A distribution network fault recovery method and system based on substation capacity evaluation

Abstract

The present invention discloses a distribution network fault recovery method and system based on substation capacity evaluation, the method comprising: establishing a de-discretized photovoltaic storage integration model; characterizing the substation feasible domain according to the established photovoltaic storage integration model; establishing a distribution network fault recovery model based on the substation feasible domain; calling a solver to solve the distribution network fault recovery model, and obtaining an islanding division scheme of the distribution network within the fault time; establishing a power generation planning model, and solving the power generation planning model according to the islanding division scheme, obtaining the power generation plan of the photovoltaic storage unit, and performing distribution network fault recovery in combination with the islanding division scheme. The present invention reduces the difficulty of solving the distribution network fault recovery problem while improving the calculation efficiency, thereby improving the applicability and flexibility of the model in dealing with the distribution network fault recovery problem considering large-scale new energy grid connection, enhancing the elasticity of the distribution network, and providing theoretical support for the operation control of building a strong power grid.

Description

Technical Field

[0001] The present invention belongs to the field of distribution network, relates to distribution network fault recovery technology, and specifically relates to a distribution network fault recovery method and system based on substation capacity evaluation. Background Art

[0002] As an important part of the power system, the stable operation of the distribution network is crucial to ensuring power supply.

[0003] Modern distribution networks are usually equipped with redundant structures and backup power supplies, and can restore power supply to non-faulty areas as quickly as possible by closing the loop and shedding loads. At the same time, with the application of advanced equipment such as intelligent soft switches (such as SOP), the fault recovery strategy of the distribution network has become more flexible and diverse, further improving the recovery efficiency and reliability.

[0004] Existing distribution network fault recovery technologies usually adopt centralized fault recovery strategies, with the distribution master station bearing most of the computing burden. As the installed capacity of distributed resources in the distribution network increases, the amount of data that the distribution master station needs to process and analyze in real time increases dramatically, which poses a severe challenge to the real-time performance and accuracy of the system. Summary of the invention

[0005] Purpose of the invention: In order to overcome the deficiencies in the prior art, a distribution network fault recovery method and system based on substation capacity assessment is provided, which can reduce the amount of data that needs to be processed and analyzed in real time by the distribution master station and reduce the computational burden of distribution network fault recovery.

[0006] Technical solution: To achieve the above purpose, the present invention provides a distribution network fault recovery method based on substation capacity evaluation, comprising the following steps:

[0007] S1: Establish a de-discrete photovoltaic-storage integrated model;

[0008] S2: Describe the feasible domain of the substation area based on the photovoltaic and energy storage integration model established in step S1;

[0009] S3: Based on the feasible region of the substation described in step S2, a distribution network fault recovery model is established;

[0010] S4: calling the solver to solve the distribution network fault recovery model established in step S3, and obtaining the island division scheme of the distribution network during the fault time;

[0011] S5: Establish a power generation planning model, and solve the power generation planning model according to the island division scheme to obtain the power generation plan of the photovoltaic storage unit, and perform distribution network fault recovery in combination with the island division scheme.

[0012] Furthermore, the establishment of the de-discretized photovoltaic-storage integrated model in step S1 includes:

[0013] Establish a de-discrete photovoltaic-storage integrated model:

[0014]

[0015]

[0016] Where: p i,t is the active interaction power between the station area i and the upper power grid at time t; q i,t is the reactive interaction power between the grid area i and the upper grid at time t; is the active power demand of station area i at time t; is the reactive power demand of the station area i at time t; Represents the apparent power of the photovoltaic unit in the station area i; represents the apparent power of the energy storage device in the station area i; is the active power output of the PV units in the grid area i at time t; is the active output of the energy storage device in the station area i at time t; is the predicted power of the PV unit in the grid area i at time t; is the maximum electric energy that can be absorbed by the energy storage device in the station area i when a fault occurs; E i ESS,Dis is the maximum electric energy that can be released by the energy storage device in the station area i when a fault occurs; η dischar is the discharge efficiency of energy storage; η char is the charging efficiency of energy storage; Δt represents the length of the period between adjacent decision points, i.e., the decision step length; Ω i,t is a set of continuous operation time periods of the energy storage power stations in the station area i.

[0017] Furthermore, the specific process of describing the feasible region of the station area in step S2 is:

[0018] A1: Generate a sufficiently large initial space φ INI :

[0019] Based on formulas (1)-(4), the constraint set φ of the entire area including the output of the photovoltaic and storage units, lines, and loads is established. FR The projection of the formed convex polytope onto the power interaction node;

[0020] φ FR ={p i,t |st(1)-(4)} (5)

[0021] φ FR Written in the compact form shown in formula (6):

[0022]

[0023] Where: is the p of the decision point in station i i,t The set is composed of; y is the adjustment variable, which can change the position of the feasible solution in the feasible domain, such as the unit output, etc.; A and B are variables and the coefficient matrix of y; b represents the constant vector in the system;

[0024] Solve the optimization problem (7) to obtain a sufficiently large initial space φ INI :

[0025]

[0026] Where: G is the number of decision points; g is the index number of the search direction;

[0027] The optimization result of the optimization problem (7) is the optimal solution in the corresponding direction g and extreme values Generate the boundary of the initial space based on the optimization objective function of the extreme value and search direction:

[0028]

[0029] A2: In the space generated in step A1, find a vertex z in the space out :

[0030] The boundaries of the initial space are written as:

[0031]

[0032] Where: D and d represent the boundary parameters of the space, respectively, and represent the decision variables The coefficient matrix and the corresponding constant vector contain the boundary information of the space;

[0033] Solve the optimization problem (10) to find a vertex z in space out :

[0034]

[0035] Where: α is a 0-1 variable, M is the maximum value using the large M method; v is the intermediate variable of the feasible domain constraint; z out is the dual variable generated when applying the dual transformation; z outT Yes out is the transpose of; b is the constant vector representing the system characteristics in formula (6); A is the variable in formula (6) The coefficient matrix of B; x represents the interactive power instruction; T is the transpose of the coefficient matrix of the adjustment variable y in equation (6);

[0036] A3: Through vertex z outGenerate a feasible region boundary z outT Ax≤z outT bf 1 , and add the border to the current space;

[0037] A4: Repeat steps A2 and A3 until f in formula (10) is 1 ≤0, then φ INI It is the feasible domain of the area.

[0038] Furthermore, the distribution network fault recovery model established in step S3 includes:

[0039]

[0040] D i P i T ≤d i (12)

[0041]

[0042] b ij,t ≤a ij (14)

[0043] h ij1,t =b ij,t (15)

[0044] h ijkmax,t =g ij,t (16)

[0045] k max =[2+log 2 (N-1)] (17)

[0046] 1<k≤k max (18)

[0047]

[0048] h ijk,t =h jik,t (20)

[0049] (c ij(k-1)q,t -1)M≤h iq(k-1),t +h qj(k-1),t -1≤c ij(k-1)q,t M(21)

[0050]

[0051] (g ij,t -1)M≤y ij,t -x j,t ≤(1-gij,t )M (24)

[0052] -g ij,t M≤y ij,t ≤g ij,t M (25)

[0053] (g ij,t -1)M≤G ij,t -p j,t ≤(1-g ij,t )M (26)

[0054] -g ij,t M≤G ij,t ≤g ij,t M (27)

[0055]

[0056] (A ij,t -1)M≤G ii,t -G ij,t ≤A ij,t M (30)

[0057]

[0058] Where: Formula (11) describes the objective function F 1 ; Equations (12) and (13) describe the power supply capacity of the substation i. D and d in equation (12) together constitute the feasible region φ of the substation i. INI ,Right now: T is the expected fault duration, which is set by the dispatcher’s experience; N is the total number of nodes in the distribution network topology; X i,t is a 0-1 variable representing the state of station i at time t, X i,t =1 means that the station area i is restored at time t; X i,t =0 means that the station area i has not been restored at time t; C i is the load weight factor; b ij,t is a 0-1 variable representing the relationship between area i and area j at time t, b ij,t =1 means that at time t, area i and area j are connected, b ij,t =0 means that at time t, area i and area j are not connected;

[0059] Equations (14) to (25) describe the topological constraints of the distribution network; a ij is a 0-1 constant indicating whether a section switch or circuit breaker is installed between the i and j sections. ij =1 indicates that there is a connecting line with a section switch or circuit breaker between the stations i and j, a ij= 0 means there is no contact line between area i and area j. When the contact line between area i and area j fails and cannot be connected, it is considered that there is no contact line between area i and area j. When there is no contact line between area i and area j or the contact line fails and cannot be connected, a ij =0, b ij,t It can only be 0, which means that the area i and area j are not connected; when there is a connecting line of a section switch or circuit breaker between area i and area j, a ij =1, b ij,t Can be 0 or 1, when the section switch or circuit breaker is open b ij,t =0, when the section switch or circuit breaker is closed b ij,t =1; [2+log 2 (N-1)] means no more than 2+log 2 The largest integer of (N-1); g ij,t is a 0-1 variable indicating whether the substation j is located in the microgrid i at time t, g ij,t =1 means that the substation j is located in the microgrid i at time t, g ij,t =0 means that the substation j is not located in the microgrid i at time t; k max is the maximum number of iterations; h ijk,t It is a 0-1 integer variable; c ijqk,t To calculate h ijk,t The intermediate value is a 0-1 integer variable, indicating h iqk,t and h jqk,t Whether both are 1, c ijqk,t =1 hour iqk,t =h jqk,t =1, c ijqk,t =1 hour iqk,t and h jqk,t At least one is 0; M is the preset maximum value; x i,t represents the total number of tie lines connected to the station area i at time t; y ij,t is the total number of tie lines from substation j to microgrid i;

[0060] Equations (26) to (28) describe the state of microgrid i; G ij,t It represents the active power contributed by substation j to microgrid i at time t;

[0061] Equations (29) to (34) describe the power flow of the distribution network; P ij,t represents the active power flowing from area i to area j at time t; Q ij,t A represents the reactive power flowing from area i to area j at time t; ij,t is a 0-1 variable representing the relationship between microgrid i and substation j at time t, A ij,t =1 means that at time t, the active power provided by area j to microgrid i is the largest, A ij,t=0 means that the active power provided by area j to microgrid i at time t is not the maximum; It represents the square of the bus voltage amplitude of the station area i at time t; Indicates the square of the bus voltage rating; R ij represents the resistance of the connecting line between area i and area j; X ij Indicates the reactance of the tie line between area i and area j;

[0062] Equation (35) describes the voltage security constraint of the distribution network; It represents the square of the lower limit of voltage in the station area i; Represents the square of the upper voltage limit of station area i.

[0063] Furthermore, the island division scheme of the distribution network during the fault time in step S4 includes: solving the model and obtaining the on / off status of each section switch and circuit breaker at different times. and the interactive power scheme between each substation and the upper grid (p i,t ,q i,t ).

[0064] Furthermore, the specific process of step S5 includes: establishing a power generation planning model, inputting the area interactive power plan obtained in step S4 into the power generation planning model, applying mathematical methods to solve, and obtaining the power generation plan of each photovoltaic storage unit, including the active output of the photovoltaic unit in the area i at time t and reactive power output Active output of energy storage device in zone i at time t and reactive power output Combine the island partitioning scheme to restore distribution network faults.

[0065] Furthermore, in step S5, the power generation plan of each photovoltaic storage unit is combined with the island division scheme to perform fault recovery in the following manner:

[0066] According to the island division plan, the on and off states of each section switch and circuit breaker at different times during the fault time are controlled. At the same time, according to the power generation plan of each photovoltaic storage unit, the output of each photovoltaic unit and energy storage device in each substation of the distribution network during the fault time is controlled to realize the distribution network fault recovery.

[0067] Furthermore, the power generation planning model established in step S5 is:

[0068]

[0069] Where: Formula (36) describes the objective function F 2 ; α ESS is the power generation cost of the energy storage device; α PV is the power generation cost of the PV unit; is the reactive power output of the PV unit in the grid area i at time t; is the reactive power output of the energy storage device in the grid area i at time t; represents the installed capacity of the PV units in the area i; is a 0-1 variable representing the state of the energy storage device in the station area i at time t, It indicates the discharge of the energy storage device in the region i at time t. Indicates the charging of the energy storage device in the station area i at time t; E i,t is the state of the energy storage device in station i at time t.

[0070] The present invention also provides a distribution network fault recovery system based on substation capacity assessment, comprising: a collection module, a model and constraint building module, a calculation solution module and a power generation planning solution module;

[0071] The acquisition module is used to collect relevant parameters of the distribution network to be processed and send them to the model and constraint building module;

[0072] The model and constraint building module is used to build a feasible region of the substation according to the collected parameters and establish a distribution network fault recovery model;

[0073] The calculation and solution module is used to obtain the on-off status of each section switch and circuit breaker of the distribution network at different times during the fault time and the interactive power scheme of each substation and the upper power grid by solving the model and the model constructed by the constraint construction module, so as to form an island division scheme of the distribution network during the fault time;

[0074] The power generation planning solution module is used to establish a power generation planning model, and solve the power generation planning model according to the island division scheme to obtain the power generation plan of each photovoltaic storage unit, and perform distribution network fault recovery in combination with the island division scheme.

[0075] The present invention proposes a distribution network fault recovery method based on substation capacity evaluation based on feasible domain analysis, and establishes a fault recovery linear model that decouples load recovery and power generation planning. It improves the calculation efficiency while reducing the difficulty of solving the distribution network fault recovery problem, thereby improving the applicability and flexibility of the model in dealing with the distribution network fault recovery problem considering large-scale renewable energy grid connection, enhancing the elasticity of the distribution network, and providing theoretical support for the operation control of building a strong power grid.

[0076] Beneficial effect: Compared with the prior art, the present invention utilizes the substation capacity assessment method to characterize the substation operation domain, thereby reducing the amount of data that needs to be processed and analyzed in real time by the distribution master station, improving the calculation efficiency while reducing the difficulty of solving the distribution network fault recovery problem, thereby reducing the computational burden of formulating fault recovery strategies, and improving the applicability and flexibility of the model to deal with distribution network fault recovery problems considering large-scale renewable energy grid connection, maintaining a balance between the real-time and accuracy of the distribution system during the fault recovery process, improving the flexibility of the distribution system operation, and can provide theoretical support for the operation control of building a strong power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 It is a flow chart of the method for recovering a power distribution network fault in the present invention;

[0078] Figure 2 is a diagram of a power grid structure used in an embodiment of the present invention;

[0079] Figure 3 is a simplified diagram of the power grid structure of an embodiment of the present invention;

[0080] Figure 4 is a schematic diagram of an island division scheme obtained in an embodiment of the present invention;

[0081] Figure 5 is a schematic diagram of the recovery of a photovoltaic unit after a fault over time according to an embodiment of the present invention;

[0082] Figure 6 is a schematic diagram of the recovery of the energy storage device after a fault over time according to an embodiment of the present invention;

[0083] Figure 7 is a schematic diagram of load recovery conditions changing over time after a fault in an embodiment of the present invention;

[0084] Figure 8 It is a structural schematic diagram of the distribution network fault recovery system in the present invention. DETAILED DESCRIPTION

[0085] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0086] Embodiment 1:

[0087] like Figure 1 As shown, this embodiment provides a distribution network fault recovery method based on substation capacity evaluation, comprising the following steps:

[0088] S1: Establish a de-discrete photovoltaic-storage integrated model;

[0089] The establishment of the de-discretized photovoltaic-storage integrated model includes:

[0090] Establish a de-discrete photovoltaic-storage integrated model:

[0091]

[0092] Where: p i,t is the active interaction power between the station area i and the upper power grid at time t; q i,t is the reactive interaction power between the grid area i and the upper grid at time t; is the active power demand of station area i at time t; is the reactive power demand of the station area i at time t; Represents the apparent power of the photovoltaic unit in the station area i; represents the apparent power of the energy storage device in the station area i; is the active power output of the PV units in the grid area i at time t; is the active output of the energy storage device in the station area i at time t; is the predicted power of the PV unit in the grid area i at time t; is the maximum electric energy that can be absorbed by the energy storage device in the station area i when a fault occurs; E i ESS,Dis is the maximum electric energy that can be released by the energy storage device in the station area i when a fault occurs; η dischar is the discharge efficiency of energy storage; η char is the charging efficiency of energy storage; Δt represents the length of the period between adjacent decision points, i.e., the decision step length; Ω i,t is a set of continuous operation time periods of the energy storage power stations in the station area i.

[0093] S2: Describe the feasible domain of the substation area based on the photovoltaic and energy storage integration model established in step S1;

[0094] The specific process of describing the feasible region of the station area is:

[0095] A1: Generate a sufficiently large initial space φ INI :

[0096] Based on formulas (1)-(4), the constraint set φ of the entire area including the output of the photovoltaic and storage units, lines, and loads is established. FR The projection of the formed convex polytope onto the power interaction node;

[0097] φ FR ={p i,t |st(1)-(4)} (5)

[0098] φ FR Written in the compact form shown in formula (6):

[0099]

[0100] Where: is the p of the decision point in station i i,t The set is composed of; y is the adjustment variable, which can change the position of the feasible solution in the feasible domain, such as the unit output, etc.; A and B are variables and the coefficient matrix of y; b represents the constant vector in the system;

[0101] Solve the optimization problem (7) to obtain a sufficiently large initial space φ INI :

[0102]

[0103] Where: G is the number of decision points; g is the index number of the search direction;

[0104] The optimization result of the optimization problem (7) is the optimal solution in the corresponding direction g and extreme values Generate the boundary of the initial space based on the optimization objective function of the extreme value and search direction:

[0105]

[0106] A2: In the space generated in step A1, find a vertex z in the space out :

[0107] The boundaries of the initial space are written as:

[0108]

[0109] Where: D and d represent the boundary parameters of the space, respectively, and represent the decision variables The coefficient matrix and the corresponding constant vector contain the boundary information of the space;

[0110] Solve the optimization problem (10) to find a vertex z in space out :

[0111]

[0112] Where: α is a 0-1 variable, M is the maximum value using the large M method; v is the intermediate variable of the feasible domain constraint; z out is the dual variable generated when applying the dual transformation; z outT Yes out is the transpose of; b is the constant vector representing the system characteristics in formula (6); A is the variable in formula (6) The coefficient matrix of B; x represents the interactive power instruction; Tis the transpose of the coefficient matrix of the adjustment variable y in equation (6);

[0113] A3: Through vertex z out Generate a feasible region boundary z outT Ax≤z outT bf 1 , and add the border to the current space;

[0114] A4: Repeat steps A2 and A3 until f in formula (10) is 1 ≤0, then φ INI It is the feasible domain of the area.

[0115] S3: Based on the feasible region of the substation described in step S2, a distribution network fault recovery model is established;

[0116] The established distribution network fault recovery model includes:

[0117]

[0118] D i P i T +d i (12)

[0119]

[0120] b ij,t ≤a ij (14)

[0121] h ij1,t =b ij,t (15)

[0122] h ijkmax,t =g ij,t (16)

[0123] k max =[2+log 2 (N-1)] (17)

[0124] 1<k≤k max (18)

[0125]

[0126] h ijk,t =h jik,t (20)

[0127] (c ij(k-1)q,t -1)M≤h iq(k-1),t +h qj(k-1),t -1≤c ij(k-1)q,t M (21)

[0128]

[0129] (g ij,t -1)M≤y ij,t -x j,t ≤(1-g ij,t )M (24)

[0130] -g ij,t M≤y ij,t ≤g ij,t M (25)

[0131] (g ij,t -1)M≤G ij,t -p j,t ≤(1-g ij,t )M (26)

[0132] -g ij,t M≤G ij,t ≤g ij,t M (27)

[0133]

[0134] (A ij,t -1)M≤G ii,t -G ij,t ≤A ij,t M(30)

[0135]

[0136] Where: Formula (11) describes the objective function F 1 ; Equations (12) and (13) describe the power supply capacity of the substation i. D and d in equation (12) together constitute the feasible region φ of the substation i. INI , that is: {P i T |D i P i T ≤d i}=φ INI ; T is the expected fault duration, which is set by the dispatcher’s experience; N is the total number of nodes in the distribution network topology; X i,t is a 0-1 variable representing the state of station i at time t, X i,t =1 means that the station area i is restored at time t; X i,t =0 means that the station area i has not been restored at time t; C i is the load weight factor; b ij,t is a 0-1 variable representing the relationship between area i and area j at time t, b ij,t =1 means that at time t, area i and area j are connected, b ij,t=0 means that at time t, area i and area j are not connected;

[0137] Equations (14) to (25) describe the topological constraints of the distribution network; a ij is a 0-1 constant indicating whether a section switch or circuit breaker is installed between the i and j sections. ij =1 indicates that there is a connecting line with a section switch or circuit breaker between the stations i and j, a ij = 0 means there is no contact line between area i and area j. When the contact line between area i and area j fails and cannot be connected, it is considered that there is no contact line between area i and area j. When there is no contact line between area i and area j or the contact line fails and cannot be connected, a ij =0, b ij,t It can only be 0, which means that the area i and area j are not connected; when there is a connecting line of a section switch or circuit breaker between area i and area j, a ij =1, b ij,t Can be 0 or 1, when the section switch or circuit breaker is open b ij,t =0, when the section switch or circuit breaker is closed b ij,t =1; [2+log 2 (N-1)] means no more than 2+log 2 The largest integer of (N-1); g ij,t is a 0-1 variable indicating whether the substation j is located in the microgrid i at time t, g ij,t =1 means that the substation j is located in the microgrid i at time t, g ij,t =0 means that the substation j is not located in the microgrid i at time t; k max is the maximum number of iterations; h ijk,t It is a 0-1 integer variable; c ijqk,t To calculate h ijk,t The intermediate value is a 0-1 integer variable, indicating h iqk,t and h jqk,t Whether both are 1, c ijqk,t =1 hour iqk,t =h jqk,t =1, c ijqk,t =1 hour iqk,t and h jqk,t At least one is 0; M is the preset maximum value; x i,t represents the total number of tie lines connected to the station area i at time t; y ij,t is the total number of tie lines from substation j to microgrid i;

[0138] Equations (26) to (28) describe the state of microgrid i; G ij,t It represents the active power contributed by substation j to microgrid i at time t;

[0139] Equations (29) to (34) describe the power flow of the distribution network; P ij,t represents the active power flowing from area i to area j at time t; Q ij,t A represents the reactive power flowing from area i to area j at time t; ij,t is a 0-1 variable representing the relationship between microgrid i and substation j at time t, A ij,t =1 means that at time t, the active power provided by area j to microgrid i is the largest, A ij,t =0 means that the active power provided by area j to microgrid i at time t is not the maximum; It represents the square of the bus voltage amplitude of the station area i at time t; Indicates the square of the bus voltage rating; R ij represents the resistance of the connecting line between area i and area j; X ij Indicates the reactance of the tie line between area i and area j;

[0140] Equation (35) describes the voltage security constraint of the distribution network; It represents the square of the lower limit of voltage in the station area i; Represents the square of the upper voltage limit of station area i.

[0141] S4: calling the solver to solve the distribution network fault recovery model established in step S3, and obtaining the island division scheme of the distribution network during the fault time;

[0142] The islanding scheme for obtaining the distribution network during the fault time includes: solving the model and obtaining the on / off status of each section switch and circuit breaker at different times and the interactive power scheme between each substation and the upper grid (p i,t ,q i,t ).

[0143] S5: Establish a power generation planning model, and solve the power generation planning model according to the island division scheme to obtain the power generation plan of the photovoltaic storage unit, and perform distribution network fault recovery in combination with the island division scheme.

[0144] The specific process of step S5 includes: establishing a power generation planning model, inputting the area interactive power plan obtained in step S4 into the power generation planning model, applying mathematical methods to solve, and obtaining the power generation plan of each photovoltaic storage unit, including the active output of the photovoltaic unit in area i at time t and reactive power output Active output of energy storage device in zone i at time t and reactive power output Combine the island partitioning scheme to restore distribution network faults.

[0145] The established power generation planning model is:

[0146]

[0147]

[0148] Where: Formula (36) describes the objective function F 2 ; α ESS is the power generation cost of the energy storage device; α PV is the power generation cost of the PV unit; is the reactive power output of the PV unit in the grid area i at time t; is the reactive power output of the energy storage device in the grid area i at time t; represents the installed capacity of the PV units in the area i; is a 0-1 variable representing the state of the energy storage device in the station area i at time t, It indicates the discharge of the energy storage device in the region i at time t. Indicates the charging of the energy storage device in the station area i at time t; E i,t is the state of the energy storage device in station i at time t;

[0149] In step S5, the power generation planning of each photovoltaic storage unit is combined with the island division scheme to perform fault recovery in the following manner:

[0150] According to the island division plan, the on and off states of each section switch and circuit breaker at different times during the fault time are controlled. At the same time, according to the power generation plan of each photovoltaic storage unit, the output of each photovoltaic unit and energy storage device in each substation of the distribution network during the fault time is controlled to realize the distribution network fault recovery.

[0151] Embodiment 2:

[0152] like Figure 8 As shown, this embodiment provides a distribution network fault recovery system based on substation capacity evaluation, including: a collection module, a model and constraint building module, a calculation and solution module and a power generation planning solution module;

[0153] The acquisition module is used to collect the relevant parameters of the distribution network to be processed and send them to the model and constraint construction module;

[0154] Model and constraint building module, used to build the feasible region of the substation according to the collected parameters and establish the distribution network fault recovery model;

[0155] The calculation and solution module is used to obtain the on-off status of each section switch and circuit breaker of the distribution network at different times during the fault time and the interactive power scheme of each substation and the upper power grid by solving the model and the model constructed by the constraint construction module, so as to form an island division scheme of the distribution network during the fault time;

[0156] The power generation planning solution module is used to establish a power generation planning model and solve the power generation planning model according to the island division plan to obtain the power generation plan of each photovoltaic storage unit, and perform distribution network fault recovery in combination with the island division plan.

[0157] This embodiment also provides a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0158] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0159] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0160] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed entirely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0161] Embodiment 3:

[0162] This embodiment applies and analyzes the method of embodiment 1 and the system of embodiment 2 as follows:

[0163] In this embodiment, a distribution network in a certain region is selected as a distribution network calculation example. Figure 2 As shown in Figure 1, the distribution network has a total of 43 buses, numbered 1 to 43, with photovoltaic units connected to buses 22, 26, 28 and 35, and energy storage devices connected to buses 25, 28 and 35. The fault point is located on the line between buses 16 and 17. The parameters of the system are shown in Table 1.

[0164] After an extreme event occurs, the substation is disconnected from the upstream power grid, and the distribution network changes its structure through section switches / circuit breakers. Therefore, if there is no section switch / circuit breaker installed between two nodes, the two nodes can be regarded as the same node during the fault recovery process. Figure 2 The installation location of the section switch / circuit breaker in the middle, merging the nodes, the regional distribution network can be simplified to a 13-node network, such as Figure 3 As shown in the figure, the 13 node networks are numbered 1 to 13. The distribution network is simplified to Figure 3 After that, the power supply connection status is shown in Table 2.

[0165] In this embodiment, the load weight coefficients are shown in Table 3, and the energy storage device parameters are shown in Table 4. The fault time T is set to 4h, and the fault time section is selected from 6:30am-10:30am, a total of 8 time sections, and Δt=0.5h.

[0166] Table 1 Distribution network example parameters

[0167]

[0168]

[0169] Table 2 Power supply connection status

[0170]

[0171] Table 3 Weight coefficients of various electrical loads

[0172]

[0173] Table 4 Energy storage device parameters

[0174]

[0175]

[0176] According to the parameters in Tables 1 to 4, the feasible region of each substation is characterized.

[0177] According to the distribution network fault recovery model provided by the present invention, the cplex solver is called by yalmip on the matlab platform to obtain a feasible solution that satisfies the constraints. The islanding solution of the distribution network within the fault time is obtained as follows: Figure 4 shown.

[0178] in accordance with Figure 4 The island division scheme shown in Figure 2 can solve the power generation planning of each distributed resource. The power generation costs of various distributed resources are shown in Table 5. The power generation planning results are shown in Table 5. Figure 5-Figure 7 shown.

[0179] Table 5 Power generation cost of each power source

[0180]

[0181] Figure 5-Figure 7 The power generation planning proves Figure 4The feasibility of the island division scheme shown. At 6:30am, the line between busbars 16 and 17 failed, and the distribution network lost contact with the main grid. From 6:30am to 7:00am, the downstream area of ​​the fault was fully restored, and the energy storage device provided most of the power; from 7:00am to 8:00am, the total load demand increased rapidly, exceeding the power supply capacity, and the loads in substations 1 to 4 and 19 to 22 were cut off; from 8:00am to 9:30am, the photovoltaic output increased rapidly, the system power supply capacity could meet the total load demand, and the downstream area of ​​the fault was fully restored; from 9:30am to 10:30am, the total load demand continued to grow and exceeded the upper limit of the system power supply capacity, and the loads in substations 9 to 15 were cut off. The total power supply increased by 17.5MWh.

[0182] analyze Figure 5-Figure 7 During the fault recovery period, ESS not only serves as a power source to restore the load, but also plays a role in absorbing new energy. During 7:30am to 8:00am, the electric energy generated by PV not only meets the load demand, but is also stored by ESS in substations 25 and 28; during 8:00am to 8:30am, PV alone can meet the total load demand in the downstream area of ​​the fault. The role of ESS is to absorb new energy and achieve a 100% photovoltaic absorption rate; during 8:30am to 9:00am, because substation 35 is at the end of the system topology, the nearby loads cannot fully absorb the electric energy generated by PV in substation 35. At this time, ESS 35 still plays a role in absorbing new energy, but ESS25 and 28 at other locations in the system topology are discharging to meet the load demand. The method proposed in the present invention optimizes the utilization rate of distributed resources and enhances the resilience of the power system.

Claims

1. A distribution network fault recovery method based on substation capacity evaluation, characterized in that: The steps include: S1: Establish a de-discrete photovoltaic-storage integrated model; S2: Describe the feasible domain of the substation area according to the photovoltaic storage integration model established in step S1; S3: Based on the feasible region of the substation described in step S2, a distribution network fault recovery model is established; S4: calling the solver to solve the distribution network fault recovery model established in step S3, and obtaining the island division scheme of the distribution network during the fault time; S5: Establish a power generation planning model, and solve the power generation planning model according to the island division scheme to obtain the power generation plan of the photovoltaic storage unit, and perform distribution network fault recovery in combination with the island division scheme; The establishment of the de-discretized photovoltaic-storage integrated model in step S1 includes: Establish a de-discrete photovoltaic-storage integrated model: Where: p i,t is the active interaction power between the station area i and the upper power grid at time t; is the active power demand of station area i at time t; represents the apparent power of the energy storage device in the station area i; is the active power output of the PV units in the grid area i at time t; is the active output of the energy storage device in the station area i at time t; is the predicted power of the PV unit in the grid area i at time t; is the maximum electric energy that can be absorbed by the energy storage device in the station area i when a fault occurs; E i ESS,Dis is the maximum electric energy that can be released by the energy storage device in the station area i when a fault occurs; η dischar is the discharge efficiency of energy storage; η char is the charging efficiency of energy storage; Δt represents the length of the period between adjacent decision points, i.e., the decision step length; Ω i,t is a set of continuous operation time periods of energy storage power stations in the station area i; The specific process of describing the feasible region of the station area in step S2 is: A1: Generate initial space φ INI : Based on formulas (1)-(4), the set of all constraints within the station area is established FR The projection of the formed convex polytope onto the power interaction node; φ FR ={p i,t |s.t.(1)-(4)}(5) φ FR Written in the compact form shown in formula (6): Where: is the p of the decision point in station i i,t The set is composed of; y is the adjustment variable; A and B are variables and the coefficient matrix of y; b is a constant vector that characterizes the characteristics of the system; Solve the optimization problem (7) to obtain the initial space φ INI : Where: G is the number of decision points; g is the index number of the search direction; The optimization result of the optimization problem (7) is the optimal solution in the corresponding direction g and extreme values Generate the boundary of the initial space based on the optimization objective function of the extreme value and search direction: A2: In the space generated in step A1, find a vertex z in the space out : The boundaries of the initial space are written as: Where: D and d represent the decision variables The coefficient matrix and the corresponding constant vector of ; Solve the optimization problem (10) to find a vertex z in space out : Where: α is a 0-1 variable, M is the maximum value using the large M method; v is the intermediate variable of the feasible domain constraint; z out is the dual variable generated when applying the dual transformation; z outT Yes out is the transpose of; b is the constant vector representing the system characteristics in formula (6); A is the variable in formula (6) The coefficient matrix of B; x represents the interactive power instruction; T is the transpose of the coefficient matrix of the adjustment variable y in equation (6); A3: Through vertex z out Generate a feasible region boundary z outT Ax≤z outT b-f1, and add the border to the current space; A4: Repeat steps A2 and A3 until f1≤0 in formula (10). At this time, φ INI It is the feasible domain of the area.

2. A distribution network fault recovery method based on area capacity evaluation according to claim 1, characterized in that: The distribution network fault recovery model established in step S3 includes: D i P i T ≤d i (12) b ij,t ≤a ij (14) h ij1,t =b ij,t (15) k max =[2+log2(N-1)] (17) 1<k≤k max (18) h ijk,t =h jik,t (20) (c ij(k-1)q,t -1)M≤h iq(k-1),t +h qj(k-1),t -1≤c ij(k-1)q,t M(21) (g ij,t -1)M≤y ij,t -x j,t ≤(1-g ij,t )M (24) -g ij,t M≤y ij,t ≤g ij,t M (25) (g ij,t -1)M≤G ij,t -p j,t ≤(1-g ij,t )M (26) -g ij,t M≤G ij,t ≤g ij,t M (27) (A ij,t -1)M≤G ii,t -G ij,t ≤A ij,t M (30) Where: Formula (11) describes the objective function F1; Formula (12) and Formula (13) characterize the power supply capacity of the substation i. D and d in Formula (12) together constitute the feasible region φ of the substation i. INI , that is: {P i T |D i P i T ≤d i }=φ INI ; T is the expected fault duration, which is set by the dispatcher’s experience; N is the total number of nodes in the distribution network topology; X i,t is a 0-1 variable representing the state of station i at time t, X i,t =1 means that the station area i is restored at time t; X i,t =0 means that the station area i has not been restored at time t; C i is the load weight factor; b ij,t is a 0-1 variable representing the relationship between area i and area j at time t, b ij,t =1 means that at time t, area i and area j are connected, b ij,t =0 means that at time t, area i and area j are not connected; q i,t is the reactive interaction power between the grid area i and the upper grid at time t; is the reactive power demand of the station area i at time t; represents the installed capacity of the PV units in the area i; Equations (14) to (25) describe the topological constraints of the distribution network; a ij is a 0-1 constant indicating whether a connecting line between substations i and j is equipped with a section switch or circuit breaker. ij =1 indicates that there is a connecting line with a section switch or circuit breaker between the stations i and j, a ij = 0 means there is no contact line between area i and area j. When the contact line between area i and area j fails and cannot be connected, it is considered that there is no contact line between area i and area j. When there is no contact line between area i and area j or the contact line fails and cannot be connected, a ij =0, b ij,t It can only be 0, which means that the area i and area j are not connected; when there is a connecting line of a section switch or circuit breaker between area i and area j, a ij =1, b ij,t Can be 0 or 1, when the section switch or circuit breaker is open b ij,t =0, when the section switch or circuit breaker is closed b ij,t =1; [2+log2(N-1)] represents the largest integer not exceeding 2+log2(N-1); g ij,t is a 0-1 variable indicating whether the substation j is located in the microgrid i at time t, g ij,t =1 means that the substation j is located in the microgrid i at time t, g ij,t =0 means that the substation j is not located in the microgrid i at time t; k max is the maximum number of iterations; h ijk,t It is a 0-1 integer variable; c ijqk,t To calculate h ijk,t The intermediate value is a 0-1 integer variable, indicating h iqk,t and h jqk,t Whether both are 1, c ijqk,t =1 hour iqk,t =h jqk,t =1, c ijqk,t =1 hour iqk,t and h jqk,t At least one is 0; M is the preset maximum value; x i,t represents the total number of tie lines connected to the station area i at time t; y ij,t is the total number of tie lines from substation j to microgrid i; Equations (26) to (28) describe the state of microgrid i; G ij,t It represents the active power contributed by substation j to microgrid i at time t; Equations (29) to (34) describe the power flow of the distribution network; P ij,t represents the active power flowing from area i to area j at time t; Q ij,t A represents the reactive power flowing from area i to area j at time t; ij,t is a 0-1 variable representing the relationship between microgrid i and substation j at time t, A ij,t =1 means that at time t, the active power provided by area j to microgrid i is the largest, A ij,t =0 means that the active power provided by area j to microgrid i at time t is not the maximum; It represents the square of the bus voltage amplitude of the station area i at time t; Indicates the square of the bus voltage rating; R ij represents the resistance of the connecting line between area i and area j; X ij Indicates the reactance of the tie line between area i and area j; Equation (35) describes the voltage security constraint of the distribution network; It represents the square of the lower limit of voltage in the station area i; Represents the square of the upper voltage limit amplitude of the station area i.

3. A distribution network fault recovery method based on area capacity evaluation according to claim 2, characterized in that: The step S4 of obtaining the island division scheme of the distribution network during the fault time includes: solving the model and obtaining the on / off status of each section switch and circuit breaker at different times and the interactive power scheme between each substation and the upper grid (p i,t ,q i,t ).

4. A distribution network fault recovery method based on substation capacity evaluation according to claim 3, characterized in that: The specific process of step S5 includes: establishing a power generation planning model, inputting the area interactive power plan obtained in step S4 into the power generation planning model, applying mathematical methods to solve, and obtaining the power generation plan of each photovoltaic storage unit, including the active output of the photovoltaic unit in the area i at time t and reactive power output Active output of energy storage device in zone i at time t and reactive power output Combine the island partitioning scheme to restore distribution network faults.

5. A distribution network fault recovery method based on area capacity evaluation according to claim 4, characterized in that: In step S5, the power generation planning of each photovoltaic storage unit is combined with the island division scheme to perform fault recovery in the following manner: According to the island division plan, the on and off states of each section switch and circuit breaker at different times during the fault time are controlled. At the same time, according to the power generation plan of each photovoltaic storage unit, the output of each photovoltaic unit and energy storage device in each substation of the distribution network during the fault time is controlled to realize the distribution network fault recovery.

6. A distribution network fault recovery method based on area capacity evaluation according to claim 4, characterized in that: The power generation planning model established in step S5 is: Where: Formula (36) describes the objective function F2; α ESS is the power generation cost of the energy storage device; α PV is the power generation cost of the PV unit; is the reactive power output of the PV unit in the grid area i at time t; is the reactive power output of the energy storage device in the grid area i at time t; is a 0-1 variable representing the state of the energy storage device in the station area i at time t, It indicates the discharge of the energy storage device in the region i at time t. Indicates the charging of the energy storage device in the station area i at time t; E i,t is the state of the energy storage device in station i at time t.

7. The fault recovery system of the distribution network fault recovery method based on the substation capacity evaluation according to claim 1 is characterized in that: include: Acquisition module, model and constraint building module, calculation and solution module and power generation planning and solution module; The acquisition module is used to collect relevant parameters of the distribution network to be processed and send them to the model and constraint building module; The model and constraint building module is used to build a feasible region of the substation according to the collected parameters and establish a distribution network fault recovery model; The calculation and solution module is used to obtain the on-off status of each section switch and circuit breaker of the distribution network at different times during the fault time and the interactive power scheme of each substation and the upper power grid by solving the model and the model constructed by the constraint construction module, so as to form an island division scheme of the distribution network during the fault time; The power generation planning solution module is used to establish a power generation planning model, and solve the power generation planning model according to the island division scheme to obtain the power generation plan of each photovoltaic storage unit, and perform distribution network fault recovery in combination with the island division scheme.

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