Reduction of electric field strength by two species of trees under power transmission lines

Electrical pollution is a worldwide concern,because it is potentially harmful to human health.Trees not only play a significant role in moderating the climate,but also can be used as shields against electrical pollution.Shielding effects on the electric field strength under transmission lines by two tree species,Populus alba and Larix gmelinii,were examined in this study.The electrical resistivity at different heights of trees was measured using a PiCUS sonic tomograph,which can image the electrical impedance for trees.The electric field strength around the trees was measured with an elf field strength measurement system,HI-3604,and combined with tree resistivity to develop a model for calculating the electric field intensity around trees using the finite element method.In addition,the feasibility of the finite element method was confirmed by comparing the calculated results and experimental data.The results showed that the trees did reduce the electric field strength.The electric field intensity was reduced by 95.6%,and P.alba was better than L.gmelinii at shielding.

Battery Charger for Electric Vehicles based on a Wireless Power Transmission

In this paper,the case of a battery charger for electric vehicles based on a wireless power transmission is addressed.The specificity of every stage of the overall system is presented.Based on calculated and measured results,relevant capacitive compensations of the transformer and models are suggested and discussed in order to best match the operating mode and aiming at simplifying as much as possible the control and the electronics of the charger.

Improved Method of Power Loss and Electric Field Calculations of HVAC Transmission Lines

An improved method for calculating the corona power loss and the ground-level electric field on HVAC transmission lines induced by corona is proposed.Based on a charge simulation method combined with a method of successive images,the proposed method has the number and location of the simulated charges not arbitrary.When the surface electric field of a conductor exceeds the onset value,charges are emitted from corona into the space around,and the space ions and the surface charges on each sub-conductor are simulated by using the images of the other sub-conductors.The displacements of the space ions are calculated at every time step during corona periods in both the positive and the negative half cycles.Several examples are calculated by using the proposed method,and the calculated electric field at the ground level and the corona power loss agree well with previous measurements.The results show that simulating 12 charges in each conductor during 600 time steps in one cycle takes less time while guarantees the accuracy.The corona discharge from a 220 kV transmission line enhances slightly(less than 2%) the electric field at the ground level,but this effect is little from a 500 kV line.The improved method is a good compromise between the time cost and the accuracy of calculation.

Manufacturing Development Emphases on Power Generation and Transmission Apparatus in 11th Five-Year Plan Period and Prospect to the Year 2020

Based on predictions on Chinese power development in the coming 20 years, this paper introduces the emphases and key technologies in power sources and power network construction, and puts for ward the major tasks and technological orientation for machinery manufacturers to supply qualified equipment to China power industry.

可视化软件包Power World Simulator在最优潮流计算中的应用

介绍了在考虑输电阻塞的情况下,采用可视化软件包Power World Simulator展示电力系统中以发电成本最小为目标的最优潮流的计算和分析方法,实例表明该软件包能够直观、形象地展示出配电网最优潮流的计算结果和分析过程.

Pricing Mechanism in Power Market Construction

The reform on electricity pricing mechanism is a critical problem in power market construction in China, and is in mutual supplementation and promotion with the latter. In particular, the pricing mechanism for electricity fed into network and that for electricity transmission and distribution as well as the relationship between coal and electricity prices, etc. have to be studied in depth. This paper presents several solutions and suggestions to these problems.

Smart Meter Development for Cloud-Based Home Electricity Monitor System

Αcloud-based home electricity data-monitoring system,which is based on an Arduino Mega controller,is proposed for monitoring the electricity consumption(electrical power)and power quality(PQ)in home.This system is also capable of monitoring the fundamental frequency and supply-voltage transients to ensure that the appliances operate in a safe operation range.The measured data(voltage and current)are transmitted through a Wi Fi device between the Arduino controller and server.The transmission control protocol(TCP)server is set up to acquire the high-data transmission rate.The server system immediately displays the calculated parameters and the waveform of the acquired signal.A comparison with a standard measurement device shows that the proposed system,which can be built at a low cost,exhibits the same functions as a factory product.

基于电场耦合的电能信号并行传输系统串扰抑制方法

针对较大功率电场耦合无线电能传输系统信号双向高速传输的需求,该文提出一种基于部分能量通道的电能与信号并行传输系统的串扰抑制方法。通过对所提出的系统拓扑进行分析,给出了电能传输增益表达式与电能串扰增益表达式,并分析了阻波电路参数变化对电能串扰增益的影响;基于交流阻抗法及香农定理分别给出了信号传输增益及信道容量表达式,分析了信号支路参数对信道容量的影响;在综合考虑信号传输增益、信道容量及阻波电路参数敏感性的情况下,给出系统信号支路参数的设计方法。该方法能保证系统在较大功率下降低电能串扰,保障信号稳定传输,实现信号的双向高速传输。通过仿真与实验验证了所提出的拓扑和参数设计方法的有效性。搭建的实验装置实现了传输530.4 W的电能,23.28 Mbit/s信号正向传输速度和24.2428 Mbit/s信号反向传输速度。

Towards a (More) Electronic Transmission and Distribution (eT&D)

The challenges and the path towards a(more)electronic transmission and distribution(eT&D)is presented in this paper.The challenges are first identified together with key stakeholders in the drive for grid modernization.A fundamental question is then asked about the investment priority.Six basic characteristics are reviewed,leading to the composition of structured microgrids as the basic functional cell of a modern grid.One example of fractal radial structure and one fractal meshed structure are presented.The likely evolution path is then proposed together with basic technology sets.Specific foundation technologies are discussed in detail,including adiabatic power conversion,3MC technology,medium voltage conversion,distribution-level electronic power transformer and FACTs hardware integration,and back-to-back converters as a universal interconnect element.The rapidly emerging on-wire sensing technology is also discussed.It is pointed out that the distribution-level large electronic power transformer will provide a key component to enable hybrid ac/dc grid flow control and ancillary support for a flexible electronic transmission and distribution(eT&D)systems.

电动汽车多车位WPT下沉式磁屏蔽系统研究

在电动汽车无线电能传输系统中,实现高效传输的同时减少磁泄漏一直是一个技术挑战。针对这一问题,本文提出了一种应用于多无线电能传输系统的下沉式屏蔽线圈结构,该结构在减小目标面漏磁的同时不会影响系统的传输效率。首先,提出了一种基于矢量磁位的矩形线圈磁场计算方法,通过此方法对系统目标面漏磁进行分析,为后续的磁泄漏优化提供了理论依据;其次,介绍了一种漏磁优化的方法,运用该方法得到满足要求的各线圈参数,为实现高效的无线电能传输提供了关键支持;最后,根据得到的线圈参数,研制了一套带磁屏蔽结构的双车位电动汽车无线充电系统,通过仿真和实验,让提出的屏蔽结构和方法的有效性得到了充分证实。结果显示,当系统输出功率恒定在4 kW时,所提出的屏蔽结构不仅使目标区域最大泄漏磁场降低了25%,且传输效率高达95%。

跟构网换流器并联的海上DRU低频交流送出方案

基于不可控整流单元(DRU)的风电低频交流送出系统不具备功率返送的能力,需采用构网型换流器实现海上风电场的自组网。同时考虑传统跟网型换流器所具备的快速功率响应能力对海上风力发电带来的正面影响,以六相永磁同步电机构成的风电机组作为研究对象,阐明在风电机组内,采用两种控制策略的换流器并联经DRU低频交流送出系统的拓扑结构和运行特性。分别设计风电机组网侧换流器的构网型控制策略与跟网型控制策略,并在此基础上探讨两组网侧换流器之间的功率不平衡问题,进一步设计环流抑制策略,实现风电功率经DRU送出。通过搭建Simulink仿真模型和RT-LAB半实物仿真系统验证方案的可行性。

无线电能传输系统高效率低漏磁的全向环绕型有源磁屏蔽结构

在电动汽车无线电能传输系统(WPT)中,如何通过电磁屏蔽技术来降低WPT系统中的漏磁,同时维持较高的传输效率是一个难题。为此本文提出了一种全向环绕型有源磁屏蔽线圈结构来减少WPT系统中的漏磁。首先,分析了该结构的磁屏蔽工作原理以及设计思路,推导了该结构的数学模型;其次,根据本文线圈结构高效率低漏磁的特点,提出了一种线圈优化方法,得到了满足设计要求的线圈参数;最后,根据得到的线圈参数,搭建了一套基于所提线圈结构的WPT系统,并通过仿真和实验验证了该结构和方法的合理性。结果显示,在传输功率为4 kW时,本文提出的线圈结构在偏移0 cm时,目标面的最大漏磁为3.76μT,相比无屏蔽线圈结构降低了43.63%的漏磁,并且传输效率高达95.58%;在偏移10 cm时目标面的最大漏磁为6.03μT,仍符合漏磁安全标准,并且传输效率为92.92%,高于同尺寸无源屏蔽线圈结构和传统有源屏蔽线圈结构的传输效率。

信号与能量极板层叠方式下的电场耦合式无线电能传输系统

为了提升共享部分能量通道式的电能与信号并行传输系统在传输极板面积受限的应用场合中的能量传输性能,并实现信号双向高速传输,提出一种信号传输极板与能量传输极板层叠方式下的电场耦合式无线电能传输(electric-field coupled wireless power transfer,EC-WPT)系统,给出系统拓扑及串扰抑制方法。基于交流阻抗分析法及香农第二定理,建立电能串扰增益、信号传输增益、信号最大传输速率及电能传输增益的数学模型,分析交叉耦合电容对电能串扰增益及信号传输的影响;以降低交叉耦合电容对信号传输增益及信号最大传输速率的影响为目标,给出层叠方式下EC-WPT系统信号传输极板面积及信号支路参数的设计方法。仿真与实验验证了所提出的系统及给出的方法能在较大传输功率下实现系统的信号双向高速传输。所搭建的实验装置实现了在系统输出功率达到520.2 W时,信号正向传输速度为18.64 Mbit/s和信号反向传输速度为19.36 Mbit/s。

电力通信网络敏感信息传输路由安全优化设计

优化电力通信网络敏感信息传输节点选取过程,可避免链路拥挤,高消耗的传输能量导致簇首分布不合理的问题。因此,为了提高敏感信息传输安全性和网络覆盖率,设计电力通信网络敏感信息传输路由安全优化方案。结合PageRank算法迭代更新连接节点,构建路由连接函数,综合考虑节点负荷容量和等级选取节点。构建路由安全优化协议整体框架,依据链路ETX值改善电力通信网络中能量损耗。计算目标节点分布概率密度,设计路由优化数据分发机制,实现敏感信息传输路由安全优化。由实验结果可知,所设计方法簇1、2、3、4的簇首中心坐标分别为(-1,2)、(1,1.8)、(0.95,-2.2)、(-1,-2),与实际簇首所在中心一致;最高网络覆盖率为96%,有效提高了网络连接安全性。

750kV单回并行输电线路电磁辐射环境研究

采用《环境影响评价技术导则输变电》(HJ 24—2020)附录C、D推荐的计算模式对750 kV单回并行输电线路电磁辐射环境进行计算与预测。结果表明,经过耕地、园地、牧草地、畜禽饲养地、道路等场所,当导线对地最小高度为15.5 m时,单回并行线路下的工频电场强度最大值超过10 kV/m;需将导线对地最小高度提至16.5 m,才能满足4 kV/m控制限值要求。750 kV单回并行输电线路产生的工频磁场强度小于公众曝露控制限值(100μT),一般情况下不会成为线路建设的环境制约因素;但其产生的工频电场是电磁环境影响的主要因素,电场强度控制限值(4 kV/m)是线路建设的环境制约因素,同时也是输变电电磁环境重点控制因素。现场实测结果与理论预测结果符合性较好,表明采用的预测模式具有较好的应用性,研究结果可为750 kV单回并行输电线路的建设和环境监管提供支持。

台风场景下基于多种分布式资源协同的弹性配电网两阶段供电恢复策略

近年来频发的自然灾害极大威胁配电网安全运行,统筹考虑不同分布式资源特点,发挥分布式资源互补互济优势,有助于解决灾后配电网部分线路损坏、电力供应不足问题,实现电网灾后快速恢复。在电网中分布式资源种类不断丰富的背景下,本文提出一种台风场景下基于多种分布式资源协同的弹性配电网灾前及灾后两阶段供电恢复策略。首先,考虑配电网和交通网耦合的影响,灾前阶段在考虑电动汽车调度的同时,以加权失电量期望最小为目标建立移动储能和抢修队应急仓库选址模型;其次,根据以上3种分布式资源以及柔性负荷的灾后响应特征,将灾后阶段分为紧急功率支撑和负荷快速恢复两个过程,搭建了配电网灾后多时段恢复优化模型;然后,通过深入研究多种分布式资源的优缺点,设计了配电网两阶段供电恢复框架;最后,设计了多组算例,验证了所提方法的有效性和可行性。

跨国跨州/跨省跨区输电定价机制及对中国专项工程定价的启示

中国资源禀赋和能源需求呈逆向分布,促进新能源资源在更大范围的优化配置是中国新型电力系统建设的内在要求。跨省跨区输电价格作为跨省跨区电力交易价格的重要组成部分,其定价机制的合理性不仅会影响输电工程投资成本的合理回收,还会影响电力市场竞争效率乃至资源在更大范围内优化配置。为此,在梳理中国及欧洲、美国典型电力市场跨省跨区和跨国跨州输电工程现状的基础上,对国际典型电力市场跨国跨州和跨市场输电定价机制的历史沿革和发展情况进行梳理,探究影响跨国跨州和跨市场输电定价的关键因素,并结合中国跨省跨区专项工程输电定价机制的发展沿革,分析了中国现行的跨省跨区专项工程输电定价机制在新型电力系统和全国统一电力市场体系建设的背景下将面临的问题,提出对中国跨省跨区专项工程输电定价的启示与未来发展方向。

混合动力汽车功率分流传动系统扭转振动及其影响因素研究

针对某款混合动力汽车,综合考虑发动机、电机、复合行星齿轮机构、离合器、减速器、差速器和半轴等部件,采用集中质量法建立功率分流传动系统动力学模型。在此基础上,分析不同运行工况下传动系统固有频率和振型,分别研究电机和发动机激振频率与传动系统固有频率之间的关系,仿真分析扭转减振器刚度对传动系统固有频率的影响规律,通过改变扭转减振器刚度从而使得传动系统共振转速远离发动机常用工作区。

基于动态平衡布局的输电网潮流图自动生成方法

为解决输电网潮流图自动生成中厂站布局与线路布线问题,提出基于动态平衡布局的输电网潮流图自动生成方法。针对厂站布局,首先,在力导向算法的基础上引入基于图纸中心点的惩罚函数,以解决力导向算法布局不均匀的问题,提高布局的均布度;然后,利用厂站分布率参数控制算法平衡次数,引导厂站向图纸边界运动,解决布局自动适应给定图幅大小的问题;最后,通过位置映射变换将围绕图纸中心点的椭圆分布转换为矩形分布,解决引入惩罚函数布局均匀但不符合传统输电网潮流图绘制习惯的问题。针对线路布线提出以构建通道树为中心的布线方法,有效降低布线交点个数,提升布线效果。所提布局与布线算法在实际工程应用中取得了良好的效果,通过案例验证了输电网潮流图自动生成的正确性和有效性。