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.

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.

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.

城市群网络联系的幂律分布规律与层级结构特征

城市群的网络联系存在幂率分布规律,在这一规律的影响下,城市网络是“有等级倾向的网络”,其网络结构必然表现为明显的层级特征。首先,基于城市引力模型测度城市之间的相互联系,实证检验城市群城市间联系强度的概率分布规律,证明城市网络联系符合幂律分布的特征,且具有标度不变性。城市群的联系网络为服从幂率分布的无标度网络。然后,基于头尾断裂法对城市群城市网络的层级结构进行了划分和比较分析。尽管不同城市群城市网络的规模、强度和发育程度存在较大差异,强关联关系的空间形态也有明显的方向性不同,但其网络结构都具有明显的“核心—边缘”层级特征。

Reactive power operability of distributed energy resources for voltage stability of distribution networks

The penetration level of distributed energy resources(DERs)is increasing and has significant impact on the voltage stability of distribution networks.Based on the various types of DERs with distinct reactive power characteristics(RPC),their different contributions to the system voltage stability require classification.Firstly,the features of DERs are reviewed and classified based on their RPC,to investigate different distributed generation technologies for reactive power support in distribution networks.Then,the concept of a relative available transmission capacity index(RATCI),which is based on power transfer margin of the power-voltage curve considering the non-negligible distribution network resistance,is proposed to quantify and evaluate the voltage stability by integrating DERs with the defined reactive power types.Case studies have been conducted for an IEEE 33-bus distribution network to calculate the system RATCI for the mixed integration of DERs.Results show that the multitype and multi-locational integration of DERs can improve the voltage stability of a distribution network.

Optimal Feeder Routing in Urban Distribution Networks Planning with Layout Constraints and Losses

We address the problem of optimally re-routing the feeders of urban distribution network in Milano,Italy,which presents some peculiarities and significant design challenges.Milano has two separate medium-voltage(MV)distribution networks,previously operated by two different utilities,which grew up independently and incoordinately.This results in a system layout which is inefficient,redundant,and difficult to manage due to different operating procedures.The current utility UNARETI,which is in charge of the overall distribution system,aims at optimally integrating the two MV distribution networks and moving to a new specific layout that offers advantages from the perspectives of reliability and flexibility.We present a mixed-integer programming(MIP)approach for the design of a new network configuration satisfying the so-called 2-step ladder layout required by the planner.The model accounts for the main electrical constraints such as power flow equations,thermal limits of high-voltage(HV)/MV substation transformers,line thermal limits,and the maximum number of customers per feeder.Real power losses are taken into account via a quadratic formulation and a piecewise linear approximation.Computational tests on a small-scale system and on a part of the Milano distribution network are reported.

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。

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。

计及SOP损耗的交直流配电网三相区间状态估计

随着分布式电源及智能软开关(SOP)等新型设备投入配电网运行,需要对交直流配电网进行精确的状态估计。首先构建了交直流配电网的区间状态估计模型,考虑三相不对称性与交直流之间的耦合;其次,为计及SOP的损耗,增设SOP两侧支路电流作为状态变量,完善了区间状态估计中的雅克比矩阵;最后采用基于迭代运算的线性规划方法进行区间状态估计。在修改IEEE33节点算例上进行仿真,结果表明所提方法能保证计及SOP损耗的状态估计结果的准确性。

三大城市群经济增长空间关联网络分析

本文研究对象为长三角城市群、京津冀城市群和珠三角城市群,借助格兰杰因果检验及网络分析法,对比分析了2000—2020年三大城市群经济增长空间关联网络的关联关系和关联特征,并分析了各城市群内部的动力传导机制。主要结论有:(1)三大城市群内部各城市之间的经济增长空间关联程度都不高;(2)长三角城市群拥有最为完整的板块分布,珠三角城市群、京津冀城市群板块分布分别为双溢出双受益、三溢出一受益;(3)长三角城市群和京津冀城市群增长原动力为“资本溢出型”,而珠三角城市群的增长原动力为“劳动溢出型”。

基于优化小波变换神经网络的分布式新能源信息预测方法

分布式新能源发电是低碳化电力系统中重要的一部分.随着分布式新能源在城市电网中的占比逐渐增加,负荷随机波动和天气随机变化对于城市电网的影响日益增强,对分布式新能源信息的预测准确性提出了更高的要求.目前,分布式新能源的主要发电方式是分布式光伏发电以及分布式风力发电.城市用电负荷的变化兼具周期性和随机性,而风速和辐照强度等因素分别对于分布式风力发电和分布式光伏发电有重要影响.为了准确预测出分布式新能源的信息,构建了基于小波变换神经网络的分布式新能源信息预测方法.首先,通过分析分布式新能源的工作原理,建立分布式新能源的模型;然后,优化小波变换神经网络,以风力发电和光伏发电为例对负荷用电功率和辐照强度等对电网作用显著的参数进行预测;最后,算例验证模型对分布式新能源信息进行预测的准确性.

电子标签技术的送变电工程物资供应管理系统

针对传统送变电工程物资管理模式效率低下的问题,提出了一种新型的基于电子标签技术的送变电工程物资供应管理系统。采用稀疏重构分块自适应算法实现送变电工程物资图像的压缩,设计电子标签RFID对送变电工程物资进行移动定位,还利用了网格化管理对供应管理系统进行了优化,提高了管理效率。所提设计的送变电工程物资管理系统中,定位误差始终低于40 cm,在有效提高送变电工程物资定位精度的同时降低了磁盘损耗。

配电网输电方向变化对系统可靠性的影响分析与评估

随着能源需求的不断增长和电力系统规模的扩大,配电网输电方向的变化成为影响系统可靠性的重要因素之一。通过深入分析输电方向变化的机理,揭示其基本原理、与电网稳定性的关系以及对系统频率、电压等参数的影响机理。在此基础上,分析系统可靠性的影响,包括可靠性评估指标与方法、输电方向变化对系统可用性的影响以及对系统平均故障间隔时间(Mean Time Between Failure,MTBF)的影响。针对发现的问题,提出一系列优化策略与措施,旨在提高配电网的可靠性和稳定性。

智能配电网关键技术在电网规划中的实践运用探索

为全面优化电网规划管理质量,要发挥智能配电网技术优势,搭建更加稳定和谐的技术控制模式,利用数据融合分析机制更好地维系电网规划的综合效能,整合信息化管理资源,实现经济效益和社会效益和谐统一的目标。文章集中介绍了智能配电网关键技术内容,并对电网规划中智能配电网技术的应用要点展开讨论。

基于PSASP和Power Factory的分解协调式输配一体化潮流计算

大量分布式电源的并网改变了配电网单向潮流特性,输电网和配电网之间的耦合更加紧密,电力系统呈现出主配网一体化的特点。文章提出了基于分解协调的主配一体化潮流计算方法,分别采用PSASP和Power Factory进行输电网和配电网的计算,设计了主网和配网潮流的边界协调方程,并采用Jacobian-Free Newton-GMRES(m)方法进行求解。测试结果表明,文章所提方法收敛性较好,计算精度高。

交直流配电网中柔性软开关接入的规划-运行协同优化方法

含分布式源-储-荷的直流配电系统需要通过柔性软开关等电力电子化配电设备与交流系统互联,构成的交直流混合系统不仅可以提高系统整体的可靠性,还可以通过灵活的潮流控制优化系统运行方式,并降低系统损耗。由于用以交直流系统互联的柔性软开关接入方案对全系统可靠性和最优运行方式都有影响,针对这一规划-运行协同问题,首先提出了交直流混合系统的改进显式可靠性计算方法,进而建立了考虑可靠性经济成本和网损的交直流混合配电系统规划-运行协同双层优化模型。上层模型基于加权功率传输分布因数,以系统传输损耗最优为目标确定柔性软开关的接入方案,下层以可靠性成本最低为目标获取交直流混合系统的最优运行方式。最后,在算例系统中进行了仿真对比验证。结果表明,所提出的规划-运行协同优化方法能够有效提升交直流混合系统的可靠性和经济性。

基于深度强化学习的V2X频谱资源管理方法

针对车辆对一切(V2X)通信所面临的频谱稀缺问题,文章提出了一种深度强化学习方法对V2X频谱资源进行管理。首先,建立单个车辆对基础设施链路的V2X通信模型,结合频谱子带和传输功率等约束条件,构建优化问题以最大化V2X通信网络综合效率;其次,考虑到优化问题的非凸性,将其建模为马尔可夫决策过程;接着,引入基于竞争构架Q网络(Dueling-DQN)算法,以获得最优频谱子带选择和传输功率分配策略,使V2X通信网络综合效率最大化;最后,通过Tensorflow软件平台进行实验仿真,以验证所提方法的性能。实验结果表明,Dueling-DQN算法与其他算法相比,能够获得更高的链路性能和V2X通信网络效率。

计及间歇性新能源的弹性城市电网输配电协同供电恢复方法

极端灾害频发,给大规模接入新能源的城市电网运行带来巨大挑战。为此,提出一种计及间歇性新能源的城市电网输配电协同供电恢复方法,以提升规模化接入新能源的城市电网系统弹性。针对新能源不确定性建模,提出了一种基于高斯Copula的新能源离线概率建模和实时更新方法,通过实时更新场景预测刻画其出力时变不确定性。基于预测场景,建立了一个计及负荷转供的城市电网双层供电恢复模型。该模型考虑主动的输电系统−配电系统协同优化,通过调整负荷分布、网络重构以及应急资源实时调度进行供电恢复,最小化系统失电量。所提双层供电恢复模型在上层优化各区域高压配网与输电系统运行边界,在下层求解各区域高压配网的重构及应急资源实时调度方案,通过检验输电网交流潮流判断计算过程是否结束。由仿真结果可知所提城市电网输配协同供电恢复方法可有效提升系统弹性,在极端灾害下可保证输电网线路潮流不越限并有效降低系统切负荷量。

利用AHP-熵权法对负荷体系的测评优化构建与实现

随着我国城市配电网规模越来越大,运行特征也越发复杂,用电负荷也在逐年提升,对其供电能力的评估也更加深入。配电网的供电能力直接代表其供电可靠性和系统结构的优劣。传统的供电能力评估方法抓取风险状态的能力略显不足,计算结果与实际情况偏差较大。基于此种背景,提出了应用AHP-熵权法法对供电能力评估方法进行优化。并通过实例分析,证明此种评估方法具备可行性和有效性。