基于GIS的配电网抢修最佳线路分析

配电网直接面向用户的电网终端,其可靠性至关重要。配电网抢修是配电网运检工作的重要内容之一,提高配电网的抢修效率有助于减少停电损失,提高供电可靠性。本文基于GIS系统,对配电网抢修的最佳线路进行了分析。阐述了配电网的特性,提出了配电网抢修最佳线路模型及改进的计算方法,试验及应用表明,该方法能对提高配电网的抢修效率具有重要的作用。     

基于“站-线-变-户”电网模型的预约停电管理模型设计

本文基于营配信息集成“站-线-变-户”电网模型,让客户参与停电计划的制定,在供电企业客服信息与互动平台实行预约停电。建立预约停电管理模型,即筛选预约停电客户群,选择最佳服务渠道与客户进行沟通,汇集分析各渠道客户的意见,通过算法处理制定最优的停电计划。     

基于双向长短时记忆网络的配电网关键线路单调性规律提取

随着风、光等可再生能源发电不断并入配电网,使配电网出现双向流动的有功潮流,由此使配电网输电线路的有功潮流不确定性程度越来越大。由此,把握配电网关键线路的有功输电规律对于保证输电安全、防止大停电事故的发生具有重要意义。对此,在配电网全时空量测环境下,提出了基于数据挖掘的配电网关键线路单调性规律提取方法。首先,建立了配电网输电网潮流计算模型;在此基础上,给出了配电网关键输电线路的识别方法;第三,基于双向长短时记忆网络方法,建立了配电网关键线路单调性的规律提取方法;最后,以某实际电网为例,表明了所提方法的有效性。     

智能配电网通信组网技术及应用要点分析

作为电力系统中重要的组成部分,城市智能配电网的作用十分重要.一旦城市配电网发生故障,就会严重影响区域供电,严重时甚至会导致大面积的区域停电,造成大量的损失.鉴于城市职能配电网的重要作用,笔者在充分检索有关文献和分析相关事件经验的基础上,研究分析了城市智能配电网的基础规划原则以及通信组网技术,研究分析城市职能配电网运行过程中存在的问题,并提出了一些切实有效地解决措施,希望给有关人员提供参考借鉴,不断提高城市智能配电网的通信水平,提高电力系统供电的稳定性和安全性.     

基于负荷损失的配电网跳闸故障定位方法

利用负荷损失法判断配电网跳闸故障,需要充分利用地调自动化系统中的变电站10KV馈线开关的信息,结合配电网分段、分支线路负荷比率表,依据馈线开关动作后的负荷损失情况,对分段线路和大分支线路的故障区域做出判断。对于小型分支线路及配变的故障,则需要利用离散的用户停电信息,综合参考配变监控系统、用户负荷采集系统、线路故障巡检系统等中的离散信息,在配电自动化终端覆盖率很低或没有实现配电自动化的情况下,实现对配电网故障设备及故障停电区域的初步判断。     

基于自适应匹配模型的停电管理系统设计与应用

文中设计了停电管理系统。该系统通过集成计量自动化系统、营销管理系统、生产系统以及营配数据中心,实现所有专变客户、公变台区停电时间的自动采集,并采用国际标准强化分析方法和停电时间统计自适应匹配模型,实现客户停电时间统计自动化、提高客户停电时间数据统计及时性和准确性。通过在东莞供电局进行的测试运行试点和应用,表明文中设计的客户停电应用管理系统可以使客户停电时间统计准确率提高50%以上。     

配电网供电可靠性的提高措施探讨

配电网是电力系统中的重要组成部分,影响着供电质量和供电稳定性,一旦配电网发生故障将直接造成停电,提高配电网供电可靠性势在必行。本文将针对配电网供电可靠性的提高措施展开讨论分析。     

配电网常见故障原因分析及对策

10kV配电网是电力系统面对广大用户的最后一公里,涉及客户最为广泛,故障次数占比最高,及时查明线路故障原因,降低跳闸次数,减少停电时间,提高供电可靠率,具有着至关重要的作用.     

提高农网供电可靠性的研究

提高农村配电网供电可靠性,是县级供电企业一个重要的任务,也是县级供电企业工作的一个难点.立足于配电网络的现状,分析了影响供电可靠率的计划停电以及故障停电中主要故障与解决方法.在配电网络还不够稳固的情况下为提高配电网络供电可靠率提供了一定的思路.     

山东智能配电网建设已经处于国内领先水平

10月24日,从国网山东省电力公司运检部获悉,目前,山东电网智能配电网建设已经处于国内领先水平,且应用成效显著,今年以来,全省累计减少停电13.4万时户、减少电量损失3457多万千瓦时。 在不断加大配电网建设改造力度的同时,国网山东电力稳步开展了配电网智能化升级改造工作。全省直供区共完成10千伏线路智能化改造5963条,配电自动化覆盖率达到92.52%,     

Performance analysis of energy harvesting cognitive relay networks with primary interference

This paper investigates the outage performance of multihop energy harvesting cognitive relay network (EH-CRN), in which the secondary nodes are powered by dedicated power beacons based on the time splitting strategy. Assuming a multihop secondary network, we derive an analytical expression for the outage probability experienced by a secondary user by taking into account the effect of interference power from primary source. The developed outage probability model can be used to assess the impact of some key parameters on the reliability of the secondary user’s link in an EH-CRN. We then investigate the optimal location of the relay node in a one dimensional two-hop secondary network that minimizes the outage probability. Next, we study how the various system parameters such as energy harvesting efficiency, path loss exponent, harvest-to-transmit time duration ratio and transmit power from primary source affect the optimal relay location. The outage improvement achieved when the relay is placed at the optimum location is also investigated. Furthermore, the sensitivity of optimal relay location to the variations in position of the primary receiver is examined. Extensive simulation results are used to corroborate the analytical findings.     

On Node Density ? Outage Probability Tradeoff in Wireless Networks

A statistical model of interference in wireless networks is considered, which is based on the traditional propagation channel model and a Poisson model of random spatial distribution of nodes in 1-D, 2-D and 3-D spaces with both uniform and non-uniform densities. The power of nearest interferer is used as a major performance indicator, instead of a traditionally-used total interference power, since at the low outage region, they have the same statistics so that the former is an accurate approximation of the latter. This simplifies the problem significantly and allows one to develop a unified framework for the outage probability analysis, including the impacts of complete/partial interference cancelation, of different types of fading and of linear filtering, either alone or in combination with each other. When a given number of nearest interferers are completely canceled, the outage probability is shown to scale down exponentially in this number. Three different models of partial cancelation are considered and compared via their outage probabilities. The partial cancelation level required to eliminate the impact of an interferer is quantified. The effect of a broad class of fading processes (including all popular fading models) is included in the analysis in a straightforward way, which can be positive or negative depending on a particular model and propagation/ system parameters. The positive effect of linear filtering (e.g. by directional antennas) is quantified via a new statistical selectivity parameter. The analysis results in formulation of a tradeoff relationship between the network density and the outage probability, which is a result of the interplay between random geometry of node locations, the propagation path loss and the distortion effects at the victim receiver.     

Performance Analysis and Enhancement for Opportunistic Analog Network Coding with Imperfect CSI

Imperfect channel state information (CSI) is among the main factors that affect system performance in wireless networks. In this paper, we investigate the impact of imperfect CSI on the performance of analog network coding (ANC) for a two-way relaying system based on opportunistic relay selection (ORS). An exact and generalized closed-form expression for system outage probability is presented in a Rayleigh flat-fading environment. To provide more insights, the closed-form asymptotic expression is then obtained. It is shown that the presence of channel estimation error causes outage probability maintain a fixed level even when a noiseless channel is adopted. Therefore, to mitigate the negative impact of imperfect CSI, we deduce the power allocation to minimize the system outage probability based on the knowledge of instantaneous channel information. Numerical results validate the accuracy of the derived expressions and highlight the effect of proposed power allocation algorithm compared with conventional uniform power allocation.     

Analysis and modeling of upstream throughput in multihop packet CDMA cellular networks

We consider the problem of throughput modeling of wireless multihop packet CDMA networks with cellular overlay using simple forwarding strategies in the upstream. Considering the effect of shadowing and distance-dependent path loss, we approximate the probability density of interference at each base station (BS) and compare numerical and simulation results for different path-loss parameters. We derive the probability density of the received power at each BS due to transmission of one packet from a random node, as well as the probability distribution of the number of packets received at each node per time slot. Subsequently, we use the above results to approximate the probability density of the total received power at each BS based on calculations of moments. We observe that the probability density of intercell interference due to transmissions from terminals and routers may be approximated by normal and log-normal densities, respectively. We quantify the network performance based on throughput, total consumed power, and outage probability for different system parameters. For homogeneous link efficiencies, introducing routers into the network while reducing the transmission power increases the mean and variance of interference to the desired signal, hence higher outage probability. However, there are ample opportunities inherent to multihop structure, applicable to any of the physical, data link, and network layers, which help increase the overall achievable network throughput.     

Jointly Optimal Congestion and Power Control for Rayleigh-Faded Channels with Outage Constraints

We address the problem of joint congestion control and power control with link outage constraints in Rayleigh fast-fading and multihop wireless networks. Because of packet loss caused by the fast-fading-induced link outage, the data rate received successfully at the destination node (the effective rate) is much lower than the transmission rate at the source node (the injection rate). In this paper, a novel model, i.e., effective network utility maximization with power control (ENUMP), is designed to formulate this scenario. In ENUMP, the network utility is associated with the effective rate, and an effective network utility maximization formulation with link outage constraints is used. Although the original problem is non-convex and non-separable, we can still construct a distributed algorithm by applying appropriate transformations. Since in our model we sufficiently take into account the statistical variations of the signal-to-interference ratio, the power updates do not follow the instantaneous state of the fast-fading channel. Simulation results show that the optimal solution of our algorithm is close to the globally optimal solution. Besides, simulation results also verify that ENUMP achieves significant gains of the effective rate, the network utility, and the network congestion control over an existing famous model.     

Analysis of downlink power control and cooperation scheme for two‐tier heterogeneous cellular network

The traditional cellular network cannot keep pace with the dramatic growth in data traffic due to exponentially increasing number of multimedia applications and mobile subscribers. Recently, femto base stations (FBSs) are deployed with the macro base station (MBS) tier for off‐loading the data traffic and to improve the indoor coverage of the heterogeneous cellular network. However, FBS deployment also increases the cross‐tier interference of the heterogeneous cellular network resulting in outage performance degradation of MBS tier. This work develops an analytical framework to limit the cross‐tier interference of MBS tier using power control scheme (PCS). The proposed PCS works on path loss inversion and location‐based power level rule for FBS. Moreover, a cooperation scheme and an association policy with MBS (CSAPM) are introduced to improve the outage performance of the FBS tier. Tools from the stochastic geometry are used for deriving the signal to interference and noise ratio outage probability, total outage probability, and area spectral efficiency (ASE) of MBS tier and FBS tier. Additionally, ASE maximization problem is formulated to evaluate the optimal density of FBSs. The effectiveness of the proposed PCS and CSAPM on outage performance and ASE are numerically demonstrated. It is noted from the results that the proposed CSAPM can compensate the loss in outage performance of FBS tier due to PCS. Finally, simulation results validate the analytical results.     

Distributed measurements for estimating and updating cellular system performance

We investigate the use of distributed measurements for estimating and updating the performance of a cellular system. Specifically, we discuss the number and placement of sensors in a given cell for estimating its signal coverage. Here, an "outage" is said to occur at a location if a mobile receiver there has inadequate signal-to-noise ratio (SNR -based outage) or, using another criterion, inadequate signal-to-interference ratio (SIR- based outage); and the "outage probability" is the fraction of the cell area over which outage occurs. A design goal is to improve measurement efficiency (i.e., minimizing the required number of measurement sensors) while accurately estimating the outage probability and mapping the coverage holes. The investigation uses a generic path loss model incorporating distance effects and spatially correlated shadow fading. Our emphasis is on the performance prediction accuracy of the sensor network, rather than on cellular system analysis per se. Through analysis and simulation, we assess several approaches to estimating the outage probability. Applying the principle of importance sampling to the sensor placement, we show that a cell outage probability of P_o can be accurately estimated using ~ 10/P_o power-measuring sensors distributed in a random uniform way over the area with base-sensor distances from 50% to 100% of the cell radius. This result applies to both SNR-based and SIR-based outage estimation for both indoor and outdoor environments.     

基于粒子群算法的配电网网格化规划技术研究

随着电力负荷的飞速增长,配电网规划尤为重要,为此提出了配电网网格化规划的思路、模型和方法。分析宜昌市城市空间发展格局和配电网现状,结合《配电网网格化规划指导原则》提出网格化划分原则,据此对宜昌市西陵区中心区配电网进行网格划分,在优化划分结果的基础上,使用粒子群算法优化变电站选址,以网络运行损耗最低为目标函数,建立了变电站选址的数学模型。     

认知无线电网络中基于功率有效性的最优功率分配

在资源受限的认知无线电网络中,如何提高次用户网络的功率利用率是一个值得考虑的问题。针对这个问题,本文首先提出了认知无线电网络中基于功率有效性的次用户最优功率分配算法,该算法不仅考虑主用户网络中断概率对次用户发射功率的限制,而且兼顾次用户网络本身的中断概率要求。其次,为了进一步降低节点的计算复杂度,本文通过降维处理将目标最优化问题转化为两个子问题进行求解,从而提出一种次优的低复杂度功率分配算法。仿真结果表明,次优算法相比最优算法仅带来有限的性能损失,但是却有效地节省了计算时间和存储空间;此外,当中继节点靠近源节点时更有利于系统功率效率的提高,源节点到目的节点链路相比中继链路对系统的性能影响更大。