A High-Voltage Distribution Network Planning Method Considering Medium-Voltage Power Transfer and Wiring Group Division

Abstract

The present invention discloses a high-voltage distribution network planning method considering medium-voltage power transfer and wiring group division. The method includes: preliminary classification of 110 kV substations based on adapting to typical wiring modes; a method for dividing the wiring groups of the high-voltage distribution network based on the preliminary classification of substations and the characteristics of high-voltage wiring modes; analysis of the main transformer outage time for different fault types considering the medium-voltage side power transfer capacity; establishing a mathematical model for optimizing the internal grid structure of the wiring group considering the medium-voltage side power transfer capacity with the goal of minimizing the annual cost of construction and operation of the wiring group; and a method for comprehensively optimizing the overall grid structure of the high-voltage distribution network based on the power supply constraints of the high-voltage distribution network. The technical solution provided by the embodiment of the present invention realizes the refined planning of the high-voltage distribution network through the wiring group division method and considering the support of the medium-voltage side power transfer capacity within the wiring group, improves the planning quality, and reduces the economic cost of the construction of the high-voltage distribution network on the premise of meeting the reliability requirements.

Description

Technical Field

[0001] The present invention relates to the field of distribution network planning, and particularly to a high-voltage distribution network planning method considering medium-voltage power transfer and connection group division. Background Art

[0002] As one of the most important basic industries in China, the rapid development of the power industry is the cornerstone for the stable improvement of the national economy and a strong guarantee for people's production and life. As the part closest to the user side, the distribution network should be able to provide high-quality and reliable electric energy to users, and undertake the task of load transfer and power supply when any component in the system is out of service due to maintenance or failure. The high-voltage distribution network generally refers to the distribution network with a voltage level of 35 kV to 110 kV. As an intermediate link that can receive electric energy from the upper-level transmission network and supply electric energy to the medium-voltage distribution network, it plays an important role in the distribution network. According to statistics, nationwide, the electricity delivered to users via the high-voltage distribution network accounts for 85% of the total power generation. Therefore, the scientific and reasonable planning of the high-voltage distribution network is of great significance for ensuring the reliable, economic, and safe operation of the power grid, meeting the power demand, and improving the social and economic benefits of the power grid.

[0003] Currently, there have been certain studies on the field of distribution network grid structure planning at home and abroad. Some studies have proposed an optimization model with the goal of minimizing the overall construction and operation cost of the distribution network and a solution method based on heuristic methods; some studies have proposed a refined grid planning method for the distribution network. However, the current research has the following problems: First, only the load transfer of the current level is considered after a fault occurs, and the supporting role of the lower-level network is not taken into account, resulting in problems such as large spare capacity, low equipment utilization rate, and poor economy in the planning area; Second, the refined planning methods based on grid and power supply unit division are mostly used in medium-voltage distribution networks, and there is a lack of application research in the grid structure planning of high-voltage distribution networks. Summary of the Invention

[0004] In order to solve the shortcomings and deficiencies existing in the prior art, the present invention proposes an optimized planning method for the grid structure of a high-voltage distribution network based on connection group division and considering the power transfer capacity on the medium-voltage side, so as to solve the problems such as large spare capacity, low equipment utilization rate, and poor economy caused by the current hierarchical planning of the distribution network and the lack of refined planning research on the high-voltage distribution network.

[0005] Specifically, the optimized planning method for the grid structure of a high-voltage distribution network considering the power transfer capacity on the medium-voltage side and connection group division includes:

[0006] (1) Preliminary classification of 110 kV substations based on the adaptation to typical connection modes;

[0007] (2) A method for dividing connection groups for the high-voltage distribution network based on the preliminary classification of substations and the characteristics of high-voltage connection modes;

[0008] (3) Analysis of the power outage time of main transformers under different fault types considering the transfer capacity of the medium-voltage side;

[0009] (4) Establish a mathematical model for optimizing the internal grid structure planning of the connection group considering the transfer capacity of the medium-voltage side with the goal of minimizing the annual cost of construction, operation, and investment of the connection group;

[0010] (5) A combined optimization method for the overall grid structure of the high-voltage distribution network based on the power supply constraints of the high-voltage distribution network.

[0011] The step (1) is based on the preliminary classification of 110 kV substations considering the adaptation of typical connection modes, specifically including:

[0012] 1) Analyze the requirements of the typical connection modes of the high-voltage distribution network for the number of main transformers and the types of outgoing lines;

[0013] 2) According to the current situation analysis and load forecast of the planning area, determine the types of outgoing lines and the number of main transformers of 110 kV substations in the target year, and obtain the optional high-voltage typical connection mode situations of 110 kV substations;

[0014] 3) Classify the substations with the same optional high-voltage typical connection mode situations into one category.

[0015] The step (2) is a method for dividing the connection groups of the high-voltage distribution network based on the preliminary classification of substations and the high-voltage connection modes, specifically including:

[0016] 1) Establish an initial adjacency matrix A and a power supply connection matrix S s

[0017] For the 110 kV substation nodes that are candidate access locations for photovoltaic power stations, a virtual node after connecting the photovoltaic power station should be added to the adjacency matrix. The properties such as the location, main transformer configuration, and adjacency relationship of the virtual node are the same as those of the original node, but the grid structure, power flow distribution, line losses, etc. of the connection group containing the virtual node may change.

[0018] The initial adjacency matrix A is a square matrix representing the feasible candidate channels between the superior power supply and 110 kV substations and among 110 kV substation nodes.

[0019] A = [a i1j1 n×n , i1, j1 = 1, 2, …… n (17)

[0020]

[0021] Define the power supply connection matrix S s ​It is a 1×n order matrix representing the connection relationship between the superior power node and the 110 kV substation node. Among them, s is the number of the superior power node, and each superior power node corresponds to a power connection matrix.

[0022]

[0023]

[0024] 2) Matrix operation '×' based on matrix cross product

[0025] Define the matrix operation '×' based on matrix cross product. Assume two matrices and The elements in the matrix are respectively and Among them, p0 and q0 represent the number of nodes included in the elements and Define the matrix operation:

[0026]

[0027]

[0028]

[0029] Among them, the '+' operation is defined as a 'and' relationship, represents the set of new elements formed by all the elements in the i0-th row of matrix A0 and the elements in the j0-th column of matrix B; the '·' operation means combining the nodes in the elements and in sequence to form a new element.

[0030] 3) Wiring group division method

[0031] ① Power connection matrix S s and adjacency matrix A s Determine. Obtain the power connection matrix S s and the initial adjacency matrix A according to the high-voltage candidate channels in the planning area. A s can be modified from the initial adjacency matrix A, and its purpose is to avoid duplicate wiring groups caused by the inversion of the start and end of the nodes. Set to zero the first s - 1 power nodes in the adjacency matrix A s corresponding to the power node s. The expression of the adjacency matrix A s is as follows:

[0032]

[0033] Among them, represents the adjacency matrix A sThe column vector of the connection relationship between the s0th power node and other nodes in represents the adjacency matrix A s is the connection relationship matrix between non-power nodes and other nodes in ; m represents the number of power nodes.

[0034] ② Calculation of high-order connection groups. The k-order connection group can be obtained by performing the '×' operation on the (k - 1)-order radial connection group after removing infeasible solutions and the adjacency matrix A s and includes the k-order connection groups from the power source s to each node in the planning area except the s node. The formula for calculating the high-order connection group is as follows:

[0035]

[0036] ③ Exclusion and splitting of high-order connection groups. During the calculation, it may occur that a 110 kV substation node appears twice in the same connection group, that is, duplicate wiring or loop formation within the connection group. Exclude such connection groups to obtain and split into a k-order radial connection group a k-order loop connection group and a k-order chain connection group

[0037]

[0038] ④ Judgment on completing the division of the connection group where a certain upper-level power source is located. There are two judgment conditions. One is to complete the calculation of the highest-order connection group. For the chain and loop connection modes, the highest order is 4, and for the radial connection mode, the highest order is 3. The other is that the feasible radial connection group is empty. Meeting one of the two conditions can end the calculation of the connection group under this upper-level power source. Otherwise, return to ② to continue calculating the high-order connection group.

[0039] ⑤ Judge whether the calculation of the connection groups of all upper-level power sources is completed. If so, end the algorithm. Otherwise, return to ① to perform the division of the connection group with the next power source as the starting node.

[0040] The step (3) analyzes and calculates the main transformer outage time of different fault types considering the medium-voltage power transfer capacity, specifically including:

[0041] 1) The fault power outage time of the high-voltage power distribution network can be divided into three types according to different power transfer channels. One is power transfer through the 110 kV line in the high-voltage power distribution network and through the main connection of the high-voltage side of the 110 kV substation. At this time, the power outage duration is the high-voltage power transfer time T1. The second is power transfer through the connection of the 10 kV side of the 110 kV substation. At this time, the power outage duration is the medium-voltage power transfer time T2. The third is that power transfer cannot be carried out, and power supply needs to be restored by repairing the faulty part. At this time, the power outage duration is the fault repair time T(x), where x is the fault type.

[0042] 2) The judgment of the high-voltage power transfer capacity includes the analysis of typical wiring modes in the wiring group and the analysis of the main connection form of the high-voltage side of the 110 kV substation. When the high-voltage power transfer capacity judgment is satisfied, the main transformer power outage time is the high-voltage power transfer time T1.

[0043] 3) The judgment of the medium-voltage power transfer capacity of the main transformer in the wiring group includes the analysis of the maximum power transfer load in the power supply grid and the analysis of the situation of the 110 kV substations in the wiring group belonging to the power supply grid.

[0044] The analysis of the situation of the 110 kV substations in the wiring group belonging to the power supply grid specifically includes:

[0045] Determine the medium-voltage power supply grid to which the 110 kV substation in the wiring group belongs and the type of the medium-voltage power supply grid to which it belongs. The first situation is that all 110 kV substations in the wiring group are located in different power supply grids. The second situation is that some 110 kV substations in the wiring group are located in the same power supply grid. The third situation is that all 110 kV substations in the wiring group are located in the same power supply grid.

[0046] The analysis of the maximum power transfer load rate in the power supply grid:

[0047]

[0048]

[0049] Among them, is the actual load rate of the nth substation in the i-th wiring group; is the maximum load rate that the medium-voltage power supply grid where the nth substation in the wiring group i meets the medium-voltage power transfer requirement under the situation q k ; is the number of in-station connections of the nth substation in the i-th wiring group under the situation q k ; is the number of inter-station connections of the nth substation in the i-th wiring group under the situation q k ; is the number of substations in the medium-voltage power supply grid to which the nth 110 kV substation in the i-th wiring group belongs. Among N(n i) is the number of main transformers in the nth 110 kV substation in the ith connection group.

[0050] When the actual load rate of the nth substation in the connection group is less than the maximum load rate required for medium-voltage power transfer in the medium-voltage power supply grid where the substation is located, the substation meets the medium-voltage power transfer requirement, and the power outage duration is the medium-voltage power transfer time T2.

[0051] 4) In the case of no power transfer available, the power outage duration of the main transformer is the fault repair time T(x), and the repair times for different component faults are different.

[0052] The step (4) establishes a mathematical model for optimizing the internal grid structure planning of the connection group considering the medium-voltage side power transfer capacity and the access of photovoltaic power plants, specifically including:

[0053] 1) Objective function

[0054] minC i (24)

[0055] C i =C line-i +C k-i +C loss-i +C cost-i

[0056] Among them, C i is the comprehensive investment cost of the ith connection group, C line-i is the investment cost for building lines in the ith connection group, C k-i is the investment cost of switches in the ith connection group, C loss-i is the line loss cost in the ith connection group, C cost-i is the cost of fault losses in the ith connection group.

[0057] ① Calculation of the line construction investment cost in the ith connection group

[0058]

[0059] Among them, d is the discount rate, m is the depreciation life, C0 is the comprehensive cost per unit length of the high-voltage line, which is related to the selected typical connection mode and line type in the connection group, M is the number of segments of the high-voltage candidate channels in the connection group, is the length of the l ith segment of the candidate channel.

[0060] ② Calculation of the switch investment cost in the ith connection group

[0061]

[0062] Among them, is the unit price of the switch, N kis the number of switches in the wiring group and is related to the selected typical wiring mode in the wiring group.

[0063] ③ Calculation of network loss cost in the i-th wiring group

[0064] C cost-i = minC cost-i (f) (27)

[0065]

[0066]

[0067] Among them, C loss-i (f) is the network loss when the i-th wiring group selects the f-th sectional point during normal operation, ξ max is the output scenario of the photovoltaic power station, P{·} represents the event probability, C loss-i-cj (f) is the network loss when the output of the photovoltaic power station in the i-th wiring group at the f-th sectional point is cj, α is the confidence level of the network loss at the sectional point f, β1 is the unit electricity price, β2 is the unit length resistance value of the line in the wiring group, is the load magnitude flowing through the i-th l candidate channel at time t when the open break point in the i-th wiring group is f, is the power flow change amount caused by the photovoltaic power station at time t on the i-th l candidate channel when the open break point in the i-th wiring group is f.

[0068] ④ Calculation of power outage loss cost in the i-th wiring group

[0069]

[0070] Among them, N i is the number of 110kV substations in the i-th wiring group, N(n i ) is the number of main transformers in the n-th 110kV substation in the i-th wiring group, N f (n i , m) is the possible number of faults that may occur in the m-th main transformer in the n-th i substation under a certain typical wiring mode, is the load magnitude on the m-th main transformer of the n-th i substation at time t, C n-m(i) (t) is the unit load power outage loss cost of the m-th main transformer in the n-th substation when the fault power outage time is t0, t0 is related to the fault transfer path, is the probability of the m-th main transformer in the n-th substation having a fault g.

[0071] 2) Constraint conditions

[0072] ① Voltage drop constraint:

[0073] P{ΔU max ≥ΔU m-cj ≥ΔU min}≥β (29)

[0074] Wherein, ΔU m-cj is the voltage drop when power is supplied from one - end power supply considering fault transfer when the output of the photovoltaic power station is cj, ΔU max , ΔU min are the upper and lower limit constraints of the voltage drop, and β is the confidence level of the voltage drop.

[0075] ② Average power outage time constraint of the 110kV substation in the wiring group:

[0076] max(SAIDI)≥SAIDI i (30)

[0077] Wherein, SAIDI i is the average power outage time of substation i, and max(SAIDI) is the maximum average power outage time when the reliability requirements are met.

[0078] ③ Short - circuit current constraint

[0079] I s ≤I smax (31)

[0080] Wherein, I s is the maximum short - circuit current of the system, and I smax is the maximum breaking current of the circuit breaker.

[0081] The step (5) proposes a combined optimization method for the overall grid structure of the high - voltage distribution network based on the power supply constraints of the high - voltage distribution network, which specifically includes:

[0082] 1) Number the optimized wiring groups. By means of integer programming, combine the feasible wiring groups that meet the constraint conditions into the overall grid structure of the high - voltage distribution network to form alternative schemes for the high - voltage distribution network grid structure.

[0083] 2) Objective function:

[0084] C=minC h (32)

[0085]

[0086] Wherein, C h is the annual construction and operation cost of the overall grid structure plan h of the high - voltage distribution network, C i is the annual construction and operation cost of the wiring group i, and Ω hIt is the set of connection groups included in the overall grid structure plan h of the high-voltage distribution network.

[0087] 3) Constraints on the overall grid structure of the high-voltage distribution network:

[0088] ① The overall grid structure composed of connection groups should be able to cover all 110 kV substations in the planned area, and there should be no situation where a 110 kV substation is located in multiple connection groups. That is, it meets the requirement that all 110 kV substations in the planned area have a superior power source to supply power to them, and there is no duplicate power supply situation caused by a station being located in multiple connection groups.

[0089] ② The overall grid structure should be able to integrate all photovoltaic power plants in the planned area into the power grid, and there is only one grid connection point for one photovoltaic power plant.

[0090] ③ The overall grid structure should meet the capacity constraints of the superior 220 kV substation and the constraints of the outgoing line intervals under the condition of considering the uncertainty of photovoltaic power plants in the planned area. Description of the drawings

[0091] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0092] Figure 1 It is the overall solution flowchart of the optimization planning method for the high-voltage distribution network grid structure.

[0093] Figure 2 It is the division situation of the high-voltage candidate channels and the medium-voltage side power supply grid in the embodiment of this method.

[0094] Figure 3 It is the planning result of the grid structure in the embodiment by the method in this article.

[0095] Figure 4 It is the planning result of the grid structure in the embodiment without considering the medium-voltage power transfer capacity. Detailed implementation manners

[0096] To make the structure and advantages of the present invention clearer, the structure of the present invention will be further described below in conjunction with the drawings.

[0097] Combined with Figure 1 The overall solution process of a high-voltage distribution network planning method considering medium-voltage power transfer and connection group division proposed by the present invention is elaborated in detail. The specific steps are as follows:

[0098] Step1: Preliminary classification of 110 kV substations based on adapting to typical wiring modes;

[0099] Step2: Analysis of the substation layout and the status quo of high-voltage candidate channels in the planning area;

[0100] Step3: Establish the initial adjacency matrix and power connection matrix in the planning area;

[0101] Step4: Obtain all wiring groups in the planning area through the wiring group division method based on the initial adjacency matrix and power connection matrix by matrix '×' operation;

[0102] Step5: Determine the main transformer outage time when different types of faults occur considering the medium-voltage transfer capacity;

[0103] Step6: Establish a mathematical model for optimizing the internal grid structure planning of the wiring group considering the medium-voltage side transfer capacity;

[0104] Step7: Determine the open breakpoints and minimum network loss cost of the wiring group by optimizing the network loss cost when different open breakpoint positions are selected under normal operating conditions;

[0105] Step8: Combine the main transformer outage time when different types of faults occur considering the medium-voltage transfer capacity to calculate the outage loss cost of the wiring group;

[0106] Step9: Optimize the grid structure planning scheme of the wiring group under all feasible typical wiring modes, select the most economical one among the planning schemes that meet the constraint conditions, and save this scheme;

[0107] Step10: Judge whether the grid structure optimization of all wiring groups is completed. If completed, proceed to Step11. If not completed, proceed to Step5;

[0108] Step11: Through integer programming, form alternative schemes for the high-voltage distribution network grid structure that meet the constraint conditions;

[0109] Step12: Conduct a technical and economic comparison of the alternative schemes for the high-voltage distribution network grid structure to determine the optimal high-voltage distribution network grid structure planning scheme.

[0110] The total power supply area of the planning area is 37 square kilometers, and the maximum load is 326 MW. After analyzing the current situation, load forecasting, and the medium-voltage side power supply model in the planning area, the distribution of substations can be obtained. The numbers of 220 kV substations and 110 kV substations are 4 and 8 respectively. There is a 20 Mwp photovoltaic power station in the planning area, which can be connected to Substation 1 through a dedicated line. The implementation example area is Class A+ and Class A power supply areas, and the high-voltage candidate channel is a cable outlet.Figure 2 This shows the high-voltage candidate channels and the medium-voltage side power supply grid division for the embodiments of this method. Table 1 shows the basic situation of the 110 kV substation in the embodiment.

[0111] Table 1. Basic situation of the 110 kV substation in the planned area

[0112]

[0113]

[0114] First, determine the adapted same typical connection mode according to the outgoing line type and the number of main transformers of the 110 kV substations in this area, and classify the substations that meet the corresponding constraints of the number of main transformers and the outgoing line type into one category. Since the high-voltage candidate channels in this area are cable channels, the number of substations in the planned area is 2, and the selectable typical connection modes include the double-chain π-type connection mode and the single-link connection mode of the chain connection, the double-ring and single-ring connection modes of the ring connection mode, and the double-radiation π-type connection mode in the radial connection mode. Therefore, the 110 kV substations in Area 1 can be classified into one category.

[0115] According to the situation of the high-voltage candidate channels in this area, form the initial adjacency matrix A and the power supply connection matrix S s .

[0116]

[0117] S 1 =[0 0 0 0 s1 1s1 2 0 0 0 0 0 0 s1 1']

[0118] S 2 =[0 0 0 0 s2 1s2 2s2 3 s2 4 0 0 0 0 s2 1']

[0119] S 3 =[0 0 0 0 0 0 0 0 s3 5s3 6 s3 7 0 0]

[0120] S 4 =[0 0 0 0 0 0 0 0 0 0 0 s4 8 0]

[0121] According to the connection group division method proposed in this article, starting from each upper-level power supply node in sequence, connect other nodes with connection relationships. Table 2 shows all the connection group division situations in Area 1.

[0122] Table 2 Connection group division situation

[0123]

[0124] Through the optimization method proposed in this paper, the grid structure inside each connection group is optimized. Tables 3, 4, and 5 respectively give the optimization results of the radial connection group, the ring connection group, and the chain connection group.

[0125] Table 3 Optimization Results of Radial Connection Group

[0126]

[0127]

[0128] Table 4 Optimization Results of Ring Connection Group

[0129]

[0130]

[0131] Table 5 Optimization Results of Chain Connection Group

[0132]

[0133]

[0134]

[0135] The connection groups obtained by optimization are combined into the grid structure scheme of the high-voltage distribution network. Through technical and economic comparison, the grid structure planning scheme with the minimum annual cost is obtained. Tables 6 and 7 respectively give the optimal results obtained by optimizing with this method and the specific planning situation when the transfer capacity of the medium-voltage side is not considered. The planning results Figure 3 、 4 。

[0136] Table 6 Specific Results of Grid Structure Planning by This Method (10,000 yuan)

[0137]

[0138] Table 7 Specific Results of Grid Structure Planning (10,000 yuan)

[0139]

[0140] Through comparative analysis, it can be seen that in the traditional planning scheme, the double-chain π-type connection mode or the triple-chain π-type connection mode with relatively high reliability is usually adopted in the A+ and A-class power supply areas. However, because the planning method in this paper considers the support of the medium-voltage side transfer to the high-voltage distribution network during faults, when the 110 kV substation in the connection group has a strong transfer capacity on the medium-voltage side, the typical connection mode of this connection group can choose the ring network or the radial connection mode with relatively low reliability, which reduces the construction and operation investment costs of the high-voltage distribution network on the premise of meeting the reliability requirements.

[0141] The serial numbers in the above embodiments are only for description purposes and do not represent the sequence in the assembly or use process of each component.

[0142] The above are only embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-voltage distribution network planning method considering medium-voltage power transfer and wiring group division, characterized in that, The method includes: (1) Preliminary classification of 110 kV substations based on adapting to typical wiring modes; (2) Division of wiring groups for high-voltage distribution networks based on the preliminary classification of substations and the characteristics of high-voltage wiring modes; (3) Analysis of the main transformer outage time under different fault types considering the transfer capacity of the medium-voltage side; The analysis of the medium-voltage transfer capacity when the 110 kV substation belongs to different wiring groups specifically includes: The analysis of the situation of 110 kV substations belonging to the power supply grid within the wiring group is as follows: Determine the medium-voltage power supply grid to which the 110 kV substation within the wiring group belongs and the type of the medium-voltage power supply grid. In the first case, the 110 kV substations in the wiring group are all located in different power supply grids. In the second case, some of the 110 kV substations in the wiring group are located in the same power supply grid. In the third case, all of the 110 kV substations in the wiring group are located in the same power supply grid; When belonging to different wiring groups, the analysis of the maximum transfer load rate of the main transformer in the power supply grid is as follows: Among them, is the actual load rate of the nth substation in the ith connection group; is the maximum load rate that the medium-voltage power supply grid where the nth substation in connection group i meets the medium-voltage transfer requirement under condition q k ; is the number of in-station connections of the nth substation in the ith connection group under condition q k ; is the number of inter-station connections of the nth substation in the ith connection group under condition q k ; is the number of substations in the medium-voltage power supply grid of the 110 kV substation in the ith connection group where the nth substation is located. N(n i ) is the number of main transformers in the 110 kV substation where the nth substation in the ith connection group is located, and n jxz is the number of 110 kV substations to which the power supply model is connected in this connection group (4) Establish a mathematical model for optimizing the internal grid structure of the wiring group considering the transfer capacity of the medium-voltage side with the goal of minimizing the annual cost of construction and operation investment of the wiring group; Establishing a mathematical model for optimizing the internal grid structure of the wiring group considering the transfer capacity of the medium-voltage side and the access of photovoltaic power stations specifically includes: Establish the objective function of the mathematical model for optimizing the internal grid structure of the wiring group considering the influence of the transfer capacity of the medium-voltage side. Specifically, it is: minC i (8) C i = C line-i + C k-i + C loss-i + C cost-i Among them, C i is the comprehensive investment cost of the i-th wiring group, C line-i is the investment cost for the construction of the line in the i-th wiring group, C k-i is the investment cost of the switch in the i-th wiring group, C loss-i is the line loss cost in the i-th wiring group, C cost-i is the fault loss cost considering the medium-voltage side transfer capacity in the i-th wiring group; The calculation of the line construction investment cost in the i-th wiring group is: where d is the discount rate, m is the depreciation period, C0 is the comprehensive cost per unit length of the high-voltage line, which is related to the selected typical connection mode and line type in the connection group, M is the number of segments of the high-voltage candidate channels in the connection group, is the length of the l ith segment of the candidate channel; The calculation of the switch investment cost in the i-th wiring group is: Among them, is the unit price of the switch, and N k is the number of switches in the wiring group, which is related to the selected typical wiring mode in the wiring group; The calculation of the network loss cost in the i-th wiring group is: C loss-i = minC loss-i (f) (11) Among them, C loss-i (f) is the network loss when the connection group i selects the f-th sectionalizing point during normal operation, ξ max is the output scenario of the PV power station, P{·} represents the event probability, C loss-i-cj (f) is the network loss when the output of the PV power station is cj at the f-th sectionalizing point of the connection group i, α is the confidence level of the network loss at the sectionalizing point f, β1 is the unit electricity price, β2 is the unit length resistance value of the lines within the connection group, is the load magnitude flowing through the i-th l candidate channel at time t when the breaking point is f in the i-th connection group, is the change in power flow caused by the PV power station at time t on the i-th l candidate channel when the breaking point is f in the i-th connection group; The calculation of the outage loss cost in the i-th wiring group is: Among them, N i is the number of 110 kV substations in connection group i, N(n i ) is the number of main transformers in the nth 110 kV substation in the ith connection group, N f (n i , m) is the number of faults occurring in the mth main transformer in the nth i substation under a certain typical connection mode, is the load magnitude of the mth main transformer in the nth i substation at time t, C n-m(i) (t) is the unit load outage loss cost of the mth main transformer in the nth substation when the fault outage time is t0, is the probability that the mth main transformer in the nth substation has a fault g; (5) A combined optimization method for the overall grid structure of the high-voltage distribution network based on the power supply constraints of the high-voltage distribution network.

2. A high-voltage distribution network planning method considering medium-voltage power transfer and wiring group division according to claim 1, characterized in that The specific step (2) is Defining a node sequence connection method based on the matrix operation '×' specifically includes: Among them, m0 and k0 are the number of rows and columns of matrix A0 respectively, n0 and k0 are the number of columns and rows of matrix B0 respectively, and p0 and q0 are the number of nodes included in elements and respectively. The "+" operation is defined as a 'sum' relationship. represents the set of new elements formed by all the elements in the i0-th row of matrix A0 and the elements in the j0-th column of matrix B; the "·" operation means combining the nodes in elements and into a new element in sequence.

3. A high-voltage distribution network planning method considering medium-voltage power transfer and wiring group division according to claim 2, characterized in that, Establishing the initial adjacency matrix and power supply connection matrix considering the access of virtual nodes of photovoltaic power stations, and proposing a wiring group division method based on the matrix '×' operation specifically includes: For the 110 kV substation node that is the candidate access location of the photovoltaic power station, a virtual node after accessing the photovoltaic power station should be added to the adjacency matrix. The properties such as the position, main transformer configuration, and adjacency relationship of the virtual node are the same as those of the original node, but the grid structure, power flow distribution, line loss, etc. of the wiring group containing the virtual node may change; The initial adjacency matrix A is a square matrix representing the feasible candidate channels between the superior power supply and the 110 kV substations and among the 110 kV substation nodes. Define the power connection matrix S s It is a 1×n matrix representing the connection relationship between the superior power node and the 110 kV substation node. Among them, s is the number of the superior power node, and each superior power node corresponds to a power connection matrix. The adjacency matrix A based on the initial adjacency matrix A s is modified to: Among them, represents the column vector of the connection relationship between the s0-th power node and other nodes in the s adjacency matrix A; represents the matrix of the connection relationship between non-power nodes and other nodes in the s adjacency matrix A; m s represents the number of power nodes, The high-order wiring group described Calculated as: Among them, is a k-order connection group, is a (k - 1)-order radial connection group for removing infeasible solutions. The high-order connection group is excluded and split as follows: Exclude the wiring group in which the same node of the 110 kV substation appears twice in a loop within the repeated wiring or wiring group, and obtain According to the nature of the end nodes, it is split into a k-order radial connection group with 110 kV substation nodes as the end nodes a k-order loop connection group with the same head-end power supply as the end nodes and a k-order chain connection group with end nodes not passing through the head-end power supply The calculation of all wiring groups is: For the chain or ring wiring mode, calculate up to the 4th-order high-order wiring group. For the radial wiring group, calculate up to the 3rd-order high-order wiring group; Complete the calculation of the high-order wiring group of the power connection matrix S formed by all the upper-level power nodes s of the high-order wiring group calculation 4. A high-voltage distribution network planning method considering medium-voltage power transfer and wiring group division according to claim 1, characterized in that The combined optimization method for the overall grid structure of the high-voltage distribution network based on the power supply constraints of the high-voltage distribution network specifically includes: Establish the objective function of the wiring group combination to form the optimal method for the high-voltage distribution network grid structure scheme considering the power supply constraints of the high-voltage distribution network. Specifically, it is: C = minC h (16) Among them, C h is the annual construction and operation cost of the overall grid structure plan h of the high-voltage distribution network, and C i is the annual construction and operation cost of the connection group i. Ω h is the set of connection groups included in the overall grid structure plan h of the high-voltage distribution network. Establish the constraints for the wiring group combination to form the high-voltage distribution network grid structure, specifically: The overall grid structure plan covers all 110 kV substations within the planned area, and there is no situation where a 110 kV substation is located in multiple connection groups; All photovoltaic power stations within the planned area are connected to the grid, and each photovoltaic power station has only one grid connection point; it meets the capacity constraints of the superior 220 kV substation and the constraints of the outgoing line intervals.

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