无线网络中文件缓存命中率和能耗的联合优化

任何一个缓存问题的重要目标都是减少网络中的流量,但在内容中心网络中能量的消耗是一个不得不考虑的因素,包含缓存能量消耗和传输能量消耗.提出了传统的缓存效率衡量指标,例如命中率,和能量消耗之间存在一定的对立关系.提出一种既可以提高命中率又考虑到减少能量消耗的新的缓存机制,并将这个优化问题表达成亚模的形式,通过贪心算法找到命中率和能量消耗的平衡点,并且找到一种近似最优的缓存机制.最后通过仿真验证了这一结果,在内容中心网络中可以达到命中率和能量消耗的一个均衡的缓存机制.     

基于sbRIO 9606的波浪发电数据采集系统设计

提出一种用于机电式波浪发电模拟实验的数据采集系统,实现对发电机电压、电流和加速度等参数的实时数据采集。系统硬件采用NI sbRIO 9606和NI 9683配合使用,避免了依靠DAQ助手的硬件采集系统的局限性,可控性强,应用性好。系统软件采用LabVIEW 语言编写,提供友好的人机界面,采用TDMS文件格式进行数据的存储及回放操作,占用存储空间小,易于维护。实际运行显示,该系统数据采集过程操作方便、稳定、可靠,可以满足波浪发电实时性分析与控制要求。     

Eigenanalysis-based small signal stability of the system of coupled sustainable microgrids

Until now, microgrids were assumed to operate either in grid-connected or islanded modes. As a third alternative, neighboring microgrids may interconnect to support each other during faults in a section of one MG, or in the course of overloading. They may also interconnect to reduce the cost of electricity generation in their systems. Thereby, a microgrid will experience a significant transformation in its structure, when coupled with one or more neighboring microgrids. Before the formation of the system of coupled microgrids, the stability of the new system is vital to be cautiously examined to intercept the transformation, if instability is to occur. An eigenanalysis-based small signal stability evaluation technique is developed in this paper which can be used to allow/deny the interconnection of the microgrids. The analysis also defines the suitable range of control parameters for the energy resources of the CMG to guarantee the stability of the new system, if it was determined unstable. Numerical analyses, realized in MATLAB, are performed for the interconnection of a few sample microgrids. The accuracy of the developed technique is validated by comparing its results with the time-domain performance of the similar system, realized in PSCAD/EMTDC.     

提高大型风电机组恒转速段发电量的变桨策略

常规认为的额定风速以下的恒定最优桨距角在机组恒转速段并不一定是最优的。恒转速段的最大功率跟踪问题等同于特定转速下的气动转矩最大化问题,以提高发电量为目标分析了在两个恒转速段内切向力系数及法向力系数与桨距角的定性关系。分析表明,在恒最低转速段通过合理地正调桨距角可以提升切向力系数并提高发电量,且可减轻轴向推力等载荷;在恒最高转速段通过合理地负调桨距角可以提升切向力系数并提高发电量,但会增大轴向推力载荷;在两个恒转速段内特定风速下均存在其对应的最优桨距角,且最优桨距角随风速单调变化。针对最优桨距角难以直接量化的问题,根据定性分析结果推断出最优桨距角的合理表达式,并给出了表达式中参数的离线辨识方法。最后采用专业软件Bladed中的商用机组实际参数模型,从稳态和动态两方面对恒转速区提高发电量的变桨策略进行了验证,仿真结果很好地证明了分析的正确性,从而更好地指导机组提高发电量。     

基于LAB+i平台的电力需求侧管理案例分析

智能电网元件引入配电网和市场系统,对电网需求侧管理提出了新的挑战和机遇。智能电网国家实验室LAB+i已经拥有必要的基础设施进行智能电网的案例研究,其中包括电力需求侧管理。介绍了哥伦比亚国立大学的应用案例,在LAB+i平台实施基于3种需求响应技术的自动化管理系统,能够为校区每个建筑找到最佳负荷曲线。     

基于节能率预测的注塑机节能模型研究及实测验证

通过对注塑机工作原理及能耗构成进行分析,研究其关键节能技术,对比建立注塑机电动机油泵系统及加热系统节能改造能耗模型,进而得出基于模型的节能率预测方法,并通过实例验证其可行性,为注塑机节能改造的节能率预测提供理论依据,为改造效果经济性评估提供算法支撑。     

太阳能/热泵技术在木材干燥领域的应用

提出在家具行业领域,采用太阳能/热泵技术替代传统能源。介绍太阳能及热泵技术的基本原理及应用范围。通过太阳能/热泵技术在江西家具行业的应用,分析该技术的主要特点及注意事项。太阳能/热泵综合能源技术应用在家具行业可实现节能环保,具有推广价值。     

An Approach for Detecting and Locating Evolving Faults on Transmission Lines Based on Transient Traveling Waves

There has not been a satisfactory solution to identifying and locating evolving faults on transmission lines until now. This paper presents an integrated detection and location approach for evolving faults based on transient traveling waves. Evolving faults include two sequential faults, resulting in the change of fault phase. The feature aerial mode of captured current traveling wave only reflects the feature of the second fault occurrence, and is used for analyzing the second fault. By combining traveling wave and transient energy features, fault phase selection can be implemented at two stages: the initial fault occurrence, and the short period before fault clearance. The evolving faults can be determined according to the consistency of the two-stage phase-selection results. Subsequently, the positions of the two successive faults can be precisely acquired by individually implementing the double-ended traveling wave fault location on the initial fault phase as well as the feature aerial mode currents, respectively. Digital simulation studies based on the simulation software PSCAD/EMTDC demonstrate that the proposed method is feasible and effective.     

A Study of Total Transient Energy During the Fault Period

The total transient energy accumulated during the fault period is an important factor affecting power system dynamics. In this paper, we present a study of the total transient energy. First, we analyze the characteristics of energy interchange during the fault period. Then, an expression is developed based on characteristics analysis to estimate the total transient energy. Such an expression allows us to study how a fault, in terms of its magnitude, clearing time, and location, affects the total transient energy. Especially, the distribution factors of the total transient energy are defined based upon the expression to analyze the impact of fault location. It is found that for a fault with the given magnitude and clearing time, the total amount of total transient energy mainly depends on the difference in the distribution factors. Furthermore, it is found that the distribution factors can be applied to the identification of potential critical fault locations, the identification of coherent generators, and the identification of critical generators. The analysis results and their applications are demonstrated in the IEEE 9-bus system and the IEEE 39-bus system.