A multi-gas source pipeline network expansion optimization method considering gas interchangeability

Abstract

The present invention provides a multi-gas source network expansion optimization method considering gas interchangeability, the method comprising: obtaining target network basic data, dividing the target network into regions with supply nodes, intermediate nodes, demand nodes and compressor nodes; designing multi-gas source network expansion optimization model constraint conditions considering gas interchangeability according to target network basic data; generating multi-gas source network expansion optimization model considering gas interchangeability according to constraint conditions and objective function; solving multi-gas source network expansion optimization model considering gas interchangeability, and outputting multi-gas source network expansion plan. Based on the consideration of gas interchangeability, the method generates a network expansion plan with the best global economy through optimization technology, which can effectively reduce the cost of expansion projects and improve the rationality of expansion pipelines and equipment.

Description

Technical Field

[0001] The present invention relates to the field of natural gas pipeline network expansion optimization, and in particular to a multi-gas source pipeline network expansion optimization method considering gas interchangeability. Background Art

[0002] For a long time, the expansion projects of natural gas pipelines have mostly referred to design manuals or formulated design plans based on the experience accumulated by field engineers over the years. This traditional method lacks certain scientific basis, overemphasizes the reliability of natural gas supply, and ignores the economic principle of natural gas pipeline construction. At the same time, under the general trend of natural gas development, more and more pipelines are facing the problem of choosing multiple natural gas sources, but generally only a single pipeline network is used to transport natural gas in the same area, forming a pattern of "mixed gas sources synergistically supplying one network". Traditional methods are difficult to adapt to the design requirements of natural gas pipelines under the multi-gas source pattern.

[0003] The natural gas pipeline network is an important part of the energy system. Its scale and complexity will increase with the increase in demand. When user demand grows over time, the natural gas pipeline network will expand over time to meet the needs of new consumption nodes. For designers and operators, design and expansion decisions must carefully consider the long-term benefits of the pipeline network to meet different needs within the planning scope. A well-designed natural gas network can help natural gas management companies minimize investment and operating costs. With the rapid development of optimization technology, program evaluation technology, and computer technology, it has not only created conditions for optimization and automation in various engineering fields, but also provided the necessary theoretical basis and implementation means for the design and research of natural gas pipeline network expansion. The natural gas pipeline network system is a large system. Due to its complexity and diversity, the workload of its optimization is quite large. It is of great importance and far-reaching significance to deeply study the layout and operation design of natural gas pipeline networks, walk in the forefront of the information and digital era, update the concepts and models of pipeline network design, and achieve the purpose of improving design quality, economic benefits and social benefits.

[0004] Therefore, in the future, with the prospect of diverse gas sources and relatively sufficient supply, the rational use of optimization technology to comprehensively plan the expansion design of the natural gas pipeline network on the basis of considering the interchangeability of gas, so as to meet the pipeline supply pattern and meet the gas demand of users, has very important guiding significance for improving the quality of pipeline network design, economic benefits and social benefits. Summary of the invention

[0005] To solve the problem, the present invention provides the following technical solutions:

[0006] The present invention provides a multi-gas source pipeline network expansion optimization method considering gas interchangeability, which is characterized by comprising the following steps:

[0007] S1: Obtain basic data of the target pipeline network, and divide the target pipeline network into areas with supply nodes, intermediate nodes, demand nodes, and compressor nodes;

[0008] S2: Based on the basic data of the target pipeline network, design the constraints of the optimization model for the expansion of the multi-gas source pipeline network considering the interchangeability of gas;

[0009] S3: Generate a multi-gas source pipeline network expansion optimization model considering gas interchangeability based on the constraints and the objective function to minimize the annual reduced cost of the pipeline network system;

[0010] S4: Solve the optimization model for multi-gas source network expansion considering gas interchangeability, and output the multi-gas source network expansion plan.

[0011] Furthermore, the basic data described in step S1 includes target pipe network structure data, newly added node supply and demand data, node operation data, pipeline operation data, compressor station configuration data and interchangeability ratio coefficient.

[0012] Furthermore, the constraints described in step S2 include node flow direction constraints, inter-node pressure drop constraints, gas pressure constraints, gas flow constraints, compressor operation status constraints, gas interchangeability constraints, and pipeline network construction constraints;

[0013] The node flow direction constraint is:

[0014] B t,(i,j) +B t,(j,i) ≤1

[0015] In the formula, B t,(i,j) is the flow direction variable from node i to node j in period t, which is 1 when natural gas flows from node i to node j, otherwise it is 0;

[0016] The inter-node voltage drop constraint is:

[0017]

[0018]

[0019]

[0020] In the formula, δ i,j is the pressure drop calculation coefficient; R is the natural gas gas constant; λ is the pipeline hydraulic friction coefficient; Z is the natural gas compression coefficient; T is the average temperature of natural gas; ζ (i,j),l is the length of the pipeline l from node i to node j; d (i,j),l is the inner diameter of the pipeline l between node i and node j; M t,i,j is the mass flow rate of natural gas between nodes i and j during period t; M max is the maximum value of mass flow rate;

[0021] The gas pressure constraints include supply node pressure constraints, demand node pressure constraints, and compressor node pressure constraints;

[0022] The supply node pressure constraint is:

[0023] P t,g =P max

[0024] Where P t,g is the pressure of supply node g at period t; P max It is the maximum operating pressure of the pipe network system;

[0025] The demand node pressure constraint is:

[0026]

[0027] In the formula, is the minimum operating pressure allowed for demand node u; P t,u is the pressure of demand node u in period t; is the maximum operating pressure allowed for demand node u;

[0028] The compressor outlet pressure must be less than the maximum pressure of the pipe network system. The compressor node pressure constraint is:

[0029]

[0030] In the formula, is the outlet pressure of compressor c at period t;

[0031] The gas flow constraints include node flow balance constraints, node supply and demand constraints, and pipeline flow constraints;

[0032] The node traffic balance constraint is:

[0033]

[0034]

[0035]

[0036] In the formula, S t,g is the amount of natural gas flowing into the pipeline network from supply node g during period t; is the PNG supply of supply node g in period t; is the LNG supply of supply node g in period t; is the amount of alternative fuel supplied to node g during period t; t,u is the gas demand of user node u; is the PNG demand of user node u in period t; is the LNG demand of user node u; is the replacement fuel demand of user node u;

[0037] There is a maximum limit on the supply of gas source nodes. The amount of gas flowing into the demand node should meet its calorific value demand. The node supply and demand constraints are:

[0038]

[0039]

[0040]

[0041]

[0042] In the formula, is the maximum PNG supply of supply node g; is the maximum LNG supply of supply node g; is the maximum alternative fuel supply to node g; H PNG is the calorific value of PNG; H LNG is the calorific value of LNG; H ALT is the calorific value of the alternative fuel; D t,u is the heat value demand of user node u in period t;

[0043] This model simplifies the compressor model and only retains the pressure increase relationship between the compressor inlet and outlet. The compressor operation state constraint is used to represent the inlet and outlet pressure relationship of the compressor node when the compressor is in the three states of operation, shutdown, and bypass.

[0044] When the compressor is in operation, the compressor operation state constraint is:

[0045]

[0046]

[0047] In the formula, is the intake pressure of compressor c at period t; ε t,c is the pressure ratio of compressor c during period t; β t,(i,j),c is the construction variable of compressor c between node i and node j in period t. When a new compressor is built between nodes, the variable is 1, otherwise it is 0;

[0048] When the compressor is in bypass state, β t,(i,j),c =0, B t,(i,j) =1, the compressor inlet pressure and outlet pressure are equal; when the compressor is in the off state, βt,(i,j),c =0, B t,(i,j) =0, there is no direct connection between the compressor inlet pressure and the outlet pressure, and the compressor operation state constraint is:

[0049]

[0050]

[0051] The gas interchangeability constraint is used to limit the gas supply ratio when multiple gas sources are supplying gas at the same time, so as to meet the gas interchangeability requirements of the user node;

[0052] When PNG and LNG are supplied in tandem, the following conditions should be met:

[0053]

[0054] In the formula, K PL The proportion of LNG when LNG and PNG are mixed to meet the interchangeability requirement;

[0055] When LNG and alternative fuels are supplied together, the following conditions shall be met:

[0056]

[0057] In the formula, K LA When LNG and alternative fuels are mixed, the proportion of LNG is required to meet the interchangeability requirements;

[0058] When PNG, LNG and alternative fuels are supplied in tandem, the following conditions should be met:

[0059]

[0060]

[0061] In the formula, and The critical coefficient of LNG proportion when PNG, LNG and alternative fuels are mixed to meet the interchangeability;

[0062] The pipeline network construction constraints include pipeline construction constraints and compressor construction constraints;

[0063] The pipeline construction constraint means that the pipeline is completed in period t and can be used at any time thereafter. The constraint relationship is:

[0064] α t,(i,j),l ≤α t+1,(i,j),l

[0065] In the formula, α t,(i,j),l is the construction variable of pipeline l between node i and node j in period t. When a pipeline is built between nodes, the variable is 1, otherwise it is 0;

[0066] The compressor station construction constraint indicates that the compressor station is completed in period t and can be used in any period thereafter, and only one compressor station can be built between node i and node j. The constraint relationship is:

[0067] β t,(i,j),c ≤β t+1,(i,j),c

[0068] β t,(i,j),c ≤1

[0069] Furthermore, the objective function of the minimum annual equivalent cost of the pipe network system in step S3 is composed of the construction investment cost and the operation cost, and the relationship is:

[0070]

[0071] In the formula, f is the annual equivalent cost of the pipeline network system; G1 is the investment cost of the pipeline network system; r is the bank interest rate; E is the life cycle of the pipeline network system; G2 is the operating cost of the pipeline network system;

[0072] The pipeline network investment cost is defined as the sum of the pipeline investment cost and the compressor investment cost, and the relationship is:

[0073]

[0074] In the formula, is the unit installation cost of compressor c in period t+1; is the unit installation cost of pipeline l in period t+1;

[0075] The pipeline network operation cost is defined as pipeline operation and maintenance cost, compressor operation and maintenance cost and pipeline network gas purchase cost, and the relationship is:

[0076]

[0077] In the formula, μ l is the conversion factor of pipeline l; is the unit operation and maintenance cost of pipeline l in period t+1; is the unit electricity cost generated by the operation of compressor c in period t+1; is the unit operation and maintenance cost of compressor c in period t+1; The cost of purchasing unit volume of LNG, PNG and alternative fuels for node i.

[0078] Furthermore, the multi-gas source network expansion plan described in step S4 includes: annual equivalent cost of the network system, structural parameters of the expanded network, compressor operating parameters, node operating pressure parameters, and new node flow distribution plan.

[0079] Beneficial effects of the present invention:

[0080] (1) By setting constraints to limit the gas supply ratio when multiple gas sources are supplied, the gas interchangeability problem in the multi-gas source pipeline network can be considered. The actual gas supply characteristics of the pipeline network can be reflected in the optimization model, making the pipeline network expansion plan more consistent with the actual situation, providing guidance for the actual expansion work.

[0081] (2) Based on the optimization technology, the optimal pipeline expansion plan with global economic efficiency is generated. Compared with the traditional plan obtained based on experience, the optimized plan is more economical and can effectively reduce the cost of the expansion project, avoid the waste caused by repeated planning and inconsistent gas supply and demand, and improve the rationality of the expansion pipeline and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 It is a flow chart of the present invention;

[0083] Figure 2 This is a node location diagram of a multi-gas source pipeline network to be expanded in a coastal area in a specific application example;

[0084] Figure 3 This is a result diagram of the expansion of a multi-gas source pipeline network in a coastal area in a specific application example;

[0085] Figure 4 This is a schematic diagram of the pressure at each node of a multi-gas source pipeline network in a coastal area in a specific application example. DETAILED DESCRIPTION

[0086] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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 part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0087] like Figure 1 As shown, the present invention provides a multi-gas source pipeline network expansion optimization method considering gas interchangeability, comprising the following steps:

[0088] S1: Obtain basic data of the target pipeline network, and divide the target pipeline network into areas with supply nodes, intermediate nodes, demand nodes, and compressor nodes;

[0089] S2: Based on the basic data of the target pipeline network, design the constraints of the optimization model for the expansion of the multi-gas source pipeline network considering the interchangeability of gas;

[0090] S3: Generate a multi-gas source pipeline network expansion optimization model considering gas interchangeability based on the constraints and the objective function to minimize the annual reduced cost of the pipeline network system;

[0091] S4: Solve the optimization model for multi-gas source network expansion considering gas interchangeability, and output the multi-gas source network expansion plan.

[0092] In one embodiment, the basic data described in step S1 includes target pipe network structure data, newly added node supply and demand data, node operation data, pipeline operation data, compressor station configuration data and interchangeability ratio coefficient.

[0093] In one embodiment, the constraints described in step S2 include node flow direction constraints, inter-node pressure drop constraints, gas pressure constraints, gas flow constraints, compressor operation status constraints, gas interchangeability constraints, and pipeline network construction constraints;

[0094] The node flow direction constraint is:

[0095]

[0096] In the formula, B t,(i,j) is the flow direction variable from node i to node j in period t, which is 1 when natural gas flows from node i to node j, otherwise it is 0;

[0097] The inter-node voltage drop constraint is:

[0098]

[0099]

[0100]

[0101] In the formula, δ i,j is the pressure drop calculation coefficient; R is the natural gas gas constant; λ is the pipeline hydraulic friction coefficient; Z is the natural gas compression coefficient; T is the average temperature of natural gas; ζ (i,j),l is the length of the pipeline l from node i to node j; d (i,j),l is the inner diameter of the pipeline l between node i and node j; M t,i,j is the mass flow rate of natural gas between nodes i and j during period t; M max is the maximum value of mass flow rate;

[0102] The gas pressure constraints include supply node pressure constraints, demand node pressure constraints, and compressor node pressure constraints;

[0103] The supply node pressure constraint is:

[0104] P t,g =P max g∈G,t∈T (5)

[0105] Where P t,gis the pressure of supply node g at period t; P max It is the maximum operating pressure of the pipe network system;

[0106] The demand node pressure constraint is:

[0107]

[0108] In the formula, is the minimum operating pressure allowed for demand node u; P t,u is the pressure of demand node u in period t; is the maximum operating pressure allowed for demand node u;

[0109] The compressor outlet pressure must be less than the maximum pressure of the pipe network system. The compressor node pressure constraint is:

[0110]

[0111] In the formula, is the outlet pressure of compressor c at period t;

[0112] The gas flow constraints include node flow balance constraints, node supply and demand constraints, and pipeline flow constraints;

[0113] The node traffic balance constraint is:

[0114]

[0115]

[0116]

[0117] In the formula, S t,g is the amount of natural gas flowing into the pipeline network from supply node g during period t; is the PNG supply of supply node g in period t; is the LNG supply of supply node g in period t; is the amount of alternative fuel supplied to node g during period t; t,u is the gas demand of user node u; is the PNG demand of user node u in period t; is the LNG demand of user node u; is the replacement fuel demand of user node u;

[0118] There is a maximum limit on the supply of gas source nodes. The amount of gas flowing into the demand node should meet its calorific value demand. The node supply and demand constraints are:

[0119]

[0120]

[0121]

[0122]

[0123] In the formula, is the maximum PNG supply of supply node g; is the maximum LNG supply of supply node g; is the maximum alternative fuel supply to node g; H PNG is the calorific value of PNG; H LNG is the calorific value of LNG; H ALT is the calorific value of the alternative fuel; D t,u is the heat value demand of user node u in period t;

[0124] This model simplifies the compressor model and only retains the pressure increase relationship between the compressor inlet and outlet. The compressor operation state constraint is used to represent the inlet and outlet pressure relationship of the compressor node when the compressor is in the three states of operation, shutdown, and bypass.

[0125] When the compressor is in operation, the compressor operation state constraint is:

[0126]

[0127]

[0128] In the formula, is the intake pressure of compressor c at period t; ε t,c is the pressure ratio of compressor c during period t; β t,(i,j),c is the variable of compressor construction between node i and node j in period t. When a compressor station is built between nodes, the variable is 1, otherwise it is 0;

[0129] When the compressor is in bypass state, β t,(i,j),c =0, B t,(i,j) =1, the compressor inlet pressure and outlet pressure are equal; when the compressor is in the off state, β t,(i,j),c =0, B t,(i,j) =0, there is no direct connection between the compressor inlet pressure and the outlet pressure, and the compressor operation state constraint is:

[0130]

[0131]

[0132] The gas interchangeability constraint is used to limit the gas supply ratio when multiple gas sources are supplying gas at the same time, so as to meet the gas interchangeability requirements of the user node;

[0133] When PNG and LNG are supplied in tandem, the following conditions should be met:

[0134]

[0135] In the formula, K PL The proportion of LNG when LNG and PNG are mixed to meet the interchangeability requirement;

[0136] When LNG and alternative fuels are supplied together, the following conditions shall be met:

[0137]

[0138] In the formula, K LA When LNG and alternative fuels are mixed, the proportion of LNG is required to meet the interchangeability requirements;

[0139] When PNG, LNG and alternative fuels are supplied in tandem, the following conditions should be met:

[0140]

[0141]

[0142] In the formula, and The critical coefficient of LNG proportion when PNG, LNG and alternative fuels are mixed to meet the interchangeability;

[0143] The pipeline network construction constraints include pipeline construction constraints and compressor construction constraints;

[0144] The pipeline construction constraint means that the pipeline is completed in period t and can be used at any time thereafter. The constraint relationship is:

[0145]

[0146] In the formula, α t,(i,j),l is the construction variable of pipeline l between node i and node j in period t. When a pipeline is built between nodes, the variable is 1, otherwise it is 0;

[0147] The compressor station construction constraint indicates that the compressor station is completed in period t and can be used in any period thereafter, and only one compressor station can be built between node i and node j. The constraint relationship is:

[0148]

[0149]

[0150] In one embodiment, the objective function of minimizing the annual equivalent cost of the pipe network system in step S3 is composed of the construction investment cost and the operation cost, and the relationship is:

[0151]

[0152] In the formula, f is the annual equivalent cost of the pipeline network system; G1 is the investment cost of the pipeline network system; r is the bank interest rate; E is the life cycle of the pipeline network system; G2 is the operating cost of the pipeline network system;

[0153] The pipeline network investment cost is defined as the sum of the pipeline investment cost and the compressor investment cost, and the relationship is:

[0154]

[0155] In the formula, is the unit installation cost of compressor c in period t+1; is the unit installation cost of pipeline l in period t+1;

[0156] The pipeline network operation cost is defined as pipeline operation and maintenance cost, compressor operation and maintenance cost and pipeline network gas purchase cost, and the relationship is:

[0157]

[0158] In the formula, μ l is the conversion factor of pipeline l; is the unit operation and maintenance cost of pipeline l in period t+1; is the unit electricity cost generated by the operation of compressor c in period t+1; is the unit operation and maintenance cost of compressor c in period t+1; The cost of purchasing unit volume of LNG, PNG and alternative fuels for node i.

[0159] The symbols of formula (1) to formula (28) are shown in Table 1, Table 2, and Table 3.

[0160] Table 1 Index and set of optimization models for multi-gas source network expansion considering gas interchangeability

[0161] i∈I=G∪U∪L∪C Node Collection (i,j)∈A Edge Set g∈G Gas source node collection u∈U User node collection l∈L Pipeline Node Collection c∈C Compressor Collection

[0162] Table 2 Known parameters of the optimization model for multi-gas source network expansion considering gas interchangeability

[0163]

[0164]

[0165] Table 3 Decision variables of the optimization model for multi-gas source network expansion considering gas interchangeability

[0166]

[0167] In one embodiment, the multi-gas source network expansion plan described in step S4 includes: annual equivalent cost of the network system, expanded network structure parameters, compressor operating parameters, node operating pressure parameters, and newly added node flow distribution plan.

[0168] To further illustrate this solution, a case analysis is conducted using a pipeline network to be expanded in a coastal area as a specific application example. The natural gas sources for users in this coastal area are mainly imported PNG, LNG from the southern coastal area, LNG imported from ports, and alternative fuels. The three gases are injected into the same pipeline system for transportation to supply users. As the gas demand in the region increases, there is a need for pipeline network expansion. The locations of the newly added nodes in the expanded pipeline network are as follows: Figure 2 As shown in Table 4, nodes 1 to 17 represent the nodes of the built pipeline network, among which nodes 1 and 16 are supply nodes, node 1 supplies PNG, and node 16 supplies LNG; nodes 18 to 23 represent the newly added nodes of the expanded pipeline network, among which nodes 22 and 23 supply LNG, and node 21 is both an alternative fuel supply node and a demand node. The coordinate positions and supply and demand parameters of the pipeline network system nodes are shown in Table 4. The design pressure of the pipeline network system is 6.0MPa, the maximum allowable operating pressure is 5.4MPa, and the minimum operating pressure is 3.0MPa.

[0169] Table 4 Pipeline system node coordinates and supply and demand parameters

[0170] serial number X coordinate (km) Y coordinate (km) Demand (MW) Supply volume (kg / s) 1 600.62 784.32 - 200(PNG) 2 596.74 789.87 459.89 - 3 481.3 756.57 364.46 - 4 491.84 722.16 - - 5 495.17 712.17 364.46 - 6 509.60 723.27 364.46 - 9 428.02 748.8 181.72 - 10 423.58 768.78 364.46 - 11 405.26 731.04 181.72 - 14 393.05 704.40 6881.03 - 15 415.25 705.51 - - 16 420.25 697.74 - 25(LNG) 17 424.69 704.40 1541.88 - 18 384.17 678.87 1887.26 19 368.63 683.31 1024.34 20 356.42 673.32 618.26 21 335.89 687.75 3034.89 25(Alternative fuels) 22 329.78 661.11 - 20(LNG) 23 229.88 709.95 - 25(LNG)

[0171] Pipeline investment also includes construction costs, cathodic protection costs, etc. The investment costs of pipelines of different diameters are shown in Table 5.

[0172] Table 5 Operation and maintenance costs of pipelines with different diameters

[0173]

[0174]

[0175] Other basic parameters are shown in Table 6.

[0176] Table 6 Other basic parameters

[0177]

[0178] After solving the optimization model, the annual equivalent cost of the expansion project is 1,012,282.18 million yuan / year, including: total pipeline investment of 431,980,700 yuan, compressor construction cost of 428,446,100 yuan, compressor electric drive cost and operation and maintenance cost of 308,201,400 yuan / year, and gas purchase cost of 895,419,360 yuan / year.

[0179] The mixed gas source pipeline network expansion project added 6 pipelines with a total investment of 431.9807 million yuan. The results of the multi-gas source pipeline network expansion are as follows Figure 3 Among them, the total length of the expanded pipeline is 210.87km, the maximum diameter is 610mm, connecting 14 nodes and 19 nodes, the pipeline flow is 87.54kg / S, the overall investment is 91.4739 million yuan, and the detailed parameters of the expansion project pipeline are shown in Table 7.

[0180] Table 7 Pipeline parameters of mixed gas source network expansion project

[0181]

[0182]

[0183] like Figure 3 As shown in Table 8, in the mixed gas source pipeline expansion project, the compressor construction cost is 428.4461 million yuan, and the operating costs of the two compressors are 151.8499 million yuan / year (CS1) and 156.3515 million yuan / year (CS2). Among them, a new compressor CS2 is built at the compressor station node 11, which completes the PNG transportation task together with the compressor CS1 of the original pipeline system. The operating parameters and costs of the two compressors are shown in Table 8. The pressure ratios of the two compressors are 1.34 (CS1) and 1.43 (CS2), respectively, which meet the design requirements that the maximum pressure ratio of the compressor is less than 1.5 and the compressor outlet pressure is less than the maximum operating pressure of the pipeline network of 5.4MPa. The pressure parameters of each node in the mixed gas source pipeline network are as follows Figure 4 As shown, the operating pressure of the farthest node 21 of the expanded pipeline system is 3.0MPa. At this time, the gas supply pressures of nodes 22 and 23 are 3.6MPa (node ​​22) and 4.9MPa (node ​​23), respectively, which meet the operating pressure requirements in the design.

[0184] Table 8 Compressor operating parameters for mixed gas source pipeline network expansion project

[0185] Compressor No. CS1 CS2 Entry Node 7 12 Inlet pressure (MPa) 3.5 3.2 Exit Node 8 13 Outlet pressure(MPa) 4.7 4.6 Pressure ratio 1.34 1.43 Flow rate (kg / s) 170.94 142.24 Electric drive cost (10,000 yuan / year) 13042.76 13492.92 Operation and maintenance costs (10,000 yuan / year) 2142.23 2142.23

[0186] The gas purchase cost of the mixed gas source pipeline expansion project is 895,419,360 yuan / year, and the new node flow distribution and gas purchase cost are shown in Table 9. The nodes that purchase gas from each node to supply gas to the newly added demand nodes still include 1, 22 and 23. Considering that the entry of the new nodes does not affect the gas demand of the original pipeline users, when calculating the gas purchase cost, only the gas distribution problem and gas purchase cost problem of the new nodes are considered. At this time, the calorific value demand of nodes 18, 19 and 20 is met by PNG supplied by gas source node 22, and the LNG supply of node 21 is 38.26kg / s, which comes from gas source node 23 (25.00kg / s) and gas source node 22 (13.27kg / s), respectively. The remaining demand is provided by gas source node 1PNG.

[0187] Table 9: Flow distribution and gas purchase cost of new nodes in the mixed gas source pipeline network expansion project

[0188]

[0189] The above description is only an example of a specific implementation method in this specification and is not intended to limit the embodiments of this specification. For those skilled in the art, the embodiments of this specification may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of this specification should be included in the scope of the claims of the embodiments of this specification.

Claims

1. A multi-gas source pipeline network expansion optimization method considering gas interchangeability, characterized in that: The following steps are involved: S1: Obtain basic data of the target pipeline network, and divide the target pipeline network into areas with supply nodes, intermediate nodes, demand nodes, and compressor nodes; The basic data include target pipe network structure data, newly added node supply and demand data, node operation data, pipeline operation data, compressor station configuration data and interchangeability ratio coefficient; S2: Based on the basic data of the target pipeline network, design the constraints of the optimization model for the expansion of the multi-gas source pipeline network considering the interchangeability of gas; The constraints include node flow direction constraints, node pressure drop constraints, gas pressure constraints, gas flow constraints, compressor operation status constraints, gas interchangeability constraints and pipeline network construction constraints; S3: Generate a multi-gas source pipeline network expansion optimization model considering gas interchangeability based on the constraints and the objective function to minimize the annual reduced cost of the pipeline network system; S4: Solve the optimization model for multi-gas source network expansion considering gas interchangeability, and output the multi-gas source network expansion plan.

2. A multi-gas source network expansion optimization method considering gas interchangeability as claimed in claim 1, characterized in that: The node flow direction constraint is: ； In the formula, for t Period, Node i -node j The flow direction variable, when the gas flows from the node i Flow to Node j 1 when it is, otherwise 0; The inter-node voltage drop constraint is: ； ； ； In the formula, is the pressure drop calculation coefficient; is the gas constant of natural gas; is the pipeline hydraulic friction coefficient; is the natural gas compression factor; is the average temperature of natural gas; For Node i -node j pipeline l Length; For Node i -node j pipeline l The inner diameter of for t Period, Node i and j The mass flow rate of natural gas between is the maximum value of mass flow rate; The gas pressure constraints include supply node pressure constraints, demand node pressure constraints, and compressor node pressure constraints; The supply node pressure constraint is: ；； In the formula, for t Period, Supply Node g pressure; It is the maximum operating pressure of the pipe network system; The demand node pressure constraint is: ； In the formula, Demand Node u Minimum allowable operating pressure; for t Period, demand node u pressure; Demand Node u Maximum allowable operating pressure; The compressor outlet pressure must be less than the maximum pressure of the pipe network system. The compressor node pressure constraint is: ；； In the formula, for t Period, compressor c Outlet pressure; The gas flow constraints include node flow balance constraints, node supply and demand constraints, and pipeline flow constraints; The node traffic balance constraint is: ； ； ； In the formula, for t Period, Supply Node g The amount of natural gas flowing into the pipeline network; for t Period, Supply Node g PNG supply; for t Period, Supply Node g LNG supply; for t Period, Supply Node g the availability of alternative fuels; For user nodes u Gas demand; for t Period, user node u PNG demand; For user nodes u LNG demand; For user nodes u Demand for alternative fuels; There is a maximum limit on the supply of gas source nodes. The amount of gas flowing into the demand node should meet its calorific value demand. The node supply and demand constraints are: ； ； ； ； In the formula, For supply nodes g The largest PNG supply; For supply nodes g Maximum LNG supply volume; For supply nodes g Maximum alternative fuel supply; is the calorific value of PNG; is the calorific value of LNG; The calorific value of the alternative fuel; for t Period, user node u Calorific value requirements; This model simplifies the compressor model and only retains the pressure increase relationship between the compressor inlet and outlet. The compressor operation state constraint is used to represent the inlet and outlet pressure relationship of the compressor node when the compressor is in the three states of operation, shutdown, and bypass. When the compressor is in operation, the compressor operation state constraint is: ； ； In the formula, for t Period, compressor c Intake pressure; for t Period, compressor c The pressure ratio; for t Period, Node i -node j Compressor c The construction variable is 1 when a new compressor is built between nodes, otherwise it is 0; When the compressor is in bypass mode, , , the compressor inlet pressure and outlet pressure are equal; When the compressor is off, , , the compressor inlet pressure and outlet pressure have no direct connection, and the compressor operating state constraint is: ； ； The gas interchangeability constraint is used to limit the gas supply ratio when multiple gas sources are supplying gas at the same time, so as to meet the gas interchangeability requirements of the user node; When PNG and LNG are supplied in tandem, the following conditions should be met: ； In the formula, The proportion of LNG when LNG and PNG are mixed to meet the interchangeability requirement; When LNG and alternative fuels are supplied together, the following conditions shall be met: ； In the formula, When LNG and alternative fuels are mixed, the proportion of LNG is required to meet the interchangeability requirements; When PNG, LNG and alternative fuels are supplied in tandem, the following conditions should be met: ； ； In the formula, and The critical coefficient of LNG proportion when PNG, LNG and alternative fuels are mixed to meet the interchangeability; The pipeline network construction constraints include pipeline construction constraints and compressor construction constraints; The pipeline construction constraint means that the pipeline t Once the construction is completed in a certain period, it can be used in any subsequent period. The constraint relationship is: ； In the formula, for t Period, Node i -node j Between pipes l The construction variable is 1 when a pipeline is being built between nodes, otherwise it is 0; The compressor construction constraint indicates that the compressor t Once the construction is completed in the period, it can be used in any period thereafter, and the node i -node j Only one compressor can be built between them, and the constraint relationship is ；； 。 3. A multi-gas source network expansion optimization method considering gas interchangeability as claimed in claim 1, characterized in that: The objective function of the pipeline network system annual equivalent cost minimum in step S3 is composed of construction investment cost and operation cost, and the relationship is: ； In the formula, The annual equivalent cost of the pipe network system; Investment cost for the pipe network system; is the bank rate; For the life cycle of the pipe network system; The operating cost of the pipe network system; The pipeline network investment cost is defined as the sum of the pipeline investment cost and the compressor investment cost, and the relationship is: ； In the formula, for t+1 Period, compressor c Unit installation cost; for t+1 Period, pipeline l Unit installation cost; The pipeline network operation cost is defined as pipeline operation and maintenance cost, compressor operation and maintenance cost and pipeline network gas purchase cost, and the relationship is: ； In the formula, For pipeline l The conversion factor of for t +1 period, pipeline l Unit operation and maintenance costs; for t +1 period, compressor c Unit electricity cost generated by operation; for t +1 period, compressor c Unit operation and maintenance costs; For Node i The cost of purchasing unit volume of LNG, PNG and alternative fuels.

4. A multi-gas source pipeline network expansion optimization method considering gas interchangeability as claimed in claim 1, characterized in that: The multi-gas source network expansion plan described in step S4 includes: annual equivalent cost of the network system, expansion network structure parameters, compressor operating parameters, node operating pressure parameters, and new node flow distribution plan.

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