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1.
In order to address spectrum resource scarcity in traditional cellular networks,television (TV) white space is considered as a potential solution to offload a portion of network traffic and enlarge network capacity.This paper describes a cognitive cellular network which allocates low geometry users to the TV white space based on a proportional fair criterion.An uplink user allocation scheme is proposed and the validity of the proposed scheme is established by simulation of the cellular network usage in conjunction with the TV white space.The simulation results show clear improvements in both the user and the system performance with the cognitive coexistent cellular network compared with the traditional cellular network,and that the performance of the proposed user allocation scheme is superior to other user allocation schemes.  相似文献   

2.
Smart grid is envisioned as a critical application of cyber-physical systems and of the internet of things.In the smart grid,smart meters equipped with wireless sensors can upload meter readings (data) to smart grid control and schedule centers via the advanced metering infrastructure to improve power delivery efficiency.However,data gathered in short intervals,such as 15minutes,will expose customers’ detailed daily activities (for example,when they get up and when they use oven) using nonintrusive appliance load monitoring.Thus,data must be hidden to protect customers’ privacy.However,data accountability is still required for emergency responses or to trace back suspected intrusions,even though the data is anonymous.In addition to desired security requirements,this imposes two extra tasks:Sensors in smart meters usually have resource constraints;thus,the desired security protocols have to remain lightweight in terms of computation and storage cost.Furthermore,scalability and flexibility are required since there exist vast meters.This paper presents a lightweight Privacy-aware yet Accountable Secure Scheme called PASS which guarantees privacy-aware accountability yet tackles the above challenges in the smart grid.A formal security analysis justifies that PASS can attain the security goals,while a performance analysis verifies that PASS requires few computations,and is scalable and flexible.  相似文献   

3.
The use of communication networks in control loops has gained increasing attention in recent years due to its advantages and flexible applications. The network quality-of-service (QoS) in those socalled networked control systems always fluctuates due to changes of the traffic load and available network resources, This paper presents an intelligent scheduling controller design approach for a class of NCSs to handle network QoS variations, The sampling period and control parameters in the controller are simultaneously scheduled to compensate for the network QoS variations. The estimation of distribution algorithm is used to optimize the sampling period and control parameters for better performance. Compared with existing networked control methods, the controller has better ability to compensate for the network QoS variations and to balance network loads. Simulation results show that the plant setting time with the intelligent scheduling controller is reduced by about 64.0% for the medium network load and 49.1% for high network load and demonstrate the effectiveness of the proposed approaches.  相似文献   

4.
Software defined networking ( SDN ) offers programmable interface to effectively control their networks by decoupling control and data plane .The network operators utilize a centralized controller to deploy advanced network management strategies .An architecture for application-aware routing which can support dynamic quality of service ( QoS) in SDN networks is proposed .The application-aware routing as a multi-constrained optimal path ( MCOP) problem is proposed , where applications are treated as QoS flow and best-effort flows.With the SDN controller applications , it is able to dy-namically lead routing decisions based on application characteristics and requirements , leading to a better overall user experience and higher utilization of network resources .The simulation results show that the improvement of application-aware routing framework on discovering appropriate routes , which can provide QoS guarantees for a specific application in SDN networks .  相似文献   

5.
This paper describes an optimal power allocation scheme for orthogonal frequency division multiple access two-way relay networks with physical network coding.The aim is to enhance the achievable sum rate of the terminals for a constrained total transmit power.Convex optimization is used to derive a closed-form solution for the power allocation between the relay node and the two terminals.This reduces the variable dimensionality of the objective function for the power assignment problem among multiple carriers when the total transmit power is constrained.This solution is then used to derive the optimal power control scheme.This method reduces the implementation complexity compared with the traditional resource allocation scheme.Numerical and simulation results show that the approach achieves almost the optimal sum rate and outperforms the fixed power assignment method with less computational load in various scenarios.  相似文献   

6.
In this paper, the effect of the computational grids on the wind turbine positioning optimization is studied. The linear wake flow model is used to calculate the turbine wake flow. The power law is used to model the power curve of wind turbine. Greedy algorithm with repeated adjustments is introduced to solve the wind turbine positioning problem, with the target of maximizing the total power output of wind farm. Square grid and triangle grid with various orientations are used to discretize the area of wind farm. Three numerical cases are introduced to study the effect of the computational grids on the optimized results. The results show that the optimized power output can be improved through choosing appro- priate grid orientation. The suggested grid orientations for single direction wind case and multi-direction wind case are given.  相似文献   

7.
Smart grid was proposed as a practical form of future power distribution system. Evaluating the reliability of smart grids was of great importance and significance. A revised fault tree model was proposed to distinguish and separate grid-connected operation mode and islanded operation mode of smart grids,focusing on the perspective of the consumers. A hierarchical Monte Carlo simulation method for reliability evaluation was also proposed based on the proposed fault tree model. A case of reliability evaluation for the future renewable electric energy delivery and management( FREEDM) system was carried out and analyzed. The proposed methods can be applicable to other forms of smart grids.  相似文献   

8.
3 GPP LTE has approved uplink intra-cell power control and defined overload indicator (OI) for uplink inter-cell power contrQ1 to mitigate the inter-cell interference (ICI), respectively. In this pa- per, we propose a hierarchical power control ( HPC ) scheme where intra-eell and inter-cell power controls interact with each other. The inter-cell power control eommand is generated by radio re- source management (RRM) entity according to the ICI-load model together with the current ICI and served load information. This ICI-load model is proposed as a guideline for coordination among cells to enable the system to approach its system specific interference over thermal noise (IoT) work area. Simulation results show that for HPC scheme, the system' s IoT is well controlled to fit its pre-de- fined work area and the power efficiency is improved significantly. Our proposed scheme is also ro- bust to different settings of its inter-cell power control period.  相似文献   

9.
The existing network security management systems are unable either to provide users with useful security situation and risk assessment, or to aid administrators to make right and timely decisions based on the current state of network. These disadvantages always put the whole network security management at high risk. This paper establishes a simulation environment, captures the alerts as the experimental data and adopts statistical analysis to seek the vulnerabilities of the services provided by the hosts in the network. According to the factors of the network, the paper introduces the two concepts: Situational Meta and Situational Weight to depict the total security situation. A novel hierarchical algorithm based on analytic hierarchy process (AHP) is proposed to analyze the hierarchy of network and confirm the weighting coefficients. The algorithm can be utilized for modeling security situation, and determining its mathematical expression. Coupled with the statistical results, this paper simulates the security situational trends. Finally, the analysis of the simulation results proves the algorithm efficient and applicable, and provides us with an academic foundation for the implementation in the security situation  相似文献   

10.
In order to understand how a network is being used or whether it is being abused, an administrator needs to inspect the flow of the traffic and "infers" the intent of the users and applications. So the network traffic measurement and analysis are crucial to network monitoring, reliable DDoS detecting and attack source locating as well. In this paper, we discuss the principle of real-time network traffic measurement and analysis through embedding a traffic measurement and analysis engine into IP packet-decoding module, and emphasize the implementation of visualizing the real-time network traffic, which are helpful to network monitoring and network traffic modeling.  相似文献   

11.
电力信息相依网络是目前智能电网发展的主要趋势,研究相依网络的鲁棒性是智能电网必须解决的挑战之一.为了实现这一目标,首先基于复杂网络建立单层电网和双层相依网络模型;其次根据评估指标从多种故障模式分析单层电网鲁棒性和相依网络的鲁棒性,并用IEEE30和IEEE118节点系统进行仿真验证,仿真结果表明相依网络的鲁棒性低于单层电网的鲁棒性;最后从边发生故障的故障模式研究实际相依网络的鲁棒性,结果也表明实际相依网络的鲁棒性低于单层电网鲁棒性.  相似文献   

12.
构建一种分布式智能电网的总体框架模型,给出分布式发电规划与优化控制总体模式;针对分布式智能电网中的电源故障问题采用一种改进微粒群算法进行优化潮流计算,获取系统正常工作发电设备的优化功率分配方案,并基于IEEE 14-bus系统进行了仿真,验证了所提方法的有效性.  相似文献   

13.
智能电网是一种新颖的数字化的电气网络,它将电能的生产、配送和控制有机地整合在一起.ZigBee网络由于具有低成本、低功耗、低数据率以及低复杂度等特点,适合应用于智能电网;但是其与无线局域网(WLAN)在同一区域共存将造成ZigBee网络性能的显著下降.针对这一问题,提出了一种多信道的干扰避免策略.通过应用多信道通信的方法,传统的信道切换算法中的"信道切换请求(CSR)的传输受干扰影响"问题得到解决,从而提高了CSR传输的可靠性.实验结果表明,与传统的信道切换算法相比,本文提出的干扰避免策略提高了信道切换的成功率,增强了ZigBee网络在 WLAN 干扰下的可靠性.  相似文献   

14.
 从智能电网的目标出发,论述了智能电网中控制技术的作用。在分析智能电网特征的基础上,论述了智能电网控制技术的主要内容。本文系统地给出了信息技术、电力电子技术、储能技术及仿真与试验技术等与电网控制密切相关的关键技术,并在此基础上,论证了这些技术在实现电网控制中的作用。  相似文献   

15.
随着风电机组装机容量的不断增加,风电场并网规范对风电机组的运行要求越来越严格,要求具有外部电网故障下不脱网运行(低压穿越)的能力.为了研究双馈风电机组(DFIG)在低压穿越控制策略的优化方面提供有效的动态仿真与分析平台,并克服Matlab/Simulink仿真环境下所建模型在动态性能方面存在的不足,采用PSCAD仿真软件建立了双馈风电系统的动态仿真模型.通过分析电网对称故障时DFIG的暂态特性,并对转子电流与定子磁链的关系分析得出涉及定子磁链动态过程的改进矢量控制方案,配合转子侧Crowbar保护电路,并对网侧变流器进行有功和无功功率的解耦控制,从而使得电网对称故障时转子过电流、直流母线电压和转矩剧烈波动的情况得到了解决.  相似文献   

16.
农村电网进一步的升级改造工程急需建设能够提供安全可靠的双向通信网络平台。农村电网地理环境的复杂性和总信息量低的特点更适合建设无线专网。为了给农村电网通信提供真正可靠、自愈和高吞吐量的无线通信网络,对如何在农村电力通信接入网中部署802.11smesh网进行了研究,分析了适用于农村电力通信接入网的mesh网络拓扑结构,选用基于簇的AP(access point)部署方案对农村电力通信接入网进行规划部署。通过NS-3仿真建模技术对新方法进行验证,仿真结果证明新方法使求的最优解更加合理,在实时性和吞吐量这两方面能够满足农村电力通信接入网的需求。  相似文献   

17.
由于智能电网含有大量的分布式新能源逆变并网,故使智能电网的潮流流向和电压分布特性发生改变,影响了智能电网的稳定性.首先建立智能电网的动态模型,采用下垂控制策略来表征新能源并网逆变器的功频特性,利用等值发电机和动态负荷模型分析智能电网的失稳过程和混沌现象.在不同的初值下,针对该模型的仿真研究表明,智能电网存在渐近稳定、周期运行、准周期运行、混沌、超混沌以及电压崩溃的运行状态.在研究过程中发现,分岔、混沌、超混沌以及电压崩溃都是智能电网失稳的中间过程.为了防止失稳事故的发生,必须在临界失稳点之前对其进行及时有效的控制.  相似文献   

18.
测控装置测量的数据是电网状态估计、潮流分析、自动电压控制等应用的数据来源,保证数据正确至关重要。针对某电厂测控装置量测数据异常波动事件展开研究,指出电网中存在35、37次高次谐波,在特定情况下混叠到基波附近,干扰测控装置的测量功能,造成数据异常波动。分析了混叠干扰量测功能的机理,并通过仿真及宽频测量数据验证了结论的正确性;针对改进措施进行了探讨,从采样频率选择、抗混叠滤波器设计、测量装置检测规范及谐波监测手段等方面给出了解决措施,加强了对高次谐波的监测能力,为分析和抑制此类振荡提供参考。  相似文献   

19.
随着智能电网和通信技术的迅速发展,电网系统采集的用户数据规模呈指数增长,传统电网负荷预测方法难以满足海量负荷数据情形下的高效分析和计算需求。据此,依托电力系统数据采集云平台,提出一种基于云计算和改进极限学习机的电网负荷预测模型,采用Map-Reduce网络架构,部署于Hadoop平台,利用分布式计算方式进行电网负荷的精准建模和预测分析。结果表明,相比已有方法,本研究方法具有负荷预测精度高、运行速度快的优势,可为后续智能电网系统建设及管理运用提供一种新颖的解决思路。  相似文献   

20.
提出了一套通信局房动力环境集中监控的行之有效的实现方案。系统采用分散采集、集中变送的方式,对各类AI和DI量及智能设备进行监控。各监控级之间可通过DDN、PSTN、FR、ATM、ISDN、FDDI等多种方式传输,实现了高精度采集、高可维护性和灵活组网。该系统具有性价比高、可扩展性好、便于组网的特点,目前已取得了良好的应用,可推广使用。  相似文献   

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