Method and device for calculating reliability of natural gas supply chain

Abstract

The invention discloses a natural gas supply chain reliability calculation method and device. The method comprises the steps of obtaining reliability of all units in a natural gas supply chain; in each simulation period, the gas supply process is simulated, and all operation states and corresponding state information occurring in the current simulation period are obtained according to the obtained reliability of the unit; respectively calculating the air supply quantity of each branch transmission point under the operation state corresponding to the state information by utilizing each obtained state information; using a preset natural gas supply chain reliability index, and calculating the gas supply reliability of each branch transportation point according to the obtained gas supply amount; wherein the natural gas supply chain reliability index is an index which is preset according to the relation between the gas supply amount and the demand amount of each branch transmission point and is used for evaluating the gas supply capacity of each branch transmission point. Whether the natural gas supply chain is reliable or not can be measured from the perspective of user requirements, and the calculation accuracy of the reliability of the natural gas supply chain is improved.

Description

Technical Field

[0001] This article relates to risk assessment technology, and more particularly to a method and device for calculating the reliability of a natural gas supply chain. Background Art

[0002] The research on the reliability of the natural gas supply chain system can evaluate the ability of the supply chain system to resist unexpected gas supply shortages caused by foreseeable probabilistic disturbances in the future, so as to make various preventive measures to ensure the demand of the natural gas market.

[0003] In related technologies, the reliability research of natural gas supply chain system is mainly based on classical reliability theories and methods, such as fault tree analysis method, which considers the failure factors of natural gas supply, production, transportation, storage, distribution and other links, and uses historical data to determine the failure probability of factors in each link, such as gas field accidents, gas storage accidents, liquefied natural gas (LNG) receiving station accidents, gas transmission station accidents, long-distance pipeline accidents and gate station accidents, so as to calculate the probability of failure of the entire supply chain.

[0004] However, this method only analyzes the probability of failure of the natural gas supply chain or key units. The failure of a unit in the system has different effects on the supply chain's ability to meet user needs. This method does not measure whether the natural gas supply chain is reliable from the perspective of user needs, so the accuracy of the reliability obtained is low. Summary of the invention

[0005] The present application provides a method and device for calculating the reliability of a natural gas supply chain, which can measure whether the natural gas supply chain is reliable from the perspective of user needs, thereby improving the calculation accuracy of the natural gas supply chain reliability.

[0006] On the one hand, the present application provides a method and device for calculating the reliability of a natural gas supply chain, including:

[0007] Obtain the reliability of all units in the natural gas supply chain;

[0008] In each simulation cycle, the gas supply process of the natural gas supply chain including various state transition processes is simulated respectively, and all the operating states of the natural gas supply chain in the current simulation cycle and the state information corresponding to each operating state are obtained according to the obtained unit reliability; and each state information obtained in the current simulation cycle is used to calculate the gas supply volume of the natural gas supply chain to each distribution point under the operating state corresponding to the state information;

[0009] By using a preset natural gas supply chain reliability index and according to the obtained gas supply volume of the natural gas supply chain to each distribution point under each operating state in all simulation cycles, the gas supply reliability of the natural gas supply chain to each distribution point is calculated; wherein the natural gas supply chain reliability index is a preset index for evaluating the gas supply capacity of the natural gas supply chain to each distribution point based on the relationship between the gas supply volume and the demand volume of each distribution point in the natural gas supply chain.

[0010] On the other hand, the present application provides a computing device for natural gas supply chain reliability, comprising: a memory and a processor, wherein the memory is used to store an executable program;

[0011] The processor is used to read and execute the executable program to implement the above-mentioned calculation method of the reliability of the natural gas supply chain.

[0012] Compared with the related art, the present application includes simulating the gas supply process of the natural gas supply chain including various state transition processes in each simulation cycle, obtaining all operating states of the natural gas supply chain in the current simulation cycle, and the state information corresponding to each operating state; and using each state information obtained in the current simulation cycle, respectively calculating the gas supply volume of the natural gas supply chain to each distribution point under the operating state corresponding to the state information; using a preset natural gas supply chain reliability index, and according to the obtained gas supply volume of the natural gas supply chain to each distribution point in each operating state in all simulation cycles, calculating the gas supply reliability of the natural gas supply chain to each distribution point, thereby taking the natural gas supply chain as a whole, considering its ability to satisfy the gas supply of each distribution point under different operating states, thereby achieving the measurement of whether the natural gas supply chain is reliable from the perspective of user needs, and improving the calculation accuracy of the reliability of the natural gas supply chain.

[0013] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0015] Figure 1 A flowchart of a method for calculating the reliability of a natural gas supply chain provided in an embodiment of the present application. DETAILED DESCRIPTION

[0016] The present application describes multiple embodiments, but the description is exemplary rather than restrictive, and it is obvious to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described in the present application. Although many possible feature combinations are shown in the drawings and discussed in the specific embodiments, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0017] The present application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features and elements disclosed in the present application may also be combined with any conventional features or elements to form a unique invention scheme defined by the claims. Any features or elements of any embodiment may also be combined with features or elements from other invention schemes to form another unique invention scheme defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in the present application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the attached claims and their equivalents, the embodiments are not subject to other restrictions. In addition, various modifications and changes may be made within the scope of protection of the attached claims.

[0018] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps of the specific order described. As will be understood by those of ordinary skill in the art, other sequences of steps are also possible. Therefore, the specific sequence of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to the steps of performing them in the order written, and those skilled in the art can easily understand that these sequences can be changed and still remain within the spirit and scope of the embodiments of the present application.

[0019] The present application embodiment provides a method for calculating the reliability of a natural gas supply chain. Figure 1 As shown, including:

[0020] Step 101, obtaining the reliability of all units in the natural gas supply chain;

[0021] Step 102: In each simulation cycle, the gas supply process of the natural gas supply chain including various transfer states is simulated respectively, and all operating states of the natural gas supply chain in the current simulation cycle and the state information corresponding to each operating state are obtained according to the obtained unit reliability; and each state information obtained in the current simulation cycle is used to calculate the gas supply volume of the natural gas supply chain to each distribution point under the operating state corresponding to the state information;

[0022] Step 103: using a preset natural gas supply chain reliability index and according to the obtained gas supply volume of the natural gas supply chain to each distribution point under each operating state in all simulation cycles, calculating the gas supply reliability of the natural gas supply chain to each distribution point; wherein the natural gas supply chain reliability index is a preset index for evaluating the gas supply capacity of the natural gas supply chain to each distribution point based on the relationship between the gas supply volume and the demand volume of each distribution point in the natural gas supply chain.

[0023] Exemplarily, the unit types in the natural gas supply chain include: natural gas pipelines, compressor stations, oil and gas fields, LNG receiving stations, and underground gas storage facilities.

[0024] The natural gas supply chain is a large and complex system consisting of natural gas supply, production, transportation, storage, and distribution. Through this system, natural gas can be transported from upstream production to downstream end users. The natural gas supply chain involves the entire process of exploration and development and pipeline transportation to downstream users, which involves multiple companies and multiple links. Companies are interconnected, interdependent, and mutually influential. Any error in any node will affect other links and ultimately affect the normal operation of the entire supply chain. Since the various links of the natural gas supply chain are closely linked to the storage and transportation infrastructure, my country's natural gas infrastructure capacity is insufficient, and the peak-shaving capacity accounts for about 6.9% of annual sales, which is far from the international level of 15% to 20%. Therefore, when encountering major risks in operation, such as reduced supply of imported gas resources, backbone pipeline accidents, climate change, and LNG cannot be normally unloaded, it poses a major challenge to the smooth operation of the natural gas supply and demand chain, seriously affecting the gas demand of downstream users. Therefore, according to the system characteristics of the natural gas supply chain, the method of calculating and evaluating the reliability of the natural gas supply chain system is established, which can evaluate the ability of the supply chain system to resist unexpected gas shortages caused by foreseeable probabilistic disturbances in the future, so as to make various preventive measures to ensure the demand of the natural gas market; it can also evaluate the ability of the natural gas supply chain to maintain gas supply security from the system level, and solve problems such as unit reliability enhancement and inter-regional resource optimization and allocation, supply and demand balance, pipeline network configuration, and optimized operation. In addition, combining system reliability with economy and establishing a comprehensive evaluation index system for the natural gas supply chain that couples system reliability and economic benefits can achieve the transition of the natural gas supply chain from single-objective management to multi-objective management.

[0025] Existing technologies only analyze the probability of failure of the natural gas supply chain or key units. However, the natural gas supply chain is a large, complex and maintainable system. The failure of a unit in the system has different effects on the supply chain meeting user needs. Existing studies treat the natural gas supply chain as a simple series-parallel system, without considering the maintainability of the units and the pipeline network technology of the natural gas supply chain, and cannot evaluate the ability of the natural gas supply chain to meet the gas demand of natural gas users under specified time and conditions. The method for calculating the reliability of the natural gas supply chain provided in the embodiment of the present application simulates the gas supply process of the natural gas supply chain including various state transition processes in each simulation cycle, and obtains all operating states of the natural gas supply chain that appear in the current simulation cycle, and the state information corresponding to each operating state; and uses each state information obtained in the current simulation cycle to calculate the gas supply volume of the natural gas supply chain to each distribution point under the operating state corresponding to the state information; uses the preset natural gas supply chain reliability index, and calculates the gas supply reliability of the natural gas supply chain to each distribution point based on the obtained gas supply volume of the natural gas supply chain to each distribution point under each operating state in all simulation cycles. Therefore, the natural gas supply chain is taken as a whole, and its ability to satisfy the gas supply of each distribution point under different operating states is considered, thereby achieving the measurement of whether the natural gas supply chain is reliable from the perspective of user needs, and improving the calculation accuracy of the reliability of the natural gas supply chain.

[0026] In an exemplary embodiment, the state information includes: the occurrence time and duration of the running state.

[0027] In an exemplary embodiment, the state transition process of the natural gas supply chain is simulated, and all operating states and corresponding state information of the natural gas supply chain in the current simulation cycle are obtained according to the obtained unit reliability, including:

[0028] Firstly, the state transition process of the natural gas supply chain is simulated by using the sequential Monte Carlo method, and all state transition moments of the natural gas supply chain in the current simulation cycle are obtained according to the obtained unit reliability, as well as the transfer unit related to the current transfer state corresponding to each state transition moment;

[0029] Secondly, the operation states corresponding to all state transfer moments are obtained, including: for each state transfer moment, the operation state corresponding to the state transfer moment is obtained according to the transfer unit corresponding to the state transfer moment and the operation state corresponding to the previous state transfer moment;

[0030] Again, each state transition moment is taken as the appearance moment of the corresponding running state;

[0031] Finally, the duration of the corresponding operating state is obtained according to the time difference between each two adjacent state transition moments.

[0032] In an exemplary embodiment, the units include: natural gas pipelines, compressor stations, oil and gas fields, liquefied natural gas (LNG) receiving stations, and underground gas storage facilities; and the reliability includes: failure rate and maintenance rate.

[0033] In an exemplary embodiment, when the unit is the natural gas pipeline, obtaining the reliability of the unit in the natural gas supply chain includes:

[0034] The failure data statistics method is used to calculate the failure rate and maintenance rate of the natural gas pipeline.

[0035] In an exemplary embodiment, when the unit is the compressor station, obtaining the reliability of the unit in the natural gas supply chain includes:

[0036] The natural gas station is simplified into a compressor station composed of multiple compressor units, and the GO method is used to calculate the failure probability of the compressor station, so as to obtain the failure rate and maintenance rate of the compressor station.

[0037] Among them, the GO method is a success-oriented system probability analysis technology. Like the commonly used fault tree method, it is suitable for system reliability, availability, safety and risk analysis, and is an effective system reliability analysis method.

[0038] In an exemplary embodiment, when the unit is the oil and gas field, the LNG receiving station or the underground gas storage, the obtaining of the reliability of the unit in the natural gas supply chain includes:

[0039] Obtain the corresponding failure rate and maintenance rate based on historical data.

[0040] In an exemplary embodiment, before simulating the state transition process of the natural gas supply chain using the sequential Monte Carlo method, the method further includes:

[0041] All units in the natural gas supply chain are numbered.

[0042] In an exemplary embodiment, the state transition process of the natural gas supply chain is simulated by using the sequential Monte Carlo method, and all state transition moments and corresponding transition units of the natural gas supply chain in the current simulation cycle are obtained according to the obtained unit reliability, including:

[0043] Performing a first operation on the numbered units until the obtained state transfer moment reaches or exceeds the current simulation cycle, obtaining all state transfer moments in the current simulation cycle and the transfer units corresponding to each state transfer moment;

[0044] The first operation includes:

[0045] First, through Calculate the system state transition rate of the natural gas supply chain; where λ system is the system state transition rate; i is the state transition rate of the ith unit. When the ith unit is in normal operation, its state transition rate is the failure rate. When the ith unit is in failure state, its state transition rate is the maintenance rate. c is the number of units in the natural gas supply chain system;

[0046] Secondly, a random number R1 between (0,1) is randomly selected and based on the system state transition rate, Calculate the next state transition time t' of the natural gas supply chain; wherein t0 is the initial state transition time of the natural gas supply chain;

[0047] Finally, a random number R2 between (0,1) is randomly selected, and the number m of the transfer unit is determined according to the state transfer rate of each unit; where n is the number of the determined transfer unit, 1 <n<n c ;

[0048]

[0049] It should be noted that when calculating the system state transition rate of the natural gas supply chain for the first time in the current simulation cycle, the default value of n in the natural gas supply chain system is c All units are in normal operation.

[0050] In an exemplary embodiment, the method of using each state information obtained in the current simulation cycle to respectively calculate the gas supply volume of the natural gas supply chain to each distribution point under the operating state corresponding to the state information includes:

[0051] The solution algorithm of the mixed integer linear programming model is adopted, and each state information obtained in the current simulation cycle is used to calculate the gas supply volume of the natural gas supply chain to each distribution point under the operating state corresponding to the state information; wherein the objective function of the mixed integer linear programming model includes: the maximum gas supply volume of the natural gas supply chain to each distribution point within the duration of each operating state; the constraint conditions of the model include: equality constraint conditions and inequality constraint conditions formulated using the hydraulic characteristics of the pipeline network.

[0052] Exemplarily, the objective function can be specifically expressed as:

[0053] Among them, T k is the duration of the system in the kth state, t is the time, D is the set of distribution points, xi (t) represents the gas volume supplied by the pipeline network to the i-th distribution point at time t.

[0054] The method for calculating the reliability of the natural gas supply chain provided in the embodiment of the present application converts the problem of solving the gas volume supplied to each distribution point by the natural gas supply chain under any operating state into an optimization problem. It can not only quickly calculate the gas volume supplied to the distribution point, but also take into account the hydraulic characteristics of the pipeline network, such as hydraulic constraints, flow, and pressure.

[0055] In an exemplary embodiment, the equality constraint condition includes:

[0056] Node flow constraints, pipeline hydraulic constraints, natural gas pipeline storage constraints, gas storage inventory constraints, and LNG receiving station tank storage constraints.

[0057] In an exemplary instance, the inequality constraints include: flow direction constraints of bidirectional pipelines, supply flow constraints of gas source points, pipeline flow constraints, constraints on the gas supply volume of each distribution point, gas injection volume constraints when the gas storage is in the gas injection stage, pressure constraints, pipeline storage constraints, inventory constraints, and tank storage constraints.

[0058] In an exemplary embodiment, the node traffic constraint condition includes:

[0059]

[0060] Among them, x ij is the flow from the i-th node to the j-th node, (i, j) and (j, l) are the pipelines from node i to node j and from node j to node l respectively, V is the node set, and E is the pipeline set;

[0061] The pipeline hydraulic constraints include:

[0062] Among them, P i and P j are the pressures of the i-th and j-th nodes, λ is the hydraulic friction coefficient, Z is the compression factor of natural gas under pipeline transportation conditions, Δ * is the relative density of natural gas, T is the gas transmission temperature, in K, L is the calculated length of the gas pipeline, D is the inner diameter of the gas pipeline, in m, and C0 is a constant, which can be obtained by querying Table 1 below;

[0063] Table 1

[0064]

[0065] The natural gas pipeline storage constraints include:

[0066]

[0067] Among them, V s is the pipe storage of the pipeline, V0 is the pipe volume of the pipeline, P pj is the average pipeline pressure, T0 is the temperature under standard conditions, Z0 is the compression factor under standard conditions, P0 is the pressure under standard conditions, T is the gas transmission temperature, Z is the compression factor of natural gas under pipeline conditions, P i and P j are the pressures at the i-th and j-th nodes respectively;

[0068] The gas storage inventory constraints include:

[0069] When in the gas production stage:

[0070]

[0071] During the gas injection phase:

[0072]

[0073] Among them, V UGS,i is the inventory of the i-th gas storage, is the initial inventory of the i-th gas storage, is the gas injection and production volume of the i-th gas storage, S u and D u are the collections of gas storages in the gas extraction stage and gas injection stage respectively;

[0074] The LNG receiving station tank storage constraints include:

[0075]

[0076] Among them, V LNG,i is the tank storage of the i-th LNG receiving station, is the initial tank storage of the i-th LNG receiving station, is the external output of the i-th LNG receiving station, S l It is a collection of LNG receiving stations.

[0077] In an exemplary embodiment, the flow direction constraint conditions of the bidirectional pipeline include:

[0078]

[0079] Among them, E b is a collection of bidirectional pipes, y ij ,y ji is a binary decision variable that controls the flow direction of a bidirectional pipeline;

[0080] The gas source point supply flow constraint conditions include:

[0081]

[0082]

[0083]

[0084] in, are the production of the i-th oil and gas field, the gas production of the i-th gas storage, and the external output of the i-th LNG receiving station; are the maximum production capacity of the i-th oil and gas field, the maximum gas production capacity of the i-th gas storage, and the maximum external transmission capacity of the i-th LNG receiving station; S f , S u , S l They are a collection of oil fields, a collection of gas storage facilities in the gas production stage, and a collection of LNG receiving stations;

[0085] The pipeline flow constraints include:

[0086]

[0087] Among them, x ij is the flow from the i-th node to the j-th node, C ij is the pipeline capacity between node i and node j, and E is the pipeline set;

[0088] The constraints on the gas supply volume of each distribution point include:

[0089]

[0090] in, is the flow rate of the ith distribution point, and are the minimum demand and maximum demand of the ith distribution point, respectively, and D is the set of distribution points;

[0091] The gas injection volume constraint conditions when the gas storage is in the gas injection stage include:

[0092]

[0093] in, is the gas injection volume of the i-th gas storage, is the maximum gas injection capacity of the i-th gas storage; D u It is a gas storage in the gas injection stage;

[0094] The pressure constraints include: pressure constraints of each node in the pipeline network, upstream and downstream pressure constraints of the compressor station, and upstream and downstream pressure constraints of the regulating valve;

[0095] The pressure constraints of each node of the pipeline network include:

[0096] P i,min ≤P i ≤P i,max

[0097] Among them, P i is the pressure of the ith node, P i,min and P i,max are the upper and lower limits of the pressure at the i-th node respectively;

[0098] The upstream and downstream pressure constraints of the compressor station include:

[0099]

[0100] in, are the upstream pressure, downstream pressure, upstream pressure limit and downstream pressure limit of the ith compressor station respectively;

[0101] The upstream and downstream pressure constraints of the regulating valve include:

[0102]

[0103]

[0104] in, are the upstream pressure, downstream pressure, lower limit of downstream pressure and upper limit of downstream pressure of the i-th regulating valve respectively;

[0105] The storage constraints include:

[0106]

[0107] Among them, V s is the pipeline inventory, and They are the minimum safe pipeline inventory and the maximum safe pipeline inventory respectively;

[0108] The inventory constraints include:

[0109]

[0110] Among them, V UGS,i is the inventory of i gas storages, and are the minimum allowable storage capacity and maximum allowable storage capacity of the i-th gas storage respectively;

[0111] The tank storage constraints include:

[0112]

[0113] Among them, VLNG,i For the i-th LNG tank storage, and are the minimum allowable tank storage and maximum allowable tank storage of the i-th LNG respectively.

[0114] In an exemplary embodiment, the natural gas supply chain reliability index includes: an expected value EGNS of demand reduction caused by the failure to meet demand in the natural gas supply chain within a given time interval, and a ratio ERNS of the demand reduction amount to the total demand of the natural gas supply chain within the given time interval;

[0115]

[0116]

[0117] Where i is the i-th distribution point in the natural gas supply chain, EGNS i and ERNS i are the EGNS and ERNS of the i-th distribution point, j is the j-th simulation, N is the number of simulation cycles, T is the simulation cycle, and They are respectively the gas supply of the natural gas supply chain to the i-th distribution point at the t-th time in the j-th simulation and the gas demand of the i-th distribution point.

[0118] The embodiment of the present application also provides a computing device for natural gas supply chain reliability, comprising: a memory and a processor, wherein the memory is used to store an executable program;

[0119] The processor is used to read and execute the executable program to implement the method for calculating the reliability of the natural gas supply chain described in any one of the above embodiments.

[0120] The calculation device for the reliability of the natural gas supply chain provided in the embodiment of the present application simulates the gas supply process of the natural gas supply chain including various state transition processes in each simulation cycle, obtains all operating states of the natural gas supply chain appearing in the current simulation cycle, and the state information corresponding to each operating state; and uses each state information obtained in the current simulation cycle to calculate the gas supply volume of the natural gas supply chain to each distribution point under the operating state corresponding to the state information; uses the preset natural gas supply chain reliability index, and calculates the gas supply reliability of the natural gas supply chain to each distribution point based on the obtained gas supply volume of the natural gas supply chain to each distribution point under each operating state in all simulation cycles. Therefore, the natural gas supply chain is taken as a whole, and its ability to satisfy the gas supply of each distribution point under different operating states is considered, thereby achieving the measurement of whether the natural gas supply chain is reliable from the perspective of user needs, and improving the calculation accuracy of the reliability of the natural gas supply chain.

[0121] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the disclosed methods above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical elements; for example, a physical element may have multiple functions, or a function or step may be performed by several physical elements in cooperation. Some or all elements may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those of ordinary skill in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A method for calculating the reliability of a natural gas supply chain, characterized in that: include: Obtain the reliability of all units in the natural gas supply chain; In each simulation cycle, the gas supply process of the natural gas supply chain including various transfer states is simulated respectively, and all the operating states of the natural gas supply chain in the current simulation cycle and the state information corresponding to each operating state are obtained according to the obtained unit reliability; and each state information obtained in the current simulation cycle is used to calculate the gas supply volume of the natural gas supply chain to each distribution point under the operating state corresponding to the state information; By using a preset natural gas supply chain reliability index and according to the obtained gas supply volume of the natural gas supply chain to each distribution point under each operating state in all simulation cycles, the gas supply reliability of the natural gas supply chain to each distribution point is calculated; wherein the natural gas supply chain reliability index is a preset index for evaluating the gas supply capacity of the natural gas supply chain to each distribution point based on the relationship between the gas supply volume and the demand volume of each distribution point in the natural gas supply chain.

2. The method according to claim 1, characterized in that: The state information includes: the occurrence time and duration of the running state; The state transition process of the natural gas supply chain is simulated, and all operating states and corresponding state information of the natural gas supply chain in the current simulation cycle are obtained according to the obtained unit reliability, including: The state transition process of the natural gas supply chain is simulated by using a sequential Monte Carlo method, and all state transition moments of the natural gas supply chain in the current simulation cycle are obtained according to the obtained unit reliability, as well as the transfer unit related to the current transfer state corresponding to each state transition moment; Obtaining the operating states corresponding to all state transfer moments, including: for each state transfer moment, obtaining the operating state corresponding to the state transfer moment according to the transfer unit corresponding to the state transfer moment and the operating state corresponding to the previous state transfer moment; Take each state transition moment as the appearance moment of the corresponding running state; The duration of the corresponding operating state is obtained according to the time difference between each two adjacent state transition moments.

3. The method according to claim 1, characterized in that The units include: natural gas pipelines, compressor stations, oil and gas fields, liquefied natural gas (LNG) receiving stations and underground gas storages; the reliability includes: failure rate and maintenance rate; When the unit is the natural gas pipeline, obtaining the reliability of the unit in the natural gas supply chain includes: Calculating the failure rate and maintenance rate of the natural gas pipeline by using failure data statistics method; When the unit is the compressor station, obtaining the reliability of the unit in the natural gas supply chain includes: The natural gas station is simplified into a compressor station composed of multiple compressor units, and the failure probability of the compressor station is calculated by using the GO method, so as to obtain the failure rate and maintenance rate of the compressor station; When the unit is the oil and gas field, the LNG receiving station or the underground gas storage, the obtaining of the reliability of the unit in the natural gas supply chain includes: Obtain the corresponding failure rate and maintenance rate based on historical data.

4. The method according to claim 2, characterized in that: Before simulating the state transition process of the natural gas supply chain by using the sequential Monte Carlo method, the method further includes: Numbering all units in the natural gas supply chain; The sequential Monte Carlo method is used to simulate the state transition process of the natural gas supply chain, and all state transition moments and corresponding transition units of the natural gas supply chain in the current simulation cycle are obtained according to the obtained unit reliability, including: Performing a first operation on the numbered units until the obtained state transfer moment reaches or exceeds the current simulation cycle, obtaining all state transfer moments in the current simulation cycle and the transfer units corresponding to each state transfer moment; The first operation includes: pass Calculate the system state transition rate of the natural gas supply chain; where λ system is the system state transition rate; i is the state transition rate of the ith unit. When the ith unit is in normal operation, its state transition rate is the failure rate. When the ith unit is in failure state, its state transition rate is the maintenance rate. c is the number of units in the natural gas supply chain system; Randomly extract a random number R1 between (0,1) and according to the system state transition rate, Calculate the next state transition time t' of the natural gas supply chain; wherein t0 is the initial time of the state transition of the natural gas supply chain; Randomly extract a random number R2 between (0,1), and determine the number m of the transfer unit according to the state transfer rate of each unit; where n is the number of the determined transfer unit, 1 <n<n c ; 5. The method according to claim 2, characterized in that: The method of using each state information obtained in the current simulation cycle to respectively calculate the gas supply volume of the natural gas supply chain to each distribution point under the operating state corresponding to the state information includes: The solution algorithm of the mixed integer linear programming model is adopted, and each state information obtained in the current simulation cycle is used to calculate the gas supply volume of the natural gas supply chain to each distribution point under the operating state corresponding to the state information; wherein the objective function of the mixed integer linear programming model includes: the maximum gas supply volume of the natural gas supply chain to each distribution point within the duration of each operating state; the constraint conditions of the model include: equality constraint conditions and inequality constraint conditions formulated using the hydraulic characteristics of the pipeline network.

6. The method according to claim 5, characterized in that The equality constraints include: Node flow constraints, pipeline hydraulic constraints, natural gas pipeline storage constraints, gas storage inventory constraints, LNG receiving station tank storage constraints; The inequality constraints include: flow direction constraints of bidirectional pipelines, supply flow constraints of gas source points, pipeline flow constraints, constraints on the gas supply volume of each distribution point, gas injection volume constraints when the gas storage is in the gas injection stage, pressure constraints, pipeline storage constraints, inventory constraints, and tank storage constraints.

7. The method according to claim 6, characterized in that The node traffic constraint conditions include: Among them, x ij is the flow from the i-th node to the j-th node, (i, j) and (j, l) are the pipelines from node i to node j and from node j to node l respectively, V is the node set, and E is the pipeline set; The pipeline hydraulic constraints include: Among them, P i and P j are the pressures of the i-th and j-th nodes, λ is the hydraulic friction coefficient, Z is the compression factor of natural gas under pipeline transportation conditions, Δ * is the relative density of natural gas, T is the gas transmission temperature, K, L is the calculated length of the gas pipeline, D is the inner diameter of the gas pipeline, m, C0 is a constant; The natural gas pipeline storage constraints include: Among them, V s is the pipe storage of the pipeline, V0 is the pipe volume of the pipeline, P pj is the average pipeline pressure, T0 is the temperature under standard conditions, Z0 is the compression factor under standard conditions, P0 is the pressure under standard conditions, T is the gas transmission temperature, Z is the compression factor of natural gas under pipeline conditions, P i and P j are the pressures at the i-th and j-th nodes respectively; The gas storage inventory constraints include: When in the gas production stage: During the gas injection phase: Among them, V UGS,i is the inventory of the i-th gas storage, is the initial inventory of the i-th gas storage, is the gas injection and production volume of the i-th gas storage, S u and D u are the collections of gas storages in the gas extraction stage and gas injection stage respectively; The LNG receiving station tank storage constraints include: Among them, V LNG,i is the tank storage of the i-th LNG receiving station, is the initial tank storage of the i-th LNG receiving station, is the external output of the i-th LNG receiving station, S l It is a collection of LNG receiving stations.

8. The method according to claim 6, characterized in that The flow constraints of the bidirectional pipeline include: Among them, E b is a collection of bidirectional pipes, y ij ,y ji is a binary decision variable that controls the flow direction of a bidirectional pipeline; The gas source point supply flow constraint conditions include: in, are the production of the i-th oil and gas field, the gas production of the i-th gas storage, and the external output of the i-th LNG receiving station; are the maximum production capacity of the i-th oil and gas field, the maximum gas production capacity of the i-th gas storage, and the maximum external transmission capacity of the i-th LNG receiving station; S f , S u , S l They are a collection of oil fields, a collection of gas storage facilities in the gas production stage, and a collection of LNG receiving stations; The pipeline flow constraints include: Among them, x ij is the flow from the i-th node to the j-th node, C ij is the pipeline capacity between node i and node j, and E is the pipeline set; The constraints on the gas supply volume of each distribution point include: Among them, Q i is the flow rate of the ith distribution point, and are the minimum demand and maximum demand of the ith distribution point, respectively, and D is the set of distribution points; The gas injection volume constraint conditions when the gas storage is in the gas injection stage include: in, is the gas injection volume of the i-th gas storage, is the maximum gas injection capacity of the i-th gas storage; D u It is a gas storage in the gas injection stage; The pressure constraints include: pressure constraints of each node in the pipeline network, upstream and downstream pressure constraints of the compressor station, and upstream and downstream pressure constraints of the regulating valve; The pressure constraints of each node of the pipeline network include: P i,min ≤P i ≤P i,max Among them, P i is the pressure of the ith node, P i,min and P i,max are the upper and lower limits of the pressure at the i-th node respectively; The upstream and downstream pressure constraints of the compressor station include: in, are the upstream pressure, downstream pressure, upstream pressure limit and downstream pressure limit of the ith compressor station respectively; The upstream and downstream pressure constraints of the regulating valve include: in, are the upstream pressure, downstream pressure, lower limit of downstream pressure and upper limit of downstream pressure of the i-th regulating valve respectively; The storage constraints include: In s min ≤V s ≤V s max Among them, V s is the pipeline inventory, V s min and V s max They are the minimum safe pipeline inventory and the maximum safe pipeline inventory respectively; The inventory constraints include: Among them, V UGS,i is the storage capacity of i gas storage reservoirs, and are the minimum allowable storage capacity and maximum allowable storage capacity of the i-th gas storage respectively; The tank storage constraints include: Among them, V LNG,i For the i-th LNG tank storage, and are the minimum allowable tank storage and maximum allowable tank storage of the i-th LNG respectively.

9. The method according to claim 1, characterized in that: The natural gas supply chain reliability index includes: an expected value EGNS of demand reduction caused by the natural gas supply chain being unable to meet demand within a given time interval, and a ratio ERNS of the demand reduction amount to the total demand of the natural gas supply chain within a given time interval; Where i is the i-th distribution point in the natural gas supply chain, EGNS i and ERNS i are the EGNS and ERNS of the i-th distribution point, j is the j-th simulation, N is the number of simulation cycles, T is the simulation cycle, and are the gas supply of the natural gas supply chain to the i-th distribution point at the t-th time in the j-th simulation and the gas demand of the i-th distribution point.

10. A calculation device for natural gas supply chain reliability, characterized in that: include: A memory and a processor, wherein the memory is used to store an executable program; The processor is used to read and execute the executable program to implement the method for calculating the reliability of the natural gas supply chain as described in any one of claims 1-9.

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