广西覆冰预报与评估系统设计及应用

摘要：为减轻覆冰问题造成的电网线路灾害,同时为了给电力部门开展防冰、融冰工作提供科学的参考依据,本文研发了一个覆冰预报与评估系统。该系统首先通过对架空线路覆冰易发区域气象观测、覆冰观测、覆冰灾情及地理信息等多源资料的综合分析,确定了覆冰气象阈值,用逐步回归分析方法建立了覆冰标准厚度气象模型,并结合地形进行订正。在此基础上,利用多元决策加权集成法,对欧洲、日本的细网格气象数值预报产品进行集成处理,建立覆冰厚度短期预报模型。其次,本系统采用欧氏距离计算方法,建立覆冰多指标综合指数评估模型。该系统运行稳定、智慧化与自动化程度高,提供的覆冰预报准确率高,评估效果与灾情实况较为一致,服务效果良好,具有较好的推广应用前景。     

基于GLOH描述子和GVF Snake的绝缘子覆冰检测算法

利用计算机视觉和图像处理技术对绝缘子覆冰情况进行检测,在保障电力系统的安全运行方面具有非常重要的作用。提出了一种基于GLOH描述子和GVF Snake的绝缘子覆冰检测算法,该算法首先对输入图像进行预处理;其次提取感兴趣的目标区域,该区域内包含绝缘子信息;然后利用GLOH描述子来定位绝缘子,再利用GVF Snake模型来精确检测绝缘子轮廓;最后对绝缘子轮廓进行分析,通过计算最大径向距离来确定绝缘子是否存在覆冰情况,并在覆冰情况下计算覆冰的厚度。实验结果说明了此方法可以有效地判断出绝缘子是否存在覆冰现象。     

自然环境输电线及绝缘子覆冰状态多维度评估

自然环境中输电线覆冰情况复杂,传统输电线状覆冰状态评估方法指标单一,评估结果不全面,导致评估效率与精度较差,提出输电线及绝缘子覆冰状态多维度评估方法.分析覆冰类型及形成条件,定义影响覆冰程度相关指标的权重值,获得输电线覆冰状况对环境、人员及经济的影响程度参数.计算出各区域输电线绝缘子水平、垂直荷载量及覆冰厚度,给出覆冰...     

基于光纤传感的输电线路覆冰监测系统研究

输电线路严重覆冰将会造成输电塔倒塌或导线断线等事故,形成大面积停电、电网崩溃瓦解的电网事故.现用人工观冰为输电线路启动融冰提供决策依据,进而来预防覆冰过重.基于光纤传感技术与覆冰计算模型开展输电导线覆冰监测方法研究,实现云南电网某110 kV输电线路主要覆冰期(2015年12月18日至2016年2月17日)的在线监测,并与人工观冰结果进行对比验证.以4个人工观冰时间点的监测数据为例,人工观冰得到最大覆冰厚度分别为0.6 mm、0.9 mm、4.2 mm、1.5 mm;而光纤监测得到的等效覆冰厚度分别为0.381 mm、0.362 mm、0.892 mm、0.415 mm.对比发现最大覆冰厚度约为等效覆冰厚度的2～4倍.因此,基于光纤传感的输电线路覆冰监测方法可用来监测导线的等效覆冰厚度,为直流融冰等除冰过程提供数据支撑,以保障电网的安全稳定运行.     

雨雾淞导线覆冰理论模型数值模拟研究

导线覆冰的理论模型及数值模拟是研究覆冰过程机理的必要手段。 本文基于国际公认的导线覆冰理论模型框架,采用合理的覆冰过程物理参数化方法,构建了一套完整的数值计算方案,并利用其对雨雾淞导线覆冰过程进行了数值模拟研究,探讨了雨凇、雾淞及雨雾凇混合覆冰过程的机理及其演变特征。数值模拟结果表明：雾凇覆冰过程的增长曲线呈对数曲线变化特征,覆冰在开始阶段增长很快而随时间逐渐变慢; 而雨淞覆冰则随时间持续增长,且覆冰质量增长比覆冰厚度增长更为明显; 雨雾淞混合覆冰状态下覆冰的增长与单纯雨淞或雾凇覆冰的增长曲线均不同,由于干、湿覆冰机制的转换使覆冰增长过程呈现复杂的变化,而开始阶段无论是雨淞覆冰还是雾凇覆冰都可能表现出明显的湿增长特征。本文的研究结果揭示了雨雾凇导线覆冰过程的机理及其演变特征,具有较大的理论参考价值。     

微气象因素和导线温度对输电线路覆冰的影响研究

影响输电线路覆冰的主要影响因素是微气象因素(环境温度、风速、风向及相对湿度等等)和导线温度等等。而目前微气候要素和覆冰的相关性分析不全面、不系统,无法确定输电线路覆冰的主要因素。统计了云南电网靖万线110 kV线路2015年12月至2016年3月输电线路覆冰在线监测系统的各个监测参量,采用改进的灰色斜率模型分析了输电导线微气象因素(环境温度、风速。相对湿度)和导线温度与覆冰之间的关系,计算得到它们之间的关联度分别为0.198、0.075、0.265、0.496;在导线温度满足输电导线覆冰的情况下,环境温度、风速及相对湿度与覆冰间的关联度分别为0.179、0.056、0.237。因此,影响覆冰较大的因素为导线温度,可以为直流融冰等除冰过程提供数据支撑,以保障电网的安全稳定运行。     

马尔可夫链中首次到达时间概率密度函数值的简化计算

为了简化马尔可夫链中首次到达时间概率密度函数值的计算,构造一个图的矩阵表示产生的有向图,形象地得出从一个状态首次到达另一个状态的所有路径．该问题被转化为对所有满足从一个状态首次到达另一个状态的情况概率值的累加．在此基础上利用所要解决的问题提供的1步平稳转移概率计算出从一个状态到另一个状态的首次到达时间的概率密度函数值．此方法不仅更加直观地计算出此函数值,免去记忆复杂的通用公式,而且省去在公式中为计算此函数值所做的在1步平稳转移概率的基础上再次计算n步平稳转移概率的计算工作.特别是在n较小的情况下,采用此方法进行手工计算比用公式法快捷且易于理解,因此体现出明显的优势．     

一种热气防冰系统的数值仿真

飞机在飞行过程中,结冰问题,会增加重量,影响稳定性.为了防冰,用2D翼型热气防冰系统,采用热气流方法并优化控制防冰腔结构,并进行了数值仿真,得到了防冰系统热力学数值仿真计算结果.计算采用计算流体力学CFD软件FLUENT,根据欧拉模型及用户自定义函数UDF,得到了局部水收集系数、翼型防冰热载荷和表面溢流水量.将外部热载荷与防冰腔内部热气流动与传热耦合计算,实现防冰腔内外表面的热交换仿真,计算出防冰腔内喷口射流以及表面换热量,保证表面温度在允许范围内达到防冰热气流量.结果表明了仿真方法在防冰系统设计研究中的可行性.     

基于隐马尔可夫链模型的软件维护性评估方法研究

针对当前软件可维护性评估主观性强,可操作性弱等问题,提出了定量描述维护性的维护时间统计概率描述方法,引入隐马尔可夫链(HMC)模型对维护性状态变迁过程进行描述,以可度量的维护性内部属性影响因素集量化值为观测序列,以维护时间统计概率为状态序列,构造了反映可维护性状态转移的HMC模型;收集配置管理库中软件模块历史维护时间从而确定完成维护任务频率来估计软件维护性初始状态,利用复杂网络特性计算软件维护性影响因素集的量化值,理论上即可评估出当前软件所处的维护性状态,最后运用实例对模型进行了训练与评估;结果表明,利用模型评估出的概率与实际维护任务统计出的可维护性概率基本一致,说明该方法可行且可重复,具有一定实践意义和研究前景。     

二阶中心差分粒子滤波FastSLAM算法

为改善SLAM算法中非线性系统状态估计精度不高,计算繁杂的问题,本文创新性地提出了基于二阶中心差分滤波并融合最新观测数据来产生建议分布函数的新算法。新算法基于二阶sterling插值公式处理SLAM中的非线性系统问题,无须计算雅可比矩阵,容易实现。此外,该算法使用Cholesky分解技术,在SLAM概率估计中直接依据协方差平方根因子进行传播,保证协方差矩阵正定性的同时减小了局部线性化的截断误差。仿真试验表明,在粒子数相同的情况下,二阶中心差分FastSLAM(SOFastSLAM)在不同噪声条件下的估计精度均优于FastSLAM2.0、UFastSLAM算法,且用时最少,证实了SOFastSLAM算法的优越性。     

基于GEE云平台的黄河源区河流径流量遥感反演研究

河流径流量是陆地上最重要的水文要素之一,准确获取径流信息对于区域的水资源评价和生态修复方面都具有重要作用。研究基于Google Earth Engine(GEE)云平台提供的Sentinel-1、Sentinel-2影像数据,结合数字高程模型(DEM)对河长、河宽、糙率、比降、河深和流速等水力学参数进行遥感估算,进而采用关系拟合法与改进的曼宁公式法对黄河源区唐乃亥站点附近河段进行径流量反演研究,探讨了河段长度差异对径流量反演精度的影响,并通过建立站点河段与上下游河段之间的河宽关系,实现了对站点河段径流量监测时间序列的扩展补充。结果表明,两种模型均能有效进行径流量的模拟估算,其纳什效率系数(NSE)均在0.80以上;关系拟合法与改进的曼宁公式法径流反演的均方根误差(RMSE)分别为233.431 m³s^-1和271.704 m³s^-1,相对均方根误差(RRMSE)分别为16%和24%,关系拟合法反演精度总体优于改进的曼宁公式法。通过对不同长度河段径流量的反演结果对比分析发现,辫状河心滩的河宽估算在汛期...     

An efficient utilization of intermittent surface–satellite optical links by using mass storage device embedded in satellites

Recently, earth observation system by using satellite network has attracted much attention due to its wide coverage and disaster resistance. Although the system is useful for collecting various data, which have an effect on a natural disaster, ecology and so forth, earth observation satellite hardly send the collected observation data to the ground station. This is because that the earth observation satellite needs to orbit near surface of the earth to get high-precision data, and it limited the time that can be used to send the observed data traffic to the ground station. Additionally, the amount of the observed data drastically increase in these days. Thus, we focus on the data relay satellite using optical communication in this network. By relaying observed data to traffic to the relay satellite, which has geostationary orbit, it is possible to increase the chance of sending data for the observation satellite due to the wide coverage of the relay satellite. In addition, laser light that is used in optical communication in satellite network has high frequency and it can deliver large data compared with radio wave. However, laser light is greatly influenced by atmosphere, and optical link capacity between satellite and ground station drastically changes according to weather condition. Therefore, we propose a new data traffic control method to use the network constructed by satellites which has mass storage device effectively according to the condition of optical downlink between satellite and optical ground station. The effectiveness of the proposed method is evaluated with numerical result.     

Application of triple-deck theory to the prediction of glaze ice roughness formation on an airfoil leading edge

A viscous–inviscid interaction triple-deck structure is developed to describe the thermomechanical interaction of an air boundary layer with ice sheets and liquid films. Linear stability results are compared with nonlinear triple-deck computations, and a number of nonlinear simulations of air–water–ice interactions are presented. An icing instability is encountered in regimes with simultaneous wall and air cooling that is believed to admit small scale and highly irregular surface roughness. The stabilization of the smallest scale icing disturbances is obtained through the Gibbs–Thomson relation. This local thermodynamic condition relates the freezing temperature of a pure substance to the surface tension and the mean curvature of the interface and provides a short scale stabilizing mechanism for icing instability modes. Comparison with available experimental data on glaze ice roughness diameters, accreted on NACA 0012 airfoil leading edges under glaze icing conditions, is provided. It is also found in all cases computed in this study that water beads can be formed on a wetted ice surface once the water film is locally ruptured by ice roughness elements.     

利用GIS方法建立山区温度分布模型

提出了一种在气象站点实测数据基础上，利用ＧＩＳ技术建立山区温度分布模型的方法。通过建立数字地形模型（ＤＴＭ），获取影响山地温度分布的地形要素，并结合太阳年运动轨迹求出任一地点的天文太阳辐射值，同时考虑海拔高度、地理位置等影响气温的因素以及站点实测数据建立山区温度分布模型。     

Impact of proxy variables of the rain column height on monthly oceanic rainfall estimations from passive microwave sensors

A major uncertainty in physically based algorithms that are used to estimate rainfall from passive microwave sensors arises from a lack of information on physical parameters such as the rain column height and the freezing level in rainy conditions. This uncertainty occurs because the rainfall integrated along a path on the rain column determines the relationship between the brightness temperature and the rainfall. The rain column height, however, is not well determined directly from simultaneous measurements. Most estimation models use the freezing level derived from an indirect method to obtain the unknown parameter. In this study, the characteristics of three variables that may be used as a proxy variable of the rain column height are investigated.

The two variables are derived from the Tropical Rainfall Measuring Mission (TRMM) microwave imager (TMI) and precipitation radar (TPR). They include the TMI-estimated freezing level (TFL) and the TPR-estimated bright-band height (BBH). The third variable is the freezing-level altitude derived from National Centers for Environmental Prediction (NCEP) reanalysis data (NCEP reanalysis freezing level (NFL)). Monthly oceanic rainfall estimations were then performed using the three aforementioned variables in place of the rain column height. As expected, the results show that differences in the rainfall estimates are greater in the regions where larger differences exist among the three variables. The analysis confirmed that an underestimate of the rain column height causes an overestimate of the rainfall. In addition, rainfalls that were underestimated with the BBH or NFL can be corrected with an empirical adjustment. This suggests that the TFL, BBH and NFL contain information related to the rain column height. However, the BBH and NFL require a correction in the mid-latitudes when their magnitude is low.     

Missing wind data forecasting with adaptive neuro-fuzzy inference system

In any region, to begin generating electricity from wind energy, it is necessary to determine the 1-year distribution characteristics of wind speed. For this aim, a wind observation station must be constructed and 1-year wind speed and direction data must be collected. For determining the distribution characteristics, the collected data must be statistically analyzed. The continuity and reliability of the data are quite important for such studies on the days when possible faults can occur in any part of the observation unit or on days when, the system is on maintenance, it is not possible to record any data. In this study, it is assumed that the station had not worked at some randomly chosen days and that for these days no data could be recorded. The missing data are predicted using the data that were recorded before and after fault or maintenance by an adaptive neuro-fuzzy inference system (ANFIS). It is seen that ANFIS is successful for such a study.     

On the net surface water exchange rate estimated from remote-sensing observation and reanalysis

This study compares the net surface water exchange rates, or surface precipitation (P) minus evapotranspiration (ET), and atmospheric water vapour sinks calculated from various observations and reanalyses, and investigates whether they are physically consistent. We use the observed precipitation from the Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measuring Mission (TRMM) 3B43, ocean evaporation from Goddard Satellite-based Surface Turbulent Fluxes Version 2c (GSSTF2c), and land ET from the Moderate Resolution Imaging Spectroradiometer (MODIS) global ET project (MOD16) and PT-JPL products to calculate observed P minus observed ET. P–ET is also obtained from atmospheric water vapour sink calculated using Atmospheric Infrared Sounder (AIRS)/Advanced Microwave Sounding Unit observation specific humidity observation and wind fields from the Modern-Era Retrospective Analysis for Research and Applications (MERRA) and ERA-interim, denoted as AIRS_M and AIRS_E, respectively. MERRA and ERA-interim water vapour budgets are also calculated for cross-comparison and consistency check. The period of study is between 2003 and 2006 based on the availability of all of the data sets. Averaged water vapour sinks from AIRS and reanalysis are consistent over the global ocean and are close to zero (range: 0.02–0.06 mm day^?1), but range between 0.14 and 0.23 mm day^?1 when land is included. Over ocean within 50^oS--50^oN, averaged observed P minus observed evaporation shows a much larger negative number than that obtained from AIRS and reanalysis. The differences mainly occur over subtropical oceans, especially in the southern hemisphere in summer and the northern hemisphere in winter. Over land, generally higher agreement between observed P minus observed ET and atmospheric water vapour sinks (calculated from AIRS and reanalysis) is found. However, large regional differences, often with strong seasonal dependence, are also observed over land. Estimates of atmospheric water vapour sinks are influenced by both winds and biases in water vapour data, especially over tropics and subtropical oceans, thereby calling for the need for further investigations and consistency checks of satellite-based and reanalysis water vapour, reanalysis winds, P observations, and surface evaporation estimates. In higher latitudes, atmospheric water vapour sinks calculated from AIRS_M, AIRS_E, MERRA, and ERA-interim are more consistent with each other.     

Estimation of cloud liquid water over oceans from dual oxygen absorption band to support the assimilation of second generation of microwave observation on board the Chinese FY-3 satellite

To make up for the absence of observation-based information of cloud liquid water (CLW) in assimilation of second generation of microwave observation on board the Chinese FengYun-3 satellite, two algorithms using double oxygen-absorption band microwave sounding observation at 52.80 and 118.75 ± 2.5 GHz, one using brightness temperatures directly and the other utilizing a cloud emission and scattering index derived from the brightness temperature, are proposed to estimate CLW over oceans. Their performance was evaluated by verifying the estimations from FY-3C double oxygen absorption band microwave observations and that from the traditional Grody scheme applied to microwave measurements at 23.8 and 31.4 GHz from the MetOp-B satellite. An additional experiment was conducted to investigate the impact of regression analysis on the actual brightness temperature and reanalysis data, or the simulated measurements. It is demonstrated that CLW can be retrieved from double oxygen absorption band microwave sounding measurements. The estimations are comparable to the results obtained using the traditional scheme applied to Advanced Microwave Sounding Unit measurements. While total precipitable water was not well obtained as the traditional scheme did, it is feasible to perform regression analysis on actual brightness temperature and reanalysis data; however, for all estimations that the regression was conducted on, the results obtained using actual brightness temperature and reanalysis data were weaker than those obtained using regression coefficients from the simulated data set. The results could be improved by better matching the satellite observations and CLW data used in the regression analysis.     

基于Landsat-5 TM数据的河南省白沙灌区地表温度反演研究

地表温度是土壤水分和植被水分状态的指示计,在干旱遥感监测中有重要作用。应用Landsat-5 TM遥感数据和气象资料,利用归一化植被指数(NDVI)区分地表覆盖类型,采用Van de Griend的经验公式法结合典型地表赋值法计算出地表比辐射率。用单窗算法和单通道算法分别对河南省白沙灌区地表温度进行反演,结果表明:两种方法均能较好地将白沙灌区地表温度分布趋势反映出来,单窗算法的反演精度较高,绝对误差为1.1 ℃,更适宜白沙灌区的地表温度反演,进而可以提高灌区旱情遥感监测精度。     

Quality evaluation for a coprime factor perturbed model set basedon frequency-domain data

Quality assessment is investigated under a probabilistic framework for a prescribed model set. The results on unfalsified probability estimation are extended from additive modeling errors to normalized coprime factor perturbations. An analytic formula has been derived for the sample unfalsified probability. It is shown that with increasing the data length, the sample unfalsified probability converges in probability to a number which is independent of experimental data. Numerical simulations show that the proposed sample unfalsified probability is appropriate in the evaluation of the quality of a model set