针对含静止同步补偿器(static synchronous compensator,STATCOM)的双馈型异步风力发电机(doublefed induction generator,DFIG)风电场,通过优化DFIG及STATCOM的多个比例积分(proportional integral,PI)控制器参数,既能有效提高风电场...针对含静止同步补偿器(static synchronous compensator,STATCOM)的双馈型异步风力发电机(doublefed induction generator,DFIG)风电场,通过优化DFIG及STATCOM的多个比例积分(proportional integral,PI)控制器参数,既能有效提高风电场的整体动态特性,又能在风电场电网发生故障后促进公共连接点(point of common coupling,PCC)电压的快速恢复。以风电场DFIG输出的有功功率、直流母线电压和风电场PCC电压响应的时间乘以误差的绝对值积分(integrated time and absolute error,ITAE)最小为优化目标函数,提出混沌正交粒子群优化求解算法。该算法利用正交优选和正交优选趋势法得到多PI控制器参数的寻优范围以及相应权重,采用混沌算法进行初始化,并应用粒子群优化算法迭代求解,有效提高了求解效率。不同工况下基于MATLAB/Simulink的某区域内含STATCOM的风电场仿真算例表明:应用优化后的PI控制器具有良好的动态性能,由此验证了该优化算法的有效性。展开更多
在野外找到老龄树群,是树木年轮气候学研究的一个关键环节.目前还没有在大尺度空间上连续的高精度的树龄数据可供使用,尝试建立一种基于遥感数据定位老龄树群的方法.以30m分辨率的卫星Landsat8OLI(Operational Land Imager)遥感影像一...在野外找到老龄树群,是树木年轮气候学研究的一个关键环节.目前还没有在大尺度空间上连续的高精度的树龄数据可供使用,尝试建立一种基于遥感数据定位老龄树群的方法.以30m分辨率的卫星Landsat8OLI(Operational Land Imager)遥感影像一景为例,首先在该影像范围内收集了22个已发表的树轮宽度年表长度数据,根据经纬度定点提取年表对应的归一化植被指数(Normalized Difference Vegetation Index,NDVI)值,然后用R语言建立树轮宽度年表的长度与NDVI之间的一元线性回归模型,利用遥感影像数据良好的监测地表空间异质性的能力,实现对树轮年表长度在空间上连续的高分辨率的估算.将该信息作为树龄的一种近似替代,可以辅助树木年轮工作者快速、准确、定量地寻找到老龄树群。展开更多
By analyzing statistical characteristics of five tree-ring standard chronologies, early-wood ring width (EWW), late-wood ring width (LWW), total ring width (TRW), minimum early-wood density (MinD), maximum late-wood d...By analyzing statistical characteristics of five tree-ring standard chronologies, early-wood ring width (EWW), late-wood ring width (LWW), total ring width (TRW), minimum early-wood density (MinD), maximum late-wood density (MaxD) and, their climatic response re-spectively, we reconstructed the May to July precipitation using late-wood ring width (LWW) over the north Helan Mountain since A.D. 1726. The explained variance is 42% (R2adj = 41%, F = 31.46, p < 0.000001). After 11-a moving average, the explained variance reaches 82% (F = 156.9, p < 0.05). On the decadal scale, the rainfall reconstruction of the northern Helan Mountain displays a quite similar variation pattern with that of the April to early July precipitation in Baiyinaobao, east of Inner Mongolia for the last 150 years. It may reflect the intensity variation of the East Asia Summer Monsoon front to a certain extent. Spectrum analysis shows 11-a and 22-a periodicities in the May to July precipitation reconstruction at the north Helan Mountain.展开更多
By using Caterpillar-SSA analysis method, through the process of embedding, singular value decompo-sition, grouping and diagonal averaging, the seasonal pre-cipitation trend at north Helan Mountain and Baiyinaobo regi...By using Caterpillar-SSA analysis method, through the process of embedding, singular value decompo-sition, grouping and diagonal averaging, the seasonal pre-cipitation trend at north Helan Mountain and Baiyinaobo regions, Inner Mongolia for the next 20 years is forecasted. The results show an increasing precipitation trend from 1992 to 2004. In the subsequent decade the precipitation should reduce quickly, and it will reach a minimum near 2012 to 2014 in both regions. The drought caused by the decrease of the precipitation from May to July in the north Helan Mountain area during the period of 2013—2014 is probably quite similar to that around 1929. Further, the period of pre-cipitation gradual increase follows in the researched regions.展开更多
文摘针对含静止同步补偿器(static synchronous compensator,STATCOM)的双馈型异步风力发电机(doublefed induction generator,DFIG)风电场,通过优化DFIG及STATCOM的多个比例积分(proportional integral,PI)控制器参数,既能有效提高风电场的整体动态特性,又能在风电场电网发生故障后促进公共连接点(point of common coupling,PCC)电压的快速恢复。以风电场DFIG输出的有功功率、直流母线电压和风电场PCC电压响应的时间乘以误差的绝对值积分(integrated time and absolute error,ITAE)最小为优化目标函数,提出混沌正交粒子群优化求解算法。该算法利用正交优选和正交优选趋势法得到多PI控制器参数的寻优范围以及相应权重,采用混沌算法进行初始化,并应用粒子群优化算法迭代求解,有效提高了求解效率。不同工况下基于MATLAB/Simulink的某区域内含STATCOM的风电场仿真算例表明:应用优化后的PI控制器具有良好的动态性能,由此验证了该优化算法的有效性。
文摘针对电池储能系统的有功和无功多控制器参数同时优化易互相影响的问题,文章提出一种改进的粒子群算法(Improved Particle Swarm Optimization,IPSO)进行有功、无功多控制器的比例积分(Proportional Integral,PI)环节参数优化整定。IPSO算法通过采取全局领域搜索的速度更新方式增加搜索范围;在粒子群初始化加入混沌思想与优化过程加入混沌扰动以提升算法空间内搜索的遍历性;对全局最优粒子增加随机学习的学习机制加强寻找全局最优值的能力。基于IPSO算法,以多控制器的综合时间与绝对误差(Integrated Time and Absolute Error,ITAE)指标最小为目标函数对P-Q控制的PI控制器参数进行优化,并以储能系统接入IEEE-14节点系统为例进行仿真。仿真结果表明,IPSO算法相较其他PSO算法具有更好的优化效果,且寻优能力更强。
文摘By analyzing statistical characteristics of five tree-ring standard chronologies, early-wood ring width (EWW), late-wood ring width (LWW), total ring width (TRW), minimum early-wood density (MinD), maximum late-wood density (MaxD) and, their climatic response re-spectively, we reconstructed the May to July precipitation using late-wood ring width (LWW) over the north Helan Mountain since A.D. 1726. The explained variance is 42% (R2adj = 41%, F = 31.46, p < 0.000001). After 11-a moving average, the explained variance reaches 82% (F = 156.9, p < 0.05). On the decadal scale, the rainfall reconstruction of the northern Helan Mountain displays a quite similar variation pattern with that of the April to early July precipitation in Baiyinaobao, east of Inner Mongolia for the last 150 years. It may reflect the intensity variation of the East Asia Summer Monsoon front to a certain extent. Spectrum analysis shows 11-a and 22-a periodicities in the May to July precipitation reconstruction at the north Helan Mountain.
文摘By using Caterpillar-SSA analysis method, through the process of embedding, singular value decompo-sition, grouping and diagonal averaging, the seasonal pre-cipitation trend at north Helan Mountain and Baiyinaobo regions, Inner Mongolia for the next 20 years is forecasted. The results show an increasing precipitation trend from 1992 to 2004. In the subsequent decade the precipitation should reduce quickly, and it will reach a minimum near 2012 to 2014 in both regions. The drought caused by the decrease of the precipitation from May to July in the north Helan Mountain area during the period of 2013—2014 is probably quite similar to that around 1929. Further, the period of pre-cipitation gradual increase follows in the researched regions.
文摘目的:观察调畅气机法配合针刺治疗血管性痴呆(vascular dementia,VD)的临床疗效。方法:90例临床症状均符合中医呆证诊断标准和西医诊断标准的VD患者,釆用随机单盲对照方法,分为治疗组、西药组和针刺组,每组30例。治疗组采用针刺结合升降散胶囊,西药组口服吡拉西坦胶囊,针刺组单纯采用针刺治疗。治疗周期12周。观察患者治疗前后的总体临床疗效,以及血管性痴呆辨证量表(vascular dementia syndrome differentiation scale,SDSVD)、简易精神状态评价量表(mini-mental state examination scale,MMSE)、Blessed行为量表(Blessed behavior scale,Blessed)、日常生活能力量表(activity of daily living scale,ADL)评分情况。结果:3组治疗后MMSE、Blessed、ADL、SDSVD评分均显著优于治疗前(P<0.05),且治疗组治疗后MMSE、Blessed、ADL、SDSVD评分显著优于西药组和针刺组(P<0.05),升降散结合针刺治疗组在改善日常生活能力、认知特征等方面显著优于西药组及针刺组(P<0.05)。结论:VD患者采用调畅气机法配合针刺治疗有较好的临床疗效,能提高患者的认知水平,有利于后期的康复。
