Whole Life Cycle Optimal Decision Of Target Reliabilities Of Natural Gas Pipeline Network

With the rapid development of the national economy,the demand for energy is also growing.As a link between the resources and the market,the natural gas pipeline network has become the lifeline of the national economy.For large natural gas pipeline network,it is an inevitable trend to plan and manage the natural gas network from the global,whole life and whole system height.Therefore,the reliability of gas pipeline network connection and the life cycle cost optimization of natural gas pipeline network are studied in this paper based on reliability theory.（1）The framework system of life cycle cost analysis of pipeline system is established,which can provide reference for the optimization of life cycle cost of pipeline system.The life cycle cost analysis is divided into 4 processes:determining the scope,data acquisition and cost structure decomposition,analysis and modeling,and reporting and decision-making.The above 4 processes can be repeated until achieving the goal of minimizing the cost of the life cycle.（2）The whole life cycle optimization decision of target reliability of natural gas pipeline network can be divided into two stages:The stage of the whole life cycle optimization decision for the target design reliability of pipeline system and the stage of the whole life cycle optimization decision for the target operation reliability of natural gas pipeline network.The objective function of life cycle cost of pipeline system shall be the sum of the system cost function,maintenance cost function,and the loss expectation function.The relationship between the three functions of the system cost function,the maintenance cost function and the loss expectation function and the design reliability are given.According to the actual situation of the project,the two stages of the whole life cycle cost of pipeline system optimal decision model is established based on the reliability constraints and investment constraints.（3）Based on the graph theory,the natural gas pipeline network is simplified into an abstract figure-topology.After that,the reliability index and the logical expression of the single gas source and multi gas source pipe network system are established.In order to calculate the connectivity reliability,the logical expression of connectivity reliability is converted into analytic expression by the way of transforming the minimal path set into a matrix and special operations on vectors and matrices.（4）The objective function of life cycle cost of natural gas pipeline network shall be the sum of the maintenance cost function,and the loss expectation function.The relationship between the two functions of the maintenance cost function and the loss expectation function and the design reliability are given.Based on the connectivity reliability of gas source and gate station,an optimal decision model for the operation reliability of natural gas pipeline network is constructed.（5）The particle swarm optimization algorithm is used to optimize the complex continuous function.The calculation result shows that when the inertia weight 0.4≤ω≤0.9,acceleration constants 1.5≤c₁≤2.0 and 1.5≤c₂≤2.0,the particle swarm algorithm can meet the requirement of precision.Finally,in order to improve the accuracy of the algorithm,the shrinkage factor is introduced into the particle swarm optimization algorithm,and the inertia weight and acceleration constants are dynamically selected in the algorithm.