针对采用常规恒功率控制方式下的光伏并网逆变器缺乏电压和频率动态调节能力的问题,提出一种基于虚拟同步发电机(VSG)的光伏并网逆变器控制策略.根据同步发电机的原理,建立同步发电机的并网等效电路和矢量关系表达式,设计了有功频率控...针对采用常规恒功率控制方式下的光伏并网逆变器缺乏电压和频率动态调节能力的问题,提出一种基于虚拟同步发电机(VSG)的光伏并网逆变器控制策略.根据同步发电机的原理,建立同步发电机的并网等效电路和矢量关系表达式,设计了有功频率控制算法和无功电压控制算法,搭建了虚拟同步发电机控制策略下的光伏发电系统.在Matlab/simulink环境中建立了10 k W的光伏并网系统.仿真结果表明,基于虚拟同步发电机的光伏并网逆变器具有与同步发电机相似的调频调压特性,能够较好地适应电网运行要求.展开更多
为帮助制造企业处理积累的海量制造过程质量数据,数据挖掘方法可以帮助企业从中发现有用的知识和模式进行有效的质量分析及改进。制造过程质量数据的特点如下:混合型数据、分布不均衡、维度灾难及数据耦合。提出一种基于等价关系的数据...为帮助制造企业处理积累的海量制造过程质量数据,数据挖掘方法可以帮助企业从中发现有用的知识和模式进行有效的质量分析及改进。制造过程质量数据的特点如下:混合型数据、分布不均衡、维度灾难及数据耦合。提出一种基于等价关系的数据预处理算法对原始数据做属性选取,解决混合型数据的特征选取及数据预处理问题。针对数据分布不均衡、维度灾难特点,提出基于优化核空间的混合流形学习及支持向量机算法(Optimized kernel based hybrid manifold learning and supportvector machines algorithm,KML-SVM)。在KML-SVM算法中,使用流形学习算法解决采集的质量数据的维度灾难问题,用支持向量机对低维嵌入数据分类预测,并优化支持向量机的核空间以达到分类精度最大化。以某制造企业实际制造过程数据为例对算法进行仿真验证。通过对仿真结果的分析找出质量数据的质量因素关系并提出质量改进方案。试验结果表明提出的ISOMAP核空间是最优核空间,提出的KML-SVM算法能够有效处理制造过程质量数据。展开更多
Quasi-classical trajectory calculations are performed to study the stereodynamics of the H（~2S） ＋ NH（a^1？） →H_2（X^1Σ_g~＋） ＋ N（~2D） reaction based on the first excited state NH_2（1~2A＇） potential energ...Quasi-classical trajectory calculations are performed to study the stereodynamics of the H（~2S） ＋ NH（a^1？） →H_2（X^1Σ_g~＋） ＋ N（~2D） reaction based on the first excited state NH_2（1~2A＇） potential energy surface reported by Li et al.[Li Y Q and Varandas A J C 2010 J. Phys. Chem. A 114 9644] for the first time. We observe the changes of differential cross-sections at different collision energies and different initial reagent rotational excitations. The influence of collision energy on the k-k＇ distribution can be attributed to a purely impulsive effect. Initial reagent rotational excitation transforms the reaction mechanism from insertion to abstraction. The effect of initial reagent rotational excitations on k-k＇ distribution can be explained by the rotational excitation enlarging the rotational rate of reagent NH in the entrance channel to reduce the probability of collision between incidence H atom and H atom of target molecular. We also investigate the changes of vector correlations and find that the rotational angular momentum vector j＇ of the product H_2 is not only aligned, but also oriented along the y axis. The alignment parameter, the disposal of total angular momentum and the reaction mechanism are all analyzed carefully to explain the polarization behavior of the product rotational angular moment.展开更多
Scalar properties and vector correlations of the reactions of O＋H2 →OH＋H, O＋HD→OH＋D, O＋DH→OD＋H, and O＋D2 -＋OD＋D at collision energies of 25 and 34.6 kcal/mole have been studied via the quasi-classical-traj...Scalar properties and vector correlations of the reactions of O＋H2 →OH＋H, O＋HD→OH＋D, O＋DH→OD＋H, and O＋D2 -＋OD＋D at collision energies of 25 and 34.6 kcal/mole have been studied via the quasi-classical-trajectory （QCT） method based on a BMS1 potential energy surface （PES）. The generalized polarization-dependent differential cross section and the distributions of the dihedral angle at the collision energy of 34.6 kacl/mole are presented. The calculated results indicate that both the reagent rotational angular momentum and the mass factor have a significant influence on the scalar properties and vector correlations of the title reactions.展开更多
文摘针对采用常规恒功率控制方式下的光伏并网逆变器缺乏电压和频率动态调节能力的问题,提出一种基于虚拟同步发电机(VSG)的光伏并网逆变器控制策略.根据同步发电机的原理,建立同步发电机的并网等效电路和矢量关系表达式,设计了有功频率控制算法和无功电压控制算法,搭建了虚拟同步发电机控制策略下的光伏发电系统.在Matlab/simulink环境中建立了10 k W的光伏并网系统.仿真结果表明,基于虚拟同步发电机的光伏并网逆变器具有与同步发电机相似的调频调压特性,能够较好地适应电网运行要求.
文摘为帮助制造企业处理积累的海量制造过程质量数据,数据挖掘方法可以帮助企业从中发现有用的知识和模式进行有效的质量分析及改进。制造过程质量数据的特点如下:混合型数据、分布不均衡、维度灾难及数据耦合。提出一种基于等价关系的数据预处理算法对原始数据做属性选取,解决混合型数据的特征选取及数据预处理问题。针对数据分布不均衡、维度灾难特点,提出基于优化核空间的混合流形学习及支持向量机算法(Optimized kernel based hybrid manifold learning and supportvector machines algorithm,KML-SVM)。在KML-SVM算法中,使用流形学习算法解决采集的质量数据的维度灾难问题,用支持向量机对低维嵌入数据分类预测,并优化支持向量机的核空间以达到分类精度最大化。以某制造企业实际制造过程数据为例对算法进行仿真验证。通过对仿真结果的分析找出质量数据的质量因素关系并提出质量改进方案。试验结果表明提出的ISOMAP核空间是最优核空间,提出的KML-SVM算法能够有效处理制造过程质量数据。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474141and 11274149)the Program for Liaoning Excellent Talents in University,China(Grant No.LJQ2015040)+2 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry,China(Grant No.2014-1685)the Special Fund Based Research New Technology of Methanol Conversion and Coal Instead of Oilthe China Postdoctoral Science Foundation(Grant No.2014M550158)
文摘Quasi-classical trajectory calculations are performed to study the stereodynamics of the H（~2S） ＋ NH（a^1？） →H_2（X^1Σ_g~＋） ＋ N（~2D） reaction based on the first excited state NH_2（1~2A＇） potential energy surface reported by Li et al.[Li Y Q and Varandas A J C 2010 J. Phys. Chem. A 114 9644] for the first time. We observe the changes of differential cross-sections at different collision energies and different initial reagent rotational excitations. The influence of collision energy on the k-k＇ distribution can be attributed to a purely impulsive effect. Initial reagent rotational excitation transforms the reaction mechanism from insertion to abstraction. The effect of initial reagent rotational excitations on k-k＇ distribution can be explained by the rotational excitation enlarging the rotational rate of reagent NH in the entrance channel to reduce the probability of collision between incidence H atom and H atom of target molecular. We also investigate the changes of vector correlations and find that the rotational angular momentum vector j＇ of the product H_2 is not only aligned, but also oriented along the y axis. The alignment parameter, the disposal of total angular momentum and the reaction mechanism are all analyzed carefully to explain the polarization behavior of the product rotational angular moment.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61127012 and 60977063)the Scientific and Technical Innovation and Troop Construction Projects of Henan Province, China (Grant No.124200510013)
文摘Scalar properties and vector correlations of the reactions of O＋H2 →OH＋H, O＋HD→OH＋D, O＋DH→OD＋H, and O＋D2 -＋OD＋D at collision energies of 25 and 34.6 kcal/mole have been studied via the quasi-classical-trajectory （QCT） method based on a BMS1 potential energy surface （PES）. The generalized polarization-dependent differential cross section and the distributions of the dihedral angle at the collision energy of 34.6 kacl/mole are presented. The calculated results indicate that both the reagent rotational angular momentum and the mass factor have a significant influence on the scalar properties and vector correlations of the title reactions.
