Regional power grid flexible interconnection planning method giving consideration to global consumption capability and investment income of new energy

Abstract

The invention relates to a regional power grid flexible interconnection planning method giving consideration to global consumption capability and investment income of new energy. The method comprises the following steps: firstly, constructing a regional power grid flexible interconnection device locating and sizing and new energy consumption index evaluation system and a to-be-planned interconnection line position-capacity set; secondly, a regional power grid flexible interconnection double-layer planning model is constructed, an upper layer decides an interconnection device locating and sizing scheme, and a lower layer evaluates the system new energy consumption capability after the flexible device is constructed and decides the new energy grid-connected access quantity; and finally, determining a target planning scheme by adopting an improved multi-target particle swarm algorithm. According to the method, the new technology of flexible interconnection between regional power grids is considered, and the model selection, site selection and capacity determination scheme of the cross-regional interconnection line is determined through the new indexes of the node topology connection degree, the neighbor node center support force and the node vulnerability resistance, so that the problem that the traditional regional power grid planning method cannot directly match the source load is solved; and the capability of flexible consumption of new energy and mutual aid of resources among regional power grids is improved.

Description

Technical Field

[0001] The present invention relates to a method for planning flexible interconnection of regional power grids taking into account global consumption capacity of new energy and investment returns, and belongs to the technical field of consumption of new energy. Background Art

[0002] Under the background of "dual carbon", the scale of new energy access continues to increase, bringing new challenges to the reliable power supply, safety, stability and economic operation of regional power grids. Specifically, the capacity of power transmission and transformation equipment is tight and surplus, the source and load distribution between regional power grids is unbalanced, and the mutual assistance capacity between grids is seriously insufficient; the relative independence of regional power grids seriously restricts the level of regional power grid absorption. Flexible interconnection technology can transform and upgrade the existing AC interconnection grid without structural adjustment of the existing regional power grid, realize the flexible absorption and resource mutual assistance of new energy between regional power grids, improve the new energy absorption capacity and power supply reliability of the power grid, and has broad application prospects.

[0003] Traditional flexible interconnection planning technology focuses on scenarios of new energy transmission under high voltage and large capacity or relieving power supply pressure in overloaded areas, and cannot adapt to new regional new energy consumption needs under strong AC and weak connection. How to plan DC interconnection lines between regions, select appropriate DC interconnection nodes and economically feasible line capacity, and maximize the flexible consumption and resource mutual assistance of new energy between regional power grids by utilizing the temporal and spatial complementary characteristics of source and load distribution between receiving and sending networks while maintaining good investment returns, and reduce wind and solar power abandonment.

[0004] For example, the invention patent with application number 202111213669.5 discloses a sizing method for multi-zone flexible interconnected converter stations in urban power grids. This sizing method only determines the active capacity of the converter station based on the maximum power supply capacity of the interconnected zone under N-1 faults, and does not analyze the impact of new energy access on the determination of the interconnection capacity; the invention patent with application number 201711470635.8 discloses a site selection method for power supply zone interconnection points. This site selection method screens alternative site selection nodes based on transmission corridor requirements, short-circuit current limits, and active and reactive power requirements of power supply zones, but does not consider the impact of the network topology characteristics of the nodes on the site selection node decision. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a regional power grid flexible interconnection planning method for improving the connection capability of interconnection lines in sub-regional power grids.

[0006] In order to achieve the above-mentioned purpose, the technical solution proposed in the present invention is: a method for planning flexible interconnection of regional power grids that takes into account the global absorption capacity of new energy and investment returns, wherein the regional power grid is a regional power grid with a 220kV voltage level line as the backbone grid, comprising the following steps:

[0007] According to the power load of the power grid at the sending and receiving ends and the interconnection demand, the location set of the interconnection lines to be planned is initially screened; and the installed capacity range of the flexible interconnection device is determined according to the power supply capacity of the sending end power grid and the power demand of the receiving end power grid; and a planning scheme set of the interconnection lines including the location and capacity is constructed in combination with the location set and capacity range of the interconnection lines to be planned;

[0008] A two-layer planning model for regional power grid flexible interconnection is established, in which the upper layer is a flexible interconnection site selection and capacity optimization model built with the optimal investment cost and interconnection node criticality as the objective function, and the lower layer is a new energy consumption evaluation model built with the optimal new energy consumption benefit as the objective function;

[0009] The improved multi-objective particle swarm algorithm is used to bring the planning scheme sets into the two-level programming model for solution to obtain the target planning scheme.

[0010] The further design of the above technical solution is: the maximum power demand of the receiving end power grid is used as the lower limit P of the installed capacity of the flexible interconnection device Nmin :

[0011]

[0012] Where: P' R-c , P' R-cLj is the power demand of the receiving grid and bus j when N-1 faults occur in component c, and there are C1 components in total; P Nmin is the maximum power demand when the receiving grid fails N-1; P Gm is the power transmitted from the 500 kV tie line from partition m to the receiving grid; the set of adjacent partitions of the receiving grid is M, m∈M; are the predicted values ​​of wind power and photovoltaic power generation near bus node j respectively.

[0013] The maximum power supply capacity of the sending-end power grid is taken as the upper limit of the installed capacity of the flexible interconnection device P. Nmax :

[0014]

[0015] Where: P Nmax is the maximum power supply capacity of the sending-end power grid; P' S-cGi Add new energy to the key node c and the power supply capacity of bus i; P Ln P Ln is the power transmitted from the sending-end grid to the partition n by the 500 kV interconnection line; the set of adjacent partitions of the sending-end grid is N, n∈N.

[0016] The investment cost includes the construction cost and the annual operating cost of the unit; the construction cost includes the construction cost of the flexible interconnection line, the sending and receiving end converter stations and the cross-river tower; the annual operating cost of the unit includes the power loss cost of the DC interconnection line and the cost of unit operation and maintenance.

[0017] The criticality of interconnected nodes includes node topological connectivity, neighbor node central support, and node anti-fragility;

[0018] The node topological connection degree is:

[0019]

[0020] Where: h ij represents the i-th row and j-th column of the unit adjacency matrix H0 in the power network; is the average degree of all nodes in the power grid; N is the total number of power grid nodes, and L is the total number of transmission lines;

[0021] The neighbor node center support force is:

[0022] G' β =β*K out *H0*e T +(1-β)*H0*K in *e T

[0023] Where: Weighted adjacency matrix The power flow value of a line is the weight of the adjacency matrix of the line; the out-degree matrix K of the node out =diag(k out ), The node in-degree matrix K in =diag(k in ), e=ones(N,1),G β Take G' β The first N of ;

[0024] The node anti-fragility is:

[0025]

[0026] Where: G V is the node antifragility, ΔP uv-γ is the active power transfer of transmission line γ caused by the change of interconnection line uv; dN is the power operating limit of the heavy-load line; P γ is the active power of the heavy-load line γ during normal operation; P uv-γis the active power of the heavy-load line γ after the interconnection line uv is built; ΔP uv-γ ≤ε(ε can be 0.5%P dN ) indicates that the addition of the interconnection line uv does not effectively increase the active power of the interconnection line. At this time, it is considered that the interconnection line cannot transfer the power flow pressure of line γ.

[0027] The objective function of the upper-level flexible interconnection site selection and capacity optimization model is:

[0028] F s =ω1f1 * +ω2f2 *

[0029]

[0030] Where: f1 * ,f2 * is the normalized function of investment cost and interconnection node criticality; ω1, ω2 are the corresponding weight coefficients; W profit (Y) is the investment cost; W operate is the annual operating cost of the unit; W build is the construction cost; G is the criticality of the interconnection node; G V , G β , G K is the topological connection degree of the node, the central support of the neighboring node, and the anti-fragility; λ1, λ2, λ3 are the weights of each node indicator.

[0031] The constraints of the upper-layer flexible interconnection site selection and capacity optimization model are:

[0032] (1) Equality and inequality constraints of conventional power systems;

[0033]

[0034] Where: P g is the node power vector; P l is the node load vector; B is the line susceptance matrix; θ is the node phase angle vector; is the planned power generation power of the conventional unit at node m at time t, the load forecast power, the node branch inflow power, and the node branch outflow power; L α-mn is the load rate of line mn; α is the line load rate constraint parameter, α∈[0,1]; P gm-min ,P gm-max The upper and lower limits of the output of conventional units at node m; is the load shedding vector of the node after N-1 failure; is the node load shedding upper limit vector;

[0035] (2) Investment cost constraints;

[0036]

[0037] Where: The maximum investment cost of the line within the planning period;

[0038] (3) Tie line power constraints;

[0039] P Nmin ≤P uv ≤P Nmax

[0040] Where: u∈I, v∈J are the interconnection nodes at the sending and receiving ends of the flexible interconnection line, and I, J are the busbar node sets of the sending and receiving ends of the power grid.

[0041] The objective function of the new energy consumption assessment model at the lower level is:

[0042]

[0043] Where: W receipt is the revenue from new energy consumption; ε is the average electricity price of the power grid at the sending end; T i The maximum annual power utilization hours of the bus node; are the predicted values ​​of wind power and photovoltaic power generation at the bus node respectively; C is the wind and photovoltaic abandonment segment penalty factor; P Gm , P Ln is the actual power of wind power, photovoltaic power, generator and load, ΔP W The amount of wind and solar power abandoned.

[0044] The constraints of the lower-level new energy consumption assessment model are:

[0045] (1) New energy output constraints are:

[0046]

[0047] Where: is the actual active power of the interconnected line planned at time t;

[0048] (2) The wind and solar power abandonment rate constraints of the sending-end power grid are:

[0049]

[0050] (3) The receiving power grid’s power receiving capacity is constrained as follows:

[0051]

[0052] Where: is the net load power of node j at time t; R gj ,Ugj They are respectively the power increase and decrease limits of the conventional units at node j in the receiving power grid.

[0053] Based on BPA and MATLAB platform, an improved multi-objective particle swarm algorithm is used to bring the planning scheme set into the two-level programming model for solution.

[0054] An electronic device includes a memory, a processor and a computer program, wherein the computer program is stored in the memory and is configured to be executed by the processor to implement the above-mentioned regional power grid flexible interconnection planning method that takes into account the global new energy absorption capacity and investment returns.

[0055] A computer-readable storage medium having a computer program stored therein, which, when executed, controls a device where the computer-readable storage medium is located to execute the above-mentioned method for planning flexible interconnection of regional power grids that takes into account both the global absorption capacity of new energy and investment returns.

[0056] The beneficial effects of the present invention are:

[0057] (1) The present invention takes into account the global absorption capacity of new energy and investment returns, and provides a method for planning flexible interconnection of regional power grids. Compared with the long-distance 500kV DC interconnection of regional power grids, the 220kV medium voltage flexible interconnection channel proposed in the present invention can achieve direct source-load matching between new energy and load electricity consumption, effectively avoid the transmission of electric energy at a higher or lower voltage, and alleviate the problem of congestion in the main grid transmission flow.

[0058] (2) The planning model of the present invention is solved based on the joint calculation method of BPA and MATLAB, which can save the work of manually converting BPA power grid data and can greatly improve the efficiency of MATLAB calling the multi-objective particle swarm algorithm to solve the power grid planning optimization problem.

[0059] (3) Compared with the traditional flexible interconnection planning method, the planning method proposed in this invention is based on graph theory and complex network theory, and defines the node topological connectivity, neighbor node center support and node anti-fragility index for identifying key interconnection nodes. The flexible interconnection device site selection and capacity planning method considering the power system topology and power flow factors can screen out the sending and receiving end interconnection nodes with strong busbar collection capacity and transformer carrying capacity, solve the problem of limited new energy transmission due to the tight capacity of internal transmission and transformation equipment and line grid constraints, alleviate the power supply pressure in overloaded areas, and improve the connection capacity of interconnection lines in sub-area power grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 The schematic diagram of the power grid structure in the studied area;

[0061] Figure 2A flowchart of flexible interconnection planning of regional power grids that takes into account the global absorption capacity of new energy and investment returns of the present invention;

[0062] Figure 3 A flow chart for model solution based on the joint calculation method of BPA and MATLAB;

[0063] Figure 4 Graph for solving the planning model based on the improved multi-objective particle swarm algorithm. DETAILED DESCRIPTION

[0064] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] Embodiment 1

[0066] In this embodiment, the flexible interconnection planning method of regional power grids taking into account the global absorption capacity of new energy and investment returns adopts a regional power grid with a main grid of 220kV, such as Figure 1 As shown; the method comprises the following steps, Figure 2 As shown:

[0067] S1. According to the power load of the sending and receiving power grids and the interconnection requirements, the location set of the interconnection lines to be planned is initially screened out; and the installed capacity range of the flexible interconnection device is determined according to the power supply capacity of the sending power grid and the power demand of the receiving power grid; combined with the location set and capacity range of the interconnection lines to be planned, a location-capacity set of interconnection lines is constructed, that is, a set of planning schemes including location and capacity.

[0068] Select regional power grids with typical power supply and reception characteristics as interconnection zones, such as those with limited power flow in regional power grid interconnection sections, power surplus or power shortage when new energy is generated, and relatively low difficulty in project implementation. Preliminary screening of the location set of interconnection lines to be planned is conducted based on transformer overload and line over-limit conditions.

[0069] Based on the obtained interconnection device location set, in this example, the installed capacity range of the flexible interconnection device is determined according to the power supply capacity of the sending-end power grid and the power demand of the receiving-end power grid, and the capacity is divided to construct the interconnection line location-capacity set.

[0070] The installed capacity range of the flexible interconnection device is determined by combining the power supply capacity of the sending-end power grid and the power demand of the receiving-end power grid;

[0071] Simulate the N-1 fault of the receiving grid and calculate the maximum power demand as the lower limit P of the installed capacity of the flexible interconnection device Nmin :

[0072]

[0073] Where: N imp is the set of receiving nodes, P I-c ,P I-cLj is the power demand of the receiving grid and bus j when N-1 faults occur in component c, and there are C1 components in total; P Nmin is the maximum power demand when the receiving grid fails N-1; P Ga is the power transmitted from the 500 kV tie line from the partition Ia to the receiving grid; the set of adjacent partitions of the receiving grid is N I-adj ; are the rated installed capacities of wind power and photovoltaic power near bus node j respectively.

[0074] When simulating the amount of new energy access to key nodes of the sending-end power grid, the maximum power supply capacity is calculated as the upper limit of the installed capacity of the flexible interconnection device P Nmax :

[0075]

[0076] Where: N tra is the set of sending nodes, P Nmax P is the maximum power supply capacity of the sending-end power grid; T-cGi Add new energy to the key node c and the power supply capacity of bus i; P La is the power transmitted from the sending-end grid to the partition Ta by the 500 kV tie line; the set of adjacent partitions of the sending-end grid is N T-adj .

[0077] According to the power supply and receiving demand of the power grid at the sending and receiving ends, the installed capacity of the flexible interconnection device P uv satisfy:

[0078] P Nmin ≤P uv ≤P Nmax (4)

[0079] Where: uv is the flexible interconnection line, u∈N tra ,v∈N imp .

[0080] S2. Considering the economic efficiency and the new energy absorption capacity of the regional power grid, an indicator evaluation system for the siting and sizing of flexible interconnection devices in the regional power grid and the absorption of new energy is established, namely a two-layer planning model. The upper-layer flexible interconnection siting and sizing planning model considers the two levels of capacity optimization and site construction, takes the rated capacity, location and type of the flexible interconnection device as the optimization variables, and constructs a flexible interconnection siting and sizing optimization model with the optimal investment cost and interconnection node criticality as the objective function, and proposes the optimal power grid topology and connection form corresponding to the new energy absorption demand; the lower-layer new energy absorption evaluation model takes the new energy access amount as the optimization variable and the optimal new energy absorption benefit as the objective function, and analyzes the upper-layer flexible interconnection parameters and the new energy absorption demand under the constraints of new energy output.

[0081] Specifically: Considering the economic efficiency and the linkage and absorption capacity of the regional power grid, an index evaluation system for the site selection and capacity determination of the flexible interconnected devices in the regional power grid and the absorption capacity of new energy is established to evaluate the location-capacity element of each interconnected line; among them, the evaluation system for the site selection and capacity determination of the flexible interconnected devices considers two levels: capacity optimization and site selection and construction. The former evaluates the investment cost, including the construction cost and the annual operation cost of the unit, and decides the rated capacity of the interconnected device; the latter evaluates the weighted sum of the node topological connection degree, the central support of the neighboring node, and the anti-fragility of the node. Based on graph theory and complex network theory, it can identify key nodes with strong power flow transmission capabilities, many adjacent branch flows, and strong support for the vulnerable links of the system, select nodes with strong busbar collection capabilities and strong transformer carrying capacity, and decide the site selection of the interconnected device; the new energy absorption evaluation index is the new energy absorption income considering the cost of wind and solar abandonment, and decides the amount of new energy access under various flexible parameters.

[0082] In this embodiment, the objective function F1 of the upper-layer flexible interconnection site selection and capacity planning model is determined by the following formula:

[0083] F1=ω1f1 * +ω2f2 * (5)

[0084] Where: f1 * ,f2 * It is the normalization function of investment cost and the normalization function of interconnection node criticality.

[0085] The specific expressions of each objective function component of the upper-level planning model are as follows:

[0086]

[0087] Where: W profit (Y) is the investment cost; W operate is the annual operating cost of the unit; W build is the construction cost; G is the key interconnection node evaluation function, ω1, ω2 are the corresponding weight coefficients; GV ,G β ,G K is the topological connection degree of the node, the central support of the neighboring node, and the anti-fragility; λ1, λ2, λ3 are the weights of each node indicator.

[0088] The objective function of the lower-level new energy consumption assessment model in this embodiment is:

[0089] The output of renewable energy units is described by a set of time series probability scenarios S to retain the time series correlation characteristics of renewable energy output. The scenarios reflect the typical daily operation mode and occurrence probability of renewable energy units within the planning period. The probability of scenario s occurring is expressed as σ s Indicated. Then the wind turbine and photovoltaic output power at the sending and receiving ends meet:

[0090]

[0091] Where: is the output power of wind turbines and photovoltaics near node i during period t; The predicted output power of wind turbines and photovoltaics near node i in period t under scenario s.

[0092] Considering the uncertainty of renewable energy output and the characteristics of real-time power balance of nodes, the abandoned power of renewable energy, that is, the renewable energy consumption demand under given flexible interconnection planning parameters, is It can be expressed as:

[0093]

[0094] Considering the benefits of new energy consumption and the penalty costs of wind and solar power abandonment, taking the benefits of new energy consumption as the optimization goal, W rec The expression is as follows:

[0095]

[0096] Where C is a piecewise function:

[0097]

[0098] Where: ε is the average electricity price of the sending power grid; T i is the maximum annual power utilization hours of bus node i, C is the wind and solar power abandonment segment penalty factor.

[0099] Normalizing the new energy consumption benefits into the objective function F2 is:

[0100]

[0101] Where: W recmax ,W recminIt is the maximum and minimum value of the new energy consumption income.

[0102] The constraints of the two-level planning model for flexible interconnection of power grids in the above regions are as follows:

[0103] The constraints of the upper-layer flexible interconnection site selection and capacity planning model include:

[0104] Conventional Power System Equality and Inequality Constraints

[0105]

[0106] Where: P g is the node power vector; P l is the node load vector; B is the line susceptance matrix; θ is the node phase angle vector; is the planned power generation of the conventional unit at node m at time t, the load forecast power, the node branch inflow power, and the node branch outflow power; L α-mn is the load rate of line mn; α is the line load rate constraint parameter, α∈[0,1]; P gm-min ,P gm-max The upper and lower limits of the output of conventional units at node m; is the load shedding vector of the node after N-1 failure; is the node load shedding upper limit vector.

[0107] Investment cost constraints

[0108]

[0109] Where: It is the maximum investment cost of the line during the planning period.

[0110] Tie line power constraint

[0111] P Nmin ≤P uv ≤P Nmax (15)

[0112] The constraints of the lower-level new energy consumption assessment model include:

[0113] New energy output constraints

[0114]

[0115] Where: is the actual active power of the interconnected lines planned at time t.

[0116] Constraints on wind and solar power abandonment rates in the power grid at the sending end

[0117]

[0118] The receiving power grid's power receiving capacity is constrained

[0119]

[0120] Where: is the net load power of node j at time t; R gj ,U gj They are respectively the power increase and decrease limits of the conventional units at node j in the receiving power grid.

[0121] S3. Construct a two-level planning model for flexible interconnection of regional power grids based on the joint calculation method of BPA and MATLAB. Based on the proposed evaluation indicators, the upper level calculates the construction cost, annual operation cost of the unit, node topological connectivity, central support capacity of neighboring nodes and node anti-fragility of the regional power grid under each planned interconnection line, and the lower level calculates the benefits of new energy consumption.

[0122] Specifically: Figure 3 As shown in the figure, based on the established evaluation system for the site selection and sizing of flexible interconnected devices, BPA and MATLAB are used to jointly calculate the site selection and sizing adaptability of the regional power grid under each planned interconnected line and the adaptability of new energy consumption; the upper-level flexible interconnected device site selection and sizing planning model uses the type, rated capacity and location of the flexible interconnected device as optimization variables, and determines the location and capacity of the flexible interconnected device according to economic constraints, power system grid topology and flow factors; the optimization variable of the lower-level planning model is the amount of new energy access, and the amount of new energy access is determined according to the upper-level flexible interconnection parameters and new energy output constraints; the power grid data of BPA is converted into data suitable for MATLAB, and the steps are as follows: 1) Establish a corresponding relationship between BPA data and MATLAB data; 2) Conversion of node matrix; 3) Conversion of branch matrix; 4) Conversion of generator matrix; BPA is responsible for flow calculation, MATLAB reads the calculation results of BPA, and calls the improved multi-objective particle swarm algorithm to calculate various indicators.

[0123] The various evaluation indicators of the regional power grid flexible interconnection planning model are calculated as follows:

[0124] (1) Calculate the construction cost determined by rated capacity

[0125] Including the construction costs of flexible interconnection lines, sending and receiving end converter stations and cross-river towers.

[0126] W build =2P uv c station +c line l uv +c tower (19)

[0127] Where: l uv is the length of the interconnection line; cstation represents the unit investment cost of the converter station; c line represents the unit investment cost of DC transmission line; c tower Investment in cross-river towers. 200kV converter station, line, and transmission tower investment checklist.

[0128] (2) Calculate the annual operating cost of the unit determined by the rated capacity

[0129] It mainly includes the power loss cost of the DC interconnection line and the cost of unit operation and maintenance.

[0130] W operate =P loss T loss C price +u f W build (20)

[0131] Where: u f is the operation and maintenance cost ratio coefficient, which can be 1.8%; T loss is the equivalent hours of the annual maximum network loss, which is 5000h in the present invention; C price is the electricity production cost, RMB / MWh; P loss is the maximum grid loss power, MW.

[0132] (3) Calculate the node topological connectivity determined by the location of the flexible interconnection device

[0133] Abstract the interconnected system as a graph G P =(V P ,E P ), V P Represents the node abstracted from the busbar and substation in the partition, E P Represents the edge abstracted from the regional power grid transmission line. The relationship between lines is represented by the adjacency matrix H0, and the edge weight can be calculated from the line power flow S mn Decide.

[0134] In the power system, the more complex the bus connection relationship is, the more important the topological structure is in the system, and the stronger the bus connection ability is. K-m Describes the ability of the node to connect different grids. The larger the value, the more grid nodes and regions the node can connect to, the more important the topological structure is, and the higher the topological connection degree L with the lines connected to it. K-mn And load factor L α-mn related.

[0135] The topological connection of a line describes the ability of the line to connect power grids in different regions. The greater the topological connection, the stronger the ability of the line to carry power flow. When N-1 fails, the connection may be interrupted.K-mn The node degrees k at both ends of the line m , k n Sure:

[0136]

[0137] Where: h mn represents the mth row and nth column of the unit adjacency matrix H0; k m Represents the number of branches connected to node m; N mn is the set of lines connected to node m; is the average degree of all nodes in the power grid; N is the total number of nodes.

[0138] The topological connection degree G of the node K Calculated as follows:

[0139]

[0140] (4) Calculate the central support force of neighboring nodes determined by the location of the flexible interconnection device

[0141] The importance of a node depends largely on the amount of power injected or outflowed by its neighboring node branches. According to the topological structure of the power grid, the value and direction of the power flow, a weighted adjacency matrix H is constructed. 1 :

[0142]

[0143] Where: is the weight of the mth row and nth column of the adjacency matrix, that is, the power flow value S of line mn m→n .

[0144] Then the directed unit adjacency matrix And the out-degree K of the directed power network out and in-degree K in It can be expressed as:

[0145]

[0146] Where: Represents a directed unit adjacency matrix The value of the mth row and nth column; K out is the out-degree matrix of the node; is the out-degree value of node m; K in is the out-degree matrix of the node; is the in-degree value of node i.

[0147] Further calculate the neighbor node center support G β :

[0148] G'β =β*K out *H 1 *e T +(1-β)*H 1 *K in *e T (28)

[0149] Where: e = ones(N,1); G β Take G' β The first N of .

[0150] (5) Calculation of the anti-fragility of nodes determined by the location of the flexible interconnection device

[0151] When the active power increment of some lines in the zone approaches or exceeds the line capacity limit, the vulnerability of the line will increase significantly, affecting the consumption and transmission of new energy. Interconnected lines can absorb the power flow of the lines and relieve the load pressure of overloaded lines. Line anti-fragility Δe uv The power flow transfer effect of the interconnection line uv on the line γ is described as:

[0152]

[0153] Where: ΔP uv-γ is the active power transfer of transmission line γ caused by the change of interconnection line uv; dN It is the power operating limit of heavy-load lines.

[0154] Where ΔP ij-γ It can be calculated by the following formula:

[0155]

[0156] Where: P γ is the active power of the heavy-load line γ during normal operation; P uv-γ It is the active power of heavy-load line γ after the interconnection line uv is built. ΔP uv -γ≤ε(ε can be 0.5%P dN ) indicates that the addition of the interconnection line uv does not effectively increase the active power of the interconnection line. At this time, it is considered that the interconnection line cannot transfer the power flow pressure of line γ.

[0157] Node anti-fragility is a derivative indicator of line anti-fragility. It uses the support strength of interconnected lines to the adjacent heavy-load lines of the connection node to comprehensively reflect the anti-fragility of the node. That is, the power flow correlation characteristics of the line are used to quantify the support strength of nodes u and v to the fragile links. The calculation formula is as follows:

[0158]

[0159] Where: N γA collection of heavy-load lines.

[0160] S4. The improved multi-objective particle swarm algorithm is used as the optimization framework to bring the planning scheme set into the two-level programming model for solution, and the comprehensive ideal sorting method is used to screen the optimal solution of the particle decision Pareto solution set to obtain the final decision plan.

[0161] like Figure 4 As shown, the planning algorithm steps are as follows:

[0162] ① Read grid and unit data from BPA; initialize particle site selection nodes, interconnection line rated capacity and new energy access volume;

[0163] ② Calculate the particle objective function, including the weighted sum of the site selection and capacity determination indicators and the new energy benefits;

[0164] The non-inferior solutions are stored in an external archive set to determine the historical optimal and global optimal solutions of each particle;

[0165] ③ Taking into account the optimization constraints, calculate the construction cost, annual operation cost of the unit, node topological connectivity, neighbor node center support, node anti-fragility index, iterate, and weightedly calculate the upper objective function;

[0166] ④ Based on the flexible interconnection configuration position and capacity of the upper layer, the lower layer calculates the corresponding new energy consumption demand and the corresponding lower layer objective function;

[0167] ⑤ Store the non-inferior solutions into the external archive set, update the external archive set according to the dominance relationship, and generate the optimal Pareto solution set, including the historical optimal and the global optimal;

[0168] ⑥Adaptively adjust the inertia factor and learning factor, update the position and velocity of the upper and lower particles, and return to ③ until the maximum number of iterations is reached;

[0169] ⑦ The optimal location, capacity and new energy revenue of the flexible interconnection device are determined from the Pareto solution generated in the last iteration using the comprehensive ideal ranking method based on multiple attribute decision making (TOPSIS), that is, the final grid planning scheme;

[0170] ⑧Finally, the actual application effect of the planning scheme is verified by indicators such as new energy consumption and investment economics.

[0171] The improved multi-objective particle swarm algorithm solution model proposed in this embodiment solves the problem that the classical particle swarm algorithm is prone to fall into local optimality. It adopts a comprehensive ideal sorting method to screen particles, controls the solution set scale and particle iteration direction based on the Pareto solution set update control strategy, introduces an adaptive inertia weight, and improves the optimization result.

[0172] Embodiment 2

[0173] The electronic device of this embodiment includes a memory, a processor and a computer program. The computer program is stored in the memory and is configured to be executed by the processor to implement the method for flexible interconnection planning of regional power grids that takes into account the global new energy absorption capacity and investment returns as described in Example 1.

[0174] Embodiment 3

[0175] The above-mentioned computer program is stored in a computer-readable storage medium. When the computer program is running, it controls the device where the computer-readable storage medium is located to execute the regional power grid flexible interconnection planning method that takes into account the global new energy absorption capacity and investment returns as described in Example 1.

[0176] Application Examples

[0177] This example uses the planning method of the present invention to plan the parameters of the flexible interconnection device of a certain regional power grid. The regional power grid uses the 92-node data of a certain regional power grid in East China in 2025. The installed capacity of wind power and photovoltaic power will exceed 90 million kilowatts, and the demand for wind power and photovoltaic power transmission sections will reach 14.26 million kilowatts, which has exceeded the limit. The planning method includes:

[0178] 1) Analyze the interconnection demand of the existing power grid, set the PZ card output coefficient, and analyze the line and transformer load of the power grid in area A and area B with typical power supply and receiving characteristics as shown in Table 1. The sending-end system interconnection node set considers A12, A16, and A27, and the receiving-end interconnection node set considers B12, B32, and B4. When A27 is used as the sending-end system interconnection node, the transmission capacity of the interconnection line is very large, and the current overload after element N-1 is more serious. Therefore, the line candidate set only considers six site selections {A12-B4, A12-B12, A12-B32, A16-B4, A16-B12, A16-B32}. According to the configuration principle proposed in Example 2, a large number of wind power and photovoltaic power at the sending end and the power load at the receiving end are directly connected to the 220kV and below power grids. This project considers direct access to the 220kV power grid. Taking into account the project positioning, land occupation and investment requirements of the project implementation, the conventional DC LCC is considered at this stage, and the parameter settings are shown in Table 2.

[0179] Table 1

[0180]

[0181] Table 2

[0182]

[0183]

[0184] 2) The parameter settings are the same as those in Example 3, the unit electricity production cost is 9000 yuan / MWh, the maintenance cost ratio coefficient is 0.018, the annual maximum network loss equivalent hours of the converter station is 5000h, the unit investment cost of the DC transmission line is about 2.7 million yuan / (km·circuit), the DC converter station cost is about 86,900 yuan / MW, the planned operating period Y=15 years, the average electricity price at the sending end is 4000 yuan / MWh, and the wind and solar abandonment loss is 6500 yuan / (MW·h). MATLAB 2019b and BPA jointly calculate, based on the improved multi-objective particle swarm algorithm to solve the evaluation indicators of the power grid planning model, the calculation method is the same as that of Example 4, and the results are shown in Table 3.

[0185] Table 3

[0186]

[0187] 3) The flexible interconnection site selection, capacity determination and new energy consumption objective function values ​​of the six alternative schemes are shown in Table 4. The installation location and device capacity of the flexible interconnection device of schemes A12-B4 and A16-B4 are more appropriate. After the flexible interconnection device is connected to these nodes, the economy of the power grid is better, and the busbar and transformer there can support the transmission or access of the flexible interconnection power. However, due to the low capacity of scheme A16-B4 to absorb new energy, it cannot well meet the demand for the external transmission of incremental new energy in the central region of northern Jiangsu. Therefore, A12 and B4 are the sending and receiving end positions of the flexible interconnection device. Conventional LCC DC technology is used to build one sending and receiving end converter station each. The capacity of the flexible interconnection device is configured to be 1172≈1200MW, the DC line is 111 kilometers, and the total investment is about 3 billion yuan. At this time, the power supply capacity of the sending and receiving end sub-grid can be improved, and the ability of the power grid to absorb new energy can be improved while ensuring the economy, safety and stability of the power grid.

[0188] Table 4

[0189]

[0190]

[0191] 4) Evaluate the flexible interconnection planning system solution according to the verification index of Example 5, and calculate the power flow and short circuit of the regional power grid after the sending and receiving ends are connected to the power grid. It is found that the grid adaptability of the 220kV power grid in area A and area B is good under the summer peak wind and solar power generation / no generation, winter valley wind and solar power generation / no generation, etc., and the short circuit of various modes does not exceed the limit; when the wind and solar power generation is large in the summer peak mode, the power flow of the sending and receiving ends meets the requirements; when the wind and solar power generation is small in the summer peak mode, the power of the interconnection line is limited by the power supply capacity of the sending end partition, and it is recommended that the sending end converter station avoid full extraction, and the maximum power extraction is about 800~900MW.

[0192] The technical solutions of the present invention are not limited to the above-mentioned embodiments, and any technical solutions obtained by equivalent replacement methods fall within the scope of protection required by the present invention.

Claims

1. A method for planning flexible interconnection of regional power grids that takes into account the global absorption capacity of new energy and investment returns, wherein the regional power grid is a regional power grid with a 220kV voltage level line as the backbone grid, characterized in that: The steps include: According to the power load of the transmitting and receiving power grids and the interconnection requirements, the location set of the interconnection lines to be planned is initially screened; and Determine the installed capacity range of the flexible interconnection device according to the power supply capacity of the sending-end power grid and the power demand of the receiving-end power grid; construct a planning scheme set of the interconnection line including the location and capacity in combination with the location set and capacity range of the interconnection line to be planned; A two-layer planning model for regional power grid flexible interconnection is established, in which the upper layer is a flexible interconnection site selection and capacity optimization model built with the optimal investment cost and interconnection node criticality as the objective function, and the lower layer is a new energy consumption evaluation model built with the optimal new energy consumption benefit as the objective function; The improved multi-objective particle swarm algorithm is used to bring the planning scheme sets into the two-level programming model for solution to obtain the target planning scheme.

2. The method for planning flexible interconnection of regional power grids taking into account the global absorption capacity of new energy and investment returns according to claim 1 is characterized in that: The maximum power demand of the receiving grid is taken as the lower limit of the installed capacity of the flexible interconnection device P Nmin : Where: P' R-c , P' R-cLj is the power demand of the receiving grid and bus j when N-1 faults occur in component c, and there are C1 components in total; P Nmin is the maximum power demand when the receiving grid N-1 fails; P Gm is the power transmitted from the 500 kV tie line from partition m to the receiving grid; the set of adjacent partitions of the receiving grid is M, m∈M; are the predicted values ​​of wind power and photovoltaic power generation near bus node j respectively.

3. The method for planning flexible interconnection of regional power grids taking into account the global absorption capacity of new energy and investment returns according to claim 2 is characterized in that: The maximum power supply capacity of the sending-end power grid is taken as the upper limit of the installed capacity of the flexible interconnection device P. Nmax : Where: P Nmax is the maximum power supply capacity of the sending-end power grid; P' S-cGi Add new energy to the key node c and the power supply capacity of bus i; P Ln P Ln is the power transmitted from the sending-end grid to the partition n by the 500 kV interconnection line; the set of adjacent partitions of the sending-end grid is N, n∈N.

4. The method for planning flexible interconnection of regional power grids taking into account the global absorption capacity of new energy and investment returns according to claim 1 is characterized in that: The investment cost includes the construction cost and the annual operating cost of the unit; the construction cost includes the construction cost of the flexible interconnection line, the sending and receiving end converter stations and the cross-river tower; the annual operating cost of the unit includes the power loss cost of the DC interconnection line and the cost of unit operation and maintenance.

5. The method for planning flexible interconnection of regional power grids taking into account the global absorption capacity of new energy and investment returns according to claim 4 is characterized in that: The criticality of interconnected nodes includes node topological connectivity, neighbor node central support, and node anti-fragility; The node topological connection degree is: Where: h ij represents the i-th row and j-th column of the unit adjacency matrix H0 in the power network; is the average degree of all nodes in the power grid; N is the total number of power grid nodes, and L is the total number of transmission lines; The neighbor node center support force is: G' β =β*K out *H0*e T +(1−β)*H0*K in *is T Where: Weighted adjacency matrix The power flow value of a line is the weight of the adjacency matrix of the line; the out-degree matrix K of the node out =diag(k out ), The node in-degree matrix K in =diag(k in ), e=ones(N,1),G β Take G' β The first N of ; The node anti-fragility is: Where: G V is the node antifragility, ΔP uv-γ is the active power transfer of transmission line γ caused by the change of interconnection line uv; dN is the power operating limit of the heavy-load line; P γ is the active power of the heavy-load line γ during normal operation; P uv-γ is the active power of the heavy-load line γ after the interconnection line uv is built; ΔP uv-γ ≤ε(ε can be 0.5%P dN ) indicates that the addition of the interconnection line uv does not effectively increase the active power of the interconnection line. At this time, it is considered that the interconnection line cannot transfer the power flow pressure of line γ.

6. The method for planning flexible interconnection of regional power grids taking into account the global absorption capacity of new energy and investment returns according to claim 5 is characterized in that: The objective function of the upper-level flexible interconnection site selection and capacity optimization model is: F s =ω1f1 * +ω2f2 * Where: f1 * ,f2 * are the normalization functions of investment cost and interconnection node criticality; ω1,ω 2 is the corresponding weight coefficient; W profit (Y) is the investment cost; W operate is the annual operating cost of the unit; W build is the construction cost; G is the criticality of the interconnection node; G V , G β , G K is the topological connection degree of the node, the central support of the neighboring node, and the anti-fragility; λ1, λ2, λ3 are the weights of each node indicator; The constraints of the upper-layer flexible interconnection site selection and capacity optimization model are: (1) Equality and inequality constraints of conventional power systems; Where: P g is the node power vector; P l is the node load vector; B is the line susceptance matrix; θ is the node phase angle vector; is the planned power generation of the conventional unit at node m at time t, the load forecast power, the node branch inflow power, and the node branch outflow power; L α-mn is the load rate of line mn; α is the line load rate constraint parameter, α∈[0,1]; P gm-min ,P gm-max The upper and lower limits of the output of conventional units at node m; is the load shedding vector of the node after N-1 failure; is the node load shedding upper limit vector; (2) Investment cost constraints; Where: The maximum investment cost of the line within the planning period; (3) Tie line power constraints; P Nmin ≤P uv ≤P Nmax Where: u∈I, v∈J are the interconnection nodes at the sending and receiving ends of the flexible interconnection line, and I, J are the busbar node sets of the sending and receiving ends of the power grid.

7. The method for planning flexible interconnection of regional power grids taking into account the global absorption capacity of new energy and investment returns according to claim 6 is characterized by: The objective function of the new energy consumption assessment model at the lower level is: Where: W receipt is the revenue from new energy consumption; ε is the average electricity price of the power grid at the sending end; T i The maximum annual power utilization hours of the bus node; are the predicted values ​​of wind power and photovoltaic power generation at the bus node respectively; C is the wind and photovoltaic abandonment segment penalty factor; P Gm , P Ln is the actual power of wind power, photovoltaic power, generator and load, ΔP W The amount of wind and solar power abandoned; The constraints of the lower-level new energy consumption assessment model are: (1) New energy output constraints are: Where: is the actual active power of the interconnected line planned at time t; (2) The wind and solar power abandonment rate constraints of the sending-end power grid are: (3) The receiving power grid’s power receiving capacity is constrained as follows: Where: is the net load power of node j at time t; R gj ,U gj They are respectively the power increase and decrease limits of the conventional units at node j in the receiving power grid.

8. The method for planning flexible interconnection of regional power grids taking into account the global absorption capacity of new energy and investment returns according to claim 1 is characterized in that: Based on BPA and MATLAB platform, an improved multi-objective particle swarm algorithm is used to bring the planning scheme set into the two-level programming model for solution.

9. An electronic device, characterized in that: It includes a memory, a processor and a computer program, wherein the computer program is stored in the memory and is configured to be executed by the processor to implement a regional power grid flexible interconnection planning method that takes into account the global new energy absorption capacity and investment returns as described in any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, which, when running, controls the device where the computer-readable storage medium is located to execute the method for planning flexible interconnection of regional power grids that takes into account the global absorption capacity of new energy and investment returns as described in any one of claims 1 to 8.

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