Power Transmission and Distribution Equipment in Steady Progress

SEC is not only one of the largest enterprise groups in China that engaged in designing and manufacturing of power generating equipment, but also is noted for designing and manufacturing power transmission and distribution equipment. Shanghai Power Transmission and Distribution Equipment Corporation is a subsidiary of SEC. It consists of key enterprises, including Shanghai Hua Tong Switchgear Works, Shanghai Relay Plant,Shanghai Instrument Transformer Works, Shang-

Shanghai Hua Tong Switchgear Works -A Major Switchgear Manufacturer for Power Transmission, Substation and Distribution in China

Founded in 1919, Shanghai Hua Tong Switchgear Works ("HTSW" in short for below) is one of large enterprises on state level. With high and new technology, it is designed as an export base for mechanical and electrical product of the Ministry of Machinery Industry as well. It has been awarded the honor of first grade factory in the competition for key and major project construction in Shanghai year by year,

Vertical Price Transmission in the China's Layer Industry Chain:an Application of FDL Approach

This paper examines the vertical price relationship between upstream and downstream products in China＇s layer industry chain by estimating elasticity coefficients of the price transmission. We use cointegration tests, error correction models and finite distributed lag models to analyze vertical price shifts between corn, layer feed, egg-laying chicken and egg prices. With monthly data from 1994 to 2010, our results show that various prices in China＇s layer industry chain are well integrated. In addition, our results indicate that both long-run and short-run price relationships between upstream and downstream products in layer industry chain exist and the long-run equilibrium, to a certain extent, may eliminate the short-run dynamics price deviation. We also found that the influence of corn and feed prices on egg prices is still more remarkable than egg-laying chicken prices. Our findings imply that governments should pay more attention to corn and layer feed prices in order to stabilize egg prices under the conditions of market integration.

A Least-squares-based Iterative Method with Better Convergence for PF/OPF in Integrated Transmission and Distribution Networks

The limitations of the conventional master-slavesplitting(MSS)method,which is commonly applied to power flow and optimal power flow in integrated transmission and distribution(I-T&D)networks,are first analyzed.Considering that the MSS method suffers from a slow convergence rate or even divergence under some circumstances,a least-squares-based iterative(LSI)method is proposed.Compared with the MSS method,the LSI method modifies the iterative variables in each iteration by solving a least-squares problem with the information in previous iterations.A practical implementation and a parameter tuning strategy for the LSI method are discussed.Furthermore,a LSI-PF method is proposed to solve I-T&D power flow and a LSIheterogeneous decomposition(LSI-HGD)method is proposed to solve optimal power flow.Numerical experiments demonstrate that the proposed LSI-PF and LSI-HGD methods can achieve the same accuracy as the benchmark methods.Meanwhile,these LSI methods,with appropriate settings,significantly enhance the convergence and efficiency of conventional methods.Also,in some cases,where conventional methods diverge,these LSI methods can still converge.

Channel Estimation and Data Transmission in Massive MIMO TDD Systems

This paper mainly elaborates the studies of channel estimation and downlink data transmission in Massive MIMO. As there are different types of interference in single-cell and multi-cell systems, this paper establishes different models for them separately. In terms of uplink training, for getting channel state information, we introduce LS and MMSE channel estimation algorithms and make a comparison between them. At the same time, the problem of pilot contamination is solved by cell classification and pilot identification. Next, this paper defines mathematical models for downlink data transmission. We use pre-coding methods (including Zero-forcing and Maximal Ratio Combining schemes) and optimize power distribution to improve channel capacity and transmission rate. Furthermore, this paper provides numerical results to show the simulation performance in both single-cell and multi-cell systems and extends to prospects in the future.

Operational Risk Assessment for Integrated Transmission and Distribution Networks

To satisfy the requirements of accurate operationalrisk assessment of integrated transmission and distribution networks (I-T&D), an integrated operational risk assessment (IORA) algorithm is proposed. Specific cases demonstrate thatan I-ORA is necessary because it provides accurate handlingof the coupling between transmission and distribution networks,accurate analysis of power supply mode (PSM) changes ofimportant users and helps to improve security and stability ofpower grid operations. Two key technical requirements in theI-ORA algorithm are realized, i.e., integrated topology analysisand integrated power flow calculation. Under a certain contingency, integrated topology analysis is used to assess the risksof substation power cuts, network split and PSM changes ofimportant users, while the integrated power flow calculation,based on the self-adaptive Levenburg-Marquard method andNewton method, can be implemented to assess risks of heavyload/overload and voltage deviation. In addition, the graphicsprocessing unit is used to parallelly process some computationintensive steps. Numerical experiments show that the proposedI-ORA algorithm can realize accurate assessment for the entireI-T&D. In addition, the efficiency and convergence are satisfying,indicating the proposed I-ORA algorithm can significantly benefitreal practice in the coordination operation of I-T&D in the future.

On distributed power control in full duplex wireless networks

In this paper, we first consider the problem of distributed power control in a Full Duplex （FD） wireless network consisting of multiple pairs of nodes, within which each node needs to communicate with its corresponding node. We aim to find the optimal transmition power for the FD transmitters such that the network-wide capacity is maximized. Based on the high Signal-to-Interference-Plus-Noise Ratio （SINR） approximation and a more general approximation method for logarithm functions, we develop effective distributed power control algorithms with the dual decomposition approach. We also extend the work to the general FD network scenario, which can be decomposed into subproblems of isolated nodes, paths, and cycles. The corresponding power control problem is then be solved with the distributed algorithm. The proposed algorithms are validated with simulation studies.

Distributed continuation power flow method for integrated transmission and active distribution network

As the integration of distributed generations(DGs)transforms the traditional distribution network into the active distribution network,voltage stability assessments(VSA)of transmission grid and distribution grid are not suitable to be studied separately.This paper presents a distributed continuation power flow method for VSA of global transmission and distribution grid.Two different parameterization schemes are adopted to guarantee the coherence of load growth in transmission and distribution grids.In the correction step,the boundary bus voltage,load parameter and equivalent power are communicated between the transmission and distribution control centers to realize the distributed computation of load margin.The optimal multiplier technique is used to improve the convergence of the proposed method.The three-phase unbalanced characteristic of distribution networks and the reactive capability limits of DGs are considered.Simulation results on two integrated transmission and distribution test systems show that the proposed method is effective.

Research and application of wireless sensor network technology in power transmission and distribution system

Power is an important part of the energy industry,relating to national economy and people’s livelihood,and it is of great significance to ensure the security and stability in operation of power transmission and distribution system.Based on Wireless Sensor Network technology(WSN)and combined with the monitoring and operating requirements of power transmission and distribution system,this paper puts forward an application system for monitoring,inspection,security,and interactive service of layered power transmission and distribution system.Furthermore,this paper demonstrates the system verification projects in Wuxi,Jiangsu Province and Lianxiangyuan Community in Beijing,which have been widely used nationwide.

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。

利用无级变速器速比调节装载机功率分配的方法

基于装载机行走系统与液压系统功率的互补规律和无级变速系统等功率调节发动机转速的特性,在发动机部分负荷和全负荷两种工况下,分别提出了无级变速装载机行走系统,利用速比实现等功率及降功率调节行走系统与液压系统功率分配比例的控制策略。在相同仿真环境下,搭建液力机械传动装载机、无级变速装载机和在速比调节功率控制下的无级变速装载机等3个仿真平台。结果表明:无级变速装载机的速比可以调节行走系统与液压系统功率分配的比例,使其分配更合理,且有效地减少发动机输出功率的波动。本研究可为需要动力分流的车辆调节行走系统与其他系统功率分配比例提供借鉴和理论支持。

用于激光无线能量传输的分布式最大功率点追踪系统研究(内封面文章)

在激光无线能量传输中,由于瞄准系统误差和物体遮挡的影响,光电池阵列接收到的激光辐照分布不均匀,导致光电池阵列组串内的电池间出现电流失配,输出功率下降。针对该问题,采用分布式最大功率点追踪(Distributed Maximum Power Point Tracking,DMPPT)技术,减少光电池阵列组串内的电池间电流失配,并用并联型Boost(PT-Boost)电路替代传统Boost电路,降低DC/DC转换器的输入电流纹波,使DMPPT系统获得高追踪效率。实验结果表明,相较于传统Boost电路,PT-Boost电路的追踪效率提高3.6%,达到93.5%。在上述研究的基础上,设置了遮光率分别为0%、25%和50%的激光无线能量传输场景,DMPPT系统整体效率分别达到了93%、92.6%和90.3%。该研究结果对激光辐照不均匀场景下激光无线能量传输的最大功率点追踪指导意义。

基于双向安德森加速分解协调算法的输配协同无功优化

新型电力系统中新能源渗透率不断增加,输电网和配电网协同运行环境复杂多变,对输配协同优化算法的收敛性提出了更高的挑战。鉴于此,应用广义主从分裂法将输配协同无功优化问题分解为输电网和多个配电网的并行优化问题;为改善广义主从分裂法的计算效率,提出了基于功率、电压等多元信息交互及历史信息修正的双向安德森加速策略;在此基础上,提出了融合原对偶内点法、启发式算法和辅助函数的输配协同无功优化方法,实现了输电网和配电网多种类灵活性资源的协调配合和优化控制。算例仿真结果表明,所提方法能有效改善主从分裂法边界的收敛性能,在大规模分布式能源接入的输配协同无功优化场景中具有更好的应用价值。

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。

双线圈并联ICPT系统的分布式补偿电流均衡方法

针对双线圈并联的高功率感应耦合电能传输(ICPT)系统存在线圈间补偿电流不均衡问题,提出一种分布式补偿电流均衡方法。首先提出了双线圈并联ICPT系统的分布式补偿网络,然后依据等效思想和迭代思想提出补偿电流均衡方法,根据该方法求解得到补偿参数和各线圈补偿电流表达式,再将该方法拓展到n线圈并联结构。在北京超算云计算中心的COMSOL云平台验证了所提出的方法不仅有效均衡了各线圈的补偿电流,而且谐振状态受参数漂移的影响程度并未因补偿网络的复杂程度增加而增加。最后搭建了实验平台,验证了所提方法的有效性。

基于多优先级排队论的配电物联网带宽分配方法

针对数据量剧增的配电物联网中存在的带宽利用率低和业务数据服务质量(quality of service,QoS)难以满足通信需求等问题,提出一种多优先级排队论的带宽分配方法。首先,对感知终端到边缘物联网关的业务数据传输过程进行改进,改进后的传输过程可根据不同业务数据对QoS的不同要求进行数据优先级的划分,对不同优先级数据设置不同的服务机制;然后,对业务数据传输中的马尔科夫过程进行分析,基于改进后的数据传输过程建立以带宽利用率为目标,丢包率和延时时间为约束的多优先级排队论带宽分配模型;并将所提出的带宽分配方法与传统方法进行对比。结果表明:QoS指标有所改善,而且带宽利用率比传统不分优先级带宽分配方法高9.73%,比弹性系数法高31.17%。最后,探究多优先级排队论带宽分配方法的动态性能,结果表明适当地提高带宽可以改善QoS指标,但要注意带宽增大时所带来的带宽利用率减小问题。合理的带宽分配可以避免资源的浪费。

柔性互联输配一体化电网有损潮流的精细化建模及应用

多端柔性互联输配一体化电网内部的运行方式复杂、网损特性差异显著,导致传统一刀切的网损补偿方法难以准确刻画网损的实际情况,影响了输(配)电交直流有损潮流模型的应用潜力和输配边界潮流的一致性。为此,该文提出一种基于双层定点迭代的精细化有损潮流模型。针对网损补偿方法不准确的问题,综合考虑网络类型、数据属性和物理特征等因素,为输、配电网及交、直流电网的精准有损潮流分析建立了差异化的网损补偿模型。针对输配边界潮流的不一致问题,将输配一体化有损潮流建模为一个双层定点迭代问题,并采用主从分裂法实现协同求解。在多个算例中分析了不同有损潮流模型的性能差异及其原因,讨论了所提模型在求解精度、收敛速度和计算效率等方面的优势,验证了所提模型在不同控制方式和优化目标下的鲁棒性和通用性。

低频交流电压下低密度聚乙烯的空间电荷特性

分频输电技术已逐步成为实现碳中和及海上风电远距离传输的主流方案之一。然而,对高压分频输电背景下的电气设备研究较为欠缺,在频率改变对电缆绝缘材料特性影响方面尚需深入研究。为此,采用具备快速检测能力的脉冲电声测试系统,研究了低密度聚乙烯材料在分频电压下不同电场强度、温度时的空间电荷特性以及频率改变对电荷积聚行为的影响。结果表明:当场强及温度条件较为苛刻时,电荷积聚明显;而随着频率的降低电荷积聚量增加,频率下降至20 Hz后,电荷增长速度显著提高。在此基础上,建立了应用于交变电场下的双极型载流子模型,通过仿真计算对实验观察进行了合理化解释,揭示了电场、温度及频率对空间电荷行为的影响机理。研究方法和结果可为海上风电分频输电系统中的频率选择及线缆绝缘优化设计提供理论支撑。

新型多频率三端口模块化多电平换流器拓扑及其控制策略

未来电网中将会存在的工频、直流与低频等多种频率,而传统换流器仅能实现交-交、交-直两种频率电气量间的能量交换。为此,提出一种新的多频率三端口模块化多电平换流器(multi-frequency triple-port modular multilevel converter,MFTP-MMC)拓扑,该拓扑结构简单对称,能够直接实现工频-低频-直流的功率变换和频率控制,不存在无功约束问题,可以输出2倍直流电压,具有直流故障自清除功能。针对MFTP-MMC拓扑建立其dq坐标下的动态数学模型,实现了系统2种交流频率分量同直流分量的解耦,在此基础上给出相应的控制策略,包括内环电流控制、环流控制、子模块均压控制以及外环功率控制,其物理概念清晰、控制性能良好。进一步,给出了桥臂无功分配系数的优化方法。同时针对其拓扑提出直流侧故障时闭锁以及故障后软起动策略。MATLAB/Simulink平台下的一系列仿真结果验证了所提MFTP-MMC拓扑和数学模型的正确性及其控制策略的有效性。