计及风电场发电功率不确定性的电力系统模糊潮流

风速随机性与间歇性的存在,给大型风电场并网后电力系统的稳定运行提出了新的问题和挑战。本文应用概率统计及模糊集的相关理论对计及风电场发电功率不确定性的电力系统模糊潮流计算进行了研究。首先取给定参数值的威布尔曲线作为风速概率统计分布,并基于随机模糊相容性原理,将其转换成风速的可能性分布,再结合笼型异步风力发电机的风速-功率关系特性曲线建立了风力发电机组出力的非线性模糊模型;并在对该模糊模型线性化的基础上,采用基于潮流分析灵敏度的方法对系统模糊交流潮流的可能性分布进行了求解。最后给出了计及风电场的IEEE14算例系统下的仿真结果。     

Calculation of Water Depth during Flood in Rivers using Linear Muskingum Method and Particle Swarm Optimization (PSO) Algorithm

Water Resources Management - To estimate the damage caused by flooding rivers, it is critical to analyze unsteady flow and determine downstream water depth. Hydraulic methods for examining unsteady...     

A Compromise Ratio Method with an Application to Water Resources Management: An Intuitionistic Fuzzy Set

Water resources management can be regarded as an iterative process of general decision making considering the applications and modifications of waters and related lands within a geographic region. This process helps decision makers to balance their diverse requirements and applications of water as an environmental resource, and to recognize how their activities can have impacts on the long-term sustainability. This paper introduces a new compromise ratio method based on Atanassov’s intuitionistic fuzzy sets under multiple criteria in real-life situations. Atanassov’s intuitionistic fuzzy weighted averaging (AIFWA) operator is applied to aggregate individual judgments of the decision makers to rate the relative importance of the selected criteria and potential alternatives. Then a new Atanassov’s intuitionistic fuzzy ranking index is proposed to analyze the potential alternatives. Finally, the performance of the proposed fuzzy decision-making method is illustrated to a real water resources management problem from the recent literature. Computational results demonstrate that the presented method can be utilized in a large-scale multi-level assessment process to assist the decision makers the optimal solution among the potential alternatives with multiple conflicting and compromising criteria.     

考虑电力系统不确定性的机组检修计划安排

针对电力系统负荷预测误差、机组随机停运及风电场出力波动性问题,采用半不变量法求解系统风险度指标,安排电力系统机组检修计划.以各检修时段风险度方差最小为目标函数,建立了含风电场的电力系统发电机组检修计划模型,给出了基于半不变量法的机组检修计划的计算步骤,并以国内某实际电网为例进行了验证.结果表明,该方法能充分考虑电力系统的不确定性,降低了负荷预测误差及风电场出力波动对机组检修计划带来的影响.     

Modelling of fluid flow and heat transfer to assess the geothermal potential of a flooded coal mine in Lorraine,France

The flooding of the Lorraine coal mines (France), representing a huge reservoir of about 154 × 10⁶ m³, began in June 2006. After attaining thermal equilibrium with the surrounding rocks, the water temperature in the deepest parts is expected to reach 55 °C, giving the opportunity for the extraction of low-enthalpy geothermal waters that may be suitable for district heating purposes. We present some numerical modelling results of the thermally driven convective flow in an open vertical shaft and in the entire mine reservoir. A dual permeability/porosity approach was used in the reservoir model, which includes open galleries and vertical shafts, coal panels backfilled with sand, and intact rock masses. Two scenarios of heat extraction with different flow regimes were investigated. A sensitivity analysis shows that the temperature decline in the production zone is highly dependent on the permeability of the surrounding porous rocks. Larger permeabilities result in higher water temperatures at the production shaft due to greater inflows of warm water from those rock masses.     

基于广义支路能量时空分布熵测度的线路脆弱度评估

为研究大扰动事故注入系统扰动能量对线路和系统冲击大小,从熵的基本原理出发,结合广义支路能量在系统中的空间分布聚集程度,建立基于能量分布熵的线路后果脆弱评估模型;依据近似熵原理和广义支路能量在线路中的周波时段振荡态势,提出基于能量周波互近似熵的线路周波冲击脆弱评估模型。通过对新英格兰10机39节点系统的模拟计算发现:线路发生大扰动后,扰动注入系统的总能量越大,能量分布熵越小,局部空间聚集的能量越多,该线路后果脆弱度越高;既定扰动故障模式下,线路的周波互近似熵越小,周波脆弱度越高,周波脆弱度动态反映了线路随周波时段推移的脆弱度,计及各周波受扰冲击的综合脆弱指标全面反映了线路的扰动冲击强度。通过与其他方法评估结果的比较分析可知,基于广义支路能量时空分布熵测度的线路受扰冲击脆弱度评估模型物理意义明确,评估结果符合实际。     

The effects of health, environmental, and socio-psychological variables on fear of crime and its consequences among urban black elderly individuals

Despite extensive research on fear of crime among elder members of the population, little attention has been paid to the fear of crime among Black urban elderly individuals. Using a sample of 372 low income urban Black persons aged sixty-two and over the causes and consequences of such fear were investigated. Fear of crime reduces subjective well-being of these older adults and limits their mobility. Age, gender, education, marital status, loneliness, self-reported health status, previous victimization experience, media exposure, trust of neighbors, length of residence, and type of housing were tested to identify significant predictors of fear of crime. Some of these variables had a diverse impact on fear of crime at home versus outside of the home. For example, while gender was the strongest predictor of fear of crime outside the home, it was not significantly associated with fear inside the home. Surprisingly, self-reported health status was not related to fear of crime among this sample of urban Black elderly individuals.     

Gel–sol synthesis and aging effect on highly crystalline anatase nanopowder

Highly crystalline TiO₂ anatase nanoparticles were synthesized via gel–sol method by using titanium isopropoxide and triethanolamine. The products were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric/differential thermal analysis and nitrogen gas absorption methods. The particle size ranged from 7 to 24 nm having specific surface area of 64 to 220 m²/g. Selective Ti(OH)₄ gel specifications and hydrothermal test conditions resulted in thermodynamically-stable phase-formation. Aging at 130°C for 4 h resulted in particle size of 7 nm; while at 130 and 160°C for 12 h resulted in 12 and 21 nm, respectively.     

Fat and protein contents, acidity and somatic cell counts in bulk milk of Holstein cows in the Khorasan Razavi Province, Iran

Relationships between total bulk milk somatic cell score (SCS) and milk fat and protein contents and acidity were investigated in the Khorasan Razavi Province, a region that contributes 6.83% of total milk production in Iran. A total of 1476 samples were analysed. Data were obtained by randomly collecting 123 samples of bulk tank milk from 41 dairy farms during April 2006 to March 2007, every month. Milk was analysed for titratable acidity, protein and fat contents and somatic cell counts (direct microscopic cell count and with Somatos, Russia). Microscopic and Somatos somatic cell counts were comparable. Results showed that the season of raw milk production did not have a significant effect on acidity. Milk fat content increased gradually from spring to winter and there were significant differences ( P <  0.05) between spring and other seasons. Higher levels of milk protein fractions were observed during the autumn and winter than in other seasons. The highest total bulk milk somatic cell counts were observed in July. Total bulk milk SCS had significant effects ( P <  0.05) on acidity and fat and protein contents. Moreover, the level of acidity and fat in milk decreased with increasing SCS. A significant positive relationship was observed between total bulk milk SCS and the protein content of milk. Elevated SCS were associated with lowered milk quality in Holsteins in the Khorasan Razavi Province.