New energy openable capacity evaluation method, system and device considering short-circuit ratio constraint and medium

Abstract

The invention discloses a new energy openable capacity evaluation method, system, equipment and medium considering short-circuit ratio constraint, and belongs to the technical field of new energy openable capacity evaluation, and the method comprises the steps: calculating a new energy multi-station short-circuit ratio based on a ratio of an AC system equivalent short-circuit capacity to a new energy equivalent grid-connected capacity; calculating a new energy multi-station short-circuit ratio after the new station is accessed by considering the influence of adding the new energy station, and constructing a short-circuit ratio constraint by considering a critical short-circuit ratio limit value; considering constraint conditions, constructing a new energy openable capacity evaluation objective function, and forming an openable capacity evaluation model; and constructing a planning problem in combination with the constraint condition and the target function, and performing iterative solution on the planning problem based on a Benders decomposition algorithm to obtain a new energy openable capacity value under the corresponding condition. According to the method, starting from the influence of the access of the new energy station on the short-circuit ratio, the evaluation result of the new energy openable capacity of the power grid can be optimized, and an effective reference is provided for evaluation of the new energy openable capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy openable capacity evaluation, and particularly relates to a new energy openable capacity evaluation method, system, device and medium considering short-circuit ratio constraints. BACKGROUND

[0002] Under the double carbon target, new energy power generation is widely concerned due to its low carbon characteristics. Various new energy power generation forms are connected to the power grid, and the proportion of traditional power sources is gradually reduced, which leads to a sharp decline in the voltage support capacity and regulation capacity of the system. If a large amount of new energy is blindly connected without reasonable evaluation of the new energy openable capacity, it will bring serious challenges to the safe and stable operation of the power grid.

[0003] The short-circuit ratio index is usually used to represent the voltage support strength of the power grid. At present, the evaluation of the new energy openable capacity is mainly based on the guidelines to consider the safety constraints of the power grid, and the influence of the newly added new energy station on the short-circuit ratio of the system is not comprehensively considered. Therefore, it is necessary to consider the short-circuit ratio constraints in the calculation process of the new energy openable capacity to evaluate the new energy openable capacity under more comprehensive safety constraints and make the evaluation results more reasonable.

[0004] To solve the above problems, the short-circuit ratio constraints proposed in the present application can consider the influence of the newly added new energy station on the short-circuit ratio of other stations, and optimize the effect of new energy openable capacity evaluation. SUMMARY

[0005] In view of the above problems, the present application is proposed.

[0006] Therefore, the technical problem solved by the present application is how to solve the problem that the evaluation of the new energy openable capacity is mainly based on the guidelines to consider the safety constraints of the power grid, and the influence of the newly added new energy station on the short-circuit ratio of the system is not comprehensively considered.

[0007] To solve the above technical problems, the present application provides the following technical scheme: a new energy openable capacity evaluation method considering short-circuit ratio constraints, which comprises the following steps: calculating the short-circuit ratio of multiple new energy stations based on the ratio of the equivalent short-circuit capacity of the alternating current system to the equivalent grid-connected capacity of the new energy; calculating the short-circuit ratio of multiple new energy stations after connecting the new station considering the influence of the newly added new energy station; constructing a short-circuit ratio constraint considering the critical short-circuit ratio limit; constructing a new energy openable capacity evaluation objective function considering the constraint conditions of the short-circuit ratio constraint, the network power flow constraint, the line power flow constraint, the node voltage constraint, the substation output constraint and the substation capacity constraint, and forming an openable capacity evaluation model; constructing a planning problem combining the constraint conditions and the objective function; iteratively solving the planning problem based on the Benders decomposition algorithm to obtain the new energy openable capacity value under the corresponding conditions.

[0008] As a preferred scheme of the new energy openable capacity evaluation method considering short-circuit ratio constraints, the short-circuit ratio of the new energy multi-station is calculated based on the ratio of the equivalent short-circuit capacity of the alternating current system to the equivalent grid-connected capacity of the new energy, which comprises obtaining the grid-connected bus voltage of the new energy station based on the Thevenin equivalent impedance; calculating the short-circuit capacity of the grid-connected bus according to the grid-connected bus voltage of the new energy station and the equivalent impedance of the alternating current grid at the grid-connected bus; and calculating the short-circuit ratio of the new energy multi-station.

[0009] As a preferred scheme of the new energy openable capacity evaluation method considering short-circuit ratio constraints, the short-circuit ratio of the new energy multi-station is calculated based on the ratio of the equivalent short-circuit capacity of the alternating current system to the equivalent grid-connected capacity of the new energy, which comprises obtaining the grid-connected bus voltage of the new energy station based on the Thevenin equivalent impedance; calculating the short-circuit capacity of the grid-connected bus according to the grid-connected bus voltage of the new energy station and the equivalent impedance of the alternating current grid at the grid-connected bus; and calculating the short-circuit ratio of the new energy multi-station.

[0010] The preferred scheme can significantly improve the accuracy of new energy station planning and ensure that the system safety margin is not broken by clearly distinguishing the short-circuit ratio calculation methods of existing stations and new stations and establishing a critical short-circuit ratio limit constraint.

[0011] As a preferred scheme of the new energy openable capacity evaluation method considering short-circuit ratio constraints, the short-circuit ratio of the new energy multi-station is calculated based on the ratio of the equivalent short-circuit capacity of the alternating current system to the equivalent grid-connected capacity of the new energy, which comprises obtaining the grid-connected bus voltage of the new energy station based on the Thevenin equivalent impedance; calculating the short-circuit capacity of the grid-connected bus according to the grid-connected bus voltage of the new energy station and the equivalent impedance of the alternating current grid at the grid-connected bus; and calculating the short-circuit ratio of the new energy multi-station.

[0012] As a preferred scheme of the new energy openable capacity evaluation method considering short-circuit ratio constraints, the short-circuit ratio of the new energy multi-station is calculated based on the ratio of the equivalent short-circuit capacity of the alternating current system to the equivalent grid-connected capacity of the new energy, which comprises obtaining the grid-connected bus voltage of the new energy station based on the Thevenin equivalent impedance; calculating the short-circuit capacity of the grid-connected bus according to the grid-connected bus voltage of the new energy station and the equivalent impedance of the alternating current grid at the grid-connected bus; and calculating the short-circuit ratio of the new energy multi-station.

[0013] The preferred scheme can make the new energy openable capacity evaluation model fully consider system operation conditions by explicitly setting new energy short-circuit ratio, network power flow, line power flow, node voltage, substation output and capacity constraints, avoid the new energy planning result from deviating from the actual operation condition due to single or partial constraints, and effectively improve the accuracy and reliability of the evaluation result.

[0014] As a preferred scheme of the new energy openable capacity evaluation method considering short-circuit ratio constraints, the Benders decomposition algorithm is used to iteratively solve the planning problem, which includes decomposing the planning problem into a 0-1 integer linear programming main problem containing discrete variables and a second-order cone programming sub-problem containing continuous variables; the main problem is used to calculate the newly added new energy station access node and corresponding access capacity; the sub-problem is used to check the feasibility of the results obtained by the main problem according to the power flow calculation; through the iterative solution of the main problem and the sub-problem, the new energy openable capacity value satisfying the constraint condition is finally determined.

[0015] The preferred scheme uses the Benders decomposition algorithm to decompose the planning problem into a main problem and a sub-problem which are easy to solve, fully utilizes the advantages of the main problem in solving discrete variables and the sub-problem in verifying the feasibility of continuous variables, effectively reduces the calculation complexity, and significantly improves the solution efficiency and convergence speed of the planning problem.

[0016] As a preferred scheme of the new energy openable capacity evaluation method considering short-circuit ratio constraints, the critical short-circuit ratio limit value includes solving the minimum reactive power and corresponding point of common coupling voltage value of each node after the newly added new energy station access according to the new energy grid-connected system operation equation; adjusting the converter reactive power to zero based on the unit power factor control strategy to determine the maximum transmission power of the converter and the maximum active power of the transmission line; determining the reactive power compensation device value range based on the condition of maximizing the point of common coupling voltage amplitude, thereby obtaining the node critical short-circuit ratio limit value.

[0017] The preferred scheme accurately calculates the minimum reactive power and corresponding voltage level after the newly added station access, explicitly determines the maximum transmission power of the converter and the maximum power transmission capacity of the transmission line, reasonably determines the value range of the reactive power compensation device, thereby accurately defining the critical short-circuit ratio limit value, ensuring that the redundant space for safe operation of the system after the new energy station access is sufficient, and avoiding the operation risk caused by insufficient short-circuit capacity.

[0018] The application provides a new energy openable capacity evaluation system considering short-circuit ratio constraints.

[0019] To solve the above technical problems, the application provides the following technical scheme: a new energy openable capacity evaluation system considering short-circuit ratio constraints, comprising a short-circuit ratio calculation module, a constraint construction module, an evaluation modeling module and a capacity solving module; the short-circuit ratio calculation module is used to calculate the short-circuit ratios of multiple new energy stations based on the ratio of the equivalent short-circuit capacity of an alternating current system to the equivalent grid-connected capacity of new energy; the constraint construction module is used to calculate the short-circuit ratios of multiple new energy stations after a new station is connected, and to construct short-circuit ratio constraints by considering the critical short-circuit ratio limit; the evaluation modeling module is used to construct a new energy openable capacity evaluation objective function by considering constraint conditions of short-circuit ratio constraints, network power flow constraints, line power flow constraints, node voltage constraints, substation output constraints and substation capacity constraints, and to form an openable capacity evaluation model; and the capacity solving module is used to construct a planning problem by combining the constraint conditions and the objective function, to iteratively solve the planning problem based on a Benders decomposition algorithm, and to obtain the new energy openable capacity value under corresponding conditions.

[0020] The application provides a computer device, comprising a memory and a processor, and the memory stores a computer program, characterized in that the processor implements the steps of the new energy openable capacity evaluation method considering short-circuit ratio constraints when executing the computer program.

[0021] The application provides a computer readable storage medium, which stores a computer program, characterized in that the computer program is executed by a processor to implement the steps of the new energy openable capacity evaluation method considering short-circuit ratio constraints.

[0022] The application has the following beneficial effects: the application firstly introduces the constraint of considering the short-circuit ratios of multiple new energy stations into the new energy openable capacity evaluation model based on the influence of the short-circuit ratio index; secondly, the new energy openable capacity objective function is constructed; then, the short-circuit ratio constraints of multiple new energy stations are combined with the power grid safety constraints to establish the openable capacity evaluation model; finally, the Benders decomposition algorithm is used to iteratively solve the model. The application starts from the influence of connecting new energy stations on the short-circuit ratio, can optimize the new energy openable capacity evaluation result of the power grid, and provides an effective reference for the new energy openable capacity evaluation. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0024] Figure 1A flow chart of a new energy openable capacity evaluation method considering short-circuit ratio constraints is provided for an embodiment of the present application.

[0025] Figure 2 A partial area of a new energy openable capacity evaluation method considering short-circuit ratio constraints is provided for an embodiment of the present application.

[0026] Figure 3 A new energy multi-station grid-connected system schematic diagram of a new energy openable capacity evaluation method considering short-circuit ratio constraints is provided for an embodiment of the present application.

[0027] Figure 4 A scheme module diagram of a new energy openable capacity evaluation system considering short-circuit ratio constraints is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the above objectives, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0029] Embodiment 1, refer to Figure 1 For an embodiment of the present application, the embodiment provides a new energy openable capacity evaluation method considering short-circuit ratio constraints, comprising:

[0030] S1, calculating the short-circuit ratio of the new energy multi-station based on the ratio of the equivalent short-circuit capacity of the alternating current system to the equivalent grid-connected capacity of the new energy.

[0031] S2, calculating the short-circuit ratio of the new energy multi-station after connecting the new station, considering the influence of adding the new energy station, and constructing the short-circuit ratio constraint considering the critical short-circuit ratio limit value.

[0032] S3, considering the constraint conditions of the short-circuit ratio constraint, the network power flow constraint, the line power flow constraint, the node voltage constraint, the substation output constraint and the substation capacity constraint, constructing the new energy openable capacity evaluation objective function, and forming the openable capacity evaluation model.

[0033] S4, combining the constraint conditions and the objective function to construct the planning problem, and iteratively solving the planning problem based on the Benders decomposition algorithm to obtain the new energy openable capacity value under the corresponding conditions.

[0034] The application realizes joint evaluation of short-circuit ratio of new energy multi-station and openable capacity by S1 to S4 steps on the basis of fully considering multiple constraint conditions, and provides theoretical support and engineering guidance basis for system operation safety evaluation and new energy planning.

[0035] The application can dynamically evaluate the influence of newly added station access on the existing system short-circuit ratio on the basis of considering the matching relationship between the equivalent short-circuit capacity of the alternating current system and the new energy grid-connected capacity, construct safety constraints in combination with the critical short-circuit ratio limit, and establish a capacity evaluation model in combination with multiple operation conditions such as network flow, node voltage and substation capacity; the model is efficiently solved by Benders decomposition algorithm, the maximum openable access capacity of each node is accurately calculated under the premise of guaranteeing safe and stable operation of the power grid, and quantitative basis and optimization support are provided for new energy planning and dispatching.

[0036] Embodiment 2, refer to Figure 2 and Figure 3 , for an embodiment of the application, based on the previous embodiment, a new energy openable capacity evaluation method considering short-circuit ratio constraints is provided, comprising:

[0037] In the embodiment of the application, the short-circuit ratio of new energy multi-station is calculated based on the ratio of the equivalent short-circuit capacity of the alternating current system to the equivalent grid-connected capacity of the new energy in step S1.

[0038] The grid-connected bus voltage of the new energy station is obtained based on the Thevenin equivalent impedance; the short-circuit capacity of the grid-connected bus of the new energy station is calculated according to the grid-connected bus voltage of the new energy station and the equivalent impedance of the alternating current grid at the grid-connected bus; and the short-circuit ratio of the new energy multi-station is calculated.

[0039] Specifically, step S1 comprises:

[0040] S11, the mutual influence between the new energy multi-station and the system station cannot be ignored, and the voltage of each node of the system is described based on the Thevenin equivalent impedance:

[0041]

[0042] Among them, is the grid-connected bus voltage of the new energy station i; Z ij is the i-th row and j-th column element of the alternating current grid equivalent impedance matrix at the grid-connected bus of the new energy, j∈Ω i ; Z ii is the self-impedance of the grid-connected bus of the new energy station i; is the current injected into the alternating current system by the new energy station i.

[0043] S12, the bus short-circuit capacity of the grid-connected point of the new energy station is:

[0044]

[0045] wherein, * represents a conjugate operation; is the rated voltage of the new energy station i grid-connected bus; is the short-circuit current at the new energy station i grid-connected bus; is the new energy station i grid-connected bus voltage; Z ii is the self-impedance of the new energy station i grid-connected bus.

[0046] S13, the new energy multi-station short-circuit ratio of the new energy station i grid-connected point is:

[0047]

[0048] wherein, S ac,i is the short-circuit capacity of the new energy station grid-connected bus; S R,j is the actual apparent power injected by the jth new energy grid-connected bus node; epsilon ij = Z ij U * i / Z ii U * j is the complex power conversion factor between the new energy grid-connected bus i and j.

[0049] In an optional embodiment, the calculation of the new energy multi-station short-circuit ratio can also include, for the case that multiple new energy stations are connected to the same power grid area, first, using Thevenin theorem to equivalent the power grid at the grid-connected point, obtaining the AC system equivalent short-circuit capacity of each new energy station grid-connected bus, and simultaneously calculating the equivalent grid-connected capacity according to the real-time power generation capacity of each station grid-connected point, and then calculating the short-circuit ratio of each grid-connected point according to the ratio formula. This method is suitable for regional power grid short-circuit capacity evaluation of medium-sized new energy station concentrated access.

[0050] In another optional embodiment, the calculation of the new energy multi-station short-circuit ratio can also include, for the case that there is strong coupling or mutual impedance between new energy stations that cannot be ignored, by establishing the mutual impedance matrix between the buses of each station, and considering the phase difference and power coupling factor of the injected power, the equivalent short-circuit capacity calculation result is dynamically corrected, so as to more accurately evaluate the effective short-circuit ratio under the actual electrical distance. This method is suitable for regions with dense access of new energy stations and complex power grid structure, and improves the accuracy of short-circuit ratio calculation.

[0051] The present application can more comprehensively reflect the system access capacity boundary, avoid the distortion of access evaluation caused by the virtual high short-circuit ratio, and improve the safety and prediction ability of system operation.

[0052] In the embodiments of the present application, the new energy multi-station short-circuit ratio after the new station is connected is calculated in step S2, considering the influence of the newly added new energy station. The short-circuit ratio constraint is constructed considering the critical short-circuit ratio limit. The schematic diagram of adding a new energy station in part of the region is shown in Figure 2 The schematic diagram of the new energy multi-station grid-connected system is shown in Figure 3 .

[0053] The short-circuit ratio constraint is constructed considering the critical short-circuit ratio limit, including: for the existing new energy station node, the new energy multi-station short-circuit ratio calculation expression considering the mutual influence of the existing stations is established; for the newly added new energy station node, the new energy multi-station short-circuit ratio calculation expression considering the influence of the newly added station on the existing stations is established; the critical short-circuit ratio limit is obtained according to the operation equation of the new energy grid-connected system, and the short-circuit ratio constraint condition is constructed.

[0054] The critical short-circuit ratio limit includes: the minimum reactive power and the corresponding point of common coupling voltage value of each node after the newly added new energy station is connected are solved according to the operation equation of the new energy grid-connected system; the maximum transmission power of the converter and the maximum active power of the transmission line are determined based on the unit power factor control strategy to adjust the reactive power of the converter to zero; the value range of the reactive power compensation device is determined based on the condition of maximizing the amplitude of the point of common coupling voltage, so as to obtain the critical short-circuit ratio limit of the node.

[0055] Specifically, step S2 includes:

[0056] S21, for the existing new energy station connected to node r, the node set where the existing new energy station is located is Ω r , the new energy multi-station short-circuit ratio of node r can be expressed as:

[0057]

[0058] Wherein, obviously Ω r is a subset of Ω i , is the rated voltage of the new energy station r grid-connected bus, is the new energy station r grid-connected bus voltage, S R,j is the actual apparent power injected by the jth new energy grid-connected bus node in the existing new energy station, Z rj is the equivalent mutual impedance of the new energy station r and the new energy station j grid-connected bus.

[0059] S22, assuming that the newly added new energy station is connected at node m and the node set of the new energy station to be selected is Ω m , the new energy multi-station short-circuit ratio of node r under the influence of the newly added station is:

[0060]

[0061] wherein, obviously Ω m is a subset of Ω i , S R,m is the actual apparent power of the new energy station set at the node m, Z rm is the equivalent mutual impedance of the node r and the node m, ξ m is in the range of 0 and 1, ξ m =1 indicates that the new new energy station is confirmed to be added at the node m, otherwise the new energy station is not added.

[0062] S23, according to the new energy grid-connected system, the simultaneous transmission of active power and reactive power expression, the system grid-connected operation equation step is:

[0063]

[0064]

[0065]

[0066] wherein, P e , Q e is the active power and reactive power transmitted to the system through the collection station, X r and X1 are the reactance values of the collection station and the transmission line respectively, U s , U q and U e are the voltages at the AC main system, the point of common coupling and the machine end outlet respectively, θ e , θ q are the phase angles at the machine end outlet and the point of common coupling respectively, β=1-X l B, B is the reactive compensation of the centralized control station.

[0067] S24, based on the new energy grid-connected system operation equation, the active power and reactive power transmitted to the system through the collection station can be rewritten as:

[0068]

[0069] Under the premise of constant AC system voltage and transmitted active power, to minimize the reactive power flowing through the collection station, the partial derivative of the transmitted reactive power to the voltage at the point of common coupling is equal to zero, and the minimum reactive power transmitted through the collection station and the corresponding effective value of the voltage at the point of common coupling under this condition can be solved:

[0070]

[0071] S25, when the grid-connected converter adopts the unit power factor control strategy, the reactive power flowing through the grid-connected converter can be adjusted to zero. The maximum transmission power of the converter, the simplified expression of the common connection point voltage and the maximum active power that can be transmitted by the transmission line are:

[0072]

[0073] S26, in order to fully utilize the power transmission capacity of the transmission line and improve the common connection point voltage level, the standard of the reactive power compensation device is that when the reactive power exchange power meets zero and the amplitude of the alternating current system voltage reaches the maximum value, the amplitude of the common connection point voltage does not exceed the maximum value, the inequality relationship is obtained and the value range of the reactive power compensation device is obtained:

[0074]

[0075]

[0076] Where, U smax is the maximum value of the amplitude of the alternating current system voltage; U qmax is the maximum value of the amplitude of the common connection point voltage.

[0077] S27, the reactive power compensation device is selected as the upper limit, and the common connection point voltage does not exceed the maximum value U qmax that the point can tolerate, then the equivalent compensation coefficient α, the common connection point voltage U q and the maximum transmission power P emax of the grid-connected station considering the limit value of the common connection point voltage can be obtained:

[0078]

[0079]

[0080]

[0081] S28, the grid stability limit takes the maximum transmission power of the new energy grid-connected system in actual operation, then the critical short-circuit ratio CSCR r of the new energy station connected to node r is:

[0082]

[0083] Where, S ac,r is the short-circuit capacity of the grid-connected bus of the new energy station located at node r, Q r is the reactive power of the new energy grid-connected node r.

[0084] S29, after adding a new energy station, the short-circuit ratio requirement of the new energy multi-station of the node r should not be lower than the critical short-circuit ratio value, and an inequality is listed, and the short-circuit ratio constraint can be obtained by arranging, and the inequality and the short-circuit ratio constraint are as follows:

[0085]

[0086]

[0087] In an optional embodiment, the short-circuit ratio constraint can also be calculated by introducing 0-1 state variables to identify whether a new energy station node is added, based on the known equivalent impedance matrix and mutual impedance parameters in the network, and the influence of the addition of the new station on the short-circuit ratio of the target node is recalculated. Combined with the superposition relationship of the short-circuit capacity of the original node and the apparent power of all access nodes, a modified multi-station short-circuit ratio calculation expression is established, and the lower limit of the critical short-circuit ratio is set as a constraint condition according to the design specification of the planned power grid, and a node set that meets the access condition is selected.

[0088] In another optional embodiment, the short-circuit ratio constraint can also further consider the operating characteristics of the collection station, derive the maximum active power transmission capability of the converter under the unit power factor control strategy, and calculate the minimum reactive power and maximum voltage level that the system can withstand after the addition of the new station based on the analytical relationship between the point of common coupling voltage and the transmission power, thereby backstepping the critical short-circuit ratio threshold, and constructing an inequality form with the short-circuit ratio not lower than the threshold as a constraint, to guarantee the voltage stability margin of the system under disturbance conditions.

[0089] The application dynamically updates the short-circuit ratio limit interval under the access condition of the added new energy station, effectively avoids the problem of insufficient local short-circuit capacity of the system caused by the addition of the station, and enhances the adaptability and engineering applicability of the grid-connected evaluation model.

[0090] In the embodiment of the application, the constraint conditions of considering the short-circuit ratio constraint, network power flow constraint, line power flow constraint, node voltage constraint, substation output constraint and substation capacity constraint in step S3 are considered, and a new energy openable capacity evaluation objective function is constructed to form an openable capacity evaluation model.

[0091] Based on the short-circuit ratio constraint, network power flow constraint, line power flow constraint, node voltage constraint, substation output constraint and substation capacity constraint, an objective function of the openable capacity of the new energy is established; and based on the objective function, a new energy openable capacity evaluation model is formed.

[0092] The short-circuit ratio constraint is used to limit the short-circuit ratio of the new energy field station to be not lower than a critical short-circuit ratio limit value; the network power flow constraint includes active and reactive power output constraints of a substation node, active and reactive power demand constraints of a load node, active and reactive power flow constraints between nodes, node voltage amplitude and phase angle constraints, and branch switch state constraints; the line power flow constraint is used to limit the actual apparent power of a branch to be not more than a maximum limit value allowed by the branch; the node voltage constraint is used to limit the node voltage amplitude to be between a preset minimum value and a maximum value; the substation output constraint is used to limit the actual output active power and reactive power of the substation to be between a preset minimum value and a maximum value; and the substation capacity constraint is used to limit the actual current passing through the transformer to be not more than an allowed maximum current.

[0093] Specifically, the step S3 includes:

[0094] S31, the new energy multi-field station short-circuit ratio constraint is:

[0095]

[0096] S32, the network power flow constraint is:

[0097]

[0098]

[0099] P ij =-U i U j (g ij cosθ ij +b ij sinθ ij )+U i 2 (g si +g ij )

[0100] Q ij =-U i U j (g ij sinθ ij +b ij cosθ ij )+U i 2 (b si +b ij )

[0101] wherein, P g , Q g are active and reactive power outputs of a substation, P d , Q d are active and reactive power demands of a load; P ij , Qij Active and reactive power flow of branch ij connecting node i and node j; g ij , b ij Conductance and susceptance of branch ij; g si , b si Ground conductance and susceptance of branch ij; U i , θ i Voltage amplitude and phase angle of node i, θ ij = θ i - θ j ; x ij Branch switch state variable, 0 means open, 1 means closed.

[0102] S33, line flow constraint is:

[0103] 0 ≤ x ij S ij ≤ S ij,max

[0104] Where, S ij is the apparent power of branch ij, S ij,max is its maximum limit.

[0105] S34, node voltage constraint is:

[0106] U i,min ≤ U i ≤ U i,max , i ∈ Ω i

[0107] Where, U i,min , U i,max are the minimum and maximum values of the node voltage amplitude respectively.

[0108] S35, substation output constraint is:

[0109] P g,min ≤ P g ≤ P g,max

[0110] Q g,min ≤ Q g ≤ Q g,max

[0111] Where, P g,min , P g,max are the minimum and maximum values of the substation output active power respectively; Q g,min , Q g,max are the minimum and maximum values of the substation output reactive power respectively.

[0112] S36, substation capacity constraint is:

[0113] 0 ≤ Ig,k ≤I g,max

[0114] wherein, I g,max is the maximum allowable current of the transformer.

[0115] S37, a target function is constructed with the maximum openable capacity of new energy as the target, and the expression is:

[0116]

[0117] wherein, A is the target function, Ω dg is the set of new energy access nodes; is the openable capacity of the new energy of node i.

[0118] In the embodiments of the present application, the planning problem is constructed in step S4 by combining the constraint condition and the target function, and the planning problem is iteratively solved based on the Benders decomposition algorithm to obtain the openable capacity value of the new energy under the corresponding condition.

[0119] The planning problem is decomposed into a 0-1 integer linear programming main problem containing discrete variables and a second-order cone programming sub-problem containing continuous variables; the main problem is used to calculate the newly added new energy field station access node and the corresponding access capacity; the sub-problem is used to check the feasibility of the results obtained by the main problem according to the power flow calculation; through the iterative solving of the main problem and the sub-problem, the openable capacity value of the new energy satisfying the constraint condition is finally determined.

[0120] Specifically, step S4 includes:

[0121] S41, a mixed integer nonlinear programming problem is obtained by arranging the target function and the constraint condition, which is expressed as:

[0122]

[0123] s.t.

[0124]

[0125]

[0126]

[0127] P ij =-U i U j (g ij cosθ ij +b ij sinθ ij )+U i 2 (g si +g ji)

[0128]

[0129] 0≤x ij S ij ≤S ij,max

[0130] U i,min ≤U i ≤U i,max

[0131] P g,min ≤P g ≤P g,max

[0132] Q g,min ≤Q g ≤Q g,max

[0133] 0≤I g,k ≤I g,max

[0134] S42. Based on the actual power grid operating parameters, set g in the planning problem. ij b ij g si b si S ij,max U i,min U i,max P g,min P g,max Q g,min Q g,max I g,max Actual parameters, etc.

[0135] S43. The Benders decomposition algorithm is used to decompose the model into a main problem of 0-1 integer linear programming with discrete variables and a subproblem of second-order cone programming with continuous variables. The main problem is used to calculate the access nodes of new energy power stations and the access capacity of new energy power stations. The subproblem verifies the feasibility of the results obtained from the main problem through power flow calculation. After iterative solution, the open capacity A of new energy corresponding to this problem can be obtained.

[0136] Example 3, referring to Figure 4 This is one embodiment of the present invention, which provides a new energy open capacity assessment system considering short-circuit ratio constraints, including a short-circuit ratio calculation module, a constraint construction module, an assessment modeling module, and a capacity solution module.

[0137] The short-circuit ratio calculation module is used to calculate the short-circuit ratio of multiple new energy power plants based on the ratio of the equivalent short-circuit capacity of the AC system to the equivalent grid-connected capacity of the new energy system.

[0138] The constraint construction module is used to calculate the new energy multi-station short-circuit ratio after the new station is accessed, and to construct the short-circuit ratio constraint by considering the critical short-circuit ratio limit value.

[0139] The evaluation modeling module is used to construct the new energy openable capacity evaluation objective function and form the openable capacity evaluation model by considering the constraint conditions of the short-circuit ratio constraint, the network power flow constraint, the line power flow constraint, the node voltage constraint, the substation output constraint and the substation capacity constraint.

[0140] The capacity solving module is used to construct the planning problem by combining the constraint conditions and the objective function, to obtain the new energy openable capacity value under the corresponding conditions by iteratively solving the planning problem based on the Benders decomposition algorithm.

[0141] The embodiment also provides an electronic device suitable for the case of the new energy openable capacity evaluation method considering the short-circuit ratio constraint, which comprises a memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions to realize the new energy openable capacity evaluation method considering the short-circuit ratio constraint as proposed in the above embodiment.

[0142] The embodiment also provides a storage medium having a computer program stored thereon, and the program is executed by a processor to realize the new energy openable capacity evaluation method considering the short-circuit ratio constraint as proposed in the above embodiment.

[0143] The storage medium proposed in the embodiment and the new energy openable capacity evaluation method considering the short-circuit ratio constraint proposed in the above embodiment belong to the same inventive concept, and the technical details not described in detail in the embodiment can be referred to the above embodiment, and the embodiment has the same beneficial effects as the above embodiment.

[0144] Through the above description of the embodiments, those skilled in the art can clearly understand that the present application can be realized by means of software and necessary general hardware, and of course can also be realized by hardware, but in many cases the former is a better embodiment. Based on such understanding, the technical solutions of the present application or the part that contributes to the prior art can be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as a floppy disk, a read-only memory (ROM), a random access memory (RAM), a FLASH, a hard disk or an optical disk, etc., including a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the method of each embodiment of the present application.

[0145] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the technical solutions of the present application, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A method for new energy openable capacity evaluation considering short circuit ratio constraint, characterized in that: The method comprises the steps of: calculating the short-circuit ratio of the multiple new energy stations based on the ratio of the equivalent short-circuit capacity of the alternating current system to the equivalent grid-connected capacity of the new energy; calculating the short-circuit ratio of the multiple new energy stations after the new station is connected, considering the influence of the new station, and constructing the short-circuit ratio constraint by considering the critical short-circuit ratio limit; constructing the new energy openable capacity evaluation objective function by considering the short-circuit ratio constraint, the network power flow constraint, the line power flow constraint, the node voltage constraint, the substation output constraint and the substation capacity constraint, and forming the openable capacity evaluation model; combining the constraint condition and the objective function to construct the planning problem, iteratively solving the planning problem based on the Benders decomposition algorithm, and obtaining the new energy openable capacity value under the corresponding condition. 2.The new energy openable capacity evaluation method considering short-circuit ratio constraint according to claim 1, wherein: The method comprises the steps of: obtaining the grid-connected bus voltage of the new energy station based on the Thevenin equivalent impedance; calculating the short-circuit capacity of the grid-connected bus according to the grid-connected bus voltage of the new energy station and the equivalent impedance of the alternating current grid at the grid-connected bus; calculating the short-circuit ratio of the multiple new energy stations. 3.The new energy openable capacity evaluation method considering short-circuit ratio constraint according to claim 2, wherein: The method comprises the steps of: establishing the short-circuit ratio calculation expression of the multiple new energy stations considering the mutual influence of the existing stations for the existing new energy station nodes; establishing the short-circuit ratio calculation expression of the multiple new energy stations considering the influence of the new station on the existing stations for the new new energy station nodes; obtaining the critical short-circuit ratio limit according to the operation equation of the new energy grid-connected system, and constructing the short-circuit ratio constraint condition.

4. The new energy openable capacity evaluation method considering short-circuit ratio constraint according to claim 3, characterized in that: The method comprises the steps of: establishing the objective function of the new energy openable capacity based on the short-circuit ratio constraint, the network power flow constraint, the line power flow constraint, the node voltage constraint, the substation output constraint and the substation capacity constraint; forming the new energy openable capacity evaluation model based on the objective function.

5. The new energy openable capacity evaluation method considering short-circuit ratio constraint according to claim 4, characterized in that: The short-circuit ratio constraint is used to limit the short-circuit ratio of the new energy station to be not lower than the critical short-circuit ratio limit; The network power flow constraint comprises the active and reactive output constraints of the substation node, the active and reactive demand constraints of the load node, the active and reactive power flow constraints between nodes, the node voltage amplitude and phase angle constraints, and the branch switch state constraints; The line power flow constraint is used to limit the actual apparent power of the branch to be not higher than the maximum limit value allowed by the branch; The node voltage constraint is used to limit the node voltage amplitude to be between the preset minimum value and maximum value; The substation output constraint is used to limit the actual output active power and reactive power of the substation to be between the preset minimum value and maximum value; The substation capacity constraint is used to limit the actual current passing through the transformer to be not higher than the allowed maximum current.

6. The new energy openable capacity evaluation method considering short-circuit ratio constraint according to claim 5, characterized in that: The method comprises the steps of: decomposing the planning problem into a 0-1 integer linear programming main problem containing discrete variables and a second-order cone programming sub-problem containing continuous variables; The main problem is used to calculate the connection node and the corresponding connection capacity of the new new energy station; The sub-problem is used to check the feasibility of the result obtained by the main problem according to the power flow calculation; Through the iterative solution of the main problem and the sub-problem, the new energy openable capacity value satisfying the constraint condition is finally determined.

7. The new energy openable capacity evaluation method considering short-circuit ratio constraint according to claim 6, characterized in that: The critical short-circuit ratio limit value comprises, According to the new energy grid-connected system operation equation, the minimum reactive power of each node and the corresponding point of common coupling voltage value after the new new energy field station is connected are solved; Based on the unit power factor control strategy, the reactive power of the converter is adjusted to zero, and the maximum transmission power of the converter and the maximum active power of the transmission line are determined; Based on the condition of maximizing the amplitude of the point of common coupling voltage, the value range of the reactive power compensation device is determined, and the node critical short-circuit ratio limit value is obtained.

8. A new energy openable capacity evaluation system considering short-circuit ratio constraints, applying a new energy openable capacity evaluation method considering short-circuit ratio constraints according to any one of claims 1-7, characterized in that, It comprises: A short-circuit ratio calculation module, a constraint construction module, an evaluation modeling module, and a capacity solving module; The short-circuit ratio calculation module is used to calculate the short-circuit ratio of the new energy multi-field station based on the ratio of the equivalent short-circuit capacity of the alternating current system to the equivalent grid-connected capacity of the new energy; The constraint construction module is used to calculate the short-circuit ratio of the new energy multi-field station after the new field station is connected, considering the influence of the added new energy field station, and to construct the short-circuit ratio constraint considering the critical short-circuit ratio limit value; The evaluation modeling module is used to construct the new energy openable capacity evaluation objective function considering the constraint conditions of the short-circuit ratio constraint, the network power flow constraint, the line power flow constraint, the node voltage constraint, the substation output constraint, and the substation capacity constraint, and to form the openable capacity evaluation model; The capacity solving module is used to construct a planning problem combined with the constraint conditions and the objective function, to solve the planning problem based on the Benders decomposition algorithm, and to obtain the openable capacity value of the new energy under the corresponding conditions. 9.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is configured to perform the method according to any one of claims 1-8 when the computer program is executed by the processor. The processor executes the computer program to realize the steps of the new energy openable capacity evaluation method considering the short-circuit ratio constraint in any one of claims 1 to 7.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the steps of the new energy openable capacity evaluation method considering the short-circuit ratio constraint in any one of claims 1 to 7.

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