Development of an integrated dynamic model for supply security and resilience analysis of natural gas pipeline network systems

An integrated dynamic model of natural gas pipeline networks is developed in this paper.Components for gas supply,e.g.,pipelines,junctions,compressor stations,LNG terminals,regulation stations and gas storage facilities are included in the model.These components are firstly modeled with respect to their properties and functions and,then,integrated at the system level by Graph Theory.The model can be used for simulating the system response in different scenarios of operation,and evaluate the consequences from the perspectives of supply security and resilience.A case study is considered to evaluate the accuracy of the model by benchmarking its results against those from literature and the software Pipeline Studio.Finally,the model is applied on a relatively complex natural gas pipeline network and the results are analyzed in detail from the supply security and resilience points of view.The main contributions of the paper are:firstly,a novel model of a complex gas pipeline network is proposed as a dynamic state-space model at system level;a method,based on the dynamic model,is proposed to analyze the security and resilience of supply from a system perspective.

A novel methodology for forecasting gas supply reliability of natural gas pipeline systems

In this paper,a novel systematic and integrated methodology to assess gas supply reliability is proposed based on the Monte Carlo method,statistical analysis,mathematical-probabilistic analysis,and hydraulic simulation.The method proposed has two stages.In the first stage,typical scenarios are determined.In the second stage,hydraulic simulation is conducted to calculate the flow rate in each typical scenario.The result of the gas pipeline system calculated is the average gas supply reliability in each typical scenario.To verify the feasibility,the method proposed is applied for a real natural gas pipelines network system.The comparison of the results calculated and the actual gas supply reliability based on the filed data in the evaluation period suggests the assessment results of the method proposed agree well with the filed data.Besides,the effect of different components on gas supply reliability is investigated,and the most critical component is identified.For example,the 48th unit is the most critical component for the SH terminal station,while the 119th typical scenario results in the most severe consequence which causes the loss of 175.61×10^4 m^3 gas when the 119th scenario happens.This paper provides a set of scientific and reasonable gas supply reliability indexes which can evaluate the gas supply reliability from two dimensions of quantity and time.

Reliability Assessment of Integrated Electricity and Natural Gas Transmission Systems in Presence of Power-to-gas and Combined Heat and Power Technologies

Assessing the reliability of integrated electricity and gas systems has become an important issue due to the strong dependence of these energy networks through the power-to-gas(P2G)and combined heat and power(CHP)technologies.The current work,initially,presents a detailed energy flow model for the integrated power and natural gas system in light of the P2G and CHP technologies.Considering the simultaneous load flow of networks,a contingency analysis procedure is proposed,and reliability is assessed through sequential Monte Carlo simulations.The current study examines the effect of independent and dependent operation of energy networks on the reliability of the systems.In particular,the effect of employing both P2G and CHP technologies on reliability criteria is evaluated.In addition,a series of sensitivity analysis are performed on the size and site of these technologies to investigate their effects on system reliability.The proposed method is implemented on an integrated IEEE 24-bus electrical power system and 20-node Belgian natural gas system.The simulation procedure certifies the proposed method for reliability assessment is practical and applicable.In addition,the results prove connection between energy networks through P2G and CHP technologies can improve reliability of networks if the site and size of technologies are properly determined.

Simulation of natural gas transmission pipeline network system performance

Simulation has proven to be an effective tool for analyzing pipeline network systems （PNS） in order to determine the design and operational variables which are essential for evaluating the performance of the system. This paper discusses the use of simulation for performance analysis of transmission PNS. A simulation model was developed for determining flow and pressure variables for different configuration of PNS. The mathematical formulation for the simulation model was derived based on the principles of energy conservation, mass balance, and compressor characteristics. For the determination of the pressure and flow variables, solution procedure was developed based on iterative Newton Raphson scheme and implemented using visual C＋＋6. Evaluations of the simulation model with the existing pipeline network system showed that the model enabled to determine the operational variables with less than ten iterations. The performances of the compressor working in the pipeline network system xvhich includes energy consumption, compression ratio and discharge pressure were evaluated to meet pressure requirements ranging from 4000-5000 kPa at various speed. Results of the analyses from the simulation indicated that the model could be used for performance analysis to assist decisions regarding the design and optimal operations of transmission PNS.

Risk analysis and maintenance decision making of natural gas pipelines with external corrosion based on Bayesian network

Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is essential.In this work,a risk analysis and maintenance decision-making model for natural gas pipelines with external corrosion is proposed based on a Bayesian network.A fault tree model is first employed to identify the causes of external corrosion.The Bayesian network for risk analysis is determined accordingly.The maintenance strategies are then inserted into the Bayesian network to show a reduction of the risk.The costs of maintenance strategies and the reduced risk after maintenance are combined in an optimization function to build a decision-making model.Because of the limitations of historical data,some of the parameters in the Bayesian network are obtained from a probabilistic estimation model,which combines expert experience and fuzzy set theory.Finally,a case study is carried out to verify the feasibility of the maintenance decision model.This indicates that the method proposed in this work can be used to provide effective maintenance schemes for different pipeline external corrosion scenarios and to reduce the possible losses caused by external corrosion.

Two-stage robust optimization of power cost minimization problem in gunbarrel natural gas networks by approximate dynamic programming

In short-term operation of natural gas network,the impact of demand uncertainty is not negligible.To address this issue we propose a two-stage robust model for power cost minimization problem in gunbarrel natural gas networks.The demands between pipelines and compressor stations are uncertain with a budget parameter,since it is unlikely that all the uncertain demands reach the maximal deviation simultaneously.During solving the two-stage robust model we encounter a bilevel problem which is challenging to solve.We formulate it as a multi-dimensional dynamic programming problem and propose approximate dynamic programming methods to accelerate the calculation.Numerical results based on real network in China show that we obtain a speed gain of 7 times faster in average without compromising optimality compared with original dynamic programming algorithm.Numerical results also verify the advantage of robust model compared with deterministic model when facing uncertainties.These findings offer short-term operation methods for gunbarrel natural gas network management to handle with uncertainties.

New Situation of China Natural Gas Industry

China natural gas industry is at a turning point. Growth of mid-long term natural gas consumption may maintain at about 10%, supply is sufficient or even "over-sufficient", natural gas price will be determined by competition, oil and gas pipeline facilities will be opened fairly, and private enterprises will play important roles in natural gas exploration, development, storage, transportation, and trade. It can been foreseen that China natural gas industry is very likely to take a turn in next 10 years, and a modern natural gas market with consumption about 500 billion cubic meters will come into being characterized by complete supervision system, diversified market, steady supply, fairly opened pipelines, transparent trading mechanism, and competitive prices.

New Situation of China Natural Gas Industry

China natural gas industry is at a turning point. Growth of mid-long term natural gas consumption may maintain at about 10%, supply is sufficient or even "over-sufficient", natural gas price will be determined by competition, oil and gas pipeline facilities will be opened fairly, and private enterprises will play important roles in natural gas exploration, development, storage, transportation, and trade. It can been foreseen that China natural gas industry is very likely to take a turn in next 10 years, and a modern natural gas market with consumption about 500 billion cubic meters will come into being characterized by complete supervision system, diversified market, steady supply, fairly opened pipelines, transparent trading mechanism, and competitive prices.

Optimal design of the gas storage surface pipeline system with injection and withdrawal conditions

Underground natural gas storage(UNGS)is an important part of the natural gas supply system to ensure a balanced energy supply.The surface system,as an important part of the gas storage,undertakes the functions of gas injection and gas production of the gas storage,and its investment economy is of vital importance.In fact,the UNGS surface pipeline network has two-way injection and production characteristics,which is different from the one-way production characteristics of conventional oil&gas gathering and transportation systems.This paper takes the minimum investment of the pipeline network as the objective function,considers the gas injection and gas withdrawal flow conditions and esablishes a mixed integer non-linear programming model(MINLP)for the surface pipeline network of the UNGS to optimize its pipeline layout and diameter parameters.Constraints including the well affiliation,the number of stations,the gathering radius,the processing capacity and the flow/pressure equilibrium equations,are also taken into consideration.Taking an UNGS in China as an example,the results of the optimal structure and diameter of the pipeline network,as well as the pipe flow,node pressure,and maximum/minimum flowrate during gas injection and gas withdrawal are obtained.Finally,the effects of constraints such as processing capacity and radius on the structure layout and investment of the UNGS are analyzed,verifying the reliability and effectiveness of the model.

考虑供能可靠性与风光不确定性的城市多能源系统规划

大数据与可再生能源接入给城市多能源系统(UMES)规划带来了机遇与挑战。该文提出了一种考虑供能可靠性与风光不确定性的城市多能源系统规划模型。首先,基于改进的DBSCAN算法产生典型场景及其概率,解决了实际工况中可能存在的大量历史数据质量欠佳的问题;其次,通过配送通道故障停运模型,获得了能量配送通道发生N-1的期望故障时间;最后,考虑城市配电网、配气网以及电转气装置(PtG)的相关约束,以UMES总利润最大为目标,提出了一种适用于辐射状网络的N-1供能可靠性评估算法,并建立了混合整数二次规划模型。通过该模型可得出能量源、配送通道及PtG的最优投运时间、类型和位置。案例分析结果表明了DBSCAN算法以及可靠性评估算法的有效性;证明了在PtG的作用下,能量配送通道发生N-1故障时,配气网能够得到配电网的有效支援,显著提升了系统供能可靠性。

城市天然气管网运行的可靠性分析

结合城市天然气管网的特点 ,对其运行的可靠性进行了分析 ,提出了城市管网可靠性评价的内容 ,给出了管网的分段原则。针对城市天然气管网运行的可靠性 ,将整个管网的管理分为初期、中期和末期三个阶段 ,并利用概率论的方法重点讨论了初期和中期管网的可靠性 ,给出了初期管网失效的故障树 ,提出了城市天然气管网可靠性运行的保证措施。

大型天然气管网系统可靠性

随着中国国民经济的快速发展,天然气需求量不断扩大。天然气管网作为连接资源与市场的纽带,已成为保障国民经济的生命线。中国拥有世界上最复杂、输送任务最艰巨的天然气管网系统。现有基于单一或少数管道的运行管理方法已不能满足大型管网系统安全生产需要,必须寻求更为科学合理的管理思路。本文首次提出大型天然气管网系统可靠性概念,分析了大型天然气管网系统可靠性面临的3个挑战:量化大系统可靠性、评价分系统(单元)可靠性、建立大系统与分系统之间的关联。同时,对大型天然气管网系统可靠性框架进行了初步设计,并针对中国天然气管道行业现状,提出大型天然气管网可靠性增强方案。

基于多源信息融合的天然气管网风险评价

为科学客观地评价城市天然气管网的运行风险,提出基于多因素信息融合的风险评价方法。运用HAZOP识别城市天然气管网的风险因素,确定评价指标并计算指标权重;采用改进后的证据理论的加权融合算法进行计算,确定城市天然气管网的风险等级;以某市天然气管网为例验证该方法。结果显示,该市管网处于中等风险状态,而管道腐蚀与设计缺陷处于较大风险状态,应该有针对性地进行维护和管理。

城市天然气供应系统半定量风险评价方法研究

城市天然气供应系统牵扯着千家万户的安全问题,探讨城市天然气供应系统半定量风险评价的思路和流程,及其气源因素、管网因素、应用因素、管理因素和自然因素五方面的失效可能性评价指标体系;构建了财产损失、人员伤亡和环境污染三方面的失效后果评价指标;给出了失效后果的评分标准;提出了一种基于半定量风险评价的城市天然气供应系统风险评价方法。在此基础上以浙江某地城市燃气供应系统为例进行风险评价,得出该城市天然气供应系统的整体风险处于低风险水平。该方法可用于拟建、在建或者在役的城市天然气供应系统的风险评价。

天然气管网系统可靠性与可维修性技术研究现状

天然气管网系统可靠性和可维修性的研究对管网系统高效安全运行的具有重要作用。从管道单元可靠性、设备单元可靠性和管网系统可靠性三个方面重点介绍了天然气管网系统可靠性技术的发展现状,并对管网系统可靠性的发展趋势做出了展望,阐述了当前使用较为广泛的天然气管网系统可维修性技术RCM,最后针对国内外管网的可靠性与可维修性技术存在的问题提出了未来研究的发展方向和建议。

浅析天然气管网建设的生态影响评价方法

分析了天然气管网建设生态影响评价的现状及存在的主要问题,阐述了生态影响评价工作的基本程序、主要方法和生态保护措施。结合天然气管网建设项目生态影响评价实际提出,应强化生态影响现场调查、构建生态影响评价指标体系和创新生态影响评价模式。

天然气管网系统可靠性评价指标研究

天然气管网系统是指由多条干线天然气长输管道及其配套储气调峰设施组成的、各子系统之间具有信息和天然气互联互通能力的大型基础设施.天然气管网系统作为连接天然气资源和市场的纽带,其可靠运行直接关系天然气的安全平稳供应.因此,有必要对天然气管网系统可靠性进行研究,保障我国公共安全和能源安全.其中,提出一套客观、明确的指标体系用以量化天然气管网系统的可靠性是管网系统可靠性研究的关键.本文归纳和总结了天然气管网系统可靠性研究成果,基于天然气管网的特征和功能,并结合管网可靠性研究的应用需求,将管网系统可靠性分为机械可靠性、水力可靠性和供气可靠性.基于此,提出三类可靠性评价指标,包括管网系统机械可靠性评价指标、水力可靠性评价指标和供气可靠性评价指标,分别用于表征系统正常运行能力、完成供气任务能力和满足市场需求能力.

基于人工智能技术的输气管道系统可靠性量化方法

天然气管网运行可靠性评估对于保障区域乃至全国天然气供应安全、改善大气环境、促进沿线经济社会发展都具有重要的意义。为了保障“全国一张网”的天然气干线管网运营机制以及上游油气资源多主体多渠道供应、中间“一张网”高效集输、下游市场化良性竞争油气市场体系(“X+1+X”体系)的安全稳定运行,借助于大数据、人工智能等现代信息技术,建立了基于长短期记忆神经网络(LSTM)方法的短周期用气量预测模型;然后基于单条管道系统的可靠性模型和各子系统可靠性先验概率等信息,结合可靠性计算失效原则和贝叶斯估计理论,提出了天然气管道系统可靠性的量化计算方法;进而以某城市192天真实用气量数据为样本,验证了该用气量预测模型的估计误差为1%~4%,得出了基于实际天然气管道的可靠性数值分析结果。结论认为,首次将人工智能技术与天然气管道系统可靠性结合起来,采用LSTM方法并基于多源异构海量数据进行短周期用气量预测,实现了天然气管道动态运行工况下的系统可靠性量化计算,为天然气管网的用气量估计和系统可靠性定量计算奠定了基础;所提出的方法在实际天然气管道系统中已经得到了应用和验证,为后续天然气管网系统可靠性研究提供了一条可行的技术路径。

综合能源系统下天然气管网供气可靠性评价方法综述

在综合能源系统背景下,可再生能源发电的间歇性、随机性传递到天然气管网,导致供气可靠性评价在不确定性来源、系统行为分析、评价时间尺度等方面都产生了新特点。因此,以综合能源系统背景下的天然气管网为研究对象,分析了供气可靠性评价的关键问题:复杂系统中不确定性量化、不确定性在系统中的传播过程、扰动对系统影响的不确定性等。提出了需要强化设备、市场和可再生能源出力的时序性和概率性耦合量化以满足系统实时供气可靠性分析、需要在考虑能源系统协调优化的基础上提升系统复杂度表征准确性和效率、需要创新探究实时后果不确定性分析方法等思路,为天然气供气可靠性评价提供了借鉴。

某省大型天然气管网可靠性分析

介绍了天然气管网可靠性的相关概念,引出了计算管网可靠性的模型,结合某省大型天然气管网的方案选择,详细阐述了计算管网可靠性模型在天然气管网中的具体应用方法和步骤,特别指出了模型在多气源环状管网应用中应注意和理清的几个问题,分析了影响管网可靠性的主要因素。通过可靠性计算表明环状管网的可靠性明显高于枝状管网。指出在确定管网方案时需要综合考虑工艺可行、经济节约和方案可靠等因素。