轻载工况下基于效率优化的双向无线电能传输系统半桥调制策略

针对基于全桥拓扑的双向双LCC无线充电系统调制策略在轻载工况下功率因数和效率下降严重的问题,该文在不改变全桥结构的基础上,提出一种半桥调制策略。首先对双向双LCC补偿电路进行通态效率建模,并定量分析影响效率的关键变量及其约束条件,从而为调制策略的优化提供理论依据;在此基础上,对所提双边半桥调制策略的工作原理、正导通角优化关系及软开关实现条件进行详细分析,证明该策略在保证开关器件零电压导通的同时,可显著减小外移相角,从而有效提高系统的功率因数和运行效率;最后,搭建3.3 kW的双向无线电能传输系统样机进行对比实验,实验结果表明,所提半桥调制策略在1/4满载及以下的轻载工况下效率最高可达95.6%,且在输出电压宽范围变化时都能够取得明显的优化效果。

基于LCCS的大尺度土地覆被遥感产品类别相对一致性研究

该文提出了一种基于LCCS分类体系的大尺度土地覆被遥感产品间类别一致性的定量计算方法,并以GLOBCOVER和MODIS COLLECTION5两种大尺度土地覆被遥感产品为数据源对该方法进行了验证。结果表明:GLOBCOVER和MODIS COLLECTION5两者间的类别一致性区域较小,且集中分布于中国的华北、四川盆地、台湾省、西北沙漠地区和喜马拉雅山东麓。类别一致性值分区统计表明,两种土地覆被遥感产品的类别一致性面积百分比存在显著的区域差异,在东北区域,高值区和低值区总面积相近,该区域一致性值以0.5~0.7为主,约占该区域总面积的35%;在西北区域,一致性值以0.7~0.9为主;在华北区域,一致性值表现出明显的高值优势,一致性值大于0.9的区域约占区域总面积的63%;在东南区域,类别一致性值表现出高值面积百分比大于低值面积百分比的特征;青藏高寒区的类别一致性值则与东南区域相反;四川盆地的陆表土地覆被类别以耕地为主,因此表现出与华北区域类似的分布特征;西南区域各个区间的类别一致性值百分比表现出较为均匀的分布特征,并无明显优势级别。

Reliability-based life-cycle cost seismic design optimization of coastal bridge piers with nonuniform corrosion using different materials

Reinforcement corrosion is the main cause of performance deterioration of reinforced concrete(RC)structures.Limited research has been performed to investigate the life-cycle cost(LCC)of coastal bridge piers with nonuniform corrosion using different materials.In this study,a reliability-based design optimization(RBDO)procedure is improved for the design of coastal bridge piers using six groups of commonly used materials,i.e.,normal performance concrete(NPC)with black steel(BS)rebar,high strength steel(HSS)rebar,epoxy coated(EC)rebar,and stainless steel(SS)rebar(named NPC-BS,NPC-HSS,NPC-EC,and NPC-SS,respectively),NPC with BS with silane soakage on the pier surface(named NPC-Silane),and high-performance concrete(HPC)with BS rebar(named HPC-BS).First,the RBDO procedure is improved for the design optimization of coastal bridge piers,and a bridge is selected to illustrate the procedure.Then,reliability analysis of the pier designed with each group of materials is carried out to obtain the time-dependent reliability in terms of the ultimate and serviceability performances.Next,the repair time of the pier is predicted based on the time-dependent reliability indices.Finally,the time-dependent LCCs for the pier are obtained for the selection of the optimal design.

考虑故障风险与不确定性的海上风电主变压器检修策略

为提高海上风电主变压器检修策略优化的科学性,在保证可靠运行的前提下,提出一种考虑故障风险与不确定性的海上风电主变压器检修策略优选方法。首先,详细分析故障风险成本模型,据此建立海上风电主变压器全寿命周期成本(life cycle cost,LCC)模型,并引入盲数理论将LCC中不确定性参数用数学模型定量进行计算,提高成本估算精度。然后,从成本管理角度出发,分析维修方案对LCC的影响,进而建立以LCC最低为目标的海上风电主变压器检修策略优化模型,并通过改进的布谷鸟搜索算法进行求解。最后,经算例验证,所提模型和检修策略优选方法具有较强的可操作性,能为海上风电主变压器的可靠运行提供一定的参考价值。

轨道车辆预防性维修全寿命周期备件数量计算模型

轨道车辆海外项目招标时,均将LCC作为一个重要指标进行考核,全寿命周期预防性维修备件成本是LCC计算的一个关键组成部分,通过固定预防性维修计划编制样式,利用excel函数组合建立备件计算模型,实现了预防性备件数量的自动计算,并根据备件计算逻辑提出维修任务编制时注意事项。同时根据实际年度运行里程与预计年度运行里程的数值比较确定备件的计算公式,实现了预防性备件数量随实际年度运行里程的自动变更,保证了LCC计算的准确性,为用户采购车组数量和年度运行里程提供了决策依据。

基于电网设备全寿命周期成本的精益化管理研究与应用

全寿命周期成本(Life Cycle Cost,LCC)理念已在许多领域得到了应用,并取得了良好的社会经济效益。本文主要基于该理念,研究对设备全寿命周期在项目可研阶段的统筹控制管理,以项目的经济效能为主要控制对象,构建LCC测算、比选模型,以变电站为实践案例,分别从单设备、单间隔、单系统、变电站整站4方面开展LCC比选应用,分析不同选型的科学性和项目实施的技术经济性,选择全寿命周期成本最优方案,提高电网精准投资能力。

基于遗传算法的双边LCC拓扑IPT系统的抗偏移性能研究

针对AGV无线电能传输过程中存在的位置偏移情况,提出一种基于双边LCC拓扑的新型磁耦合结构,并基于遗传算法进行了优化设计以进一步提升IPT系统在水平方向的抗偏移性能。首先,详细推导了双边LCC拓扑的补偿网络参数和各支路的电流表达式;其次,介绍了在双极性平面绕组4D线圈的基础上增加一个正交Q线圈的新型复合磁路机构,以提高系统的抗偏移性能和传输性能;然后以SM作为优化目标,采用遗传算法对4D线圈各物理参数进行迭代优化,进一步提升系统的性能;最后,搭建实验样机对该新型磁耦合结构进行了验证,实验结果表明:正对时新型磁耦合结构传输功率为300 W,传输效率为87.12%;接收线圈在水平向偏移百分比δ<20%的范围内输出功率最大波动率小于48%,并保持传输效率始终高于80%,满足实际的需求。

轨道车辆全寿命周期费用分析系统研究

轨道车辆产品全寿命周期费用分析对产品设计制造具有十分重要的意义,其中产品的可靠性、可用性与可维护性是制约产品全生命周期费用分析的关键因素,如何结合RAM研究成果及LCC研究成果,为决策提供最优支持,是当前RAMS研究和LCC研究的主流方向,针对以上问题,本文研究了一种轨道车辆全寿命周期费用分析系统,加强全寿命周期费用分析能力,支撑检修成本分析和修程修制优化。

基于节能经济目标的电网项目LCC论证难点分析及对策

电力企业已逐步开展电网项目LCC论证研究,但论证总体水平还不高。重点收集了电力企业对于LCC论证的相关要求及优势,了解了LCC论证存在的管理难点及技术难点。以典型35 kV开关改造项目LCC论证为例,开展了项目方案LCC深入论证比选研究,分析了不同项目类型LCC论证方法及深度要求,以加强项目论证水平。

用于PVD电源的新型三相LCC变换器

PVD直流等离子体电源在电源领域属于特种应用产品,广泛应用于集成电路制造中的金属及非金属材料溅射镀膜。针对集成电路制造产业中对PVD直流等离子体电源的应用需求,本文提出一种用于PVD电源的新型三相LCC变换器。

Studies of commutation failures in hybrid LCC/MMC HVDC systems

A hybrid of line commutated converters(LCCs)and modular multi-level converters(MMCs)can provide the advantages of both the technologies.However,the commutation failure still exists if the LCC operates as an inverter in a hybrid LCC/MMC system.In this paper,the system behavior during a commutation failure is investigated.Both halfbridge and full-bridge MMCs are considered.Control strategies are examined through simulations conducted in PSCAD/EMTDC.Additionally,commutation failure protection strategies for multi-terminal hybrid LCC/MMC systems with AC and DC circuit breakers are studied.This paper can contribute to the protection design of future hybrid LCC/MMC systems against commutation failures.

Optimal Configuration for Design of Stand-Alone PV System

This paper presents a design for a stand-alone photovoltaic (PV) system to provide the required electricity for a single residential household in rural area in Jordan. The complete design steps for the suggested household loads are carried out. Site radiation data and the electrical load data of a typical household in the considered site are taken into account during the design steps. The reliability of the system is quantified by the loss of load probability. A computer program is developed to simulate the PV system behavior and to numerically find an optimal combination of PV array and battery bank for the design of stand-alone photovoltaic systems in terms of reliability and costs. The program calculates life cycle cost and annualized unit electrical cost. Simulations results showed that a value of loss of load probability LLP can be met by several combinations of PV array and battery storage. The method developed here uniquely determines the optimum configuration that meets the load demand with the minimum cost. The difference between the costs of these combinations is very large. The optimal unit electrical cost of 1 kWh for LLP = 0.049 is $0.293;while for LLP 0.0027 it is $0.402. The results of the study encouraged the use of the PV systems to electrify the remote sites in Jordan.

Life-cycle cost model and evaluation system for power grid assets based on fuzzy membership degree

Life-cycle cost(LCC)theory can be effectively applied to improve the efficiency and quality of power plant equipment and asset management.However,specific aspects of the LCC calculation and evaluation model require further research for practical application.This paper proposes an LCC assessment model for the management of electric power plant equipment during its service life.A membership function method based on fuzzy logic is used to improve the allocation of modernization and overhaul projects to multiple equipment assets.An LCC assessment model and evaluation system for power equipment are proposed and successfully applied to the equipment and project management of a Guangzhou power plant in the China Southern Power Grid,providing a decision-making mechanism that facilitates efficient operation and optimal utilization of power plant equipment and assets.

Energy Systems Maintenance

The subject of maintenance is of much importance in the implementation of projects in today’s industries. Maintenance is carried on energy systems to keep their performance within acceptable standards and to maintain their average life expectancy. The cost associated with maintenance work is largely dependent on how often maintenance routines are carried out and the extent the work are done. Current maintenance work are usually carried out in accordance with the equipment manufacturer’s guide line and modified by experts as maintenance experience is gained. This paper discusses the various maintenance schemes and the impact of maintenance on the life cycle costs of a system.

LCCS地表覆盖分类系统简介及图例翻译

地表覆盖信息及其变化反映着人类活动及环境变化,多数据源、多尺度的地表覆盖产品应运而生,但由于尺度不同、分类系统不同,导致各分类产品之间缺乏互操作性,而其对应的多种地表覆盖分类系统中类的定义也不尽相同,各图例类之间缺乏可比性.为解决该问题,联合国粮农组织与联合国环境规划署联合开发了LCCS(Land Cover Classification System)分类系统,建立了LCCS分类系统的基本构架.我们以美国NLCD 2011图例及Glob Cover2009图例为例,对LCCS分类系统的翻译功能进行具体讲解,并对其优缺点进行总结归纳.

Application of Grey System Theory in Design For Cost (DFC)

Design For Cost (DFC) is a branch of Design For X (DFX). In this paper, wedefined DFC as a design method that analyzed and evaluated the product's life cycle cost (LCC), thenmodified the design to reduce the LCC. Nowadays it is a very difficult thing to obtain LCC data inChina or in developing countries. Statistical methods can not be used because available LCC data arefew. In order to solve this problem, we used grey system theory. Then relations of cost factorswere analyzed in LCC using grey relevant methods, and a GM(1,1) model between design parameters andLCC was established. Using this model, we can estimate and control LCC by changing design parametersat the beginning of the design stage.

基于LCC的三相四线制逆变器特性分析与控制

传统的三相四线制逆变器存在拓扑结构与控制复杂、工频变压器导致体积庞大等问题。以一种简单的基于LCC网络的三相四线制逆变器为研究对象,深入分析了其构造原理与工作特性,其每一相输出电压独立于负载,因此在为多种不平衡负载供电时具有输出电压自平衡功能。LCC网络的增益还可以提高直流母线电压利用率,满足电气化交通领域的应用需求。给出了LCC网络的参数设计流程。针对LCC网络内部复杂的耦合关系,采用双序αβ坐标系与单序dq坐标系结合的解耦控制方法,对其进行计算机仿真,并且搭建了1 kW/105 V的原理性实验平台,与4种典型三相四线制逆变器进行对比,验证了理论分析的正确性与所提控制方法的有效性。

Land Cover Map Delineation, for Agriculture Development, Case Study in North Sinai, Egypt Using SPOT4 Data and Geographic Information System

Land cover map for a part of North Sinai was produced using the FAO—Land Cover Classification System (LCCS) of 2004. The standard FAO classification scheme provides a standardized system of classification that can be used to analyze spatial and temporal land cover variability in the study area. This approach also has the advantage of facilitating the integration of Sinai land cover mapping products to be included with the regional and global land cover datasets. The total study area is 7450 km2 (1,773,842) feddans. The landscape classification was performed on SPOT4 data acquired in 2011 using combined multi-spectral bands of 20 meter spatial resolution. Geographic Information System (GIS) was used to edit the classification result in order to reach the maximum possible accuracy. GIS was also used to include all necessary information. The identified vegetative land cover classes of the study area are irrigated herbaceous crops, irrigated tree crops and rain fed tree crops. The non-vegetated land covers in the study area include: bare rock, bare soil, bare soil stony, bare soil very stony, bare soil salt crusts, loose and shifting sands and sand dunes. The water bodies were classified as artificial perennial water bodies (fish ponds and irrigated canals) and natural perennial water bodies as lakes (standing) and rivers (flowing). Artificial surfaces in the study area include linear and non-linear. The produced maps and the statistics of the different land covers are included in the following sub-sections.

LCC型无线恒流/恒压充电系统的控制

为了满足电动汽车动力锂电池的充电需求,提出了一种恒流/恒压切换控制,通过调整逆变级的移相角实现该控制策略。为了适应负载的变化,提高控制性能,将整流级之前的电路用戴维南等效与降阶处理,简化控制模型,通过最小二乘法辨识整流级的输入电压和电流基波,确定等效负载。使用该等效电路与简化模型,分别设计了恒流输出和恒压输出时的PI控制器,实现电动汽车动力锂电池“先恒流后恒压”的充电需求,最后在MATLAB/Simulink中搭建了仿真模型,验证了理论分析和控制方法的正确性和可行性。

电动汽车无线充电系统双LCC型补偿拓扑研究

为了提高无线电能传输(WPT)系统的传输效率,通常在原、副边添加谐振补偿拓扑。目前研究的谐振补偿拓扑包括SS型、双LCL型和双LCC型。对双LCC型补偿拓扑进行分析,并通过MATLAB软件对其进行仿真,分别研究不同负载、互感和角频率下系统的输入功率、输出功率、传输效率。研究结果表明该补偿拓扑的传输特性良好。