农村配电网无功优化算法与分布式控制系统

在农网线路无功补偿位置和补偿容量确定的情况下,提出一种改进的TS搜索算法,建立以网损最小为目标的电容器优化投切模型,并根据实时负荷变化以及系统运行状态控制补偿电容器组自动投切,从而实现整个网络损耗最小且实时电压不越限.基于该方法建立的无功优化分布式控制系统包括无功补偿终端和后台控制中心.实际应用表明,该系统可实现配电线路全局无功优化控制,适于农村配电网络.     

无功功率动态补偿

一般无功功率自动补偿的主要缺点是 :(1)　在自动投切过程中不能控制电容器回路的合闸角和开断角 ,因而不可避免地会引起合闸过电流、开断过电压 ,使断路器触头烧损严重、检修频繁 ,电容器使用寿命缩短。(2 )　对波动负荷和冲击负荷 ,不能抑制电压波动和电压闪变。(3)　达不到最理想的高效节能效果。无功动态补偿则克服了前述缺点 :无功动态补偿装置由微机调节器控制可控硅无触点容性开关 ,跟踪负载无功电流变化 ,对多级电力电容器组采用过零快速投切 ,切除过程中无操作过电压、电弧重燃现象 ,响应时间快 ,可频繁投切、无噪音 ,整机使用寿命…     

农村有源配电网电压无功优化控制方法

针对越来越多的分布式电源接入农村配电网,导致电压无功控制难度增大的问题,提出了适用于含分布式电源农村配电网的电压无功优化控制方法,通过调控分布式电源无功出力、调整有载调压变压器分接头位置、投切无功补偿设备等手段,建立了考虑分布式电源利用率、网损、电压波动和无功设备投切费用的多目标协调优化控制模型,并采用收敛性较好的协同粒子群算法进行求解。最后,算例仿真验证了所提模型和算法的正确性与有效性。     

VQC─Ⅱ型电压无功综合控制装置

ＶＱＣ─Ⅱ型电压无功综合控制装置一、概述ＶＱＣ─Ⅱ型电压无功综合控制装置是对有载调压变压器分接头切换和并联电容器投切进行综合优化自动控制的通用设备。它适用于电力系统中各种类型、各种运行方式的变电站。该装置由控制器，打印机和自动控制屏组成，采用微机及数...     

调压式无功自动补偿装置

目前国内的变电站无功补偿设备主要采用并联电容器组,控制方式采用手动投切和自动投切方式。采用手动投切电容器组,一般电容器容量配置较大,一段母线装一组电容器,容易出现过补偿和欠补偿情况。而且,电容器的容量都较大。当电容器的补偿容量大于变电站的无功缺额时,投入电容器就会出现过补,而不投又会欠补。为了克服上述弊端,部分变电站虽然采用了自动装置来投切电容器,     

低压无功补偿应注意的问题

1无功补偿装置的选择无功补偿按工作特性可分为静态补偿和动态补偿。静态补偿一般采用机械式接触器投切电容器组,适用于负载变化比较小的场合。动态补偿是以晶闸管作为执行元件,用工业PC机进行控制,通过跟踪检测负荷的无功电流或无功功率,对多级电容器组进行分组投切。晶闸管作为无触点开关能快速通断,不产生电弧及噪声。     

低压配电网不平衡和谐波治理

正1低压配电网不平衡和谐波治理方案1.1晶闸管投切电容过程补偿器件所有相在无功容量上不同,负荷将发生变化,因此对负载不变的情况,按照分布式补偿方法,先确定晶闸投切电容器TSC总容量,再作出分组~([3])。因为需要一些装置,并对控制进行简化,要避免将分组进行细化。运用的TSC控制方式多种多样,为了实现不平衡补偿,通过无功补偿法予以控制。1.2确定有源滤波器要选用最适宜的有源滤波器,关系着三相三线制     

并联电容器的选择及补偿容量计算

1电力电容器补偿、控制及安装方式的选择1.1采用并联电力电容器作为人工无功补偿装置时,为了尽量减少线损和电压损失,宜就地平衡补偿,即低压部分的无功功率宜由低压电容器补偿,高压部分的无功功率宜由高压电容器补偿。对于容量较大,负荷平稳且经常使用的用电设备的无功功率,宜单独就地补偿。1.2补偿电容器组的投切方式分为手动和自动两种。对于补偿低压基本无功功率的电容器组,以及常年稳定的无功功率和投切次数少的高压电容器组,宜采用手动投切;为避免过补偿或在轻载时电压过高,造成某些用电设备损坏等,宜采用自动投切。在采用高、低压自动…     

基于通信组网的低压配电网无功补偿

文章提出了一种基于通信组网的低压配电网无功补偿建设方案,无功补偿设备不仅可就地补偿负荷无功需求,实现无功就地平衡,还可以通过Zigbee与配变终端实现级联,并通过配变终端的GPRS信道与管理控制中心通信,实现现场低压无功补偿的在线监视及低压配电网无功优化管理。     

农村电网线路无功优化智能控制策略与装置

在农网线路无功补偿位置和补偿容量已经确定的情况下,提出一种智能控制策略,使整个网络损耗最小且实时电压不越限。建立以网损最小为目标的电容器优化投切模型,根据无功补偿对潮流影响的特点以及负荷特性,通过对Tabu搜索方法进行改进来寻求最优解。根据农村配电网现有的自动化条件,采用GPRS远程通信技术实现调度室上位机和线路中各智能无功补偿装置之间的数据交换,从而实现配电线路无功优化控制。     

Overland water and salt flows in a set of rice paddies

Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m⁻¹) and an infiltration rate of 5.8 mm day⁻¹. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day⁻¹), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day⁻¹ was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration.     

瓦房店市水果生产标准化发展研究

瓦房店市是我国重要的水果生产基地,在国内水果生产领域占有重要地位。随着水果市场化的不断深入,如何满足和适应国内外市场需求成为瓦房店市水果生产的关键问题。从瓦房店市水果生产实际出发,阐述了实施水果生产标准化的必要性,提出了发展水果生产标准化的具体措施。     

金谷子耐旱TG118引种试种及推广应用

对引进的谷子新品种金谷子耐旱TG118进行品种比较试验和多点试种。结果表明：该品种抗旱、耐瘠、适应性强,稳产、高产、抗病抗风抗倒伏强,品质优良,粮草兼用,种植简单,省工易管;一般产量在6000kg/hm2以上,比当地主栽品种增产20%以上。最高产量达9450kg/hm2,适于在辽西北地区推广应用。     

对《种子法》存在问题的探讨

《种子法》是我国种植业第一部法律。自实施以来,为依法加强种子管理提供了有力的法律支撑,促进我国种子产业发生翻天覆地的变化。但随着依法管理工作的深入和种子产业的快速发展,《种子法》及配套规章的一些问题逐步显现出来。对《种子法》及配套规章存在的问题进行深入分析,对需要进一步补充的章节以及需要调整的内容进行深入探讨,以求更加完善和明确。     

Review of the Egyptian experience in implementing land drainage projects

About 30 years have passed since the Government of Egypt embarked on implementing a series of large scale drainage projects. At present, about 3.8 million acres have been provided with drainage systems on the basis of systematic pre-drainage investigations and designs. The target is to provide drains in approximately 6.4 million acres in the Nile Valley and Delta.The implementation of the subsurface drainage system is carried out by the public sector and private contractors under direct supervision of governmental regional departments. The implementation process depends on many factors related to the drainage material, machinery, manpower, site requirements, farmers and organizations involved. Problems and constraints are sometimes challenging, however, the annual rate of implementation has gradually increased to 170,000 acre/year.This paper discusses the different aspects involved in the implementation process of drainage systems. The development in materials, machinery and construction technologies will be reviewed. Institutional and management factors are going to be also considered.     

和谐社会理论建设的几点哲学思考

在新世纪,面对机遇和挑战,党的十六大把“社会更加和谐”作为全面建设更高水平的小康社会的一个重要目标。中国人素有社会和谐的理想;西方人自古也向往社会和谐;借鉴东西方两种和谐社会思想的经验、教训,构建社会主义和谐社会理论。     

A European irrigation map for spatially distributed agricultural modelling

We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications.     

粉质仪和拉伸仪在面粉生产中的应用

在介绍粉质仪和拉伸仪结构和原理的基础上,探讨了粉质曲线中吸水率、形成时间、稳定时间、弱化度和评价值等指标与面粉品质的关系,以及如何根据拉伸曲线中面团最大拉伸阻力、延伸度和拉伸曲线面积等指标来评价面团品质,并结合生产实际,概述了粉质仪和拉伸仪在面粉生产中的作用。     

农村信息化服务的现状及建设措施

分析当前我国农村信息化服务的现状,提出加强农村信息化服务的新举措。     

车辆ABS控制算法的研究及探讨

对现代汽车的ABS控制算法作了一些简单的介绍,同时指出了它们的一些缺陷,相应地提出了几种对ABS的其它控制方法并加以探讨,其中着重论述了ABS门限值控制算法中参考车速的确定方法和基于附着系数的控制算法。