A CSMA/CA based MAC protocol for hybrid Power-line/Visible-light communication networks:Design and analysis

Hybrid Power-line/Visible-light Communication(HPVC)network has been one of the most promising Cooperative Communication(CC)technologies for constructing Smart Home due to its superior communication reliability and hardware efficiency.Current research on HPVC networks focuses on the performance analysis and optimization of the Physical(PHY)layer,where the Power Line Communication(PLC)component only serves as the backbone to provide power to light Emitting Diode(LED)devices.So designing a Media Access Control(MAC)protocol remains a great challenge because it allows both PLC and Visible Light Communication(VLC)components to operate data transmission,i.e.,to achieve a true HPVC network CC.To solve this problem,we propose a new HPC network MAC protocol(HPVC MAC)based on Carrier Sense Multiple Access/Collision Avoidance(CSMA/CA)by combining IEEE 802.15.7 and IEEE 1901 standards.Firstly,we add an Additional Assistance(AA)layer to provide the channel selection strategies for sensor stations,so that they can complete data transmission on the selected channel via the specified CSMA/CA mechanism,respectively.Based on this,we give a detailed working principle of the HPVC MAC,followed by the construction of a joint analytical model for mathematicalmathematical validation of the HPVC MAC.In the modeling process,the impacts of PHY layer settings(including channel fading types and additive noise feature),CSMA/CA mechanisms of 802.15.7 and 1901,and practical configurations(such as traffic rate,transit buffer size)are comprehensively taken into consideration.Moreover,we prove the proposed analytical model has the solvability.Finally,through extensive simulations,we characterize the HPVC MAC performance under different system parameters and verify the correctness of the corresponding analytical model with an average error rate of 4.62%between the simulation and analytical results.

Power-line interference suppression of MT data based on frequency domain sparse decomposition

Power-line interference is one of the most common noises in magnetotelluric(MT)data.It usually causes distortion at the fundamental frequency and its odd harmonics,and may also affect other frequency bands.Although trap circuits are designed to suppress such noise in most of the modern acquisition devices,strong interferences are still found in MT data,and the power-line interference will fluctuate with the changing of load current.The fixed trap circuits often fail to deal with it.This paper proposes an alternative scheme for power-line interference removal based on frequency-domain sparse decomposition.Firstly,the fast Fourier transform of the acquired MT signal is performed.Subsequently,a redundant dictionary is designed to match with the power-line interference which is insensitive to the useful signal.Power-line interference is separated by using the dictionary and a signal reconstruction algorithm of compressive sensing called improved orthogonal matching pursuit(IOMP).Finally,the frequency domain data are switched back to the time domain by the inverse fast Fourier transform.Simulation experiments and real data examples from Lu-Zong ore district illustrate that this scheme can effectively suppress the power-line interference and significantly improve data quality.Compared with time domain sparse decomposition,this scheme takes less time consumption and acquires better results.

Adaptive resource allocation for multi-user multi-server power-line communication OFDM systems

The bits and power allocation model of adaptive power-rate mixture for multi-user multi-server power-line communication systems was analyzed with the restrictions of maximal total power,fixed rate for each real time (RT) user,minimal rate for each non-real time (NRT) user,maximal bits and power for each subcarrier in each orthogonal frequency division multiplexing (OFDM) symbol. An algorithm of resource dynamic allocation in the first OFDM symbol of each frame and resource optimal adjustment in the latter OFDM symbol of each frame was proposed. In the first OFDM symbol of every frame,resource is firstly assigned for RT users so as to minimize their total used power until satisfying their fixed rates; secondly the remainder resource of power and subcarriers are assigned for NRT users so as to minimize their total used power until satisfying their minimal rates also; lastly the remainder resource is again assigned for NRT users according to the proportional fairness strategy so as to maximize their total assigning rate. In the latter OFDM symbol of each frame,bits are swapped and power is adjusted for every user based on the resource allocation results of anterior OFDM symbol. The algorithm is tested in the typical power-line channel scenarios and the simulation results indicate that the proposed algorithm has better performances than the classical multi-user resource allocation algorithms and it realizes the multiple aims of multi-user multi-server resource allocation for power-line communication systems.

Power-line Modem over the Low Voltage Grid Using Direct Sequence Spread Spectrum Techniques

Power-line networks are designed to deliver electricity. They reach most of the domiciles and other buildings nowadays, so most of the people have access to it. On the other hand the backbone for the communications networks is not available in all countries especially the developing ones. A high cost and changing the design for the networks may be needed to construct this backbone. If data can be transmitted over the power-line networks, a recognized cost and time save can be achieved. In Egypt, the infrastructure is not always available for constructing a communications network backbone due to the already designed buildings before the need for these backbones. In this paper, we overcome this problem by designing a reliable Power-line Modem that operates safely on the low voltage grid. The modem is based on the Direct Sequence Spread Spectrum technique. It uses the mains zero crossing as an efficient way for the synchronization between the transmitter and the receiver. The Modem takes into account the problems of the Power-line including noise, attenuation and impedance dismatching.

Dynamic Balance Control Based on an Adaptive Gain-scheduled Backstepping Scheme for Power-line Inspection Robots

This paper presents an adaptive gain-scheduled backstepping control(AGSBC) scheme for the balance control of an underactuated mechanical power-line inspection(PLI) robotic system with two degrees of freedom and a single control input.First, a nonlinear dynamic model of the balance adjustment process of the PLI robot is constructed, and then the model is linearized at a nominal equilibrium point to overcome the computational infeasibility of the conventional backstepping technique. Second, to solve generalized stabilization control issue for underactuated systems with multiple equilibrium points,an equilibrium manifold linearized model is developed using a scheduling variable, and then a gain-scheduled backstepping control(GSBC) scheme for expanding the operational area of the controlled system is constructed. Finally, an adaptive mechanism is proposed to counteract the impact of external disturbances. The robust stability of the closed-loop system is ensured by Lyapunov theorem. Simulation results demonstrate the effectiveness and high performance of the proposed scheme compared with other control schemes.

基于雷电分形模型的架空线路绕击特性分析试验

近年来,一类在电气几何模型、先导发展模型等基础上提出的可以体现雷电曲折性和分散性的分形模型逐步被用于架空线路雷电屏蔽性能研究。文中基于模拟试验和自然雷电的等效性,搭建1∶40缩比试验平台,以常见500 kV输电线路用ZB6T型杆塔为研究对象,施加160/2 500μs负极性操作冲击波,分别研究绕击率与空间分布和保护角的关系。基于WZ模型和有限差分法建立雷电分形模型,在缩比试验间隙配置下进行线路绕击特性仿真分析。模拟试验和仿真结果均表明:输电线绕击率高的点集中在靠近传输线处,绕击空间整体呈现倒抛物线型,符合绕击规律。保护角减小,则绕击率相应降低,同时绕击空间略有减小。仿真结果与试验数据对比表明,文中构建的雷电分形模型在线路绕击率预测上具有较高可靠性。

一种基于用电标识的新型用电量计量系统

详细的用户用电信息是推进节能减排、实施能源优化的关键。针对在获取精确的用电信息过程中存在的电力线干扰问题,文中提出了一种基于用电标识的新型用电量计量系统。该计量系统由用电标识端与采集计量端两部分组成。用电标识端通过ASK(Amplitude Shift Keying)数字调制为各用电器的用电信息进行独立编码,经电容耦合至电力线。采集计量端通过电力线载波通信对独立编码信息进行采集,并分析处理从而实现用电量计量。通过Multisim与MATLAB仿真软件对所提计量方案进行仿真验证,根据用电器特性可独立编码用电信息,采集计量端通过对独立编码数据分析处理可还原用电器的用电特性波形,实现较好的抗干扰性。

雷电保护装置在油田电力线路上的应用

随着油田生产建设不断发展,电力配电网络的运行可靠性、安全性越来越受到重视。作为电力配电网络主要组成部分的10(6)kV配电线路,由于长期在空旷的野外运行,当遇到雷雨天气时,极易遭受到雷击,导致电力线路经常跳闸断电,甚至引发绝缘子击穿、导线烧毁等事故发生,还会因停电导致大批机采井停产,给油田生产造成了巨大的经济损失。通过针对雷电对架空电力线路造成的各种危害原因进行调查、分析、统计和研究,结合油田地理环境的特点,提出了一种新的设计思路,改变以往防直击雷为主的传统的设计理念,采用以防感应雷为主、防直击雷为辅的防雷方案。经多方调研论证,在边远容易落雷地区的架空电力线路上,设计了国内新型的多腔吹弧式雷电保护装置,其技术先进、结构合理、性能优越,具有工频续流遮断能力,既能防直击雷又能防感应雷。正常运行时,避雷装置的空气间隙可与电力线路脱离,当雷电作用在线路上时,可短暂建弧释放电流,不跳闸、不断电,既消除了雷电对电力线路的危害,又能确保电力线路在雷电天气安全、可靠运行。

基于在线式微波功率检测的磁控管稳功率研究

针对以磁控管作为微波源的微波治疗仪输出功率波动严重,对治疗效果产生不利影响的问题,基于耦合式微波功率传感器工作原理设计了一种小型的在线式微波功率检测装置。通过设计优化,改善了磁控管工作过程中温度升高影响检测精度的问题。实验结果表明,该检测装置在30~90 W功率范围内,功率测量值和实际输出功率值的平均绝对误差仅为0.47 W。稳功率环节中,以功率测量值作为反馈信号,采用增量式PID控制器对磁控管输出功率进行负反馈调节,实现了微波开启5 s内,磁控管输出功率与设定功率的相对误差维持在5%以内,有效解决了磁控管输出功率波动严重导致的治疗效果不佳的问题。

光伏电站供电线路绝缘皮破损漏电故障无人机巡检研究

由于光伏电站供电线路存在的电磁辐射问题,对无人机巡检的飞行过程造成了一定的干扰,影响了巡检结果的有效性。为了缓解电磁干扰问题,提出了光伏电站供电线路绝缘皮破损漏电故障无人机巡检方法的研究。解析光伏电站环境下的供电线路电磁干扰强度及其衰减特性,结合巡检需求,确定无人机的视野范围,以此规划无人机巡检的路径。获取该路径下的巡检图像数据并修正其畸变问题,通过二值化处理提取识别并提取绝缘皮破损漏电范围的边缘点。在此基础上,根据线路参数计算得出漏电故障的状态参数。经过测试可知,该方法在实践应用中得出的巡检结果,所表现出的准确度更高,有效性更好,满足了光伏电站供电线路的安全运维需求。

基于无人机低空摄影测量的电力线路巡检

为了提升电力线路巡检的效率和准确性,本文通过介绍基于无人机低空摄影测量的电力线路巡检方案,详细分析了无人机低空摄影方案的设计与实施、电力线通道地表摄影图像的密集影像匹配技术、电力线特征的自动检测与二维矢量提取方法,以及巡检结果的全面检验流程。本文提出了一套集成化的电力线路巡检解决方案,旨在实现电力线路的快速巡检与智能分析。研究结果表明,该方案显著提高了巡检数据的采集与处理效率,确保了电力线路状态监测的及时性与准确性,为电力安全运维提供了有力支持。

基于光纤光栅的输电导线振动频率在线监测系统

架空输电导线受微风振动形式最为普遍,其在设计时风荷载是需要考虑的主要因素之一。文章利用光纤光栅具有抗电磁干扰强的特点,将光纤光栅应变计用于测量架空导线的振动监测。光纤光栅应变计将导线的振动信号转变为光的波长变化信号,光信号经光纤传输到OPM(optical performance monitor),OPM将采集的数据传输到单片机进行频谱分析,提取导线振动频率,单片机控制GSM模块将相关数据发到上位机,进行数据分析与处理。实验结果表明,系统能够有效监测导线振动频率,精度达到0.01 Hz。

复杂地理背景下电力线自动提取方法

为实现电力线走廊更加快捷、有效的巡检,本文提出了一种从机载激光雷达(LiDAR)扫描点云数据中提取电力线的方法。首先,利用不规则三角网(TIN)滤波和角度滤波对原始点云数据进行电力线粗提取;其次,采用基于高斯核的霍夫变换方法来检测和提取电力线;最后,使用最小二乘拟合法对电力线进行分段拟合。实验结果表明,使用该方法提取电力线的准确率达到97.5%,误判率低于1.5%。电力线直线拟合误差在5 cm以下,满足电力线巡线的要求。该方法能够更快速、准确地获取电力线数据,提高电力线检测和监测的效率和可靠性。

矿山供电线路的故障快速定位及预警方法研究

在煤矿开采过程中,受复杂地质环境影响,矿井的供电线路容易发生过载、短路和过流等故障,从而影响了整体的开采进度。首先,基于WVD(Wigner-Ville Distribution,时频分析方法),提出了一种新的故障定位方法;其次,结合线路运维经验,从线路故障信号采集和故障信号处理出发,在合理应用双端定位方法后,参考故障信号的能量分布和初始故障信号的到达时间,明确了矿山线路的故障位置;最后,经过仿真试验和实际验证,证明了该方法可为矿山供电线路的管理提供数据支持,确保了煤矿供电的安全性。

配电线路故障行波特征分析及提取研究

在配电线路中,一旦发生小电流接地故障,就需要对配电线路故障点进行精确快速的定位,从而找出故障点,及时解决故障线路问题。这对我国煤矿配电线路有直接帮助,对电力系统的保护也有着重大意义。在国内外输配电线路故障测距研究的基础上,结合煤矿的配电线路故障的特点,主要研究行波法理论在配电线路的特征。针对配电线路研究行波的特性,如在配电线路中行波的折射和反射,行波的衰减以及行波线模分量具有相对稳定的传播特性。通过综合分析与研究大多数行波测距原理,可以得出A型行波测距原理可以用于对复杂的配电线路进行测距。对波形进行FFT频谱分析,验证在0~100 Hz之间的波形较易提取;利用小波变换,得出对创建好的Matlab仿真模型进行分析以及行波提取。最后通过研究认为,单端A型行波测距方法可适用复杂配电线路的故障定位以及测距。

新建化工装置单机试车临时供电方案的研究与应用

某年产25万吨化工装置项目正在建设中,计划于某年某月完工。但由于110 kV电源线路未能按计划时间建设送电,为满足装置单机试车用电需要,考虑从其他现有35 kV变电站敷设1路10 kV电源电缆至新建10 kV装置变电站,为新装置试车提供电力支撑。经现场勘查电源电缆敷设路由,需重点校核最大功率电动机的起动以及系统电容电流负荷载量,确保该装置临时供电方案的可行性,为装置单机试车创造条件。

基于回归分析的人体工频电场畸变影响分析预测研究

为探究输电线路下人体周围工频电场分布规律,量化分析人体位于工频电场时对场强的畸变作用,文中以500 kV架空线路边导线工频电场为研究对象,通过便携式工频电场测量装置,检测在人体垂直和水平方向上不同部位和不同距离处的电场强度,得出输电线路下人体周围工频电场分布规律。结果表明,人体头部、肩部、上臂、腰部、臀部、膝部、脚部均对电场场强产生不同的畸变效果,且当距离人体大于100 cm时,人体对周围空气域内电场的畸变作用可以忽略不计。在此基础上,通过对人体水平方向和垂直方向上不同点位的电场场强检测结果进行回归分析,得出人体不同部位和距离电场中心不同位置对工频电场场强影响的修正方程,为提出工作人员防护措施奠定重要基础。

电力设施多模态精细化机器人巡检关键技术及应用

电力设施巡检对于加快电网基础设施智能化改造和智能微电网建设,提高电力系统互补互济和智能调节能力的需求具有重要作用.近年来,智能巡检机器人开始在电力巡检中广泛应用,在提高电力设施巡检效率和准确性、提升安全性、降低成本和促进电力智能化发展等方面发挥关键作用.本文从电力巡检机器人的智能感知和导航技术出发,重点介绍目标检测、语义分割、自主导航等共性关键技术的国内外发展现状.然后以可见光红外双光融合、可见光图像和点云数据融合、声纹和可见光融合为例,阐述电力场景多模态数据融合方式.并进一步介绍电力部件精准分割和异物检测、线路点云杆塔倾斜检测、输电线路覆冰多模态检测和电力架空线路缺陷分析及台账异常检测等电力设施多模态机器人相关案例.最后探讨电力设施多模态精细化机器人巡检关键技术的发展趋势和所面临的挑战.

基于深度强化学习的Π型阻抗匹配网络多参数最优求解方法

针对电力线信道阻抗变化复杂、负载阻抗不匹配造成通信质量差等问题,提出一种基于深度强化学习的Π型阻抗匹配网络多参数最优求解方法,并验证分析了深度强化学习对于寻找最优匹配参数的可行性。首先,建立Π型网络结构,推导窄带匹配和宽带匹配场景下的最优匹配目标函数。其次,采用深度强化学习,利用智能体的移动模拟实际匹配网络的元件参数变化,设置含有理论值与最优匹配值参数的公式作为奖励,构建寻优匹配模型。然后,分别仿真验证了窄带匹配和宽带匹配两种应用场景并优化模型的网络参数。最后,仿真结果证明,经过训练后的最优模型运行时间较短且准确度较高,能够较好地自动匹配电力线载波通信负载阻抗变化,改善和提高电力线载波通信质量。

新型可控电网换相换流器故障特性及控制优化研究

基于可控电网换相型换流器(controllable line commutated converter,CLCC)的高压直流输电技术避免了常规直流换相失败问题,为高压直流馈入电网提供了崭新途径。文章揭示CLCC高压直流输电系统的故障响应机理,对比CLCC与电网换相型换流器、电压源型换流器等直流输电技术的功率特性差异。针对CLCC可控换流的技术特点,提出一种基于最大触发角提升的CLCC优化控制方法,改善了CLCC的故障响应特性,提升了受端电网交流电压的恢复速度。最后,基于PSD-PSModel电力系统仿真软件,建立送受端电网机电暂态和CLCC直流电磁暂态的混合仿真模型,验证理论分析的准确性和优化控制的有效性。