Active power distribution network power supply capability evaluation method and evaluation system considering demand response and N-1 security constraint

Abstract

The invention relates to the field of active power distribution network planning, in particular to a power supply capability evaluation method and evaluation system for an active power distribution network considering demand response and N-1 security constraints. The method specifically comprises the following steps: obtaining an objective function of a power supply capability evaluation model of the active power distribution network; determining constraint conditions; eliminating invalid constraints; effective sampling points are obtained; and calculating a power supply capability index. In the power supply capability evaluation method and evaluation system of the active power distribution network considering the demand response and the N-1 security constraint, the N-1 security constraint and the reverse power flow security constraint accessed by a distributed power supply (DG) are considered at the same time, demand response resources are considered, and the power supply capability evaluation method and evaluation system of the active power distribution network considering the demand response and the N-1 security constraint have the advantages that the power supply capability evaluation method and evaluation system of the active power distribution network considering the demand response and the N-1 security constraint; according to the method, the complete power supply capacity range of the active power distribution network considering the demand response and the N-1 safety constraint at the same time can be accurately evaluated, the complete power supply capacity of the active power distribution network is visualized into a curve, the relation between the complete power supply capacity of the power distribution network and the total output of the DG is accurately reflected, and the complete power supply capacity is quantified into a specific interval value.

Description

Technical Field

[0001] The present invention relates to the field of active distribution network planning, and in particular to a power supply capacity evaluation method and an evaluation system for an active distribution network considering demand response and N-1 safety constraints. Background Art

[0002] Power supply capacity is a classic distribution network planning indicator. Accurately evaluating the power supply capacity of distribution networks is of great significance and value to their planning and construction. In the evaluation of the power supply capacity of distribution networks, most existing studies have calculated the maximum power supply capacity of distribution networks. The following documents record the technical solutions:

[0003] Reference 1: Peng Hanmei, Xiao Qianhao, Tan Mao, et al. Short-term maximum power supply capacity evaluation of low-voltage flexible interconnected distribution network based on time series convolutional neural network [J / OL]. China Southern Power Grid Technology, 1-11 [2024-11-15].

[0004] Reference 2: Maximum power supply capacity of distribution network considering flexible interconnection of low-voltage substations[J]. Automation of Electric Power Systems, 2023, 47(7): 84-93.

[0005] Reference 3: Research on evaluation of maximum power supply capacity of distribution network based on graph computing[J]. Power System Technology, 2022, 46(3): 1039-1049.

[0006] Reference 4: Evaluation of the maximum power supply capacity of distribution network considering feeder segmentation and wind and solar power output[J]. Acta Energiae Solaris Sinica, 2021, 42(4): 168-174.

[0007] However, the maximum power supply capacity can only be achieved when the distribution network reaches certain specific loads and distributed generation (DG) distribution. Therefore, the maximum power supply capacity cannot describe the complete power supply capacity of the distribution network under various loads and distributed generation distribution. In order to evaluate the complete power supply capacity of the distribution network, some technical solutions are also disclosed in the prior art, such as:

[0008] Document 5: Xiao Jun, ZhangMiaomiao, Bai Linquan, et al. Boundary supplycapability for distribution systems: concept, indices and calculation[J]. IETGeneration Transmission&Distribution, 2018, 12(2): 499-506.

[0009] Reference 6: Xiao Jun, Liang Ziyu, She Buxin. Mathematical model and formation mechanism of power supply capacity curve of distribution network[J]. Proceedings of the CSEE. 2021, 41(9): 3158-3172.

[0010] Literature 7: XiaoJun, Wangchuanqi, SheBuxin, et al. Total supply-accommodationcapability curve for distribution network concept and model [J]. International Journal of Electrical Power and Energy Systems, 2021, 133: 107279.

[0011] References 5-6 propose power supply capacity curves for traditional passive distribution networks that take into account N-1 safety constraints, but do not consider the important resource of distributed power sources. Therefore, they do not consider the reverse power flow safety constraints brought by the access of distributed power sources to the distribution network, nor do they consider the flexibility resource of demand response. Therefore, the technical solutions recorded in references 5-6 cannot calculate the complete power supply capacity of the active distribution network that simultaneously considers demand response and N-1 safety constraints.

[0012] Reference 7 proposes a power supply capacity curve of an active distribution network under normal operating constraints, but does not consider demand response or N-1 safety constraints. Therefore, the technical solution recorded in Reference 7 cannot calculate the complete power supply capacity of the active distribution network considering demand response and N-1 safety constraints.

[0013] In summary, for active distribution networks containing distributed generation, existing studies have not considered both the N-1 safety constraint and the reverse power flow safety constraint of distributed generation access, nor have they taken into account demand response resources. Therefore, existing studies cannot accurately evaluate the complete power supply capacity of active distribution networks that consider both demand response and N-1 safety constraints. On the other hand, the horizontal axis of the power supply capacity curve of existing studies has no actual physical meaning and cannot reflect the relationship between the complete power supply capacity and the total output of distributed generation. Summary of the invention

[0014] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art, to provide a method and system for evaluating the power supply capacity of an active distribution network that simultaneously considers N-1 safety constraints and reverse power flow safety constraints of DG access, and takes into account demand response resources, and can accurately evaluate the complete power supply capacity range of an active distribution network that simultaneously considers demand response and N-1 safety constraints, visualize the complete power supply capacity of the active distribution network as a curve, accurately reflect the relationship between the complete power supply capacity of the distribution network and the total output of DG, and quantify the complete power supply capacity into a specific interval value.

[0015] The technical solution adopted by the present invention to solve the technical problem is: the power supply capacity evaluation method considering demand response and N-1 safety constraint active distribution network is characterized by comprising the following steps:

[0016] For a given active distribution network, the objective function of the power supply capacity evaluation model of the active distribution network is obtained;

[0017] According to the objective function of the power supply capacity evaluation model of the active distribution network, the constraints of the power supply capacity evaluation model of the active distribution network are determined, and the constraints include: state space safety constraints, normal operation safety constraints, N-1 safety constraints considering demand response, and load growth criticality safety constraints;

[0018] Through the objective function of the power supply capacity evaluation model of the active distribution network, and various constraints: state space safety constraint, normal operation safety constraint, N-1 safety constraint considering demand response and load growth criticality safety constraint, the final power supply capacity evaluation model of the active distribution network is obtained by eliminating invalid constraints;

[0019] According to the sampling algorithm and the final power supply capacity evaluation model of the active distribution network, effective sampling points are obtained;

[0020] The complete power supply capacity of the active distribution network is visualized according to the effective sampling points, and the power supply capacity indicators are calculated.

[0021] Furthermore, when obtaining the objective function of the power supply capacity evaluation model of the given active distribution network, according to the grid structure and parameters of the given active distribution network, the sum of the loads of the working points is used as the ordinate, and the sum of the corresponding DG outputs is used as the abscissa. The sum of the loads is sorted from small to large, and the power supply capacity of the working points after sorting is used as the objective function to represent the complete power supply capacity of the active distribution network; the expression of the objective function of the power supply capacity evaluation model of the active distribution network is:

[0022]

[0023] Among them, P SC Represents the complete power supply capacity of the active distribution network; the jth working point Wj Power supply capability Γ(W L,j ) is the working point W j The sum of the loads is equal to the sum of the apparent powers of all load nodes. The jth working point W j The total output of DG Γ(W DG,j ) is the working point W j The sum of the DG outputs is equal to the sum of the apparent powers of all DG nodes. S L,k is the kth load node L k The apparent power of DG,l is the lth DG node DG l Apparent power; W L,j is the jth operating point W consisting of the apparent power of the load nodes j The load vector; W DG,j is the jth operating point W composed of the apparent power of the DG node j is the DG vector; n is the number of load nodes; m is the number of DG nodes.

[0024] Furthermore, when determining the state space security constraints in the constraints of the power supply capacity assessment model of the active distribution network: the apparent power of the load node and the apparent power of the DG node are kept within a certain safety range due to the constraints of the distribution transformer and the DG capacity. According to the constraints of the distribution transformer and the DG capacity, the constraints satisfied by the apparent power of the load node and the apparent power of the DG node are listed separately, which is the state space security constraint, and its expression is:

[0025]

[0026] Among them, W is the L and W DG The working point of the composition; W L is the load vector composed of the apparent power of the load nodes; W DG is the DG vector composed of the apparent power of the DG nodes; For S L,k The maximum apparent power of For S DG,l The maximum apparent power of the load nodes; L is the set consisting of all load nodes; G is the set consisting of all DG nodes.

[0027] Furthermore, when determining the normal operation safety constraint in the constraint conditions of the power supply capacity evaluation model of the active distribution network: the constraint that the net power absolute value of all lines and substation main transformers does not exceed the rated capacity of their components during normal operation of the active distribution network is the normal operation safety constraint, and its expression is:

[0028]

[0029] Among them, S B,i For line B i The net power of B,i For line B i The set of downstream nodes; k∈Π B,i is the load node L k On line B i Downstream of; l∈Π B,i DG node l On line B i Downstream; Downstream refers to the direction from the main transformer of the substation to the line terminal; c B,i For line B i The rated capacity of the line; B is the collection of all lines; S T,h Main transformer T h The net power of T,h Main transformer T h The set of downstream nodes; k∈Π T,h is the load node L k In the main transformer T h Downstream of; l∈Π T,h DG node l In the main transformer T h Downstream of T,h Main transformer T h The rated capacity of the substation; T is the set of main transformers of all substations.

[0030] Furthermore, when determining the constraints of the power supply capacity assessment model of the active distribution network, the N-1 safety constraint of the demand response is that after the N-1 accident occurs in the active distribution network, in order to ensure that the N-1 safety constraint is met, the active distribution network is allowed to participate in the demand response after N-1, actively reduce or interrupt a certain proportion of load, and perform network reconstruction to complete the load transfer. The rated capacity of all lines and substation main transformers after network reconstruction is not less than the absolute value of their net power. The expression is:

[0031]

[0032] Where X = {χ1,...,χ b ,...,χ y} is the set of N-1 unexpected events (fault set); y N-1 unexpected events (component y failure) occur to component y (line or substation main transformer); S B,i (y) is line B after N-1 unexpected events occur in component y i Net power; S T,h (y) is the main transformer T of the substation after N-1 unexpected events occurred in component y h The net power ofB,i (y) is line B after N-1 unexpected events occur in component y i The set of downstream nodes, Π T,h (y) is the main transformer T after N-1 accident occurs in component y h The set of downstream nodes; θ k is the kth load node L k The proportional coefficient (load reduction coefficient) of the load that is allowed to be reduced or interrupted reflects the effect of load participation in demand response.

[0033] Furthermore, when determining the constraints of the power supply capacity assessment model of the active distribution network, all load variables at the working point are subject to equality constraints. The equality constraint indicates that after the forward flow of the component reaches the upper capacity limit, no load can be increased. If there is a load increase, it will violate the equality constraint and cause the forward flow to exceed the limit. The criticality safety constraint of load growth is determined by X in the equality constraint. L,eq Without pure zero column guarantee, some inequalities in the state space security constraint, normal operation security constraint, and N-1 security constraint considering demand response are equalized, and the other inequalities remain unchanged. The load growth criticality security constraint including the forward power flow security constraint and the reverse power flow security constraint is obtained, and its expression is:

[0034]

[0035] Among them, Φ is all safety boundaries, and the safety boundary is the set of all working points that meet the load growth criticality safety constraints; η q is the qth safety boundary; X L,eq is the load factor matrix in the equality constraint, whose elements are 0 or 1 and are determined by the network structure of the active distribution network; X DG,eq is the DG coefficient matrix in the equality constraint, whose elements are 0 or 1 and are determined by the network structure of the active distribution network; c eq is the constant column vector in the equality constraint, whose elements are the rated capacity of the corresponding substation main transformer or line; X L,ieq is the load factor matrix in the inequality constraint; X DG,ieq is the DG coefficient matrix in the inequality constraint; c ieq is the constant column vector in the inequality constraints.

[0036] Furthermore, effective sampling points are obtained according to the sampling algorithm and the final power supply capacity evaluation model of the active distribution network. The specific steps are as follows:

[0037] Uniform sampling is performed in the state space of the load and DG with a step size of λ to obtain Y sampling points. The expression for calculating Y is:

[0038]

[0039] In the formula, For S L,k The maximum apparent power of For S DG,l The maximum apparent power of

[0040] Filter out effective sampling points that meet the final power supply capacity evaluation model of the active distribution network from the Y sampling points.

[0041] Furthermore, the complete power supply capacity of the active distribution network is visualized according to the effective sampling points, and the power supply capacity index is calculated. The specific steps are as follows:

[0042] Step S5-1, based on the obtained valid sampling points, calculate the sum of the loads of all valid sampling points Γ(W L,j ) and DG total output Γ(W DG,j ), and the power supply capacity of all effective sampling points Γ(W L,j ), the power supply capacity of all effective sampling points Γ(W L,j ) are sorted from small to large, and the total output of DG after sorting is Γ(W DG,j ) is the horizontal axis, and the power supply capacity of the effective sampling point is Γ(W L,j ) is the vertical coordinate, and the complete power supply capacity of the active distribution network is visualized as a curve, and the relationship between the complete power supply capacity of the active distribution network and the total output of DG is accurately inverted according to the curve;

[0043] Step S5-2: Based on the power supply capacity Γ(W of all effective sampling points L,j ), filter out the maximum value of the power supply capacity of the effective sampling point, and obtain the maximum power supply capacity (denoted as PSC max ) indicator; filter out the minimum value of the power supply capacity of the effective sampling point and obtain the minimum power supply capacity (denoted as PSC min ) indicator; calculate the average power supply capacity of all valid sampling points and obtain the average power supply capacity (denoted as ) indicator, and quantify the complete power supply capacity of the active distribution network into specific interval values ​​based on the power supply capacity indicator.

[0044] An evaluation system for implementing an electric capability evaluation method for an active distribution network considering demand response and N-1 safety constraints, characterized in that it includes:

[0045] An objective function generating module is used to obtain an objective function of a power supply capacity evaluation model of an active distribution network for a given active distribution network;

[0046] A constraint condition generating module, whose input end is connected to the output end of the objective function generating module, is used to determine the constraint condition of the power supply capacity evaluation model of the active distribution network according to the objective function of the power supply capacity evaluation model of the active distribution network;

[0047] A constraint condition elimination module, whose input end is connected to the output end of the constraint condition generation module, is used to eliminate invalid constraints and obtain a final power supply capacity evaluation model of the active distribution network;

[0048] A sampling point generation module, whose input end is connected to the output end of the constraint condition elimination module, is used to obtain effective sampling points of the final power supply capacity evaluation model of the active distribution network;

[0049] The power supply capacity calculation module has an input end connected to the output end of the sampling point generation module and is used to visualize the complete power supply capacity of the active distribution network according to the effective sampling points and calculate the power supply capacity index.

[0050] Furthermore, the constraint generation module includes:

[0051] The first constraint generating unit is used to generate state space safety constraints;

[0052] The second constraint generating unit is used to generate a normal operation safety constraint;

[0053] The third constraint generating unit is used to generate N-1 safety constraints considering demand response;

[0054] The fourth constraint generating unit: its input end is connected to the output ends of the first constraint generating unit, the second constraint generating unit and the third constraint generating unit, and is used to generate load growth criticality safety constraints.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] The technical solution of the present application takes into account both the N-1 safety constraint and the reverse power flow safety constraint of DG access, and takes into account the demand response resources. It can accurately evaluate the complete power supply capacity range of the active distribution network taking into account both the demand response and the N-1 safety constraint, visualize the complete power supply capacity of the active distribution network as a curve, accurately reflect the relationship between the complete power supply capacity of the distribution network and the total output of DG, and quantify the complete power supply capacity into a specific interval value.

[0057] In the technical solution of the present application, the total output of DG is used as the horizontal coordinate. Therefore, the power supply capacity evaluation model of the active distribution network has practical physical significance, and can accurately reflect the complete power supply capacity of the active distribution network under the total output of DG, thus overcoming the problem in the prior art that the relationship between the power supply capacity and the total output of DG cannot be reflected.

[0058] In the N-1 safety constraint considering demand response proposed in the technical solution of this application, the reverse power flow safety constraint and the forward power flow safety constraint of DG access are considered at the same time, and the load reduction coefficient in the N-1 safety constraint considering demand response indicates that a certain load ratio is allowed to be actively reduced or interrupted after considering the active distribution network N-1, which can reflect the effect of participating in demand response. This solves the problem that the N-1 safety constraint in the prior art does not consider the reverse power flow safety constraint of DG access, only considers the forward power flow safety constraint, and does not consider demand response.

[0059] In the load growth criticality safety constraint obtained by the technical solution of the present application, the load reduction coefficient indicates that a certain load proportion is allowed to be actively reduced or interrupted after considering the active distribution network N-1. Compared with the equality constraint proposed in the prior art, it can reflect the effect of participating in demand response. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 Flowchart of the power supply capability assessment method for active distribution networks considering demand response and N-1 security constraints.

[0061] Figure 2 A flowchart for listing the constraints of the power supply capability assessment model for active distribution networks.

[0062] Figure 3 This is a schematic diagram of an active distribution network example considering demand response;

[0063] Figure 4 Visualization of the complete power supply capacity of the active distribution network considering demand response and N-1 security constraints. DETAILED DESCRIPTION

[0064] Figures 1 to 4 The best embodiment of the present invention is shown below in conjunction with the attached Figures 1 to 4 The present invention is further described.

[0065] like Figure 1 As shown in FIG. 1 , a power supply capability evaluation method for an active distribution network considering demand response and N-1 security constraints (hereinafter referred to as the evaluation method) includes the following steps:

[0066] Step S1, for a given active distribution network, write the objective function of the power supply capacity evaluation model of the active distribution network;

[0067] According to the grid structure and parameters of the given active distribution network, the sum of the loads at the working point is taken as the ordinate, and the sum of the corresponding DG outputs (hereinafter referred to as the total DG output) is taken as the abscissa. The sum of the loads is sorted from small to large, and the power supply capacity of the working point after sorting is taken as the objective function to represent the complete power supply capacity of the active distribution network, as shown in the following formula:

[0068]

[0069] Among them, P SC Represents the complete power supply capacity of the active distribution network; the jth working point W j Power supply capability Γ(W L,j ) is the working point W j The sum of the loads is equal to the sum of the apparent powers of all load nodes. The jth working point W j The total output of DG Γ(W DG,j ) is the working point W j The sum of the DG outputs is equal to the sum of the apparent powers of all DG nodes. S L,k is the kth load node L k The apparent power of DG,l is the lth DG node DG l Apparent power; W L,j is the jth operating point W consisting of the apparent power of the load nodes j The load vector; W DG,j is the jth operating point W composed of the apparent power of the DG node j is the DG vector; n is the number of load nodes; m is the number of DG nodes.

[0070] In the power supply capacity evaluation model of the active distribution network shown above, the total output of DG Γ(W DG,j ) as the horizontal axis, so the power supply capacity evaluation model of the active distribution network has practical physical significance, and can accurately reflect the complete power supply capacity of the active distribution network under the total output of DG, overcoming the problem in the prior art that the relationship between the power supply capacity and the total output of DG cannot be reflected.

[0071] Step S2, listing the constraints of the power supply capacity evaluation model of the active distribution network;

[0072] Combination Figure 2 In this evaluation method, for the power supply capacity evaluation model of the active distribution network proposed in step S1, the following constraints are proposed: state space security constraints, normal operation security constraints, N-1 security constraints considering demand response, and load growth criticality security constraints. Specifically:

[0073] The specific state space safety constraints are:

[0074] The apparent power of the load node and the apparent power of the DG node are kept within a certain safety range due to the constraints of the distribution transformer and DG capacity. Therefore, the constraints satisfied by the apparent power of the load node and the apparent power of the DG node are listed separately according to the constraints of the distribution transformer and DG capacity, which are the state space safety constraints. The expression is:

[0075]

[0076] The bounded set of all operating points that satisfy the state space safety constraints is called the state space. L and W DG The working point of the composition; W L is the load vector composed of the apparent power of the load nodes; W DG is the DG vector composed of the apparent power of the DG nodes; For S L,k The maximum apparent power of For S DG,l The maximum apparent power of the load nodes; L is the set consisting of all load nodes; G is the set consisting of all DG nodes.

[0077] The column writes the normal operation safety constraints specifically as follows:

[0078] When the active distribution network is operating normally, the absolute value of the net power of all lines and substation main transformers does not exceed the rated capacity of their components. The expression is:

[0079]

[0080] The absolute value symbol in the normal operation safety constraint indicates that the forward power flow safety constraint and the reverse power flow safety constraint due to the access to DG are taken into account. B,i For line B i The net power of B,i For line B i The set of downstream nodes; k∈Π B,i is the load node L k On line B i Downstream of; l∈Π B,i DG node l On line B i Downstream; Downstream refers to the direction from the main transformer of the substation to the line terminal; c B,i For line B i The rated capacity of the line; B is the collection of all lines; S T,h Main transformer T h The net power of T,h Main transformer T h The set of downstream nodes; k∈Π T,h is the load node L k In the main transformer T h Downstream of; l∈Π T,h DG node l In the main transformer T h Downstream of T,h Main transformer T hThe rated capacity of the substation; T is the set of main transformers of all substations.

[0081] The N-1 safety constraints considering demand response are as follows:

[0082] After an N-1 accident occurs in the active distribution network, in order to ensure that the N-1 safety constraint is met, the active distribution network is allowed to participate in demand response after N-1, actively reduce or interrupt a certain proportion of load, and perform network reconstruction to complete load transfer. The rated capacity of all lines and substation main transformers after network reconstruction is not less than the absolute value of their net power. The expression is:

[0083]

[0084] Where X = {χ1,...,χ b ,...,χ y} is the set of N-1 unexpected events (fault set); y N-1 unexpected events (component y failure) occur to component y (line or substation main transformer); S B,i (y) is line B after N-1 unexpected events occur in component y i Net power; S T,h (y) is the main transformer T of the substation after N-1 unexpected events occurred in component y h The net power of B,i (y) is line B after N-1 unexpected events occur in component y i The set of downstream nodes, Π T,h (y) is the main transformer T after N-1 accident occurs in component y h The set of downstream nodes; θ k is the kth load node L k The proportional coefficient (load reduction coefficient) of the load that is allowed to be reduced or interrupted reflects the effect of load participation in demand response.

[0085] The N-1 security constraint considering demand response proposed in this evaluation method considers both the reverse power flow security constraint and the forward power flow security constraint of DG access, and the load reduction factor θ in the N-1 security constraint considering demand response k It means that after considering the active distribution network N-1, a certain proportion of load can be actively reduced or interrupted, which can reflect the effect of participating in demand response. It solves the problem that the N-1 safety constraints in the prior art do not consider the reverse flow safety constraints of DG access, only consider the forward flow safety constraints, and do not consider demand response.

[0086] The column write load growth criticality safety constraint is specifically:

[0087] All load variables at the operating point are subject to equality constraints. The equality constraint indicates that after the forward flow of the component reaches the upper capacity limit, no load can increase any further. If there is a load increase, it will violate the equality constraint and cause the forward flow to exceed the limit. The load growth criticality safety constraint is determined by the equation constraint X L,eq It does not contain pure zero column guarantee. By taking the above state space security constraints, normal operation security constraints, and some inequalities in the N-1 security constraints considering demand response as equal, and keeping the other inequalities unchanged, we can obtain the load growth criticality security constraints including the forward flow security constraints and the reverse flow security constraints, and its expression is:

[0088]

[0089] Among them, Φ is the total safety margin, which is the set of all operating points that meet the load growth criticality safety constraint; η q is the qth safety boundary; X L,eq is the load factor matrix in the equality constraint, whose elements are 0 or 1 and are determined by the network structure of the active distribution network; X DG,eq is the DG coefficient matrix in the equality constraint, whose elements are 0 or 1 and are determined by the network structure of the active distribution network; c eq is the constant column vector in the equality constraint, whose elements are the rated capacity of the corresponding substation main transformer or line; X L,ieq is the load factor matrix in the inequality constraint; X DG,ieq is the DG coefficient matrix in the inequality constraint; c ieq is the constant column vector in the inequality constraints.

[0090] The load growth criticality safety constraint obtained in this evaluation method is as follows: k It means that after considering the active distribution network N-1, it is allowed to actively reduce or interrupt a certain proportion of load. Compared with the equality constraints proposed in the prior art, it can reflect the effect of participating in demand response.

[0091] Step S3, eliminating invalid constraints to obtain a final power supply capacity assessment model;

[0092] The objective function of the power supply capacity evaluation model of the active distribution network obtained in step S1 and the constraints obtained in step S2: state space safety constraint, normal operation safety constraint, N-1 safety constraint considering demand response and load growth criticality safety constraint are combined to obtain the power supply capacity evaluation model of the active distribution network.

[0093] The obtained evaluation model may contain redundant invalid constraints. The final power supply capacity evaluation model is obtained by eliminating the invalid constraints. The method of eliminating the invalid constraints is implemented by using existing technology, such as the method recorded in the following literature: Paulraj S, Sumathi P. A comparative study of redundant constraints identification methods in linear programming problems [J]. Mathematical Problems in Engineering, 2010, 2010: 242-256.

[0094] Step S4, obtaining effective sampling points according to the sampling algorithm and the final power supply capacity evaluation model of the active distribution network;

[0095] The specific steps are:

[0096] Step S4-1, uniformly sample the state space of the load and DG with a step size of λ to obtain Y sampling points. The expression for calculating Y is:

[0097]

[0098] In the formula, For S L,k The maximum apparent power of For S DG,l The maximum apparent power of

[0099] Step S4-2, selecting effective sampling points that satisfy the final power supply capability evaluation model obtained in step S3 from the Y sampling points.

[0100] Step S5, visualizing the complete power supply capacity of the active distribution network according to the effective sampling points, and calculating the power supply capacity index;

[0101] The specific steps include:

[0102] Step S5-1, based on the effective sampling points obtained in step 4, calculate the sum of the loads of all effective sampling points Γ(W L,j ) and DG total output Γ(W DG,j ), and the power supply capacity of all effective sampling points Γ(W L,j ), the power supply capacity of all effective sampling points Γ(W L,j ) are sorted from small to large, and the total output of DG after sorting is Γ(W DG,j ) is the horizontal axis, and the power supply capacity of the effective sampling point is Γ(W L,j) is taken as the vertical axis, and the complete power supply capacity of the active distribution network is visualized as a curve. According to the curve, the relationship between the complete power supply capacity of the active distribution network and the total output of DG is accurately inverted.

[0103] Step S5-2: Based on the power supply capacity Γ(W of all effective sampling points L,j ), filter out the maximum value of the power supply capacity of the effective sampling point, and obtain the maximum power supply capacity (denoted as PSC max ) indicator; filter out the minimum value of the power supply capacity of the effective sampling point and obtain the minimum power supply capacity (denoted as PSC min ) indicator; calculate the average power supply capacity of all valid sampling points and obtain the average power supply capacity (denoted as ) indicator, and quantify the complete power supply capacity of the active distribution network into specific interval values ​​based on the power supply capacity indicator.

[0104] From the above, it can be seen that in this evaluation method, for any given active distribution network, the objective function of the power supply capacity evaluation model of the active distribution network is listed, and the state space safety constraints, normal operation safety constraints, N-1 safety constraints considering demand response and load growth criticality safety constraints are gradually listed. The invalid constraints are eliminated to obtain the final power supply capacity evaluation model. According to the sampling algorithm and the final power supply capacity evaluation model, the effective sampling points are obtained. According to the effective sampling points, the complete power supply capacity of the active distribution network is visualized as a curve. According to the curve, the relationship between the complete power supply capacity of the active distribution network and the total output of DG is accurately inverted, and the maximum power supply capacity index, the minimum power supply capacity index and the average power supply capacity index are calculated. According to the power supply capacity index, the complete power supply capacity of the active distribution network is quantified into a specific interval value.

[0105] The following is an example to further illustrate the above evaluation method:

[0106] In such Figure 3 The active distribution network example shown in the figure contains two 33 / 11kV substation main transformers (T1 and T2). The two substation main transformers and their lines are connected through a tie switch (Tie switch, T S ) The main transformer capacity of the substation is 6.0MVA, the line capacity is 4.0MVA, the capacity of the distribution transformer is 4.0MVA (i.e. the power range of a single load node is [0, 4.0]MVA), and the capacity of the DG is 2.0MVA (i.e. the power range of a single DG node is [-2.0, 0]MVA). Only load node L2 participates in demand response and the load reduction coefficient is θ2 = 0.1.

[0107] Combined with the above steps S1 to S5:

[0108] For a given Figure 3According to step S1, the objective function of the power supply capacity evaluation model of the active distribution network is obtained:

[0109]

[0110] For a given Figure 3 According to step S2, the following constraints of the power supply capacity evaluation model of the active distribution network are obtained:

[0111] (1) State space safety constraints:

[0112]

[0113] (2) List the normal operation safety constraints:

[0114]

[0115] (3) Considering the N-1 security constraint of demand response:

[0116]

[0117] (4) Load growth criticality safety constraints:

[0118]

[0119] According to step S3, the above objective function, state space safety constraint, normal operation safety constraint, N-1 safety constraint considering demand response and load growth criticality safety constraint are combined, and Figure 3 The active distribution network example shown in the figure removes invalid constraints and obtains Figure 3 The final power supply capability assessment model for the active distribution network example:

[0120]

[0121] Combined with step S4: uniform sampling is performed in the load state space ([0,4.0]MVA) and the DG state space ([-2.0,0]MVA) with a step size of λ = 0.1, and the obtained From the 30394161 sampling points obtained, 20173 valid sampling points that meet the above-obtained final power supply capacity evaluation model are screened out, and the results are shown in Table 1.

[0122] Table 1 Figure 3 Effective sampling points for active distribution network examples

[0123]

[0124] Combined with the above step S5, according to the valid sampling point data in Table 1, calculate the sum of the loads of all valid sampling points and DG total output The results are shown in the last two columns of Table 1. The power supply capacity Γ(W) of all effective sampling points is obtained. L,j ), the power supply capacity of all effective sampling points Val (W L,j ) are sorted from small to large, and the total output of DG after sorting is Γ(W DG,j ) is the horizontal axis, and the power supply capacity of the effective sampling point is Γ(W L,j ) is the vertical axis, and the complete power supply capacity of the active distribution network is visualized as a curve. The results are shown in Figure 4 shown.

[0125] According to the last column of Table 1, the effective sampling point power supply capability Γ(W L,j ), filter out the maximum and minimum power supply capacity of the effective sampling point, and obtain the maximum power supply capacity PSC max and minimum power supply capacity PSC min , calculate the power supply capacity Γ(W) of all effective sampling points in the last column of Table 1 L,j ) to obtain the average power supply capacity The power supply capacity index results are shown in Table 2.

[0126] Table 2 Figure 3 Power supply capability index of active distribution network example

[0127]

[0128] Depend on Figure 4 It can be seen that the complete power supply capacity range of the active distribution network example considering demand response and N-1 safety constraints is the curve, rather than a single maximum power supply capacity (8.4MVA). The range of the curve is [4.0,8.4]MVA, indicating that the Figure 3 The power supply capacity of the active distribution network under the total DG output range of [-4.0, 0.0] MVA is between [4.0, 8.4] MVA. Specifically, taking the last row of working point W in Table 1 as 20173 Taking the data as an example, when the total output of DG is -4.0MVA, the power supply capacity of the active distribution network that meets various safety constraints is 8.4MVA.

[0129] On the other hand, Table 2 also considers the demand response and N-1 security constraints based on the power supply capacity index. Figure 3 The complete power supply capacity of the active distribution network example is quantified into a specific interval value ([4.0,8.4]MVA), where the maximum power supply capacity is 8.4MVA, the minimum power supply capacity is 4.0MVA, and the average power supply capacity is 6.0MVA.

[0130] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A power supply capability evaluation method for active distribution networks considering demand response and N-1 security constraints, characterized by: The steps include: For a given active distribution network, the objective function of the power supply capacity evaluation model of the active distribution network is obtained; According to the objective function of the power supply capacity evaluation model of the active distribution network, the constraints of the power supply capacity evaluation model of the active distribution network are determined, and the constraints include: state space safety constraints, normal operation safety constraints, N-1 safety constraints considering demand response, and load growth criticality safety constraints; Through the objective function of the power supply capacity evaluation model of the active distribution network, and various constraints: state space safety constraint, normal operation safety constraint, N-1 safety constraint considering demand response and load growth criticality safety constraint, the final power supply capacity evaluation model of the active distribution network is obtained by eliminating invalid constraints; According to the sampling algorithm and the final power supply capacity evaluation model of the active distribution network, effective sampling points are obtained; The complete power supply capacity of the active distribution network is visualized according to the effective sampling points, and the power supply capacity indicators are calculated.

2. The power supply capability evaluation method of the active distribution network considering demand response and N-1 safety constraints according to claim 1 is characterized by: When obtaining the objective function of the power supply capacity evaluation model of the given active distribution network: according to the grid structure and parameters of the given active distribution network, the sum of the loads at the working points is used as the ordinate, and the sum of the corresponding DG outputs is used as the abscissa. The sum of the loads is sorted from small to large, and the power supply capacity of the working points after sorting is used as the objective function to represent the complete power supply capacity of the active distribution network; the expression of the objective function of the power supply capacity evaluation model of the active distribution network is: Among them, P SC Represents the complete power supply capacity of the active distribution network; the jth working point W j Power supply capability Γ(W L,j ) is the working point W j The sum of the loads is equal to the sum of the apparent powers of all load nodes. The jth working point W j The total output of DG Γ(W DG,j ) is the working point W j The sum of the DG outputs is equal to the sum of the apparent powers of all DG nodes. S L,k is the kth load node L k The apparent power of DG,l is the lth DG node DG l Apparent power; W L,j is the jth operating point W consisting of the apparent power of the load nodes j The load vector; W DG,j is the jth operating point W composed of the apparent power of the DG node j is the DG vector; n is the number of load nodes; m is the number of DG nodes.

3. The power supply capability evaluation method of the active distribution network considering demand response and N-1 safety constraints according to claim 1 is characterized by: When determining the state space safety constraints in the constraints of the power supply capacity assessment model of the active distribution network: the apparent power of the load node and the apparent power of the DG node are kept within a certain safety range due to the constraints of the distribution transformer and the DG capacity. According to the constraints of the distribution transformer and the DG capacity, the constraints satisfied by the apparent power of the load node and the apparent power of the DG node are listed separately, which is the state space safety constraint, and its expression is: Among them, W is the L and W DG The working point of the composition; W L is the load vector composed of the apparent power of the load nodes; W DG is the DG vector composed of the apparent power of the DG nodes; For S L,k The maximum apparent power of For S DG,l The maximum apparent power of the load nodes; L is the set consisting of all load nodes; G is the set consisting of all DG nodes.

4. The power supply capability evaluation method of the active distribution network considering demand response and N-1 safety constraints according to claim 1 is characterized by: When determining the normal operation safety constraint in the constraint conditions of the power supply capacity evaluation model of the active distribution network: the constraint that the absolute value of the net power of all lines and substation main transformers does not exceed the rated capacity of their components during normal operation of the active distribution network is the normal operation safety constraint, and its expression is: Among them, S B,i For line B i The net power of B,i For line B i The set of downstream nodes; k∈Π B,i is the load node L k On line B i Downstream of; l∈Π B,i DG node l On line B i Downstream; Downstream refers to the direction from the main transformer of the substation to the line terminal; c B,i For line B i The rated capacity of the line; B is the collection of all lines; S T,h Main transformer T h The net power of T,h Main transformer T h The set of downstream nodes; k∈Π T,h is the load node L k In the main transformer T h Downstream of; l∈Π T,h DG node l In the main transformer T h Downstream of T,h Main transformer T h The rated capacity of the substation; T is the set of main transformers of all substations.

5. The power supply capability evaluation method of the active distribution network considering demand response and N-1 safety constraints according to claim 1 is characterized by: When determining the constraints of the power supply capacity evaluation model of the active distribution network, the N-1 safety constraint of the demand response is considered. After the N-1 accident occurs in the active distribution network, in order to ensure that the N-1 safety constraint is met, the active distribution network is allowed to participate in the demand response after N-1, actively reduce or interrupt a certain proportion of load, and perform network reconstruction to complete the load transfer. After the network reconstruction, the rated capacity of all lines and substation main transformers is not less than the absolute value of their net power. The expression is: Where X = {χ1,...,χ b ,...,χ y } is the set of N-1 unexpected events, i.e., the failure set; y N-1 unexpected events occur for component y; S B,i (y) is line B after N-1 unexpected events occur in component y i Net power; S T,h (y) is the main transformer T of the substation after N-1 unexpected events occurred in component y h The net power of B,i (y) is line B after N-1 unexpected events occur in component y i The set of downstream nodes, Π T,h (y) is the main transformer T after N-1 accident occurs in component y h The set of downstream nodes; θ k is the kth load node L k The proportional coefficient of load reduction or interruption allowed is the load reduction coefficient, which reflects the effect of load participation in demand response.

6. The power supply capability evaluation method of the active distribution network considering demand response and N-1 safety constraints according to claim 1 is characterized by: When determining the constraints of the power supply capacity assessment model of the active distribution network, all load variables at the working point are subject to equality constraints. The equality constraint indicates that after the forward flow of the component reaches the upper capacity limit, no load can increase any more. If there is a load increase, it will violate the equality constraint and cause the forward flow to exceed the limit. The criticality safety constraint of load growth is determined by X in the equality constraint. L,eq Without pure zero column guarantee, some inequalities in the state space security constraint, normal operation security constraint, and N-1 security constraint considering demand response are equalized, and the other inequalities remain unchanged. The load growth criticality security constraint including the forward power flow security constraint and the reverse power flow security constraint is obtained, and its expression is: Among them, Φ is all safety boundaries, and the safety boundary is the set of all working points that meet the load growth criticality safety constraints; η q is the qth safety boundary; X L,eq is the load factor matrix in the equality constraint, whose elements are 0 or 1 and are determined by the network structure of the active distribution network; X DG,eq is the DG coefficient matrix in the equality constraint, whose elements are 0 or 1 and are determined by the network structure of the active distribution network; c eq is the constant column vector in the equality constraint, whose elements are the rated capacity of the corresponding substation main transformer or line; X L,ieq is the load factor matrix in the inequality constraint; X DG,ieq is the DG coefficient matrix in the inequality constraint; c ieq is the constant column vector in the inequality constraints.

7. The power supply capability evaluation method of the active distribution network considering demand response and N-1 safety constraints according to claim 1 is characterized by: According to the sampling algorithm and the final power supply capacity evaluation model of the active distribution network, the effective sampling points are obtained. The specific steps are as follows: Uniform sampling is performed in the state space of the load and DG with a step size of λ to obtain Y sampling points. The expression for calculating Y is: In the formula, For S L,k The maximum apparent power of For S DG,l The maximum apparent power of Filter out effective sampling points that meet the final power supply capacity evaluation model of the active distribution network from the Y sampling points.

8. The power supply capability evaluation method of the active distribution network considering demand response and N-1 safety constraints according to claim 1 is characterized by: The complete power supply capacity of the active distribution network is visualized according to the effective sampling points, and the power supply capacity index is calculated. The specific steps are as follows: Step S5-1, based on the obtained valid sampling points, calculate the sum of the loads of all valid sampling points Γ(W L,j ) and DG total output Γ(W DG,j ), and the power supply capacity of all effective sampling points Γ(W L,j ), the power supply capacity of all effective sampling points Γ(W L,j ) are sorted from small to large, and the total output of DG after sorting is Γ(W DG,j ) is the horizontal axis, and the power supply capacity of the effective sampling point is Γ(W L,j ) is the vertical coordinate, and the complete power supply capacity of the active distribution network is visualized as a curve, and the relationship between the complete power supply capacity of the active distribution network and the total output of DG is accurately inverted according to the curve; Step S5-2: Based on the power supply capacity Γ(W of all effective sampling points L,j ), filter out the maximum value of the power supply capacity of the effective sampling point, and obtain the maximum power supply capacity, recorded as PSC max Indicator: Filter out the minimum value of the power supply capacity of the effective sampling point and obtain the minimum power supply capacity, which is recorded as PSC min index; The average power supply capacity of all valid sampling points is calculated to obtain the average power supply capacity, which is recorded as the PSC index. According to the power supply capacity index, the complete power supply capacity of the active distribution network is quantified into a specific interval value.

9. An evaluation system for implementing the power supply capability evaluation method of an active distribution network considering demand response and N-1 safety constraints as described in any one of claims 1 to 8, characterized in that: include: An objective function generating module is used to obtain an objective function of a power supply capacity evaluation model of an active distribution network for a given active distribution network; A constraint condition generating module, whose input end is connected to the output end of the objective function generating module, is used to determine the constraint condition of the power supply capacity evaluation model of the active distribution network according to the objective function of the power supply capacity evaluation model of the active distribution network; A constraint condition elimination module, whose input end is connected to the output end of the constraint condition generation module, is used to eliminate invalid constraints and obtain a final power supply capacity evaluation model of the active distribution network; A sampling point generation module, whose input end is connected to the output end of the constraint condition elimination module, is used to obtain effective sampling points of the power supply capacity evaluation model of the active distribution network; The power supply capacity calculation module has an input end connected to the output end of the sampling point generation module and is used to visualize the complete power supply capacity of the active distribution network according to the effective sampling points and calculate the power supply capacity index.

10. The evaluation system according to claim 9, characterized in that: The constraint generation module includes: The first constraint generating unit is used to generate state space safety constraints; The second constraint generating unit is used to generate a normal operation safety constraint; The third constraint generating unit is used to generate N-1 safety constraints considering demand response; The fourth constraint generating unit: its input end is connected to the output ends of the first constraint generating unit, the second constraint generating unit and the third constraint generating unit, and is used to generate load growth criticality safety constraints.

Images