配电变压器无弧有载自动调容仿真分析

对配电变压器的有载自动调容技术进行了论述,提出了以电力电子开关为关键部件的无弧有载自动调容技术新方案,该方案以反并联大功率耐高压晶闸管作为调容开关,克服了机械式调容开关结构复杂、体积大、故障率高的缺点。探讨了配电变压器实现无弧有载自动调容的关键技术,利用电力系统仿真工具PSCAD/EMTDC建立了无弧有载调容方案的仿真模型,对电力电子开关实现自动调容进行了仿真分析,验证了所提方案的可行性。为农村和城市配电网配电变压器实施有效的季节性调容和峰谷调容提供了解决办法。     

无弧有载自动调容配电变压器切换策略及其控制系统设计

通过对有载调容变压器经济运行方式的分析,阐述了一种计算临界经济容量的方法,设计了一套由数据采集模块、负荷预测模块、切换策略以及晶闸管触发模块等组成的无弧有载调容配电变压器的控制系统,提出了一种基于灰色理论负荷预测模型的切换策略。该切换策略克服了仅凭经验确定有载调容变压器临界经济容量的非科学性与不合理性等缺点,避免了负荷由于短时波动而引起调容开关频繁切换,延长了调容开关的使用寿命。通过对某单班制企业的实际数据的负荷预测与切换过程的仿真分析,验证了该控制策略的有效性。通过计算分析可知,SZ11-M-T-315（100）型调容变压器年综合损耗电量节约1 821 kW·h,节电率达15.79%。     

计及配变无载调压分头位置的电压/无功优化方法

结合中国10kV配电系统结构和运行特征,提出了计及配电变压器无载调压分头位置的配电线路无功运行优化数学模型.根据配电变压器分接头位置只能在特定时期无载调节的特点,将实际配电负荷等值为多时段动态负荷.由该优化模型可以求得能够适应各时段负荷变化的最佳变压器分头位置和各时段最佳无功补偿容量及运行电压.介绍了采用遗传算法求解以网损最小为目标的该优化模型的主要步骤和处理方法,用实际10 kV配电线路的仿真计算验证了在电压/无功优化模型中计及无载调压分头位置优化必要性和可行性.     

考虑分布式电源影响的配电网降损分析

配电网的降损节能始终是电力行业业内人士关注的重要问题之一。该文研究通过分布式电源（distributed generation,DG）的配置实现配电网降损的方法。首先,在不考虑DG接入最大容量限制的前提下,在负荷均匀分布条件下的配电网,以降损效果最明显为原则,确定了配置DG的“2/3原则”。对于负荷非均匀分布条件的配电网,根据“2/3原则”确定DG的初始配置点,然后在满足功率平衡、节点电压、线路传输功率、DG接入容量限制的条件下,以负荷的平均功率因数为基准,以配电网的损耗最小为原则确定DG配置容量和位置。以实际配电网为例,进行计算、分析和比较,结果表明,该文提出的方法在不同负荷情况下降损效果非常明显。利用该文提出的方法,可以有效地实现配电网降损节能的目标,而且在实际配电网中非常容易使用。     

配电线路无功优化就地控制与系统控制效果比较

针对就地控制策略的不足,该文提出一种系统控制策略,即一种采用考察整条线路无功补偿效果的控制策略。在补偿容量和补偿位置确定的条件下,通过控制电容器的投切达到配电线路无功运行优化的目的。对基本TS算法作了改进,以网损最小为目标进行无功优化控制。用.NET编写程序,比较了2种控制策略下,某条10 kV线路日无功负荷水平时段的电容器投切、有功损耗以及电压情况。计算结果表明,在相同的安装位置和补偿容量下,系统控制策略对配电线路的降损节能效果更显著。     

面向高比例分布式光伏发电消纳的复合型需求侧响应控制

在大力推进分布式光伏发电的形势下,利用负荷侧灵活性资源提升光伏消纳水平并改善电网运行经济性已成为促进新能源发展的重要措施,如何高效进行需求侧响应控制是目前该领域研究的关键问题之一。传统的峰谷分时电价仅根据区域电网内的负荷变化的总体情况确定分时段电价实现削峰填谷,该方法未考虑区域内新增电源的发电特性,从而导致负荷调整的灵活性较差,无法有效解决区域内光伏消纳的问题。该研究针对光伏装机比例较高的区域配电网尤其是乡村配电网,提出一种基于优化调整分时电价时段的激励型需求侧响应和区域集中优化调控相结合的配电网复合型需求响应控制策略。该策略首先结合负荷需求和光伏出力曲线对分时电价峰谷时段进行因地制宜的自适应调整;其次,基于新的电价时段进行用户侧分布式最优出力计划建模,并给出用户侧可削减、可时移负荷的响应调整范围的计算方法;最后由区域调度中心实现负荷集中控制。通过算例对比验证该文方法在计及用户舒适度的基础上,弃光率和系统综合运行成本较优化前均有明显降低,解决了含高比例光伏配电网的光伏消纳及经济运行问题,为配电网精细化管理水平的提升提供了理论依据。     

基于改进卡尔曼滤波算法的雷达定量降雨估算

针对雷达定量降雨估算误差较大的问题,本文提出一种使用改进卡尔曼滤波对雷达估算值进行校准的方法。先确立G/R(自动气象站测量值/天气雷达估算值)校准因子模型,并应用普通卡尔曼滤波方法对G/R校准因子建立预测系统和测量系统,同时引入系统参数的校准过程和系统误差的自适应估计过程,动态调整卡尔曼滤波中各项参数值;最后将滤波后的G/R因子用于校正雷达定量降雨估算,得到较准确的降雨估算值。利用长春市天气雷达2015年8月19-20日和2016年月8月6-7日两次降雨过程的雷达产品和加密自动站逐小时的降雨资料,对卡尔曼滤波方法进行检验分析。结果表明:改进卡尔曼滤波和普通卡尔曼滤波校准后雷达降雨估算结果优于未校准的降雨估算结果,普通卡尔曼滤波方法和改进卡尔曼滤波方法的平均相对误差分别从0.6047减至0.3557和0.2645,从0.8052减至0.3096和0.1715,且改进算法效果优于普通卡尔曼滤波算法,校准后雷达降雨估算准确度明显提高。     

基于遥感的东北地区水稻延迟型冷害动态监测

水稻延迟型冷害大范围准确的同步跟踪监测,可为提高稻米品质和产量提供帮助。在明确东北地区水稻种植区域和水稻低温冷害年的基础上,基于MODIS MOD13A2数据产品划分了东北地区水稻各发育普遍期植被指数判识指标的参考范围,构建了基于地理信息的水稻发育期模型,在此基础上制作了水稻静态发育期空间分布图,并以2009年5月24日和8月7日为例开展了东北地区水稻延迟型冷害动态监测的应用研究。结果表明:东北三省发生较大范围水稻延迟型冷害的年份有2002年、2003年、2008年和2009年,其中黑龙江省是水稻延迟型冷害的重灾区;EVI在水稻发育期判识中较NDVI更具优势;利用经度、纬度和海拔高度与日序的相关关系构建水稻发育期模型,推算无观测地区的发育期具有一定的可行性;在同一时间东北三省各地的水稻发育期分布推算结果的基础上,实现了2009年5月24日和8月7日东北地区水稻延迟型冷害动态监测,所得监测结果与2009年农业气象观测记录在时间和空间上有很好的一致性,监测结果正确。     

新疆棉田小区域碳变化量研究

为研究膜下滴灌条件下棉田小区域碳变化量,在棉花生长期内采用Li-8100A土壤碳通量自动测定仪和LCpro+光合仪连续观测不同样地土壤呼吸速率和净光合速率。结果表明:不同样地的土壤呼吸速率日变化均表现为单峰型曲线,峰值出现在16:00;而棉田净光合速率日变化则表现为单双峰曲线交替变化规律。两者月变化均呈现先升高后降低的趋势,7月土壤呼吸速率和净光合速率达到最大值。不同样地间土壤呼吸速率和净光合速率存在差异,土壤呼吸速率表现为垄间>垄上>裸地,净光合速率表现为垄间>垄上。棉田小区域在棉花整个生育期内均表现为碳汇,6-9月棉田净固碳总量为2 203.7 C g/m^2,光合作用固碳量为土壤呼吸排碳量的2.67倍。     

基于大系统递阶理论的区域抗旱应急调水方案

为了解决旱情紧急情况下关中西部各灌区和各用水部门之间的用水矛盾,该文以大系统递阶理论为基础,采用动态规划方法建立了以总用水量最大为目标的区域水量优化调配模型,根据需水与来水的不同频率组合,拟定了3种一级备选配水方案（第3方案有27种二级备选配水方案）,通过对各方案调度结果分析,并考虑实际调度运行的可操作性,推荐采用第3种方案以夏灌调水量作为主要控制因素进行归类合并后形成4灌区11种调水方案。该调水方案在2005－2007年的实际使用中,取得了很好的效果,对该区域的抗旱应急调水提供了科学依据。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.