Right now

[0026] P m1 =min(P λ1 ,P u1 )

[0027] S2.6 Comparison of 10kV line distributed photovoltaic carrying capacity P m1 The smaller value of the corresponding 10kV bus distributed photovoltaic carrying capacity is taken as the final result of the line carrying capacity.

[0028] As a further improvement of the present invention, step S3 includes the following steps:

[0029] S3.1 Use the methods of S2.1-S2.3 in step S2 to evaluate the thermal stability of the area and calculate the distributed photovoltaic carrying capacity P of the area based on the reverse load rate. λ2 ;

[0030] S3.2 If the thermal stability assessment of the substation passes, the voltage deviation check is performed, that is, whether the voltage amplitude of the substation is within the range of [198V-235.4V]. If the voltage deviation check fails, the load-bearing capacity assessment level of the substation is red, and the load-bearing capacity calculation of the substation is terminated; if it passes, the line loss check is performed;

[0031] S3.3 performs line loss verification in the substation and calculates the distributed photovoltaic carrying capacity of the substation based on the line diameter constraint condition: if the line loss is less than 4%, the distributed photovoltaic carrying capacity is determined according to the line diameter of the transformer outlet in the substation, the power supply radius and the distributed photovoltaic distribution. The specific corresponding relationship is shown in the following table:

[0032]

[0033] By looking up the table and combining the distributed photovoltaic installed capacity that has been connected to the current area, the distributed photovoltaic carrying capacity P of the area based on the line diameter constraint condition can be obtained. w2 ,Right now

[0034] P w2 =k 2 *P w1 -P G2

[0035] In the formula, k 2 is the adjustment coefficient, P w1 The carrying capacity of the substation line obtained from the table above according to the line diameter and power supply radius, P G2 The installed capacity of distributed photovoltaic power generation that has been connected to the current area;

[0036] Photovoltaic distribution <![CDATA[Adjustment coefficient k 2 > Terminal concentration 1 Average distribution 2 Gradually increase 1.5 Gradually reduce 3 Middle-heavy distribution 4

[0037] At this time, take P w2 and P λ2 The smaller value of is temporarily used as the distributed photovoltaic carrying capacity P of the area m2 ,Right now

[0038] P m2 =min(P w2 ,P λ2 )

[0039] S3.4 If the line loss in the area is greater than 4%, the load level of the area needs to be further considered to calculate the distributed photovoltaic carrying capacity P based on the line loss constraint condition. ls ,Right now

[0040] P ls =k 3 *P L -P G2

[0041] In the formula, k 3For coefficients between 1 and 2, P L For the area load.

[0042] At this time, take P w2 , P λ2 and P ls The minimum value of is temporarily taken as the distributed photovoltaic carrying capacity of this area as P m3 ,Right now

[0043] P m3 =min(P ls , P λ2 , P w2 )

[0044] S3.5 Comparison of distributed photovoltaic carrying capacity in the area (P m2 or P m3 ) and the distributed photovoltaic carrying capacity of the 10kV line to which it belongs, and the smaller value of the two is taken as the final result of the distributed photovoltaic carrying capacity of the substation.

[0045] Beneficial effects:

[0046] The present invention proposes a fast calculation method for the carrying capacity of distributed photovoltaic power generation in 10kV lines and substations of distribution networks, which has the following advantages:

[0047] 1) It maintains good calculation accuracy and efficiency without the need for modeling and accurate distribution network topology;

[0048] 2) The data processing process and algorithm are simple and easy to apply in practical engineering. The proposed method can meet the needs of power grid companies to update the available capacity on a quarterly basis, and help the orderly access and high-quality development of distributed photovoltaics. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 :Calculation process of distributed photovoltaic carrying capacity of 10kV lines and connected substations;

[0050] Figure 2 : Evaluate regional power grid topology;

[0051] Figure 3 :Calculation process of distributed photovoltaic carrying capacity of 10kV line;

[0052] Figure 4 :Calculation process of distributed photovoltaic carrying capacity in low-voltage areas. DETAILED DESCRIPTION

[0053] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0054] The present invention is further described in conjunction with the embodiments and drawings, and the present invention includes but is not limited to the following embodiments. Figure 1 As shown, this embodiment relates to a method for evaluating the carrying capacity of distributed photovoltaic power connected to a 10kV line and a substation of a distribution network, including the following steps:

[0055] Step 1: Determine the assessment area, draw the power grid topology of the area to be assessed and collect data:

[0056] 1.1 Determine the distribution network to which the 10kV line to be evaluated belongs and the low-voltage area, and draw the power grid topology diagram of the area, such as Figure 2 Collect the required historical operation data, equipment parameters, measured data, distribution network planning and other data.

[0057] 1.2 Use the existing method to evaluate the carrying capacity of the 10kV line to be evaluated and the upper-level distribution network to which the low-voltage area belongs. After evaluation, the upper-level distribution network to which the area to be evaluated belongs can be connected to distributed photovoltaics, and proceed to step 2.

[0058] Step 2: Follow Figure 3 The evaluation process shown calculates and evaluates the distributed photovoltaic carrying capacity of the 10kV line. The required relevant data are shown in the following table.

[0059]

[0060] 2.1 Conduct thermal stability assessment on 10kV lines. Select the spring noon period when the grid acceptance level in the region to be assessed is the most saturated to calculate the distributed photovoltaic carrying capacity. Calculate the reverse load rate of the 10kV line during this period as

[0061] 2.2 Reverse load rate λ 1 ≈-2.67%<0, so the 10kV line carrying capacity level is assessed as green.

[0062] 2.3 Calculate the distributed photovoltaic carrying capacity P of the line based on the reverse load rate λ1 ,Right now

[0063] P λ1 =((1+0.0267)×5196kW)×0.8≈4.27MW

[0064] 2.4 Calculate the distributed photovoltaic carrying capacity P of the 10kV line based on voltage deviation conditions u1 ,Right now

[0065]

[0066]

[0067] 2.5 Comparison Pλ1 With P u1 The smaller value of the two is temporarily set as the distributed photovoltaic carrying capacity P of the line. m1 ,Right now

[0068] P m1 =min(P λ1 ,P u1 )=1.56MW

[0069] 2.6 Because the 10kV line distributed photovoltaic carrying capacity P m1 It is smaller than the corresponding 10kV bus distributed photovoltaic carrying capacity, and the final distributed photovoltaic carrying capacity of the 10kV line is 1.56MW.

[0070] Step 3: Follow Figure 4 The evaluation process shown calculates and evaluates the distributed photovoltaic carrying capacity of the low-voltage area 1 connected to the above-mentioned 10kV line. The required relevant data are shown in the following table.

[0071]

[0072] 3.1 Use the methods 2.1-2.3 in step 2 to evaluate the thermal stability of area 1, and calculate the distributed photovoltaic carrying capacity P of the area based on the reverse load rate λ2 Using the data in the above table, we can get:

[0073] According to the reverse load rate λ 2 , the distributed photovoltaic carrying capacity level of this substation is assessed to be green.

[0074] Calculate the distributed photovoltaic carrying capacity P of the area based on the reverse load rate λ2 ,Right now

[0075] P λ2 =((1+0.138)×200kW)×0.8≈182.1kW

[0076] 3.2 Because the thermal stability assessment of this area has passed, the voltage deviation verification is continued. The average voltage amplitude value of area 1 at noon is 226.4V, which is within the range of [198V-235.4V]. That is, the voltage deviation verification has passed, and the line loss verification is continued.

[0077] 3.3 Perform line loss verification in the substation and calculate the distributed photovoltaic carrying capacity of the substation based on the line diameter constraint condition: the line loss rate of the substation is 3.6%, so the line loss verification passes. Then, based on the substation power supply radius of 0.75km and the substation outgoing line diameter of 120mm 2 , PV distribution data can be obtained by querying the following two tables. The distributed PV carrying capacity of this area based on the line diameter constraint condition is Pw2 =(2*141-16.5)kW=265.5kW.

[0078]

[0079] Photovoltaic distribution <![CDATA[Adjustment coefficient k 2 > Terminal concentration 1 Average distribution 2 Gradually increase 1.5 Gradually reduce 3 Middle-heavy distribution 4

[0080] Finally, take P w2 and P λ2 The smaller value of is temporarily used as the distributed photovoltaic carrying capacity P of the area m2 ,Right now

[0081] P m2 =min(265.5kW,182.1kW)=182.1kW

[0082] 3.4 Distributed photovoltaic carrying capacity P in area 1 m2 Less than the distributed photovoltaic carrying capacity P of the upper 10kV line m1 =1.56MW, and finally the distributed photovoltaic carrying capacity of area 1 is 182.1kW.

[0083] Step 4: Repeat step 3 to calculate the distributed photovoltaic carrying capacity of area 2 and area 3 respectively.

[0084] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. A method for evaluating the carrying capacity of distributed photovoltaic power generation in 10kV lines and substations, characterized in that: The following steps are involved: Step S1: determine the assessment area, draw the power grid topology of the area to be assessed and collect data; Step S2: Calculate and evaluate the distributed photovoltaic carrying capacity of the 10kV line; Step S3: Calculate and evaluate the distributed photovoltaic carrying capacity of the low-voltage area connected to the above 10kV line; Step S4: Repeat step 3 to calculate the distributed photovoltaic carrying capacity of other substations under the 10kV line in step 2.

2. A 10kV line and distributed photovoltaic carrying capacity assessment method according to claim 1, characterized in that: Step S1 includes the following steps: S1.1 Determine the distribution network to which the 10kV line and low-voltage substation to be evaluated belong, draw the power grid topology map of the area, clearly identify each 10kV line and its connected substation, and collect the required historical operation data, equipment parameters, measured data and distribution network planning data; S1.2 Use the existing method to evaluate the carrying capacity of the 10kV line to be evaluated and the upper-level distribution network to which the low-voltage substation belongs. If the evaluation result of the upper-level distribution network is that the distributed photovoltaic can be connected, then proceed to step S2; if the evaluation result is that the distributed photovoltaic cannot be connected, then the area cannot be connected to the distributed photovoltaic, and the distribution network carrying capacity evaluation of the area is terminated.

3. A 10kV line and distributed photovoltaic carrying capacity assessment method according to claim 1, characterized in that: Step S2 includes the following steps: S2.1 evaluates the thermal stability of the 10kV line, selects the period when the grid acceptance level is the most saturated to calculate the distributed photovoltaic carrying capacity, and calculates the reverse load rate λ of the 10kV line during this period, where: P D is the distributed photovoltaic output within the power supply range of 10kV line during this period, P L is the power load during this period, S e is the actual operation limit of the line; S2.2 According to the reverse load rate λ, the distributed photovoltaic carrying capacity of 10kV lines can be divided into three levels: if λ≤0, it means that the distributed photovoltaics that have been connected can be consumed locally, and there is no reverse power flow in the power grid. It is recommended to connect distributed photovoltaics, and the carrying capacity of this line is evaluated as green; if 0≤λ≤80%, it means that the reverse power flow of the power grid does not exceed 80%. It is recommended to carry out special analysis for the projects to be connected, and the carrying capacity of this line is evaluated as yellow; if λ>80%, it means that the reverse power flow of the power grid exceeds 80% or there are hidden dangers in the operation of the power grid. It is recommended to suspend the connection of distributed photovoltaics before the carrying capacity of the power grid is improved, and the carrying capacity of this line is evaluated as red, and the distribution network carrying capacity evaluation in this area is terminated; S2.3 If λ≤80%, calculate the distributed photovoltaic carrying capacity P of the line based on the reverse load rate λ λ1 ,Right now P λ1 =((1-λ)×S e )×k1 In the formula, k1 is 0.8; S2.4 Calculate the distributed photovoltaic residual carrying capacity P of the 10kV line based on the voltage deviation condition u1 ,Right now In the formula, ΔU is usually taken as 0.07U N , r1, x1 are the resistance and reactance per unit length of 10kV line, is the power factor, L is the length of the 10kV line, P G1 The installed capacity of distributed photovoltaic power generation connected to the current line; S2.5 Comparison P λ1 With P u1 The smaller value of the two is temporarily set as the distributed photovoltaic carrying capacity P of the line. m1 ,Right now P m1 =min(P λ1 ,P u1 ) S2.6 Comparison of 10kV line distributed photovoltaic carrying capacity P m1 The smaller value of the corresponding 10kV bus distributed photovoltaic carrying capacity is taken as the final result of the line carrying capacity.

4. A method for evaluating the carrying capacity of distributed photovoltaic power generation in 10kV lines and substations according to claim 3, characterized in that: Step S3 includes the following steps: S3.1 Use the methods of S2.1-S2.3 in step S2 to evaluate the thermal stability of the area and calculate the distributed photovoltaic carrying capacity P of the area based on the reverse load rate. λ2 ; S3.2 If the thermal stability assessment of the substation passes, the voltage deviation check is performed, that is, whether the voltage amplitude of the substation is within the range of [198V-235.4V]. If the voltage deviation check fails, the load-bearing capacity assessment level of the substation is red, and the load-bearing capacity calculation of the substation is terminated; if it passes, the line loss check is performed; S3.3 Check the line loss in the substation and calculate the distributed photovoltaic carrying capacity of the substation based on the line diameter constraint condition: if the line loss is less than 4%, the distributed photovoltaic carrying capacity is determined according to the line diameter of the transformer outlet in the substation, the power supply radius and the distributed photovoltaic distribution; Combined with the current distributed photovoltaic installed capacity in the area, the distributed photovoltaic carrying capacity P of the area based on the line diameter constraint can be obtained: w2 ,Right now P w2 =k2*P w1 -P G2 In the formula, k2 is the adjustment coefficient, P w1 The carrying capacity of the substation line obtained from the table above according to the line diameter and power supply radius, P G2 The installed capacity of distributed photovoltaic power generation that has been connected to the current area; At this time, take P w2 and P λ2 The smaller value of is temporarily used as the distributed photovoltaic carrying capacity P of the area m2 ,Right now P m2 =min(P w2 ,P λ2 ) S3.4 If the line loss in the area is greater than 4%, the load level of the area needs to be further considered to calculate the distributed photovoltaic carrying capacity P based on the line loss constraint condition. ls ,Right now P ls =k3*P L -P G2 Where k3 is a coefficient between 1 and 2, P L For the area load. At this time, take P w2 , P λ2 and P ls The minimum value of is temporarily taken as the distributed photovoltaic carrying capacity of this area as P m3 ,Right now P m3 =min(P ls ,P λ2 ,P w2 ) S3.5 Comparison of distributed photovoltaic carrying capacity in the area (P m2 or P m3 ) and the distributed photovoltaic carrying capacity of the 10kV line to which it belongs, and the smaller value of the two is taken as the final result of the distributed photovoltaic carrying capacity of the substation.

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