Reliability evaluation analytical calculation method for integrated energy system

Abstract

The application provides a reliability evaluation analytical calculation method of a comprehensive energy system, establishes a correlation matrix of load points and lines, and obtains a power supply path matrix by inversion; the correlation matrix of the load points and the lines in the comprehensive energy system and the power supply path matrix are obtained; a target function and a constraint condition of a power supply model of the comprehensive energy system are determined, the power supply model of the comprehensive energy system is solved, and the reliability index of the comprehensive energy system is calculated. The application provides a matrix comprehensive energy system power supply recovery model, and the reliability index is calculated in a matrix form, so that the model has good accuracy and can be used for guiding improvement of power distribution network reliability.

Description

Technical Field

[0001] This invention relates to the technical field of power systems, and in particular to an analytical calculation method for reliability assessment of integrated energy systems. Background Technology

[0002] The distribution network, located at the end of the power system, is a crucial link in supplying power to users and directly affects whether users can safely and reliably obtain electricity from the grid. Distribution network reliability assessment is a quantitative evaluation of the level of continuous and reliable power supply to users over a period of time. The assessment results can guide the planning, construction, operation, and maintenance of the distribution network.

[0003] Integrated energy systems couple traditionally independent energy subsystems together, enabling them to supply a certain amount of load to the faulty network when one subsystem fails, thereby improving the overall system's power supply reliability. The application of integrated energy distribution systems increases the number of operating devices and the tighter the energy coupling, making the power supply methods of the distribution network more complex and diverse. Therefore, the reliability assessment methods for integrated energy distribution systems differ significantly from those for traditional distribution networks. While the load points of the distribution network can be powered by the integrated energy system after a fault, the highly coupled nature of integrated energy systems means that the distribution network reliability assessment model involves multiple energy networks, making the establishment of the power supply model complex. Therefore, constructing an appropriate assessment model and adopting suitable assessment methods are crucial for improving the reliability of integrated energy distribution systems. Summary of the Invention

[0004] To address the aforementioned issues, this invention employs a simplified analytical evaluation method based on the power supply path matrix to process the distribution network structure, establishes power supply-related constraints for the integrated energy system and a matrix-form integrated energy system power supply model, and proposes an analytical calculation method for reliability evaluation of the integrated energy system.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] An analytical calculation method for reliability assessment of an integrated energy system, comprising the following steps:

[0007] Step 1: Equip the distribution network with the switch as the boundary, and calculate the equivalent fault rate and equivalent repair time of each equivalent unit;

[0008] Step 2: Establish the correlation matrix between load points and lines, and inverse it to obtain the power supply path matrix;

[0009] Step 3: Calculate the matrix of the affected area after the instantaneous trip switch operates based on the position of the instantaneous trip switch;

[0010] Step 4: Obtain the first type of load point matrix and the second type of load point matrix after the fault;

[0011] Step 5: Reverse the power flow of the power supply path from the main power source to the energy station, and calculate the correlation matrix of the load points and lines and the power supply path matrix in the integrated energy system.

[0012] Step 6: Assume i represents the line and 1 represents the fault, let i = 1;

[0013] Step 7: Determine the objective function and constraints of the integrated energy system power supply model when the i-th equivalent line fault occurs, and solve the integrated energy system power supply model for the i-th equivalent line fault.

[0014] Step 8: Once all equivalent circuit faults have been calculated, proceed to Step 9; otherwise, i = i + 1 and jump to Step 7.

[0015] Step 9: Calculate the third type of load point matrix and the fourth type of load point matrix;

[0016] Step 10: Calculate the reliability index of the integrated energy system.

[0017] In step two, the methods for solving the correlation matrix of load points and lines, as well as the power supply path matrix, are as follows:

[0018] In a distribution network, each load point is considered as the start or end point of an adjacent line. A corresponding correlation matrix A between the line and the load point is established based on the connection relationships. e If the power flow is from line i to load point j, then the correlation matrix A e (i,j)=1; if the power flow is from load point j to line i, then the correlation matrix A e (i,j) = -1; otherwise, take 0.

[0019] If the energy station is connected via an auxiliary virtual line, then the correlation matrix A... e Inverting the power supply path matrix (PSPM) yields the power supply path matrix. Elements of 1 in PSPM represent the power flow path from the main power source to the load point. Removing the columns containing auxiliary virtual lines and the rows containing energy stations from PSPM yields the power supply path matrix PSPM for both the load point and the lines. a .

[0020] In step three, the matrix formation method for the affected area after the instantaneous trip switch operation is as follows:

[0021] PSPM matrix representing the path relationship between circuits and instantaneous circuit breakers l,s And the matrix S from the main power supply to all instantaneous trip switches in each line p The calculation method is shown in equation (1):

[0022]

[0023] Among them, Sbf Let S be a diagonal matrix consisting of all instantaneous switches. If the i-th instantaneous switch is a circuit breaker or a fuse, then S bf (i,i) = 1, otherwise 0;

[0024] When there are other instantaneous switches downstream of the activated instantaneous switch, this instantaneous switch should remain in its original state, forming a matrix S after subtracting all downstream instantaneous switches. a If matrix S a If the value is negative or 0, it means the original state should be maintained; matrix S a The negative values ​​are set to 0 to obtain matrix S. c Matrix S c Each row in matrix S represents the instantaneous trip switch that actually tripped after a line fault. Elements that are 1 represent the instantaneous trip switches that actually tripped. a Sum of matrix S c The calculation method is shown in equation (2):

[0025]

[0026] Where E is the identity matrix;

[0027] The load point and the instantaneous trip switch have the same topological relationship as the load point and the line. The matrix PSPM represents the path relationship between the load point and the instantaneous trip switch. lp,s Power supply path matrix (PSPM) with load points and lines a Equal to the matrix PSPM corresponding to the instantaneous trip switch that actually operates after a line fault. lp,s The columns are retained to form a load point matrix LP representing the area affected by the instantaneous trip switch operation. s The above calculation method is shown in equation (3):

[0028]

[0029] In step four, the expressions for the first type of load point matrix and the second type of load point matrix are shown in equation (4):

[0030]

[0031] Where ONE is a matrix with all elements equal to 1; LP s LP represents the load point matrix of the area affected by the operation of the instantaneous trip switch; T1 Represents the first type of load point matrix; LP T2 This represents the second type of load point matrix.

[0032] In step five, the correlation matrix expression of the load points and lines in the integrated energy system is shown in equation (5):

[0033]

[0034] Where, diag(Res PSPM) represents the diagonal matrix of the elements in the row where the power supply path matrix PSPM is located. E-2diag(Res PSPM) makes the diagonal elements of the path from the main power source to the power station be -1, and the rest be 1.

[0035] The method for forming the power supply path matrix of load points and lines in an integrated energy system is as follows:

[0036] The lines connected to the main power supply have no impact when the integrated energy system supplies power; therefore, the correlation matrix A is... es Delete the rows containing the auxiliary virtual lines of the line and other energy stations, and then delete all columns containing the energy stations. Invert the resulting matrix to obtain the power supply path matrix of load points and lines in the integrated energy system. Further modify the power supply path matrix: delete the columns containing the auxiliary virtual lines so that the lines connected to the main power source do not overlap with the paths from the energy stations to any load point. Therefore, add a column of all zeros corresponding to the line.

[0037] In step seven, the optimization objective is to minimize the total power loss of the power grid and maximize the total load supplied by the integrated energy system. The objective function expression of the integrated energy system power supply model is shown in equation (6):

[0038]

[0039] Among them, P LP C is the row vector of the load; k LPT4 For LP T4 The column corresponding to faulty line k in the middle;

[0040] For any line fault, the instantaneous trip switch state constraint expression is shown in equation (7):

[0041]

[0042] N es The power supply constraint expression for the integrated energy system is shown in equation (8):

[0043]

[0044] Wherein, matrix A only represents the connection relationship and does not consider the power flow direction; S k Let diag(C) be the column vector consisting of the states of each instantaneous trip switch when the k-th line fails. k Yi ) is Y i The diagonal matrix consisting of the elements in the column containing the faulty line k; diag(S k ) is S kA diagonal matrix composed of the elements; diag(C k LPT4 ) is C k LPT4 A diagonal matrix composed of the elements;

[0045] Since a fuse can only break a circuit by melting, it cannot be used as a quick-break switch to isolate and reduce load when there is no fault downstream. The states of the load points on both sides are the same, and the constraint expression is shown in equation (9):

[0046]

[0047] Where FUSE is a diagonal matrix. If the i-th instantaneous switch is a fuse, then the i-th diagonal element is 1, otherwise it is 0.

[0048] The energy balance constraint expression for the energy station is shown in equation (10):

[0049] C es P equ =P es,out -P es,in (10)

[0050] The output constraint expression of the energy station is shown in equation (11):

[0051] P equ,min ≤P equ ≤P equ,max (11)

[0052] Among them, P gas P represents the total gas input obtained by the energy station from the natural gas network. es P is a vector composed of inputs from various devices in the energy station. es,max Let P be a vector composed of the ratio of the upper limit of each device's output to the conversion coefficient. es,min A vector composed of the ratio of the lower limit of each device's output to the conversion coefficient;

[0053] By limiting the node air pressure and pipeline flow rate to a certain range, the constraint expressions for node air pressure and pipeline flow rate are shown in equations (12) and (13), respectively:

[0054] P node,min ≤P node ≤P node,max (12)

[0055] Q branch,min ≤Q branch ≤Q branch,max (13)

[0056] Among them, P node,max P is a vector consisting of the upper limits of the pressure values ​​at each node;node,min Q is a vector composed of the lower limits of the pressure values ​​at each node; branch,max Q is a vector composed of the upper limits of the flow rates of each pipe. branch,min A vector consisting of the lower limits of the flow rates of each pipe;

[0057] The flow rate and initial and final temperatures of each pipeline should be within the constraints. The pipeline flow rate constraint expression is shown in Equation (14), and the initial and final temperature constraint expression is shown in Equation (15).

[0058] M branch,min ≤M branch ≤M branch,max (14)

[0059]

[0060] Among them, M branch,max M is a vector composed of the upper limits of the flow rates of each pipe. branch,min T is a vector composed of the lower limits of the flow rates of each pipe. s,max Let T be a vector consisting of the upper temperature limits at the beginning of the pipe. s,min Let T be a vector consisting of the lower temperature limits at the beginning of the pipe. e,max Let T be a vector consisting of the upper temperature limits at the end of the pipe. e,min These are vectors composed of the lower temperature limits at the end of the pipe;

[0061] The constraint expression for the power supply model of the integrated energy system is shown in equation (16):

[0062]

[0063] In step nine, the expression for the fourth type of load point matrix is ​​shown in equation (17):

[0064]

[0065] Among them, Y i This is a comprehensive energy system supply coefficient matrix, which represents the supply coefficient to each load point when each line fails. The positions of its variables are related to LP. T4 Consistent, N es The number of integrated energy systems;

[0066] The expression for the third type of load point matrix is ​​shown in equation (18):

[0067] LP T3 =PSPM a -LP T4 (18).

[0068] In step ten, the reliability index of the integrated energy system is calculated as follows:

[0069] The expressions for the outage time and number of outages at each load point are shown in Equations (19) and (20), respectively, and the expression for the reliability index is shown in Equation (21).

[0070] T LP =(t op LP T2 Λ fr +LP T3 Λ fr T mttr +t es LP T4 Λ fr )ONE C (19)

[0071] F LP =(ONE-LP) T1 )Λ fr ONE C (20)

[0072]

[0073] Among them, T LP For the power outage time at each load point; F LP Number of power outages at each load point; Λ fr T is a diagonal matrix composed of failure rates; mttr t is a diagonal matrix consisting of average power outage times; op For the operation time of the instantaneous trip switch; ONE c t represents a column vector consisting entirely of 1s; es The integrated energy system's power supply operation time; SAIFI is the integrated energy system's average outage frequency, representing the average number of power outages for users in the distribution network within a year; SAIDI is the integrated energy system's average continuous outage duration, representing the average duration of power outages for users in the distribution network within a year; ENS is the integrated energy system's power shortage, representing the total power outage amount in the distribution network; ASAI is the integrated energy system's average power availability, representing the degree of normal power supply in the distribution network within a year; N LP N is a row vector consisting of the number of users at each equivalent load point; user This represents the total number of users.

[0074] The beneficial effects of this invention are:

[0075] The present invention provides an analytical calculation method for reliability assessment of integrated energy systems. It proposes a matrix-based power supply recovery model for integrated energy systems and uses a matrix form to calculate reliability indicators. The model exhibits high accuracy and can be used to guide improvements in distribution network reliability. After the integrated energy system is integrated, it can supply power to downstream areas during faults, making reliability assessment more complex and reducing efficiency. Simultaneously, it reduces repeated network searches. The power supply path model in this invention also uses a matrix form, avoiding the steps involved in searching for power supply path constraints in the integrated energy system and reducing computation time. Attached Figure Description

[0076] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0077] Figure 1 This is a flowchart of the analytical calculation method for comprehensive energy system reliability assessment of the present invention;

[0078] Figure 2 This is a wiring example diagram of the integrated energy system of the present invention;

[0079] Figure 3 This is a structural diagram of the energy station of the integrated energy system of the present invention. Detailed Implementation

[0080] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0081] An analytical calculation method for reliability assessment of an integrated energy system includes the following steps:

[0082] Step 1: Equip the distribution network with the switch as the boundary, and calculate the equivalent fault rate and equivalent repair time of each equivalent unit;

[0083] Step 2: Establish the correlation matrix between load points and lines, and inverse it to obtain the power supply path matrix;

[0084] The methods for solving the correlation matrix between load points and lines, as well as the power supply path matrix, are as follows:

[0085] In a distribution network, each equivalent load point can be considered as the start or end point of an adjacent equivalent line. A corresponding line-to-load point or energy station correlation matrix A can be established based on the connection relationships. e .

[0086] For a load point, if the power flow is from line i to load point j, then the correlation matrix A e (i,j)=1; if the power flow is from load point j to line i, then the correlation matrix A e (i,j) = -1; otherwise, take 0.

[0087] For the energy station, for ease of processing, we assume it is connected via an auxiliary virtual line, which can be analogous to the load point pair correlation matrix A. e Values. For the correlation matrix A... e Inverse the matrix, the power supply path matrix PSPM can be obtained. Elements of 1 in PSPM represent the power flow path from the main power source to the load point or energy station. Removing the columns containing auxiliary virtual lines and the rows containing energy stations from PSPM yields only the power supply path matrix PSPM for the load point and its corresponding lines. a .

[0088] Step 3: Calculate the matrix of the affected area after the instantaneous trip switch operates based on the position of the instantaneous trip switch;

[0089] The matrix of the affected area after the instantaneous trip switch trips and disconnects is formed as follows:

[0090] PSPM matrix representing the path relationship between circuits and instantaneous circuit breakers l,s And the matrix S from the main power supply to all instantaneous trip switches in each line p The calculation method is shown in equation (1):

[0091]

[0092] In the formula, S bf Let S be a diagonal matrix consisting of all instantaneous switches. If the i-th instantaneous switch is a circuit breaker or a fuse, then S bf (i,i) = 1, otherwise 0;

[0093] When there are other instantaneous switches downstream of a disconnected instantaneous switch, this instantaneous switch should remain in its original state, forming a matrix S after subtracting all downstream instantaneous switches. a If matrix S a If the value is negative or 0, it means the original state should be maintained; matrix S a By setting the negative value to 0, we can obtain matrix S. c Matrix S c Each row represents the instantaneous trip switch that actually disconnected after a fault in the line; elements that are 1 represent the actual trip switches that disconnected. disconnect Instantaneous disconnect switch; matrix Sa Sum of matrix S c The calculation process is shown in equation (2):

[0094]

[0095] In the formula, E is the identity matrix;

[0096] The load point and the instantaneous trip switch have the same topological relationship as the load point and the line. The matrix PSPM represents the path relationship between the load point and the instantaneous trip switch. lp,s Power supply path matrix (PSPM) with load points and lines a Equal to the actual value after a line fault. disconnect The matrix PSPM corresponding to the instantaneous trip switch lp,s By retaining the columns in the matrix, an equivalent load point matrix LP representing the area affected by the instantaneous trip switch being disconnected can be formed. s The above process is shown in equation (3):

[0097]

[0098] Step 4: Obtain the first type of load point matrix and the second type of load point matrix after the fault;

[0099] The expressions for the first type of load point matrix and the second type of load point matrix are shown in equation (4):

[0100]

[0101] In the formula, ONE is a matrix with all elements equal to 1; LP s This represents the load point matrix indicating the area affected by the instantaneous trip switch opening; LP T1 Represents the first type of load point matrix; LP T2 This represents the second type of load point matrix.

[0102] Step 5: Reverse the power flow of the power supply path from the main power source to the energy station, and calculate the correlation matrix of the load points and lines and the power supply path matrix in the integrated energy system.

[0103] The correlation matrix expression of the load points and lines supplying power in the integrated energy system is shown in equation (5):

[0104]

[0105] In the formula, diag(Res PSPM) represents the diagonal matrix of the elements in the row where the power supply path matrix PSPM is located. E-2diag(Res PSPM) makes the diagonal elements of the path from the main power source to the power station be -1, and the rest be 1.

[0106] The process of forming the power supply path matrix of load points and lines in an integrated energy system is as follows:

[0107] The lines connected to the main power supply have no impact when the integrated energy system supplies power; therefore, the correlation matrix A is... es Delete the rows containing the auxiliary virtual lines of the line and other energy stations, and then delete all columns containing the energy stations. Inverting the resulting matrix yields the power supply path matrix for load points and lines in the integrated energy system. Further refine this power supply path matrix: delete the columns containing auxiliary virtual lines to ensure that the lines connected to the main power source do not overlap with the paths from the energy stations to any load point; therefore, add a column of all zeros corresponding to the line.

[0108] Step 6: Assume i represents the equivalent circuit and 1 represents the fault, let i = 1;

[0109] Step 7: Determine the objective function and constraints of the integrated energy system power supply model when the i-th equivalent line fault occurs, and solve the integrated energy system power supply model for the i-th equivalent line fault.

[0110] Among them, the optimization objective is to minimize the total power loss of the power grid, that is, to maximize the total load supplied by the integrated energy system. The objective function expression of the integrated energy system power supply model is shown in equation (6):

[0111]

[0112] In the formula, P LP C is the row vector of the load; k LPT4 For LP T4 The column corresponding to faulty line k in the middle;

[0113] For any equivalent line fault, the instantaneous trip switch state constraint expression is shown in equation (7):

[0114]

[0115] N es The power supply constraint expression for the integrated energy system is shown in equation (8):

[0116]

[0117] Wherein, matrix A only represents the connection relationship and does not consider the power flow direction; S k For the k-th equivalent line fault, the column vector composed of the switch states; diag(C k Yi ) is Y i The diagonal matrix consisting of the elements in the column containing the faulty line k; diag(S k ) is S k A diagonal matrix composed of the elements; diag(C k LPT4) is C k LPT4 A diagonal matrix composed of the elements;

[0118] Since a fuse can only break a circuit by melting, it cannot be used as a switch to isolate and reduce load when there is no fault downstream. The states of the load points on both sides are consistent. The constraint expression is shown in equation (9):

[0119]

[0120] In the formula, FUSE is a diagonal matrix. If the i-th instantaneous switch is a fuse, then the i-th diagonal element is 1, otherwise it is 0.

[0121] The energy balance constraint expression for the energy station is shown in equation (10):

[0122] C es P equ =P es,out -P es,in (10)

[0123] The output constraint expression of the energy station is shown in equation (11):

[0124] P equ,min ≤P equ ≤P equ,max (11)

[0125] Among them, P gas P represents the total gas input obtained by the energy station from the natural gas network. es P is a vector composed of inputs from various devices in the energy station. es,max Let P be a vector composed of the ratio of the upper limit of each device's output to the conversion coefficient. es,min A vector composed of the ratio of the lower limit of each device's output to the conversion coefficient;

[0126] To ensure the safe and stable operation of the natural gas network, the node gas pressure and pipeline flow rate need to be limited within a certain range. The node gas pressure constraint expression and the pipeline flow rate constraint expression are shown in Equation (12) and Equation (13), respectively:

[0127] P node,min ≤P node ≤P node,max (12)

[0128] Q branch,min ≤Q branch ≤Q branch,max (13)

[0129] Among them, P node,max P is a vector consisting of the upper limits of the pressure values ​​at each node; node,min Q is a vector composed of the lower limits of the pressure values ​​at each node;branch,max Q is a vector composed of the upper limits of the flow rates of each pipe. branch,min A vector consisting of the lower limits of the flow rates of each pipe;

[0130] To ensure the stable operation of the heating and cooling network, the flow rate and the initial and final temperatures of each pipe must be within the constraints. The expression for the pipe flow rate constraint is shown in equation (14), and the expression for the initial and final temperature constraint is shown in equation (15).

[0131] M branch,min ≤M branch ≤M branch,max (14)

[0132]

[0133] Among them, M branch,max M is a vector composed of the upper limits of the flow rates of each pipe. branch,min T is a vector composed of the lower limits of the flow rates of each pipe. s,max Let T be a vector consisting of the upper temperature limits at the beginning of the pipe. s,min Let T be a vector consisting of the lower temperature limits at the beginning of the pipe. e,max Let T be a vector consisting of the upper temperature limits at the end of the pipe. e,min These are vectors composed of the lower temperature limits at the end of the pipe;

[0134] The objective expression for the model can be obtained as shown in equation (6):

[0135]

[0136] The constraint expression for the power supply model of the integrated energy system is shown in equation (16):

[0137]

[0138] Step 8: Once all equivalent circuit faults have been calculated, proceed to Step 9; otherwise, i = i + 1 and jump to Step 7.

[0139] Step 9: Calculate the third type of load point matrix and the fourth type of load point matrix;

[0140] The expression for the fourth type of load point matrix is ​​shown in equation (17):

[0141]

[0142] In the formula, Y i This is a comprehensive energy system supply coefficient matrix, which represents the supply coefficient to each load point when each line fails. The positions of its variables are related to LP. T4 Consistent, N es The number of integrated energy systems;

[0143] The expression for the third type of load point matrix is ​​shown in equation (18):

[0144] LP T3 =PSPM a -LP T4 (18).

[0145] Step 10: Calculate the reliability index of the integrated energy system;

[0146] The calculation methods for the various reliability indicators of the integrated energy system are as follows:

[0147] The expressions for the power outage time and number of power outages at each load point are shown in Equations (19) and (20), respectively, and the system reliability index is shown in Equation (21):

[0148] T LP =(t op LP T2 Λ fr +LP T3 Λ fr T mttr +t es LP T4 Λ fr )ONE C (19)

[0149] F LP =(ONE-LP) T1 )Λ fr ONE C (20)

[0150]

[0151] In the formula, T LP For each equivalent load point, the power outage time is F. LP The number of power outages at each equivalent load point; Λ fr T is a diagonal matrix composed of equivalent failure rates; mttr The diagonal matrix consisting of equivalent average power outage times; t op For the operation time of the instantaneous trip switch; ONE c t represents a column vector consisting entirely of 1s; es The integrated energy system's power supply operation time; SAIFI is the integrated energy system's average outage frequency, representing the average number of power outages for users in the distribution network within a year; SAIDI is the integrated energy system's average continuous outage duration, representing the average duration of power outages for users in the distribution network within a year; ENS is the integrated energy system's power shortage, representing the total power outage amount in the distribution network; ASAI is the integrated energy system's average power availability, representing the degree of normal power supply in the distribution network within a year; N LPN is a row vector consisting of the number of users at each equivalent load point; user This represents the total number of users.

[0152] To verify the performance advantages of the proposed integrated energy system power supply matrix model, two calculation methods were selected to compare the calculation speed and accuracy of the reliability index.

[0153] Method 1: The power distribution network uses the main power supply path matrix method to obtain the first type of load point and the second type of load point. The integrated energy system power supply restoration model adopts the step-by-step modeling method and does not use the matrix form.

[0154] Method 2: Using the integrated energy system power supply model proposed in this invention, the distribution network uses the main power supply path matrix method to obtain the first type of load point and the second type of load point, and the integrated energy system power supply recovery model is modeled in matrix form.

[0155] Based on the impact of the fault on the load points, the load points can be divided into the following four categories: Category 1 load points are not affected by the fault; these are load points that do not lose power after the upstream switch in the fault area operates. Category 2 load points are restored to power after the fault is isolated; these load points are affected by the operating sequence of the circuit breaker and the quick-break switch, and there will be a brief power outage during the fault isolation process. This category includes load points between the upstream circuit breaker and the quick-break switch used to isolate the fault. Category 3 load points are completely affected by the fault; these load points can only regain power after the fault is repaired, and they remain in a power outage state during the duration of the fault. Category 4 load points are load points that are restored to power by the integrated energy system after the fault is isolated; these load points are in a power outage state before being powered by the integrated energy system.

[0156] To verify the accuracy of the proposed model, the performance metrics of different calculation methods were compared, and the calculation results are shown in Table 1. The optimized model was solved using MATLAB calling the SCIP solver. To avoid the influence of randomness, the calculation time in the table is the average of 30 calculations.

[0157] Table 1 Comparison of performance indicators of different modeling methods

[0158]

[0159] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An analytical calculation method for reliability assessment of an integrated energy system, characterized in that: The specific steps are as follows: Step 1: Equip the distribution network with the switch as the boundary, and calculate the equivalent fault rate and equivalent repair time of each equivalent unit; Step 2: Establish the correlation matrix between load points and lines, and inverse it to obtain the power supply path matrix; Step 3: Calculate the matrix of the affected area after the instantaneous trip switch operates based on the position of the instantaneous trip switch; Step 4: Obtain the first type of load point matrix and the second type of load point matrix after the fault; Step 5: Reverse the power flow of the power supply path from the main power source to the energy station, and calculate the correlation matrix of the load points and lines and the power supply path matrix in the integrated energy system. Step 6: Assume i represents the line and 1 represents the fault, let i = 1; Step 7: Determine the objective function and constraints of the integrated energy system power supply model when the i-th line fails, and solve the integrated energy system power supply model when the i-th line fails. Step 8: Once all line faults have been calculated, proceed to Step 9; otherwise, i = i + 1 and jump to Step 7. Step 9: Calculate the third type of load point matrix and the fourth type of load point matrix; Step 10: Calculate the reliability index of the integrated energy system; In step seven, the optimization objectives are to minimize the total power loss of the power grid and maximize the total load supplied by the integrated energy system. The objective function expression of the integrated energy system power supply model is shown in equation (6): （6） Among them, P LP C is the row vector of the load; k LPT4 For LP T4 The column corresponding to faulty line k in the middle; For any line fault, the instantaneous trip switch state constraint expression is shown in equation (7): （7） N es The power supply constraint expression for the integrated energy system is shown in equation (8): （8） Wherein, matrix A only represents the connection relationship and does not consider the power flow direction; S k Let diag(C) be the column vector consisting of the states of each instantaneous trip switch when the k-th line fails. k Yi ) is Y i The diagonal matrix consisting of the elements in the column containing the faulty line k; diag(S k ) is S k A diagonal matrix composed of the elements; diag(C k LPT4 ) is C k LPT4 A diagonal matrix composed of the elements; Since a fuse can only break a circuit by melting, it cannot be used as a quick-break switch to isolate and reduce load when there is no fault downstream. The states of the load points on both sides are consistent. The constraint expression is shown in equation (9): （9） Where FUSE is a diagonal matrix. If the i-th instantaneous switch is a fuse, then the i-th diagonal element is 1, otherwise it is 0. The energy balance constraint expression for the energy station is shown in equation (10): （10） The output constraint expression of the energy station is shown in equation (11): （11） Among them, P gas P represents the total gas input obtained by the energy station from the natural gas network. es P is a vector composed of inputs from various devices in the energy station. es,max Let P be a vector composed of the ratio of the upper limit of each device's output to the conversion coefficient. es,min A vector composed of the ratio of the lower limit of each device's output to the conversion coefficient; By limiting the node air pressure and pipeline flow rate to a certain range, the constraint expressions for the node air pressure and pipeline flow rate are shown in equations (12) and (13), respectively: （12） （13） Among them, P node,max P is a vector consisting of the upper limits of the pressure values ​​at each node. node,min Q is a vector composed of the lower limits of the pressure values ​​at each node; branch,max Q is a vector composed of the upper limits of the flow rates of each pipe. branch,min A vector consisting of the lower limits of the flow rates of each pipe; The flow rate and the initial and final temperatures of each pipeline should be within the constraints. The pipeline flow rate constraint expression is shown in Equation (14), and the initial and final temperature constraint expression is shown in Equation (15). (14) (15) Among them, M branch,max M is a vector consisting of the upper limits of the flow rates of each pipe. branch,min T is a vector composed of the lower limits of the flow rates of each pipe. s,max Let T be a vector consisting of the upper temperature limits at the beginning of the pipe. s,min Let T be a vector consisting of the lower temperature limits at the beginning of the pipe. e,max Let T be a vector consisting of the upper temperature limits at the end of the pipe. e,min These are vectors composed of the lower temperature limits at the end of the pipe; The constraint expression for the power supply model of the integrated energy system is shown in equation (16): （16）。 2. The analytical calculation method for reliability assessment of an integrated energy system according to claim 1, characterized in that: In step two, the methods for solving the correlation matrix of load points and lines, as well as the power supply path matrix, are as follows: In a distribution network, each load point is considered as the start or end point of an adjacent line. A corresponding correlation matrix A between the line and the load point is established based on the connection relationships. e If the power flow is from line i to load point j, then the correlation matrix A e (i,j)=1; if the power flow is from load point j to line i, then the correlation matrix A e (i,j)=-1; otherwise, take 0; If the energy station is connected via an auxiliary virtual line, then the correlation matrix A... e Inverting the power supply path matrix (PSPM) yields the power supply path matrix. Elements of 1 in PSPM represent the power flow path from the main power source to the load point. Removing the columns containing auxiliary virtual lines and the rows containing energy stations from PSPM yields the power supply path matrix PSPM for both the load point and the lines. a .

3. The analytical calculation method for reliability assessment of an integrated energy system according to claim 1, characterized in that: In step three, the matrix formation method for the affected area after the instantaneous trip switch operation is as follows: PSPM matrix representing the path relationship between circuits and instantaneous circuit breakers l,s And the matrix S from the main power supply to all instantaneous trip switches in each line p The calculation method is shown in equation (1): （1） Among them, S bf Let S be a diagonal matrix consisting of all instantaneous trip switches. If the i-th instantaneous trip switch is a circuit breaker or a fuse, then S bf (i,i)=1, otherwise 0; When there are other instantaneous switches downstream of the activated instantaneous switch, this instantaneous switch should remain in its original state, forming a matrix S after subtracting all downstream instantaneous switches. a If matrix S a If the value is negative or 0, it means the original state should be maintained; matrix S a The negative values ​​are taken as 0 to obtain matrix S. c Matrix S c Each row in matrix S represents the instantaneous trip switch that actually tripped after a line fault. Elements that are 1 represent the instantaneous trip switches that actually tripped. a S and matrix S c The calculation method is shown in equation (2): （2） Where E is the identity matrix; The load point and the instantaneous trip switch have the same topological relationship as the load point and the line. The matrix PSPM represents the path relationship between the load point and the instantaneous trip switch. lp,s Power supply path matrix (PSPM) with load points and lines a Equal to the matrix PSPM corresponding to the instantaneous trip switch that actually operates after a line fault. lp,s The columns are retained to form a load point matrix LP representing the area affected by the instantaneous trip switch operation. s The above calculation method is shown in equation (3): （3）。 4. The analytical calculation method for reliability assessment of an integrated energy system according to claim 1, characterized in that: In step four, the expressions for the first type of load point matrix and the second type of load point matrix are shown in equation (4): （4） Where ONE is a matrix with all elements equal to 1; LP s LP represents the load point matrix of the area affected by the operation of the instantaneous trip switch; T1 Represents the first type of load point matrix; LP T2 This represents the second type of load point matrix.

5. The analytical calculation method for reliability assessment of an integrated energy system according to claim 1, characterized in that: In step five, the correlation matrix expression of the load points and lines in the integrated energy system is shown in equation (5): （5） Where, diag(Res PSPM) represents the diagonal matrix of the elements in the row where the power supply path matrix PSPM is located. E-2diag(Res PSPM) makes the diagonal elements of the path from the main power source to the power station be -1, and the rest be 1. The method for forming the power supply path matrix of load points and lines in an integrated energy system is as follows: The lines connected to the main power supply have no impact when the integrated energy system supplies power; therefore, the correlation matrix A is... es Delete the rows containing the auxiliary virtual lines of the line and other energy stations, and then delete all columns containing the energy stations. Invert the resulting matrix to obtain the power supply path matrix of load points and lines in the integrated energy system. Further modify the power supply path matrix: delete the columns containing the auxiliary virtual lines so that the lines connected to the main power source do not overlap with the paths from the energy stations to any load point. Therefore, add a column of all zeros corresponding to the line.

6. The analytical calculation method for reliability assessment of an integrated energy system according to claim 1, characterized in that: In step nine, the expression for the fourth type of load point matrix is ​​shown in equation (17): （17） Among them, Y i This is a comprehensive energy system supply coefficient matrix, which represents the supply coefficient to each load point when each line fails. The positions of its variables are related to LP. T4 Consistent, N es The number of integrated energy systems; The expression for the third type of load point matrix is ​​shown in equation (18): （18）。 7. The analytical calculation method for reliability assessment of an integrated energy system according to claim 1, characterized in that: In step ten, the reliability index of the integrated energy system is calculated as follows: The expressions for the outage time and number of outages at each load point are shown in Equations (19) and (20), respectively, and the expression for the reliability index is shown in Equation (21). （19） （20） （21） Among them, T LP For the power outage time at each load point; F LP Number of power outages at each load point; Λ fr T is a diagonal matrix composed of failure rates; mttr t is a diagonal matrix consisting of average power outage times; op For the operation time of the instantaneous trip switch; ONE c t represents a column vector consisting entirely of 1s; es The integrated energy system's power supply operation time; SAIFI is the integrated energy system's average outage frequency, representing the average number of power outages for users in the distribution network within a year; SAIDI is the integrated energy system's average continuous outage duration, representing the average duration of power outages for users in the distribution network within a year; ENS is the integrated energy system's power shortage, representing the total power outage amount in the distribution network; ASAI is the integrated energy system's average power availability, representing the degree of normal power supply in the distribution network within a year; N LP N is a row vector consisting of the number of users at each load point; user This represents the total number of users.

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