Discrete-event system simulation technology is used to analyze distribution system reliability in this paper. A simulation model, including entity state models, system state models, state transition models, reliabilit...Discrete-event system simulation technology is used to analyze distribution system reliability in this paper. A simulation model, including entity state models, system state models, state transition models, reliability criterion model, is established. ‘Next happen event’ is taken as impulse principle of simulator clock to determine the sequence of random event occurrence dynamically. The results show this method is feasible.展开更多
Reliable planning and operation of power distribution systems are of great significance. In this paper, the impactincrement based state enumeration(IIBSE) method is modified to adapt to the features of distribution sy...Reliable planning and operation of power distribution systems are of great significance. In this paper, the impactincrement based state enumeration(IIBSE) method is modified to adapt to the features of distribution systems. With the proposed method, the expectation, probabilistic, and duration reliability indices can be accurately obtained with a lower enumerated order of contingency states. In addition, the time-consuming optimal power flow(OPF) calculation can be replaced by a simple matrix operation for both independent and radial series failure states. Therefore, the accuracy and efficiency of the assessment process are improved comprehensively. The case of RBTS bus 6 system and IEEE 123 node test feeder system are utilized to test the performance of the modified IIBSE. The results show the superiority of the proposed method over Monte Carlo(MC) sampling and state enumeration(SE) methods in distribution systems.展开更多
A modified Bayesian reliability assessment method of binomial components was proposed by fusing prior information of similar products.The traditional Bayesian method usually directly used all the prior data,ignoring t...A modified Bayesian reliability assessment method of binomial components was proposed by fusing prior information of similar products.The traditional Bayesian method usually directly used all the prior data,ignoring the differences between them,which might decrease the credibility level of reliability evaluation and result in data submergence.To solve the problem,a revised approach was derived to calculate groups of prior data's quantitative credibility,used for weighted data fusion.Then inheritance factor was introduced to build a mixed beta distribution to illustrate the innovation of new products.However,in many cases,inheritance factor was determined by Chi-square test that could not give out exact result with respect to rare failures.To make the model more precise,Barnard's exact test was suggested being used to calculate the inheritance factor.A numerical example is given to demonstrate that the modified method is successful and rational,while the classical method is too conservative and the traditional Bayesian method is too risky.展开更多
Small sample size problem is one of the main problems that heavy numerical control(NC) machine tools encounter in their reliability assessment. In order to deal with the small sample size problem, many indirect reliab...Small sample size problem is one of the main problems that heavy numerical control(NC) machine tools encounter in their reliability assessment. In order to deal with the small sample size problem, many indirect reliability data such as reliability data of similar products, expert opinion, and engineers' experience are used in reliability assessment. However, the existing mathematical theories cannot simultaneously process the above reliability data of multiple types, and thus imprecise probability theory is introduced. Imprecise probability theory can simultaneously process multiple reliability data by quantifying multiple uncertainties(stochastic uncertainty,fuzzy uncertainty, epistemic uncertainty, etc.) together. Although imprecise probability theory has so many advantages, the existing natural extension models are complex and the computation result is imprecise. Therefore,they need some improvement for the better application of reliability engineering. This paper proposes an improved imprecise reliability assessment method by introducing empirical probability distributions to natural extension model, and the improved natural extension model is applied to the reliability assessment of heavy NC machine tool spindle to illustrate its effectiveness.展开更多
分布式能源在电力系统中的渗透率不断提升,使得配电网系统呈现出更大的复杂性和不确定性,这将对电力网络的可靠性产生影响。为确定配电网系统中可再生能源发电机组的最优安装位置和容量,文章结合随机模糊期望值算子和马尔科夫蒙特卡洛法...分布式能源在电力系统中的渗透率不断提升,使得配电网系统呈现出更大的复杂性和不确定性,这将对电力网络的可靠性产生影响。为确定配电网系统中可再生能源发电机组的最优安装位置和容量,文章结合随机模糊期望值算子和马尔科夫蒙特卡洛法(Markov Chain Monte Carlo,MCMC),提出了一种可靠性评估框架。该模型建立了风电和光伏出力的多状态概率密度函数,采用随机模糊期望值算子模拟配电网功率损耗和电压稳定性的不确定性。在考虑配电系统拓扑结构的情况下,利用MCMC模拟配电网系统中所有非源元件的随机性,由指数分布生成配电网组件故障事件及恢复时间。最后,在IEEE-33节点标准配电网上,对系统平均停电次数、系统平均停电持续时间、电量不足期望值3种可靠性指数进行评价,实验结果证明了所提出方法的有效性。展开更多
As a bladder accumulator is a high reliable and long life component in a hydraulic system,its cost is high and it takes a lot of time to test its reliability,therefore,a reliability test with small sample is performed...As a bladder accumulator is a high reliable and long life component in a hydraulic system,its cost is high and it takes a lot of time to test its reliability,therefore,a reliability test with small sample is performed,and no failure data is obtained using the method of fixed time truncation. In the case of Weibull distribution,a life reliability model of bladder energy storage is established by Bayesian method using the optimal confidence intervals method,a model of one-sided lower confidence intervals of the reliability and one-sided lower confidence intervals model of the reliability life are established. Results of experiments show that the evaluation method of no failure data under Weibull distribution is a good way to evaluate the reliability of the accumulator,which is convenient for engineering application,and the reliability of the accumulator has theoretical and practical significance.展开更多
基金SupportedbyNationalNatureScienceFoundation No .5 0 1770 17
文摘Discrete-event system simulation technology is used to analyze distribution system reliability in this paper. A simulation model, including entity state models, system state models, state transition models, reliability criterion model, is established. ‘Next happen event’ is taken as impulse principle of simulator clock to determine the sequence of random event occurrence dynamically. The results show this method is feasible.
基金supported in part by the National Natural Science Foundation of China (No.52077150)the National Key Research and Development Program of China (No.2019YFE0118000)。
文摘Reliable planning and operation of power distribution systems are of great significance. In this paper, the impactincrement based state enumeration(IIBSE) method is modified to adapt to the features of distribution systems. With the proposed method, the expectation, probabilistic, and duration reliability indices can be accurately obtained with a lower enumerated order of contingency states. In addition, the time-consuming optimal power flow(OPF) calculation can be replaced by a simple matrix operation for both independent and radial series failure states. Therefore, the accuracy and efficiency of the assessment process are improved comprehensively. The case of RBTS bus 6 system and IEEE 123 node test feeder system are utilized to test the performance of the modified IIBSE. The results show the superiority of the proposed method over Monte Carlo(MC) sampling and state enumeration(SE) methods in distribution systems.
基金National Natural Science Foundation of China(No.71371182)
文摘A modified Bayesian reliability assessment method of binomial components was proposed by fusing prior information of similar products.The traditional Bayesian method usually directly used all the prior data,ignoring the differences between them,which might decrease the credibility level of reliability evaluation and result in data submergence.To solve the problem,a revised approach was derived to calculate groups of prior data's quantitative credibility,used for weighted data fusion.Then inheritance factor was introduced to build a mixed beta distribution to illustrate the innovation of new products.However,in many cases,inheritance factor was determined by Chi-square test that could not give out exact result with respect to rare failures.To make the model more precise,Barnard's exact test was suggested being used to calculate the inheritance factor.A numerical example is given to demonstrate that the modified method is successful and rational,while the classical method is too conservative and the traditional Bayesian method is too risky.
基金the National Natural Science Foundation of China(No.51405065)the National Science and Technology Major Project of China(No.2014ZX04014-011)
文摘Small sample size problem is one of the main problems that heavy numerical control(NC) machine tools encounter in their reliability assessment. In order to deal with the small sample size problem, many indirect reliability data such as reliability data of similar products, expert opinion, and engineers' experience are used in reliability assessment. However, the existing mathematical theories cannot simultaneously process the above reliability data of multiple types, and thus imprecise probability theory is introduced. Imprecise probability theory can simultaneously process multiple reliability data by quantifying multiple uncertainties(stochastic uncertainty,fuzzy uncertainty, epistemic uncertainty, etc.) together. Although imprecise probability theory has so many advantages, the existing natural extension models are complex and the computation result is imprecise. Therefore,they need some improvement for the better application of reliability engineering. This paper proposes an improved imprecise reliability assessment method by introducing empirical probability distributions to natural extension model, and the improved natural extension model is applied to the reliability assessment of heavy NC machine tool spindle to illustrate its effectiveness.
文摘分布式能源在电力系统中的渗透率不断提升,使得配电网系统呈现出更大的复杂性和不确定性,这将对电力网络的可靠性产生影响。为确定配电网系统中可再生能源发电机组的最优安装位置和容量,文章结合随机模糊期望值算子和马尔科夫蒙特卡洛法(Markov Chain Monte Carlo,MCMC),提出了一种可靠性评估框架。该模型建立了风电和光伏出力的多状态概率密度函数,采用随机模糊期望值算子模拟配电网功率损耗和电压稳定性的不确定性。在考虑配电系统拓扑结构的情况下,利用MCMC模拟配电网系统中所有非源元件的随机性,由指数分布生成配电网组件故障事件及恢复时间。最后,在IEEE-33节点标准配电网上,对系统平均停电次数、系统平均停电持续时间、电量不足期望值3种可靠性指数进行评价,实验结果证明了所提出方法的有效性。
基金Supported by the National Natural Science Foundation of China(No.51405424,51675461,11673040)
文摘As a bladder accumulator is a high reliable and long life component in a hydraulic system,its cost is high and it takes a lot of time to test its reliability,therefore,a reliability test with small sample is performed,and no failure data is obtained using the method of fixed time truncation. In the case of Weibull distribution,a life reliability model of bladder energy storage is established by Bayesian method using the optimal confidence intervals method,a model of one-sided lower confidence intervals of the reliability and one-sided lower confidence intervals model of the reliability life are established. Results of experiments show that the evaluation method of no failure data under Weibull distribution is a good way to evaluate the reliability of the accumulator,which is convenient for engineering application,and the reliability of the accumulator has theoretical and practical significance.