Improved Discrete Interval-Valued Stress-Strength Interference Model Based on Extended Universal Generating Function

In practical engineering,sometimes the probability density functions( PDFs) of stress and strength can not be exactly determined,or only limited experiment data are available. In these cases,the traditional stress-strength interference( SSI) model based on classical probabilistic approach can not be used to evaluate reliabilities of components. To solve this issue, the traditional universal generating function( UGF) is introduced and then it is extended to represent the discrete interval-valued random variable.Based on the extended UGF,an improved discrete interval-valued SSI model is proposed, which has higher calculation precision compared with the existing methods. Finally,an illustrative case is given to demonstrate the validity of the proposed model.

混合不确定多态系统可靠性的EUGF分析方法

在进行多状态系统可靠性分析时,很多情况下系统中同时存在着多个类型不确定信息,如一些复杂系统中,由于样本量的差异,一些信息可以作为随机信息,而另一些信息由于缺少足够的样本,只能以区间形式给出。提出一种基于证据通用生成函数理论的多状态系统可靠性分析方法,来处理多类不确定性信息的多态系统。该方法基于证据不确定性量化理论,能够充分利用区间信息和认知信息,避免了系统中信息的浪费。基于证据量化理论建立证据通用生成函数模型,采用信度和似然度对多态系统进行可靠性评价,提高了基于认知不确定性的可靠性分析结果的可信性。对于同时含有随机信息和认知信息的多态系统,该方法首先通过将随机信息离散处理,然后建立统一的证据通用生成理论模型进行多态可靠性分析。通过案例分析对所提出的方法进行了验证。

基于UGF的发电系统区间可靠性评估及其仿射算法改进

文章在元件可靠性指标为区间概率的基础上,结合区间概率和区间数运算来计算发电系统的可靠性指标。运用区间一般生成函数方法(IUGF)得到发电系统的区间值可靠性指标,但是此方法忽略了变量间的相关性,导致计算所得区间值过宽。仿射区间一般生成函数方法(AIUGF)考虑了原始数据中的相关性,能得到更窄且更为准确的发电系统区间可靠性指标。算例分别采用2种方法得到了RTS79的区间值可靠性指标,验证了AIUGF方法比IUGF方法能得到更窄的区间,并且系统不确定性越大,AIUGF方法在减小由于相关性造成的区间过宽上越有效果。

低碳背景下基于改进通用生成函数法的随机生产模拟

通用生成函数法(universal generating function,UGF)具有计算简单,运算快等优点,但其传统的应用中忽略了时序性,评估结果粗糙。为此,提出基于改进UGF法的随机生产模拟算法。首先,采用主成分分析法(principal componentanalysis,PCA)和分层聚类法相结合的方法获得典型风电出力时序样本,然后采用均摊法建立风电出力UGF模型。在建立UGF模型时,通过选择合适的公因子,将状态值转化为公因子的整数倍,以有效抑制状态数指数增长,减缓了状态数爆炸问题。其次,对聚类后的时序风电出力模式进行UGF建模,得到时序UGF模型,该模型既可以体现风电出力的波动性,也可以体现风电出力的不确定性,克服了传统UGF法因缺乏时序性所致的风电特征代表性差的问题。最后,采用修正的IEEE-RTS79算例验证了所提算法的有效性。

舰船装备多状态可修复系统可靠性通用生成函数解算方法

远洋舰船装备结构复杂、系统庞大,可靠性要求高。开展舰船装备复杂系统可靠性研究,对于科学控制装备成本、实施维修决策,具有重要意义。针对舰船装备复杂系统,以可修复双锅汽轮发电系统为例,开展多状态系统可靠性建模。在此基础上,通过引入通用生产算子和通用生产函数,完成多状态复杂系统可用度、期望性能、性能失效等可靠性指标解算,并给出稳态、瞬态数值分析结果。研究表明,解算方法通用性强、适用范围广、计算资源依赖程度低,远优于马尔可夫直接法;多状态模型建立合理,有效反映复杂装备系统可靠性变化规律,能为可靠性评估、装备采购及维修决策提供技术借鉴。

基于通用生成函数的混流制造系统脆弱性评价方法

为了解决基于状态熵的脆弱性评价方法在面对多状态系统组合爆炸问题时的困难,提出了一种基于通用生成函数的混流制造系统脆弱性量化评价方法。首先,分析求解各制造单元的状态及其概率,得到制造单元的通用生成函数,定义并计算各单元的脆性熵,建立制造单元的脆弱性分析模型;其次,根据混流制造系统结构特征和通用生成函数的串并联构造算子,得到系统通用生成函数,定义其脆性熵,基于脆性熵建立混流制造系统的脆弱性评价模型;最后,以某典型的混流制造系统为例,利用所提出的脆弱性评价方法,评估其脆弱性,并与基于状态熵的评价方法进行对比,结果表明该方法可显著提高脆弱性评价的效率。

采用通用生成函数法的自治微网旋转备用充裕性评估

自治微网中可再生能源的随机波动特性对旋转备用容量的运行规划提出了新的要求。基于通用生成函数法(UGF),结合马尔可夫技术建立了自治微网内各元件的多状态概率预测模型,提出了自治微网旋转备用概率预测充裕性评估方法与流程。模型综合考虑了风速、光照强度的预测不确定性,以及风机、光伏系统的随机故障特性和拓扑结构。针对UGF处理多状态会产生组合爆炸问题,采用合并同类项、均摊法以及改进K-means聚类进行状态削减,以减小计算负担、提高计算速度。通过MATLAB编程对自治微网算例系统进行仿真分析,结果表明增大传统机组爬坡速率、合理设置光风容量以及初始储能状态有助于提升旋转备用裕度程度。

基于可用度评价的混联生产线缓冲区配置优化

为快速有效地分配缓冲区容量,提高混联生产线的可用度和生产率,提出了一种基于可用度评价的缓冲区分配方法。在考虑混联生产线特性的同时,通过分析设备状态与缓冲区状态之间的转化规律,将缓冲区进行等效处理,以获得等效设备的可用度;结合通用发生函数(UGF)法,建立混联生产线的可用度与缓冲区容量关系的数学模型,以整线可用度最大为目标,利用遗传算法(GA)求解得到最优的缓冲区配置策略。多个生产线实例缓冲区优化分配结果表明,基于可用度评价的缓冲区分配方法能够在有效解决缓冲区配置问题的同时,明显减少生产线的平均在制品数量。

分层多态加权k/n系统的可用性建模与设计优化

鉴于多态加权k/n系统在刻画分层性能要求方面的不足,定义一种扩展的分层系统,提出了新的分层运算符结合通用生产函数的系统可用性建模方法.构建了可用度约束下解决“多层部件综合选择问题”的系统总成本优化模型,利用遗传算法编程获取各层部件配置类型及数量.算例结果验证了方法和模型的有效性,揭示了分层性能要求对系统可用性和成本的影响.对比分析说明本文模型更通用灵活,可为复杂系统设计优化提供方法支持.

应力—强度干涉的直方图模型及可靠度计算的发生函数法

为解决应力与强度的精确概率分布密度函数未知时的结构可靠性分析问题,提出了一种基于通用发生函数和直方图的可靠度近似计算方法。对于应力与强度的有限个实验数据,经过统计分析后绘出其直方图。对传统的通用发生函数法进行扩展,提出了一种区间值型的发生函数。用扩展后的发生函数对应力与强度的统计直方图进行数学表征,进而提出了一种基于直方图的应力-强度干涉模型。用区间值型发生函数法对结构的极限状态函数进行组合运算,获得极限状态函数的区间值型发生函数表示。定义了极限状态函数的概率质量加权系数,通过安全域内所有概率质量的加权累加获得结构的可靠度。给出了三个典型的可靠度计算实例。实例表明,所提出的方法具有较高的可靠度计算精度,是一种有效的可靠性分析新方法。

考虑概率共因失效的多状态系统可靠度计算

[目的]对于共因失效(CCF)的可靠性分析,现有研究基本上都假设发生共因失效事件必将导致相关单元失效。该假设对于电子元器件是准确的,但是对于可靠度高、结构复杂的机械设备会出现状态缺失的问题。为此,通过理论推导,提出一种考虑概率共因失效(PCCF)的多状态可靠度计算方法。[方法]该方法将共因分为致命型和非致命型,且将每种共因的作用分解在各单元上,采用显式法建立各单元的通用生成函数(UGF)模型,分别采用现有方法和所提方法对单元独立失效与致命型概率及非致命型概率共因失效的计算结果进行对比。[结果]结果表明对概率共因失效假设具有正确性,提出的可靠度计算方法有效。[结论]相比传统的CCF分析法,采用PCCF分析法的可靠度计算结果准确度更高,能较好地解决单元和系统状态丢失的问题。

Universal generating function based probabilistic production simulation for wind power integrated power systems

According to the demand of sustainable development and low-carbon electricity, it is important to develop clean resources and optimize scheduling generation mix. Firstly, a novel method for probabilistic production simulation for wind power integrated power systems is proposed based on universal generating function(UGF), which completes the production simulation with the chronological wind power and load demand. Secondly,multiple-period multiple-state wind power model and multiple-state thermal unit power model are adopted, and both thermal power and wind power are coordinately scheduled by the comprehensive cost including economic cost and environmental cost. Furthermore, the accommodation and curtailment of wind power is synergistically considered according to the available regulation capability of conventional generators in operation. Finally, the proposed method is verified and compared with conventional convolution method in the improved IEEE-RTS 79 system.

基于通用生成函数的结构可靠性优化策略

为提高工程结构可靠性设计优化(RBDO)的求解精度,提出一种基于通用生成函数(UGF)的RBDO新方法。一方面通过系列响应面建立设计变量与概率指标的动态映射,消除传统双循环算法的内层循环;另一方面引入UGF进行可靠性分析,避开传统矩法在处理随机变量非正态、功能函数高度非线性问题时精度低或无法收敛的劣势。同时,结合非均匀离散化技术在既定的计算成本下提高分析精度。算例表明,所提方法合理可行且具有较好的鲁棒性。

Reliability Evaluation of Compressor Systems Based on Universal Generating Function Method

At present, universal generating function(UGF) is a reliability evaluation technique which holds the bare-looking and easily program-realized merits in multi-state system. Thus, it is meaningful to apply this method to an actual industry system. Compressor systems in natural gas pipelines are series-parallel multi-state systems,where the compressor units in each compressor station work in a parallel way and these pressure-boosting stations in the pipeline are series connected. Considering the characteristic of gas pipelines, this paper develops two different UGFs to evaluate the system reliability. One(Model 1) establishes a system model from every compressor unit while the other(Model 2) considers the whole system as a combination of multi-state components. Besides, all the parameters of "weight" in UGFs are obtained from thermal-hydraulic models based on the actual engineering and"probability" from Monte Carlo simulation. The results show that the system reliabilities calculated by different UGFs are approximately equal. In addition, the demand of gas and the gas pipeline transportation system show a reverse trend. Because the number of parameters needed in Model 2 is far less than that needed in Model 1,Model 2 is simpler programming and faster solved.

Probabilistic production simulation of a power system with wind power penetration based on improved UGF techniques

Universal Generating Function(UGF)techniques have been applied to Multi-State System(MSS)reliability analysis,such as long term reserve expansion of power systems with high wind power penetration.However,using simple steady-state distribution models for wind power and large generating units in reliability assessment can yield pessimistic appraisals.To more accurately assess the power system reliability,UGF techniques are extended to dynamic probabilistic simulation analysis on two aspects of modelling improvement.Firstly,a principal component analysis(PCA)combined with a hierarchal clustering algorithm is used to achieve the salient and time-varying patterns of wind power,then a sequential UGF equivalent model of wind power output is established by an apportioning method.Secondly,other than the traditional two-state models,the conventional generator UGF equivalent model is established as a four discrete-state continuous-time Markov model by Lztransform.In the construction process of such a UGF model,the state values are transformed into the integral multiples of one common factor by choosing proper common factors,thus effectively restraining the exponential growth of its state number and alleviating the explosion thereof.The method is suitable for reliability assessment with dynamic probabilistic distributed random variables.In addition,by acquiring the clustering information of wind power,the system reliability indices,such as fuel cost and CO_(2) emissions through different seasons and on different workdays,are calculated.Finally,the effectiveness of the method is verified by a modified IEEE-RTS 79 system integrated with several wind farms of historical hourly wind power data of Zhangbei wind farm in North China.

考虑性能分布信息的多态系统可靠性评估模型

针对通用生成函数只能用于求解多态部件离散性能状态的情形,在分析其用于评估多态系统可靠性实质的基础上,定义了多状态系统可用度、输出性能期望和性能失效值等可靠性评价指标参数。考虑部件及系统性能随机变量的分布信息,分别对离散型、连续型以及既有离散又有连续的多性能状态系统的可靠性进行分析建模。从两部件的一般串并联系统推广至多个部件的多态系统上去,扩展了多状态系统可靠性分析的理论及应用范畴。最后通过对文献中案例的对比计算验证了所提方法的科学性与合理性,证明了该方法具有更强的工程实践价值且能处理多种不确定性的信息融合问题。