Power Flow Analysis of System with UPFC

This paper first analyzes the working mechanism of the UPFC,and a practical method of power flow simulation is presented.The method can bring controlling of UPFC to accord with power flow simulation in the best,and can calculate the power flow with several UPFC.IEEE 5 nodes system and IEEE 30 nodes system are tested.     

Modelling and Analysis of Multi-terminal Unified Power Flow Controller

To control the complex powers emanating from a bus in power system, there are two solutions. The obvious solution is to equip each of the n lines radiating from the node with its own UPFC. The next evolution of the idea is to equip with a multi-terminal UPFC. First, the configuration and the principle of the Two-terminal UPFC (when n=2) are presented. In consideration of the existing shortages of output model-constructing method and topological model-constructing method for T-UPFC, a switching function mathematical model of this device is constructed by introducing the concept of switching function. It has more generality than the output and the topological model with the consideration of the internal switching character and the physical course of the T-UPFC.     

PARAMETRIC DESINGN OF DC FILTERS

The effect of phase angles of commutating voltages on the performance of dc filters is analgzed for the first time and a heurestic method is presented to choose appropriate parameters for swoothing reactors and dc filters.     

Synchronization of Chaotic Systems Employing the Theory of Application of Linear Time-varying Impulsive Differential Equations

Employing the stability theory of linear non-autonomous impulsive differential equations, some sufficient conditions for the synchronization of unified chaotic systems and Lorenz chaotic systems are derived. This method can be applied to most of chaotic systems. The numerical simulations also demonstrate the efficiency of impulsive control.     

Mountain oases in northern Oman: An environment for evolution and<Emphasis Type="Italic"> in situ</Emphasis> conservation of plant genetic resources

Several botanical studies have been conducted in different parts of Oman, but knowledge about agro-biodiversity in the rapidly decaying ancient mountain oases of this country remains scarce. To fill this gap we assessed the genetic resources of three mountain oases in the al-Hajar range using a GIS-based field survey and farmer interviews. While arid conditions prevail throughout the mountain range, the different elevations of Balad Seet (950–1020 m a.s.l.), Maqta (930–1180 m a.s.l.) and Al Jabal al Akhdar (1750–1930 m a.s.l.) provide markedly differing agro-climatic conditions. Overall, 107 different crop species were identified belonging to 39 families. Species number was highest among fruits (33 spp.), followed by vegetables (24 spp.). Intensive irrigation allows cultivation of a broad range of species at all oases. However, the number of species varied significantly between sites. Fruit species diversity and homogeneity of distribution of individual fruit species was highest at Balad Seet and lowest at Maqta as indicated by respective Shannon indices of 1.00 and 0.39 and evenness values of 32% and 16%. Century plant (Agave americana L.), faba bean (Vicia faba L. var. minor Peterm. em. Harz) and lentil (Lens culinaris Medik.) were identified as relict crops, supporting oral reports of past cultivation and providing evidence of genetic erosion. Some species, such as the temperate fruits of Al Jabal al Akhdar, were exclusively found at the coolest site, while others only occurred at the hotter locations. Overall greatest species similarity was found between Balad Seet and Al Jabal al Akhdar as indicated by a Sørensen coefficient of similarity of 67%. At all oases a multilayered vegetation structure dominated with a canopy, an understory and a ground layer. Greatest species richness was recorded in the lowest stratum. Overall the study shows a location-specific but surprisingly diverse mosaic of crops in Omani mountain oases which merits further studies and conservation efforts.     

基于增强回归树的麦-玉轮作农田蒸散影响因素分析

为探讨华北典型轮作农田蒸散(ET)变化规律,以山东禹城试验站冬小麦-夏玉米(麦-玉)轮作田为研究对象,基于涡度相关技术实测的8年观测数据与增强回归树方法,分析了农田ET逐日变化特征及其对环境因子的响应。结果表明：研究时段内逐日ET变化范围在0～9.6 mm/d之间,且不同阶段(小麦季、玉米季和农闲期)ET总量存在较大差异。一般而言,每年小麦季ET的峰值和总量均明显高于玉米季,而农闲期ET占全年ET总量的比例不足4%。净辐射是影响麦-玉轮作田不同阶段ET变化的首要因素,对各阶段ET的贡献率由高到低依次为小麦季(81.4%)、玉米季(52.7%)、农闲期(36.8%)。除净辐射外,其他环境因子对ET的影响则具有阶段性差异。饱和水汽压差对小麦季和玉米季ET存在一定的影响,而土壤含水率和风速对农闲期ET的贡献率相对较高。研究可为变化环境下农业水资源高效利用以及作物模型优化等提供科学依据。     

基于多光谱图像的土壤有机质含量检测系统与APP研究

受到土壤种类、水分等客观因素的干扰,基于图像预测土壤有机质(Soil organic matter, SOM)含量与传统方法在检测精度上仍存在差距,限制了相关技术的推广和普及。为提升基于图像预测SOM含量的精度,本研究提出N＿DenseNet网络模型,在DenseNet169基础上加入多尺度池化模块,通过获取更多的维度特征提升模型的性能,并结合Android端开发SOM实时检测应用程序(APP),通过内网透射实现PC端与手机端数据的及时传输。以黑龙江省友谊县、北京市昌平区、山东省泰安市3地的350份土样为基础,通过手机以及多光谱无人机获取原位土壤的高清图像,R波段、红边波段与近红外波段图像,以丰富数据信息,并通过室内胁迫的方式拍摄土壤样品在不同水分梯度下的图像缓解水分对图像造成的影响。对比不同深度学习模型,基于多光谱图像数据训练的N＿DenseNet表现最好,整体表现优于DenseNet169,测试集R²为0.833,RMSE为3.943 g/kg,R²相比于可见光数据提升0.016,证明了训练过程加入R波段与红边和近红外波段图像后有助于提升...     

稻田不同轮作模式的后效研究

对稻田年内水旱轮作及连作的后效应进行了研究。结果表明：年内水旱轮作可增加晚稻有效穗、结实率和实粒数,能显著地提高后作晚稻产量,经冬种、冬闲再连作的水稻则表现不明显。     

福鼎槟榔芋主要轮作模式及其栽培技术

轮作是保持福鼎槟榔芋产量和品质的最有效技术措施,本文综述了槟榔轮作的主要优点,介绍了福鼎槟榔芋主要轮作模式以及关键栽培技术。     

山区冬油菜轮作夏季甜玉米栽培技术

2009年莲都区被列入农业部农技推广示范县项目实施单位,2010年在黄村乡开展山区冬油菜轮作夏季甜玉米耕作模式的探索,示范推广126 hm2,年产值780多万元、纯收益671多万元。该文从地域选择、茬口安排、冬油菜栽培、夏甜玉米栽培几个方面总结山区冬油菜轮作夏季甜玉米栽培技术要点。