Joint power control and relay selection scheme for cognitive two-way relay networks

A joint power control and relay selection scheme is considered for a cooperative and cognitive radio system where a secondary network shares spectrum with the primary network. In the secondary network, two secondary users （SUs） communicate with each other via an assist relay. The main point is to provide the best system performance to SUs while maintaining the interference power at primary user （PU） under a certain level. Using convex optimization, a closed-form solution is obtained when optimizing the power allocation among the two nodes and relay. Based on this result, a joint power control and relay selection scheme with fewer variable dimensions is proposed to maximize the achievable rate of the secondary system. Simulation results demonstrate that the sum rate of the cognitive two-way relay network increases compared with a random relay selection and fixed power allocation.

A 10kW-scale Distributed Power Plant of Natural Gas-Proton Exchange Membrane Fuel Cell

A 10 kW-scale natural gas fueled proton exchange membrane fuel cell(PEMFC) distributed power plant is presented in this paper,which is designed for cogeneration of power and heat. With homemade catalysts for CO removal in a two-stage methanation process and integrated reactor in the fuel processing system,the reformed fuel with CO molar fraction less than 10-5 is obtained for the fuel cell stack. Based on Matlab/Simulink/Stateflow and xPC Target platform,a rapid control prototype(RCP) is developed for real-time condition management,signal tracking and parameter tuning,data storing,and man-machine interaction. In a typical running with 4.3 kW stack power,the hydrogen production efficiency,gross power generation efficiency and heat recovery efficiency approach to 76%,41% and 50%,respectively. The peak stack power reaches 7.3 kW. Though there is still considerable dis-tance to long-term operation at 10 kW-scale net power generation,it is a milestone for the PEMFC-based stationary application in China.

Pressure control of PEMFC distributed power generator

Control design is important for PEMFC （proton exchange membrane fuel cell） distributed power generator to satisfy user requirement for safe and stable operation. For a complex multi-variable dynamic system, a dynamic simulation model is first established. In view of close coupling and non-linear relationships between variables, the intelligent auto-adapted PI decoupling control method is used. From the simulation results it is found that, by bringing quadratic performance index in the single neuron, constructing adaptive PI controller, and adjusting gas flow rates through the second pressure relief valve and air compressor coordinately, both anode and cathode pressures can be maintained at ideal levels.

基于最大净功率输出的PEMFC阴极供气系统优化控制研究

通过建立质子交换膜燃料电池(PEMFC)阴极供气系统数学模型,分析空气压缩机电压和背压阀开度对系统净功率输出的影响;针对负载电流变化,研究PEMFC系统对应的最优过氧比和最优阴极压力,建立最大输出净功率-过氧比-阴极压力寻优表;考虑过氧比和阴极压力之间的耦合关系,基于辨识出的传递函数矩阵,设计针对空气压缩机电压和背压阀开度的前馈解耦控制器,优化氧气供给和压力控制,并进行相应的仿真验证。结果表明,所提解耦控制器能有效减小过氧比和阴极压力之间的耦合影响,在实现最大净功率闭环控制的同时,具有更快的响应速度和更小的超调量。

基于功率-温度自适应控制的多堆质子交换膜电解制氢系统效率优化

随着可再生能源发电及电解制氢技术的发展,基于质子交换膜(PEM)技术的可再生能源制氢将成为氢能供应的主要手段之一。新能源发电具有随机性和波动性,现有多堆PEM电解制氢系统功率分配策略难以在功率波动场景下保证系统高效运行。对此,该文首先建立了包含主要能耗环节的制氢系统整体效率模型,探究了制氢效率与电流密度、温度的特性关系。然后,根据该效率特性提出了基于功率-温度自适应控制的多堆PEM电解制氢系统效率优化策略,包含离线优化与在线控制两部分:离线优化部分根据制氢系统效率模型预先制定不同电解总功率下的电解槽功率及温度设定方案;在线控制部分根据离线优化方案、制氢功率进行电解槽功率和温度调节。最后,采用实际风电功率进行算例分析,结果表明,相比于传统的功率平均分配策略和链式分配策略,该文提出的效率优化策略将产氢量分别提高了6.4%和5.7%。

质子交换膜燃料电池性能优化控制

质子交换膜燃料电池(proton exchange membrane fuel cell,PEMFC)的热管理,是影响PEMFC安全、稳定、高效运行的核心关键因素。该文在分析PEMFC热管理子系统的结构,以及关键组成部件(包括空气压缩机、冷却液循环泵和冷却风扇)的工作原理基础上,首先搭建耦合热管理子系统的PEMFC非线性仿真模型,进一步将其简化处理得到用于控制的线性模型;在此基础上,设计基于卡尔曼滤波的状态观测器,以实现对状态和不可测量扰动的估计,从而消除模型稳态误差;随后设计目标计算器,以净输出功率跟踪误差最小化和系统效率最大化为目标,对PEMFC系统工作状态进行优化;进而基于线性控制模型,设计无偏显式模型预测控制(offset-free explicit model predictive control,offset-free EMPC),对优化工作状态进行跟踪控制;最后,搭建一个软件在环(softwareintheloop,Si L)测试平台,通过与传统MPC控制策略的仿真结果对比可得,无偏EMPC控制策略可以显著将净输出功率的平均跟踪误差绝对值从344.29W减小到82.19W,系统效率从40.32%提升到46.56%,算法平均单步计算耗时从26ms降低到11.8ms,并且可以约束PEMFC系统运行在稳定和安全的工况。

Energy efficiency optimization of relay-assisted D2D two-way communications with SWIPT

Aiming at the energy consumption of long-distance device-to-device(D2D) devices for two-way communications in a cellular network,this paper proposes a strategy that combines two-way relay technology(TWRT) and simultaneous wireless information and power transfer(SWIPT) technology to achieve high energy efficiency(EE) communication.The scheme first establishes a fractional programming problem to maximize EE of D2D,and transforms it into a non-fractional optimization problem that can be solved easily.Then the problem is divided into three sub-problems:power control,power splitting ratios optimization,and relay selection.In order to maximize EE of the D2D pair,the Dinkelbach iterative algorithm is used to optimize the transmitted power of two D2D devices simultaneously;the one-dimensional search algorithm is proposed to optimize power splitting ratios;an improved optimal relay selection scheme based on EE is proposed to select relay.Finally,experiments are carried out on the Matlab simulation platform.The simulation results show that the proposed algorithm has faster convergence.Compared with the one-way relay transmission and fixed relay algorithms,the proposed scheme has higher EE.

计及多种需求响应资源的虚拟电厂运行机制及控制策略优化

需求响应是虚拟电厂应对电力市场交易中由不确定性因素带来交易风险的重要资源。本文提出一种计及多种需求响应资源的虚拟电厂运行机制以及控制策略。首先,通过v型支持向量回归机对虚拟电厂可再生能源出力、负荷出力、电力市场价格等不确定量进行日前预测,并利用自回归移动平均对预测误差进行典型场景生成。其次,考虑来自虚拟电厂内部直接可控负荷以及外部需求响应交换市场所购得的需求响应资源,基于多阶段随机规划优化框架,以预期利润最大化以及可再生能源未消纳率最小化为目标,构建了不考虑风险控制和考虑风险控制两种条件下的虚拟电厂竞价策略优化模型。最后,通过算例分析不确定性和风险偏好对虚拟电厂的预期收益及可再生能源消纳率的影响,验证了所提运行策略的有效性。

Optimal Power Control for OFDM Signals over Two-Way Relay with Physical Network Coding

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.

Power control for two-way amplify-and-forward relaying over Rayleigh fading channels

We propose two novel power control policies for a two-way amplify-and-forward (AF) relaying system,in which each node (two sources and one relay) is assumed to operate under bothminimum and peak power constraints.Through the exploitation of instantaneous channel gains,the first policy can maximize the sum rate of the system.However,the instantaneous channel gains may be unavailable in a rapid time-varying system,where the first policy is inoperable.Consequently,a robust power control policy which requires only mean channel gains is proposed to maximize the upper bound of the average sum rate,and the properties of this policy are investigated.Simulation results show that,by comparison with the policy in which all the nodes use their peak transmit power,the proposed power control policies can provide considerable system performance improvement.Furthermore,the performance difference between the two proposed policies is negligible when the relay is close to one source.

向家坝—上海特高压直流系统孤岛运行方式

向家坝—上海±800 kV特高压直流在失去与四川主网全部500 kV联络线后,将进入孤岛运行。为此,讨论了向-上直流进入孤岛和孤岛运行两种运行方式下的控制策略,提出了孤岛运行对某些的交换功率限制,以及孤岛运行时的通信系统配置和频率控制器模型及参数。对进入孤岛及孤岛运行时的多种故障的仿真表明,在设计的频率控制器作用下,向-上直流可以保持稳定运行。

电源送出安全稳定控制系统典型方案及装置主辅运设置原则分析

研究了与不同送出电网相匹配的安全稳定控制系统方案及各方案下安控装置的主辅运原则。分析了单点大电源远距离输电、多电源跨区域输电以及地区小网通过联络线向主网送电等不同送出电网存在的突出稳定问题;指出了为保证安控措施的恰当性与经济性,不同电网对安控系统的差别要求。通过对安控方案在拓扑结构、通道组织、站间交互信息、故障决策算法等方面的对比说明,给出了送出电网各种典型的安控设计方案,并分析了不同方案不同的主辅运设置原则。针对安控系统运行管理模式,给各方案提出了厂站间装置接点信号交互、双套装置柜间数据交换等建议。

电动车无线能量互充系统及其恒流控制

针对电动车行驶途中可能出现电量不足的突发情况,提出了一种新的能量互充系统,用有富余电量的私人车辆或者专门提供能量补给服务的车辆为缺电车辆提供应急性能量补给。给出一种结构对称和参数对称的主电路拓扑,并引入移相控制策略来实现恒流充电。建立了系统的等效电路模型,推导出了发射端逆变器移相角与充电电流、发射线圈与拾取线圈距离之间的函数关系式。仿真和实验结果均验证了该系统及控制策略的可行性。

电力系统机电暂态和电磁暂态混合仿真程序设计和实现

电力系统混合仿真对常规电力系统进行机电暂态仿真,对重点关注的局部网络或者特定元件采用电磁暂态仿真。它综合考虑了机电暂态过程和电磁暂态过程的相互影响,为研究大规模电力系统的稳定性和动态特性提供了新的思路。文中基于自主开发的机电和电磁暂态混合仿真程序,结合具体的接口算法,设计并实现了电力系统混合仿真系统平台,并提出了一种新的数据时序交互方式以及在此基础上的数据通信和同步控制算法。所建立的仿真平台代码透明可控,功能易于扩展,提高了仿真的灵活性和效率。最后给出的仿真算例证实了所提出的方案的可行性及接口算法的正确性。

主动配电网中多微网鲁棒环境经济调度研究

针对多微网调度问题,兼顾其经济性与环境性,同时考虑多微网之间的功率交互以及可再生能源和负荷预测的不确定性,建立基于鲁棒优化的多微网鲁棒环境经济调度模型。采用拉丁超立方抽样方法和平均有效目标函数进行模型转化,并利用多目标细菌群体趋药性算法(multi-objective bacterial colony chemotaxis,MOBCC)求得4种情景的Pareto最优解。仿真结果证明,微网间功率交互可减少微网对微型燃气轮机、储能装置和大电网等的依赖性,可降低成本,增强电网的可靠性。由仿真结果可知,鲁棒解的获得是以经济成本和环境成本为代价的,预测误差越大鲁棒解所需成本越大,因此预测准确性对微电网调度至关重要。

分期建设的发电厂监控系统开发与实现

对于分期建设的发电厂监控系统应该采用开放式系统结构,标准的通信接口,人机界面开发平台应该选用面向对象的组态软件。这样的设计可以节约工程投资,降低后期工程施工的难度和风险。从发电厂监控系统功能设计与工程施工2个方面,提出了系统开发与实现的总体思路。从监控系统结构选择、人机界面开发技术、通信协议转换等方面作了详细介绍,对同期并网、备用电源自动投入等发电厂特殊监控功能的实现方式给出了具体方案。为了提高发电厂监控系统的可靠性,所有智能单元与后台监控系统配备了双通信通道,并通过脚本语言程序实现了后台监控系统的在线故障诊断和自动切换,从而在软硬件2个方面保证了整个监控系统的可靠性。

未来电网—多层次直流环形电网与“云电力”

化石能源的日益枯竭和环境压力的日益增加,将促使人类从传统能源向以可再生能源为主的清洁能源过渡。可再生能源资源及电力负荷的空间分布特点,决定了未来电网将呈现大电网与分布式电网平行发展的格局;同时,由于可再生能源具有不稳定性的特征,从而对电网的实时功率平衡与调度带来了重大的挑战。因此,为了保障电力供应,人们认识到必须对现有电网进行升级改造,其中,选择合理的电网结构是升级电网的重要手段。基于我国的现实情况,本文提出了未来电网的多层次直流环形电网结构,并进一步对"云电力"的概念进行了讨论,供参考和商讨。

基于动态数据交换的地调操作票系统

将ＳＣＡＤＡ（监视控制和数据采集系统）的实时信息引入地调操作票专家系统，利用Ｉｎｔｏｕｃｈ和Ｅｘｃｅｌ之间的动态数据交换（ＤＤＥ）功能，形成电网、厂站的图形及实时数据库，保证了开票时电网的结构和运行方式与本系统的电网拓扑数据库和实时数据库的一致性。

中点钳位式三电平D-STATCOM的鲁棒电流和中点电位控制策略研究

中点电位的平衡控制是中点钳位式三电平拓扑安全可靠运行的关键,但现有文献均未能通过建立精确的数学模型对中点电位漂移的物理机理进行精确分析,控制参数整定困难。该文建立了考虑未知干扰和参数摄动影响的中点钳位式三电平D-STATCOM的精确数学模型,利用重复控制与无源性控制相结合的方法实现了基于鲁棒L_2性能准则的电流控制器设计,精确分析了参数摄动导致的有功能量分配不均是中点电位漂移的根本原因。通过零序分量注入,利用直流侧上下端电容器之间的有功能量交换实现了中点电位的平衡控制。通过仿真以及1.14 k V,±400 k Var煤矿供电系统的工程应用,验证了该文所建立模型的准确性以及所提控制算法的可行性和有效性。

基于实时数据同步交换技术的统一潮流控制器监控系统

研制了一种基于实时数据同步交换技术的统一潮流控制器(UPFC)监控系统,阐述了UPFC的基本工作原理,介绍了其结构、功能和通信特点。该监控系统利用双口RAM 作为共享的数据缓冲区,实现实时数据的同步交换。系统以同步并行方式工作,确保了监控的实时性。系统采用模块化设计,有很好的兼容性和扩展性。为提高可靠性,该系统还具有自检功能。