A daily specified gas transmission optimization method for natural gas pipeline networks considering user characteristics

Abstract

The present invention provides a daily specified gas transmission optimization method for natural gas pipelines considering user characteristics. The method includes: generating the constraint conditions of the model based on the structural parameters of the natural gas pipeline network, user demand parameters, and compressor station parameters; generating a gas transmission optimization model for the natural gas pipeline network considering user characteristics according to the constraint conditions and the objective function of minimizing compressor energy consumption; and solving the gas transmission optimization model for the natural gas pipeline network considering user characteristics to output the gas transmission optimization scheme for the natural gas pipeline network. This method can select appropriate gas transmission modes for different types of natural gas users, improve the gas supply accuracy of users and the operation efficiency of the natural gas pipeline network caused by differences in user gas consumption characteristics. At the same time, it reduces the energy consumption of compressor stations during the operation of the pipeline network, and has guiding significance for the daily scheduling management and overall operation of pipeline network companies.

Description

Technical Field

[0001] The present invention relates to the field of optimization of natural gas pipeline network sub - transmission, and particularly to a daily specified sub - transmission optimization method for natural gas pipeline network considering user characteristics. Background Technique

[0002] Daily specification refers to the daily gas consumption demand plan declared by the end - users of the natural gas pipeline network to the natural gas shipper, which is a definite value. And daily specified sub - transmission is a transient process in which, according to the gas - using rules of different types of natural gas users, different sub - transmission modes are adopted to sub - transmit the daily specified amount of natural gas to users at different time periods within a day. As natural gas in China is gradually applied in various fields, there are great differences in the gas - using characteristics of downstream users of the natural gas pipeline network. If manual daily specified sub - transmission is carried out for user demands, it will consume a large amount of manpower and the accuracy of sub - transmission control is not high. To improve the pipeline operation efficiency and the level of user sub - transmission control, it is necessary to adopt different sub - transmission modes according to the differences in the gas - using characteristics of natural gas users, so as to improve the management of natural gas users.

[0003] At present, sub - transmission modes are mostly used in the macro - control of natural gas pipeline network scheduling, and there is less research on the optimization of natural gas pipeline network sub - transmission using mathematical models at the micro - level. Therefore, in order to improve the precise management of gas supply to natural gas users, it is very necessary to introduce sub - transmission modes into the daily specified optimization research of natural gas pipeline network. Based on this, the present invention proposes a daily specified sub - transmission optimization method for natural gas pipeline network considering user characteristics. This method can select appropriate sub - transmission modes for different types of natural gas users, improve the accuracy of gas supply to users caused by differences in user gas - using characteristics and the operation efficiency of natural gas pipeline network. At the same time, it reduces the energy consumption of compressor stations during the operation of the pipeline network. Summary of the Invention

[0004] To solve the problem of great difficulty in the management of daily specified sub - transmission of natural gas pipeline network, the present invention provides the following technical solutions:

[0005] A daily specified sub - transmission optimization method for natural gas pipeline network considering user characteristics provided by the present invention includes:

[0006] S1: Generate the constraint conditions of the model according to the structural parameters of the natural gas pipeline network, user demand parameters, and compressor station parameters;

[0007] S2: Generate a sub - transmission optimization model for natural gas pipeline network considering user characteristics according to the constraint conditions and the objective function of minimizing compressor energy consumption;

[0008] S3: Solve the sub - transmission optimization model for natural gas pipeline network considering user characteristics and output the sub - transmission optimization plan for the natural gas pipeline network.

[0009] In one embodiment, the natural gas user flow distribution modes considered in the present invention include: the arrival-volume stop-transmission method, the remaining hourly average volume method, the improved remaining hours method, and the weight coefficient method;

[0010] The so-called arrival-volume stop-transmission method means that the system monitors the total gas transmission volume of the current user in real time. When the gas transmission volume reaches 95% of the daily specified volume, a high alarm is issued. When the gas transmission volume reaches 99% of the daily specified distribution volume, a very high alarm is issued. After completing the daily specified distribution volume issued on the same day, the gas transmission to downstream users is stopped;

[0011] The so-called remaining hourly average volume method means that the daily specified distribution volume is supplied according to the average flow rate in t time periods. After the first hour of transmission, the remaining gas supply volume is calculated, and the remaining gas supply volume is evenly distributed according to the remaining hours, one by one until the last hour, until the daily distribution is completed;

[0012] The so-called improved remaining hours method means that the distribution process is divided into two stages. In the first stage, constant-pressure distribution is adopted; when the time for distributing natural gas reaches a preset threshold, it enters the second stage, that is, the remaining natural gas distribution plan is adjusted to the remaining hourly average volume method for transmission. After each hour of transmission, the remaining gas supply volume is calculated, and the remaining gas supply volume is evenly distributed according to the remaining time until the daily distribution is completed;

[0013] The so-called weight coefficient method means that the daily specified volume of the user is divided into t time periods. According to the gas consumption law in the past n days, the uneven coefficient of each time period on the same day is calculated by weighted average, and the set value of the instantaneous gas transmission flow rate in each time period is the product of the daily natural gas distribution volume and the uneven coefficient of the current time period.

[0014] In one embodiment, the structural parameters of the natural gas pipeline network described in step S1 include the gas source location, the compressor station location, the distribution station location, the user location, and the pipeline length; the user demand parameters include: the daily specified declared flow rate, the daily specified changed flow rate; the compressor station parameters include: the number of compressors, the compressor power range, and the compressor speed range.

[0015] In one embodiment, the constraint conditions described in step S1 include: the daily specified volume constraint of natural gas users, the distribution mode constraint, the node parameter constraint, and the compressor operation constraint;

[0016] The daily specified volume constraint of natural gas users is:

[0017]

[0018] In the formula, Q t,u is the natural gas distribution volume of user u within time layer t; Q u is the daily specified transmission volume of natural gas user u;

[0019] The sub - transmission mode constraints include: the control logic constraint of the volume - reached stop - transmission method, the control logic constraint of the remaining average hourly volume method, the control logic constraint of the improved remaining hours method, and the control logic constraint of the weight coefficient method;

[0020] The control logic constraint of the volume - reached stop - transmission method uses binary variables to control the gas supply to users. When the gas supply to user u does not reach the daily specified demand within time layer t, θ t = 1, θ t+1 = 1; when it reaches the daily specification at time layer t, θ t = 1, θ t+1 = 0, and the constraint is:

[0021] θ t+1 -θ t ≤0

[0022] Q t,u ≤Q t,u ·θ t

[0023] Q t,u ≥θ t

[0024] In the formula, θ t is the binary variable of the volume - reached stop - transmission method within time layer t;

[0025] The control logic constraint of the remaining average hourly volume method is:

[0026]

[0027] In the formula, T is the total number of time layers;

[0028] The control logic constraint of the improved remaining hours method is:

[0029]

[0030]

[0031]

[0032] Q u = Q1 + Q2

[0033] In the formula, Y is the preset number of time layers; Q1 is the natural gas transmission volume when reaching the preset number of time layers Y; v t,u is the binary variable of the improved remaining hours method; is the natural gas transmission volume within a single time layer when using the average transmission volume; Q2 is the total natural gas transmission volume of the remaining time layers;

[0034] The control logic constraint of the weight coefficient method is:

[0035] Q t,u = Q u ·x t,u

[0036] where x t,u is the non-uniformity coefficient of user u within time layer t;

[0037] The node parameter constraints include: node flow constraint, node pressure drop constraint, and node pressure constraint;

[0038] The node flow constraint is:

[0039]

[0040]

[0041] where β t,i is the flow direction variable of node i within time layer t. When β t,i = 1, the flow enters the node; when β t,i = 0, the flow exits the node; Q t,i is the absolute value of the flow into (or out of) node i within time layer t; β t,c is the flow direction variable of compressor station c within time layer t; Q t,c is the absolute value of the flow into (or out of) compressor station c within time layer t; β t,l is the flow direction variable of pipeline l within time layer t; Q t,l is the absolute value of the flow into (or out of) pipeline l within time layer t; is the minimum allowable gas distribution volume of distribution station d within time layer t; Q t,d is the gas distribution volume of distribution station d within time layer t; is the maximum allowable gas distribution volume of distribution station d within time layer t;

[0042] The node pressure constraint is:

[0043]

[0044] where is the minimum allowable pressure of node i within time layer t; P t,i is the pressure of node i within time layer t; is the maximum allowable pressure of node i within time layer t;

[0045] The node pressure drop constraint relationship is:

[0046]

[0047] where Q i,l is the volume flow rate of natural gas in node i - pipeline l; di,l is the inner diameter of pipeline l at node i; P i|(i,l) is the starting pressure of pipeline l at node i; P l|(i,l) is the ending pressure of pipeline l at node i; Z is the natural gas compression factor; Δ is the relative density of natural gas; T i,l is the average thermodynamic temperature of natural gas in pipeline l at node i; L i,l is the length of pipeline l at node i;

[0048] The described natural gas flow constraint is:

[0049]

[0050]

[0051]

[0052] In the formula, P g is the natural gas pressure; t g is the natural gas flow time; M g is the natural gas mass flow rate; S is the cross-sectional area of the pipeline; a g is the adiabatic propagation speed of the gas; λ g is the friction coefficient of the natural gas pipeline network; ρ g is the natural gas density; R is the gas constant;

[0053] The described compressor constraints include: compressor pressure constraint, compressor speed constraint, compressor inlet flow constraint, compressor power constraint, compressor start-stop constraint;

[0054] The described compressor pressure constraint is:

[0055]

[0056]

[0057]

[0058] In the formula, is the minimum allowable inlet pressure of compressor j; is the inlet pressure of compressor j at time layer t; is the maximum allowable discharge pressure of compressor j; is the discharge pressure of compressor j at time layer t; ε t,j is the compression ratio of compressor j;

[0059] The described compressor speed constraint is:

[0060]

[0061] Wherein, is the minimum allowable speed of compressor j; r t,j is the speed of compressor j within time layer t; is the maximum allowable speed of compressor j;

[0062] The intake flow constraint of the compressor is:

[0063]

[0064]

[0065]

[0066] Wherein, is the minimum allowable intake flow of compressor j; q t,j is the intake flow of compressor j within time layer t; is the maximum allowable intake flow of compressor j; A su , B su , C su , A st , B st , C st are the compressor characteristic parameters;

[0067] The power constraint of the compressor is:

[0068]

[0069]

[0070] Wherein, N t,j is the operating power of compressor j within time layer t; k is the specific heat of the gas, is the gas compression factor under the suction condition of compressor j; is the gas compression factor under the discharge condition of compressor j; η j is the operating efficiency of compressor j; is the minimum allowable operating power of compressor j; is the maximum allowable operating power of compressor j;

[0071] The constraint on the number of compressors started in the compressor station is:

[0072]

[0073] Wherein, e t,c,j is the operating variable of compressor j in compressor station c within time layer t, which is 1 when the compressor is in the started state and 0 otherwise; φ c is the number of compressors in compressor station c;

[0074] The compressor start-stop constraint is as follows:

[0075]

[0076]

[0077] In the formula, τ t,c,j is the operating state variable of compressor j in compressor station c within time layer t. When the compressor is in the operating state, τ t,c,j = 1. When the compressor is in the operating state, τ t,c,j = 0; B is the shortest continuous operating duration of the compressor, and b is the shortest continuous shutdown time of the compressor.

[0078] In one embodiment, the objective function described in step S2 is to minimize the compressor energy consumption cost, and the objective function relationship is:

[0079]

[0080] In the formula, f is the compressor energy consumption cost; t is the operating time of a single time layer; M t,j is the inlet mass flow rate of compressor j within time layer t; H t,j is the head of compressor j within time layer t; η j is the adiabatic efficiency of compressor j; is the mechanical efficiency of compressor j; δ c is the electricity price of compressor station c.

[0081] In one embodiment, the natural gas pipeline subtransmission optimization model considering user characteristics described in S3 belongs to a transient optimization model. When solving this model, the independent time layer method is adopted, that is, the time from 0 to T is divided into t time layers. The operation of the pipeline network within each time layer is regarded as a steady-state operation, and the mathematical average value of the compressor energy consumption at the start time and end time of each time layer is used to replace the compressor energy consumption within each time layer in the objective function. The relationship is:

[0082]

[0083] In the formula, f(t) is the total compressor energy consumption of the target pipeline network within time layer t.

[0084] In one embodiment, the natural gas pipeline subtransmission optimization scheme described in S3 includes: compressor operation energy consumption, compressor operation scheme, and subtransmission gas volume of each user period.

[0085] Advantages of the present invention: Compared with the prior art, the method of the present invention is based on the split transportation mode theory, takes into account the characteristics of natural gas users, and constructs an optimization model for the split transportation of natural gas pipelines with the minimum compressor operation energy consumption as the objective function. The optimization result of this model can select appropriate split transportation modes for different types of natural gas users, improve the accuracy of user gas supply and the operation efficiency of natural gas pipelines caused by differences in user gas consumption characteristics. At the same time, it reduces the energy consumption of compressor stations during the operation of the pipeline network, which has guiding significance for the daily scheduling management and overall operation of pipeline network companies and is an effective method to solve the daily designated split transportation problem of natural gas pipelines. Brief Description of the Drawings

[0086] Figure 1 It is a flow chart of the present invention;

[0087] Figure 2 It is a structure diagram of natural gas pipeline network E in Application Example 1 of the present invention;

[0088] Figure 3 It is the daily designated quantity of users in Application Example 1 of the present invention;

[0089] Figure 4 It is a structure diagram of a domestic natural gas pipeline network in Application Example 2 of the present invention;

[0090] Figure 5 It is the daily designated quantity of users in Application Example 2 of the present invention;

[0091] Figure 6 It is the number of compressor units started at different time levels in Application Example 2 of the present invention;

[0092] Figure 7 It is the rotational speed of the compressor at different time levels in Application Example 2 of the present invention;

[0093] Figure 8 It is the split transportation gas volume of each natural gas user at different time levels in Application Example 2 of the present invention. Detailed Embodiments

[0094] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0095] As Figure 1 shown, a method for optimizing the daily designated split transportation of a natural gas pipeline network considering user characteristics provided by the present invention includes the following steps:

[0096] S1: Generate the constraint conditions of the model based on the structural parameters of the natural gas pipeline network, user demand parameters, and compressor station parameters;

[0097] S2: Generate an optimized sub - transmission model for the natural gas pipeline network considering user characteristics based on the constraint conditions and the objective function of minimizing compressor energy consumption;

[0098] S3: Solve the optimized sub - transmission model for the natural gas pipeline network considering user characteristics and output the optimized sub - transmission plan for the natural gas pipeline network.

[0099] In one embodiment, the sub - transmission modes of natural gas user flow considered in the present invention include: the arrival - volume stop - transmission method, the remaining hourly average volume method, the improved remaining hours method, and the weight coefficient method;

[0100] The arrival - volume stop - transmission method refers to that the system monitors the total gas transmission volume of the current user in real time. When the gas transmission volume reaches 95% of the daily specified volume, a high - level alarm is issued. When the gas transmission volume reaches 99% of the daily specified sub - transmission volume, a very - high - level alarm is issued. After completing the daily specified sub - transmission volume issued on the current day, the gas transmission to downstream users is stopped;

[0101] The remaining hourly average volume method refers to supplying gas according to the average flow rate in t time periods for the daily specified sub - transmission volume. After the first hour of gas transmission, calculate the remaining gas supply volume, and the remaining gas supply volume is evenly distributed according to the remaining hours, and is distributed one by one until the last hour to complete the daily sub - transmission;

[0102] The improved remaining hours method refers to dividing the sub - transmission process into two stages. In the first stage, constant - pressure sub - transmission is adopted; when the time of sub - transmitting natural gas reaches a preset threshold, it enters the second stage, that is, adjusting the remaining natural gas sub - transmission plan to the remaining hourly average volume method for transmission. After each hour of gas transmission, calculate the remaining gas supply volume, and the remaining gas supply volume is evenly distributed according to the remaining time until the daily sub - transmission is completed;

[0103] The weight coefficient method refers to dividing the gas consumption of a user in a day into t time periods. According to the gas - using rules in the past n days, calculate the uneven coefficient of each time period on the current day through weighted average, and the set value of the instantaneous gas transmission flow rate in each time period is the product of the daily natural gas distribution volume and the uneven coefficient of the current time period.

[0104] In one embodiment, the structural parameters of the natural gas pipeline network described in step S1 include the gas source location, compressor station location, sub - transmission station location, user location, and pipeline length; the user demand parameters include: the daily specified declared flow rate, the daily specified changed flow rate; the compressor station parameters include: the number of compressors, the compressor power range, and the compressor speed range.

[0105] In one embodiment, the constraint conditions described in step S1 include: the daily specified volume constraint of natural gas users, the sub - transmission mode constraint, the node parameter constraint, and the compressor operation constraint;

[0106] The specified daily quantity constraint relation for natural gas users is as follows:

[0107]

[0108] In the formula, Q t,u is the sub - transmission volume of natural gas for user u within time layer t; Q u is the specified daily transmission volume for natural gas user u;

[0109] The sub - transmission mode constraints include: arrival - volume stop - transmission method control logic constraint, remaining average hourly volume method control logic constraint, improved remaining hours method control logic constraint, and weight coefficient method control logic constraint;

[0110] The arrival - volume stop - transmission method control logic constraint uses binary variables to control the gas supply volume for users. When the gas supply volume for user u within time layer t does not reach the daily specified demand, θ t = 1, θ t+1 = 1; when it reaches the daily specification within time layer t, θ t = 1, θ t+1 = 0, and the constraint is:

[0111] θ t+1 -θ t ≤0 t∈T (2)

[0112] Q t,u ≤Q t,u ·θ t t∈T,u∈U (3)

[0113] Q t,u ≥θ t t∈T,u∈U (4)

[0114] In the formula, θ t is the binary variable for the arrival - volume stop - transmission method control within time layer t;

[0115] The remaining average hourly volume method control logic constraint is as follows:

[0116]

[0117] In the formula, T is the total number of time layers;

[0118] The improved remaining hours method control logic constraint is as follows:

[0119]

[0120]

[0121]

[0122] Qu = Q1 + Q2 where u ∈ U(9)

[0123] In the formula, Y is the preset number of time layers; Q1 is the natural gas transmission volume when the preset number of time layers Y is reached; v t,u is the control binary variable for the improved remaining hours method; is the natural gas transmission volume within a single time layer when the average transmission volume is adopted; Q2 is the total natural gas transmission volume of the remaining time layers;

[0124] The control logic constraint of the weight coefficient method is:

[0125] Q t,u = Q u ·x t,u where t ∈ T, u ∈ U(10)

[0126] In the formula, x t,u is the uneven coefficient of user u within time layer t;

[0127] The node parameter constraints include: node flow constraint, node pressure drop constraint, and node pressure constraint;

[0128] The node flow constraint is:

[0129]

[0130]

[0131] In the formula, β t,i is the flow direction variable of node i within time layer t. When β t,i = 1, the flow enters the node; when β t,i = 0, the flow leaves the node; Q t,i is the absolute value of the flow entering (leaving) node i within time layer t; β t,c is the flow direction variable of compressor station c within time layer t; Q t,c is the absolute value of the flow entering (leaving) compressor station c within time layer t; β t,l is the flow direction variable of pipeline l within time layer t; Q t,l is the absolute value of the flow entering (leaving) pipeline l within time layer t; is the minimum allowable gas distribution volume of distribution station d within time layer t; Q t,d is the gas distribution volume of distribution station d within time layer t; is the maximum allowable gas distribution volume of distribution station d within time layer t;

[0132] The node pressure constraint is:

[0133]

[0134] In the formula, is the minimum allowable pressure of node i within time layer t; P t,i is the pressure of node i within time layer t; is the maximum allowable pressure of node i within time layer t;

[0135] The node pressure drop constraint relationship is:

[0136]

[0137] In the formula, Q i,l is the volume flow rate of natural gas in the pipeline from node i to pipeline l; d i,l is the inner diameter of the pipeline from node i to pipeline l; P i|(i,l) is the starting pressure of the pipeline from node i to pipeline l; P l|(i,l) is the ending pressure of the pipeline from node i to pipeline l; Z is the natural gas compression factor; Δ is the relative density of natural gas; T i,l is the average thermodynamic temperature of natural gas in the pipeline from node i to pipeline l; L i,l is the length of the pipeline from node i to pipeline l;

[0138] The natural gas flow constraint is:

[0139]

[0140]

[0141]

[0142] In the formula, P g is the natural gas pressure; t g is the natural gas flow time; L is the pipeline length; M g is the natural gas mass flow rate; S is the pipeline flow cross-sectional area; a g is the gas adiabatic propagation speed; λ g is the friction factor of the natural gas pipeline network; ρ g is the natural gas density; R is the gas constant;

[0143] The compressor constraints include: compressor pressure constraint, compressor speed constraint, compressor inlet flow rate constraint, compressor power constraint, compressor start-stop constraint;

[0144] The compressor pressure constraint is:

[0145]

[0146]

[0147]

[0148] In the formula, is the minimum intake pressure allowed for compressor j; is the intake pressure of compressor j within time layer t; is the maximum discharge pressure allowed for compressor j; is the discharge pressure of compressor j within time layer t; ε t,j is the compression ratio of compressor j;

[0149] The rotational speed constraint of the compressor is as follows:

[0150]

[0151] In the formula, is the minimum rotational speed allowed for compressor j; r t,j is the rotational speed of compressor j within time layer t; is the maximum rotational speed allowed for compressor j;

[0152] The intake flow rate constraint of the compressor is as follows:

[0153]

[0154]

[0155]

[0156] In the formula, is the minimum intake flow rate allowed for compressor j; q t,j is the intake flow rate of compressor j within time layer t; is the maximum intake flow rate allowed for compressor j; A su 、B su 、C su 、A st 、B st 、C st are the compressor characteristic parameters;

[0157] The power constraint of the compressor is as follows:

[0158]

[0159]

[0160] In the formula, N t,j is the operating power of compressor j within time layer t; k is the specific heat of the gas, is the gas compression factor under the suction condition of compressor j; is the gas compression factor under the discharge condition of compressor j; η j is the operating efficiency of compressor j; is the minimum operating power allowed for compressor j; The maximum operating power allowed for compressor j;

[0161] The constraint on the number of compressors started is:

[0162]

[0163] where e t,c,j is the operating variable of compressor j in compressor station c at time layer t, which is 1 when the compressor is in the started state and 0 otherwise; φ c is the number of compressors in compressor station c;

[0164] The constraint on starting and stopping of the compressor is:

[0165]

[0166]

[0167] where τ t,c,j is the operating state variable of compressor j in compressor station c at time layer t. When the compressor is in the operating state, τ t,c,j = 1, and when the compressor is in the operating state, τ t,c,j = 0; B is the shortest continuous operating duration of the compressor, and b is the shortest continuous shutdown time of the compressor.

[0168] In one embodiment, the objective function described in step S2 is to minimize the compressor energy consumption cost, and the objective function relationship is:

[0169]

[0170] where f is the compressor energy consumption cost; t is the operating time of a single time layer; M t,j is the inlet mass flow rate of compressor j at time layer t; H t,j is the head of compressor j at time layer t; η j is the adiabatic efficiency of compressor j; is the mechanical efficiency of compressor j; δ c is the electricity price of compressor station c.

[0171] The symbol explanations of formulas (1) to (30) are shown in Tables 1, 2, and 3.

[0172] Table 1 Model Indexes and Sets

[0173] t ∈ T Set of time levels i ∈ I = D ∪ U ∪ C Set of nodes d ∈ D Set of distribution stations u ∈ U Set of users l∈L Set of pipelines j ∈ J Set of compressors c ∈ C Set of compressor station nodes

[0174] Table 2 Model Known Parameters

[0175]

[0176] Table 3 Model Decision Variables

[0177] <![CDATA[Q t,u > Gas distribution volume of user u within time level t <![CDATA[e t,c,j > Operating variables of compressor j in compressor station c within time level t <![CDATA[r j > Rotation speed of compressor j

[0178] In one embodiment, the natural gas pipeline transmission optimization model considering user characteristics described in S3 belongs to a transient optimization model. When solving this model, the independent time layer method is adopted, that is, the time from 0 to T is divided into X t time layers. The operation of the pipeline network within each time layer is regarded as steady-state operation. The mathematical average value of the compressor energy consumption at the starting and ending moments of each time layer is used to replace the compressor energy consumption within each time layer in the objective function. The relationship is as follows:

[0179]

[0180] In the formula, f(t) is the total compressor energy consumption of the target pipeline network within time layer t.

[0181] In one embodiment, the natural gas pipeline transmission optimization plan described in S3 includes: compressor operation energy consumption, compressor operation plan, gas transmission volume of each user in each period, and pipeline network operation parameters.

[0182] According to the daily specified gas transmission law of users and the pipeline network simulation results, it is determined that interruptible industrial users, interruptible other users, and power generation users adopt the method of stopping transmission when reaching the specified volume. For non-interruptible industrial users, the average volume per remaining hour method and the improved remaining hour method can be considered. For non-interruptible other users, the method of stopping transmission when reaching the specified volume, the average volume per remaining hour method, and the improved remaining hour method can be considered. For urban gas users, the weight coefficient method, the average volume per remaining hour method, and the improved remaining hour method can be considered.

[0183] To determine the gas transmission modes of different users, a study is carried out with the natural gas pipeline network E as Application Example 1. This pipeline network includes 1 main pipeline, 2 compressor stations, and 2 gas transmission nodes. There are a total of 4 natural gas users along the pipeline. The pressure at each node during pipeline operation does not exceed the maximum operating pressure of 9.5 MPa, the starting pressure of the main pipeline does not exceed 8 MPa, and the ending pressure of the main pipeline is not lower than 5 MPa. The pipeline network structure is as Figure 2 shown.

[0184] The total gas transmission volume of the gas source in the pipeline network is 2020×10 4 m 3 / d. The daily specified volumes of the 4 natural gas users along the pipeline are as Figure 3 shown. To determine the best gas transmission modes of different types of users, 4 working conditions are set, as shown in Table 5.

[0185] Table 5 Pipeline Network Working Condition Parameters

[0186]

[0187] The compressor energy consumption of different types of users under different sub - transmission modes obtained by solving the model is shown in Table 6. As can be seen from Table 6, the improved remaining - hour method is adopted for the sub - transmission mode of uninterruptible industrial users, the improved remaining - hour method is adopted for the sub - transmission mode of other uninterruptible users, and the weight - coefficient method is adopted for the sub - transmission mode of urban gas users.

[0188] Table 6 Compressor Energy Consumption of Different Types of Users in Sub - transmission Modes

[0189]

[0190] To further verify this method, a case study on the daily specified sub - transmission optimization of a natural gas pipeline network considering user characteristics is carried out with a certain domestic natural gas pipeline network as Application Example 2. The pipeline network consists of 1 main pipeline, 2 branch pipelines, 1 gas source, 4 compressor stations and 18 sub - transmission stations. There are a total of 30 natural gas users along the pipeline network. When the pipeline is operating, the maximum operating pressure at each node is 9.5 MPa, the starting pressure of the main pipeline does not exceed 8 MPa, and the ending pressure of the main pipeline is not lower than 5 MPa. The pipeline network structure is as Figure 4 shown.

[0191] The total transmission volume of the gas source in the pipeline network is 2417×10 4 m 3 / d. There are a total of 30 gas users along the way, and their daily specified quantities are as Figure 5 shown. The natural gas sub - transmission modes adopted by different types of users are shown in Table 7.

[0192] Table 7 Natural Gas Sub - transmission Modes of Different Types of Users

[0193]

[0194] The parameters of the compressor stations are shown in Table 8. The electricity price in the area where the compressor stations are located is 0.5174 yuan / (kW·h), and the penalty cost coefficient for compressor shutdown is 6320 yuan / unit.

[0195] Table 8 Configuration Parameters of Compressor Stations

[0196]

[0197] By solving the optimization model, the compressor operation energy consumption under its optimized scheme is 15.1603×10 4 yuan, and the compressor operation schemes in different time layers are as Figure 6 and Figure 7 shown. From Figure 6 and Figure 7It can be seen that during the daily specified sub - transportation process, the number of compressors in operation and the operating speeds of the compressors in each compressor station remain at a constant value. That is, during the entire daily specified sub - transportation process, the operating parameters of the compressors are not adjusted, which is reasonable in the actual natural gas pipeline network dispatching process. Regarding the phenomenon that the compressor speed has not changed, most of the 30 natural gas users are urban gas users, and the sub - transportation mode adopts the weight coefficient method. Therefore, the total sub - transported volume of natural gas users in each time layer is similar, which also makes the operating plan of the compressors consistent in each time layer.

[0198] The sub - transported gas volumes of each natural gas user in different time layers in the natural gas pipeline network sub - transportation optimization plan are as Figure 8 shown. From Figure 8 it can be seen that it can be found that the daily specified sub - transported gas volumes of users u2, u3, u5, u7 and u24 fluctuate greatly, and the sub - transported gas volumes of other users in each time period are sub - transported according to the ratio of the weight coefficients in each time layer. Although the sub - transported gas volumes of users u2, u3, u5, u7 and u24 vary greatly in each time period, when the sub - transported gas volume of a certain user is large in a certain time layer, the sub - transported gas volumes of the other 4 natural gas users will decrease in this time layer, reasonably avoiding the phenomenon of large sub - transported gas volumes in the same time layer. This also makes the difference in sub - transported gas volumes in each time layer during the daily specified sub - transportation process smaller, and further makes the operation of the compressor more stable and reasonable.

[0199] The above description is only for the embodiments of this specification and does not limit the embodiments of this specification. For those skilled in the art, various changes and modifications can be made to the embodiments of this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of this specification shall be included within the scope of the claims of the embodiments of this specification.

Claims

1. A daily designated sub - transmission optimization method for natural gas pipeline networks considering user characteristics, characterized in that, It includes the following steps: S1: Generate the constraint conditions of the model according to the natural gas pipeline network structure parameters, user demand parameters, and compressor station parameters; The said constraint conditions include: daily specified quantity constraint for natural gas users, branch transportation mode constraint, node parameter constraint, and compressor operation constraint; S2: Generate an optimized branch transportation model for the natural gas pipeline network considering user characteristics according to the constraint conditions and the objective function of minimizing compressor energy consumption; The objective function is to minimize the compressor energy consumption cost, and the relational expression of the objective function is: where f is the energy consumption cost of the compressor; t is the running time of a single time layer; M t,j is the inlet mass flow rate of compressor j within time layer t; H t,j is the head of compressor j within time layer t; η j is the adiabatic efficiency of compressor j; is the mechanical efficiency of compressor j; δ c is the electricity price of compressor station c; S3: Solve the optimized branch transportation model for the natural gas pipeline network considering user characteristics and output the optimized branch transportation plan for the natural gas pipeline network.

2. The daily specified sub - transmission optimization method for natural gas pipeline networks considering user characteristics according to claim 1, characterized in that, The branch transportation modes described in step S1 include: arrival volume stop transportation method, remaining hourly average volume method, improved remaining hours method, and weight coefficient method; The arrival volume stop transportation method refers to that the system monitors the total gas transmission volume of current users in real time. When the gas transmission volume reaches 95% of the daily specified quantity, a high alarm is given. When the gas transmission volume reaches 99% of the daily specified branch transportation volume, a very high alarm is given. After completing the daily issued daily specified branch transportation volume, the gas transmission to downstream users is stopped; The remaining hourly average volume method refers to supplying gas according to the average flow rate in t time periods for the daily specified branch transportation volume. After the first hour of transportation, calculate the remaining gas supply volume, and the remaining gas supply volume is evenly distributed according to the remaining hours one by one until the daily branch transportation is completed; The improved remaining hours method refers to dividing the branch transportation process into two stages. In the first stage, constant pressure branch transportation is adopted; when the time for transporting natural gas reaches the preset threshold, enter the second stage, that is, adjust the remaining natural gas branch transportation plan to the remaining hourly average volume method for transportation. After each hour of transportation, calculate the remaining gas supply volume, and the remaining gas supply volume is evenly distributed according to the remaining time until the daily branch transportation is completed; The weight coefficient method refers to dividing the daily specified quantity of users into t time periods. According to the gas consumption rules in the past n days, calculate the uneven coefficient of each time period on the current day through weighted average, and the set value of the instantaneous gas transmission flow rate in each time period is the product of the daily natural gas distribution volume and the uneven coefficient of the current time period.

3. The daily specified sub - transmission optimization method for natural gas pipeline network considering user characteristics according to claim 1, wherein, The natural gas pipeline network structure parameters described in step S1 include the gas source location, compressor station location, branch transportation station location, user location, and pipeline length; User demand parameters include: daily specified declared flow rate, daily specified changed flow rate; compressor station parameters include: number of compressors, compressor power range, compressor speed range.

4. The natural gas pipeline daily specified sub - transmission optimization method considering user characteristics according to claim 1, characterized in that, The daily specified quantity constraint for natural gas users is: Where, Q t,u is the natural gas sub - transmission volume of user u within the time layer t; Q u is the specified daily transmission volume of natural gas user u. The branch transportation mode constraints include: arrival volume stop transportation method control logic constraint, remaining hourly average volume method control logic constraint, improved remaining hours method control logic constraint, weight coefficient method control logic constraint; The control logic constraint of the stop - gas - supply - at - specified - volume method uses binary variables to control the gas supply to users. When the gas supply to user u does not reach the daily specified demand within time layer t, θ t = 1, θ t+1 = 1; when it reaches the daily specification at time layer t, θ t = 1, θ t+1 = 0, and the constraint is: θ t+1 -θ t ≤0 Q t,u ≤Q t,u ·θ t Q t,u ≥θ t where θ t is the control binary variable of the quantity stopping transportation method within the time layer t; The control logic constraint of the remaining hourly average volume method is: In the formula, T is the total number of time layers; The control logic constraint of the improved remaining hours method is: Q u = Q1 + Q2 Where Y is the preset number of time layers; Q1 is the natural gas throughput when the preset number of time layers Y is reached; v t,u is the improved remaining hours method to control binary variables; is the natural gas throughput within a single time layer when the average throughput is adopted; Q2 is the total natural gas throughput of the remaining time layers; The control logic constraint of the weight coefficient method is: Q t,u = Q u ·x t,u where x t,u is the non-uniformity coefficient of user u within time layer t; The node parameter constraints include: node flow constraint, node pressure drop constraint, node pressure constraint; The node flow constraint is: where β t,i is the flow direction variable of node i within the time layer t. When β t,i = 1, the flow enters this node; when β t,i = 0, the flow exits this node; Q t,i is the absolute value of the flow rate of node i within the time layer t; β t,c is the flow direction variable of compressor station c within the time layer t; Q t,c is the absolute value of the flow rate of compressor station c within the time layer t; β t,l is the flow direction variable of pipeline l within the time layer t; Q t,l is the absolute value of the flow rate of pipeline l within the time layer t; is the minimum allowable gas distribution volume of the gas distribution station d within the time layer t; Q t,d is the gas distribution volume of the gas distribution station d within the time layer t; is the maximum allowable gas distribution volume of the gas distribution station d within the time layer t; The node pressure constraint is: In the formula, is the minimum allowable pressure of node i within time layer t; P t,i is the pressure of node i within time layer t; is the maximum allowable pressure of node i within time layer t; The node pressure drop constraint relationship is: Where, Q i,l is the volume flow rate of natural gas in pipeline l of node i; d i,l is the inner diameter of pipeline l of node i; P i|(i,l) is the starting pressure of pipeline l of node i; P l|(i,l) is the ending pressure of pipeline l of node i; Z is the natural gas compression factor; Δ is the relative density of natural gas; T i,l is the average thermodynamic temperature of natural gas in pipeline l of node i; L i,l is the length of pipeline l of node i; The natural gas flow constraint is: Wherein, P g is the natural gas pressure; t g is the natural gas flow time; M g is the natural gas mass flow rate; S is the cross-sectional area of the pipeline; a g is the adiabatic propagation velocity of the gas; λ g is the friction coefficient of the natural gas pipeline network; ρ g is the natural gas density; R is the gas constant; The compressor operation constraints include: compressor pressure constraint, compressor speed constraint, compressor inlet gas flow constraint, compressor power constraint, compressor startup unit number constraint, and compressor start-stop constraint; The compressor pressure constraint is: wherein, is the minimum intake pressure allowed for compressor j; is the intake pressure of compressor j within time layer t; is the maximum discharge pressure allowed for compressor j; is the discharge pressure of compressor j within time layer t; ε t,j is the pressure ratio of compressor j; The compressor speed constraint is: wherein, is the minimum allowable speed of compressor j; r t,j is the speed of compressor j within time layer t; is the maximum allowable speed of compressor j; The compressor inlet gas flow constraint is: Wherein, is the minimum intake air flow allowed for compressor j; q t,j is the intake air flow of compressor j within time layer t; is the maximum intake air flow allowed for compressor j; A su , B su , C su , A st , B st , C st are the characteristic parameters of the compressor; The compressor power constraint is: Where N t,j is the operating power of compressor j within the time layer t; k is the specific heat of the gas, is the gas compression factor under the suction condition of compressor j; is the gas compression factor under the discharge condition of compressor j; η j is the operating efficiency of compressor j; is the minimum allowable operating power of compressor j; is the maximum allowable operating power of compressor j; The compressor startup unit number constraint is: where, e t,c,j is the operating variable of compressor j in compressor station c within time layer t, which is 1 when the compressor is in the startup state and 0 otherwise; φ c is the number of compressors in compressor station c; The compressor start-stop constraint is: where τ t,c,j is the operating state variable of compressor j in compressor station c within time layer t. When the compressor is in the operating state, τ t,c,j = 1. When the compressor is in the shutdown state, τ t,c,j = 0; B is the shortest continuous operation duration of the compressor, and b is the shortest continuous shutdown time of the compressor.

5. The natural gas pipeline daily specified sub - transmission optimization method considering user characteristics according to claim 1, wherein, The natural gas pipeline transmission optimization model considering user characteristics described in S3 belongs to a transient optimization model. When solving this model, the independent time layer method is adopted, that is, the time from 0 to T is divided into t time layers. The operation of the pipeline network within each time layer is regarded as steady-state operation. The mathematical average value of the compressor energy consumption at the start and end times of each time layer is used to replace the compressor energy consumption within each time layer in the objective function. The relationship is: In the formula, f(t) is the total compressor energy consumption of the target pipeline network within time layer t.

6. The natural gas pipeline daily specified sub - transmission optimization method considering user characteristics according to claim 1, characterized in that, The natural gas pipeline transmission optimization scheme described in S3 includes: compressor operation energy consumption, compressor operation scheme, and gas transmission volume of each user in each period.

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