广域稳控系统通信网络性能仿真及分析

广域稳控系统对覆盖面积广阔的电力系统运行状态进行监测和分析，对实时性与可靠性要求很高。分析了广域稳控系统的通信网络需求，基于现网架构设计了相应的通信方案；理论上分析了广域稳控系统分段时延产生机理，建立了广域稳控系统通信时延的计算模型；基于Exata网络仿真平台建立了电力设备模型及SDH（Synchronous Digital Hierarchy，同步数字体系）传输网网络模型，并通过电力通信联合仿真接口模型接入电力实物设备，验证了仿真模型的有效性；最后通过对比不同业务传输通道下的广域稳控系统通信网络时延，结果表明在广域规模达3 000 km以上时，专有通道传输时延仍能满足50 ms以内的需求，而基于SPDnet的三级IP网络通道受厂站负载的影响，无法保证所有厂站业务均满足时延需求，且交换时延的不稳定带来了极大的时延抖动。     

Arise: operating PCTE over a wide-area network

A case study in which the feasibility of operating the Portable Common Tools Environment (PCTE) across a wide-area network was determined as part of the Arise project is discussed. Simple benchmarks and experiments with a configuration-management application indicate that a wide-area PCTE is feasible, provided there is a suitable data-distribution strategy     

多干扰情况下的电力系统闭环辨识研究

电力系统中多处负荷投切与变化等随机性质小扰动,导致系统响应始终存在类似噪声的小幅波动.本文提出利用广域测量类噪声信号辨识被控电力系统模型,及时准确地反映系统当前运行特性,进而解决因仿真模型及参数误差造成的系统分析及控制器设计可信度难以评估等难题.重点对多干扰情况下的系统模型闭环辨识问题进行理论性研究,包括闭环可辨识性、辨识一致性及收敛性等方面,分析得出类噪声环境下要实现系统闭环辨识需具备的条件,并对理论研究结果进行了仿真验证.     

Improved Design of Interval Type-2 Fuzzy based Wide Area Power System Stabilizer for Inter-area Oscillation Damping

The interconnection of power system due to the ever-time increase in power demand has caused inter-area oscillations as a challenge to power system stability. The present paper proposes the novel design of an Interval Type-2 Fuzzy based Wide Area Power System Stabilizer to damp the inter-area mode of oscillations for improving the power system stability. The usage of Wide Area Measurement Systems for continuous monitoring of the power grid plays a significant role in maintaining the stability of the power grid. The proposed controller uses wide-area signals from WAMS as the input signals. The controllability index calculation performs the selection of the most affected wide-area signals. The participation factor is used to identify the location of the controller. Sliding Surface approach is introduced in the controller to upgrade the performance of the controller during different operating conditions. The sliding surface approach has made the system insensitive to the parameter variations. The interval type-2 fuzzy control is a model-free approach with better control performance, due to its higher degree of freedom of interval type-2 fuzzy sets. Finally, the optimal tuning of sliding surface parameters has been considered as an optimization problem with the minimization of Integral Time Square Error using Real Coded Genetic Algorithm to enhance the damping control. The proposed Fuzzy controller has been tested in two area, four machine, 11 bus IEEE benchmark system. From the simulation responses and the comparison with different controllers, the proposed controller shows robustness and effectiveness with more accurate dynamic response and better damping of inter-area oscillations under different system operating conditions and load perturbations.     

婴幼儿视网膜广域成像系统

为实现婴幼儿眼底疾病的及时诊断与治疗,开发的婴幼儿视网膜广域成像系统可以解决成像时大视场要求.系统包括照明部分、成像部分和图像采集装置.设计了角膜接触眼底镜,采用像差小、折射率大的非球面设计,满足大视场的要求;设计了图像采集装置,使用C++编写图像采集处理软件,进行图像采集、相机标定和几何畸变校正.实验结果表明：采用多环光纤光线照明的婴幼儿视网膜广域成像系统可以实现85°视场的较清晰广域成像;采用基于相机标定的图像几何畸变校正方法,可有效补偿视网膜成像光路的畸变.该婴幼儿视网膜广域成像系统可以为眼科疾病的诊断、筛查提供客观、清晰的依据.     

Fail-safe concurrency in the EcliPSe system

Local or wide-area heterogeneous workstation clusters are relatively cheap and highly effective, though inherently unstable operating environments for long-running distributed computations. We found this to be the case in early experiments with a prototype of the EcliPSe system, a software toolkit for replicative applications on heterogeneous workstation clusters. Hardware or network failures in computations that executed for over a day were not uncommon. In this work, a variety of features for the incorporation of failure resilience in the EcliPSe system are described. Key characteristics of this fault-tolerant system are ease of use, low state-saving cost, system scalability and good performance. We present results of some experiments demonstrating low state-saving overheads and small system-recovery times, as a function of the amount of state saved.     

面向钢轨监测的无线传感器网络网关设计与性能测试

针对我国铁路钢轨实时广域监测的重大需求,通过研究异构无线传感器网络（WSNs）通信技术,设计并实现了一种基于Zig Bee-3G通信的无线传感器网络网关.进行了通信电路设计和电磁兼容设计,并在WinCE操作系统平台上实现了Zig Bee网络与3G网络之间的互联,开发了网关远程维护管理模块.对网关设备分别进行了网络传输性能测试和电磁兼容测试,测试结果表明：此网关传输效率高、抗电磁干扰能力强,能够满足铁路轨道监测现场的应用要求.     

广域污染源自动监控系统分布式网络平台研究

针对广域污染源自动监控系统的特点和技术要求,必须采用中间分布式网络平台来满足系统的要求。通过对Microsoft的.NET、Sun的JavaONE以及OMG的CORBA这三种主要分布式网络平台的深入分析和比较研究,得出采用CORBA分布式平台是目前最佳方案的结论,并在“广东省广域水质污染源在线监测监控系统”课题中得到成功验证。     

Automatic Flow-Control Adaptation for Enhancing Network Performance in Computational Grids

With the advent of computational Grids, networking performance over the wide-area network (WAN) has become a critical component in the Grid infrastructure. Unfortunately, many high-performance Grid applications only use a small fraction of their available bandwidth because operating systems and their associated protocol stacks are still tuned for yesterday's WAN speeds. As a result, network gurus undertake the tedious process of manually tuning system buffers to allow TCP flow control to scale to today's WAN Grid environments. And although recent research has shown how to set the size of these system buffers automatically at connection set-up, the buffer sizes are only appropriate at the beginning of the connection's lifetime. To address these problems, we describe an automated and lightweight technique called dynamic right-sizing that can improve throughput by as much as an order of magnitude while still abiding by TCP semantics.     

Implementing location independent invocation

The problems of finding objects in large and wide-area networks where objects may change their location in volatile memory as well as on stable storage are presented. The authors discuss possible solutions and describe those adopted in the Hermes system (a corporate wide, real life office application). They have designed and developed a location-independent-invocation (LII) mechanism that combines finding with invocation, using temporal location information. The mechanism also updates the system's knowledge of an object's location as a side-effect of invocation and object migration. Assumptions about object mobility indicate that objects are likely to be found within a few propagations of an invocation. If they cannot be found in this way, stable-storage and name services are used to locate the object. The major contribution of this work is to show how LII can be achieved in a large and dynamic environment in which objects are supported by neither are operating system nor the programming language     

SeWDReSS: on the design of an application independent,secure, wide-area disaster recovery storage system

Distributed wide-area storage systems must tolerate both physical failure and logic errors. In particular, these functions are needed to enable the storage system to support remote disaster recovery. There are several solutions for distributed wide-area backup/archive systems implemented at application level, file system level or at storage subsystem level. However, they suffer from high deployment cost and security issues. Moreover, previous researches in literature only focus on any disk-related failures and ignore the fact that storage server linked predominantly to a Wide-Area-Network (WAN) which may be unavailable or owing to network failures. In this paper, we first model the efficiency and reliability of distributed wide area storage systems for all media, taking both network failures and disk failures into consideration. To provide higher performance, efficiency, reliability, and security to the wide-area disaster recovery storage systems, we present a configurable RAID-like data erasure-coding scheme referred to as Replication-based Snapshot Redundant Array of Independent Imagefiles (RSRAII). We argue that this scheme has benefits resulting from the consolidation of both erasure-coding and replication strategies. To this end, we propose a novel algorithm to improve the snapshot performance referred to as SMPDP (Snapshot based on Multi-Parallel Degree Pipeline). We also extend this study towards implementing a prototype system, called as SeWDReSS, which is shown to strike a tradeoff between reliability, storage space, security, and performance for distributed wide-area disaster recovery.     

Mariposa: a wide-area distributed database system

The requirements of wide-area distributed database systems differ dramatically from those of local-area network systems. In a wide-area network (WAN) configuration, individual sites usually report to different system administrators, have different access and charging algorithms, install site-specific data type extensions, and have different constraints on servicing remote requests. Typical of the last point are production transaction environments, which are fully engaged during normal business hours, and cannot take on additional load. Finally, there may be many sites participating in a WAN distributed DBMS. In this world, a single program performing global query optimization using a cost-based optimizer will not work well. Cost-based optimization does not respond well to site-specific type extension, access constraints, charging algorithms, and time-of-day constraints. Furthermore, traditional cost-based distributed optimizers do not scale well to a large number of possible processing sites. Since traditional distributed DBMSs have all used cost-based optimizers, they are not appropriate in a WAN environment, and a new architecture is required. We have proposed and implemented an economic paradigm as the solution to these issues in a new distributed DBMS called Mariposa. In this paper, we present the architecture and implementation of Mariposa and discuss early feedback on its operating characteristics. Edited by Henry F. Korth and Amith Sheth. Received November 1994 / Revised June 1995 / Accepted September 14, 1995     

(Deep) Reinforcement learning for electric power system control and related problems: A short review and perspectives

This paper reviews existing works on (deep) reinforcement learning considerations in electric power system control. The works are reviewed as they relate to electric power system operating states (normal, preventive, emergency, restorative) and control levels (local, household, microgrid, subsystem, wide-area). Due attention is paid to the control-related problems considerations (cyber-security, big data analysis, short-term load forecast, and composite load modelling). Observations from reviewed literature are drawn and perspectives discussed. In order to make the text compact and as easy as possible to read, the focus is only on the works published (or “in press”) in journals and books while conference publications are not included. Exceptions are several work available in open repositories likely to become journal publications in near future. Hopefully this paper could serve as a good source of information for all those interested in solving similar problems.     

The performance of the Amoeba distributed operating system

Amoeba is a capability-based distributed operating system designed for high-performance interactions between clients and servers using the well-known RPC model. The paper starts out by describing the architecture of the Amoeba system, which is typified by specialized components such as workstations, several services, a processor pool, and gateways that connect other Amoeba systems transparently over wide-area networks. Next the RPC interface is described. The paper presents performance measurements of the Amoeba RPC on unloaded and loaded systems. The time to perform the simplest RPC between two user processes has been measured to be 1-4 ms. Compared to SUN 3/50's RPC, Amoeba has one ninth of the delay, and over three times the throughput. Finally we describe the Amoeba file server. The Amoeba file server is so fast that it is limited by the communication bandwidth. To the best of our knowledge this is the fastest file server yet reported in the literature for this class of hardware.     

A wide area measurement based neurocontrol for generation excitation systems

Power system is a highly interconnected nonlinear system that needs optimal and accurate control for continuous operation. Large power transfer through long transmission line between different electrical areas, stressed system and adverse interaction between local controllers, may give rise to slow frequency inter-area oscillations. The inter-area modes may not be visible from local measurements and hence it is useful to use remote measurement based centralized supplementary control. Wide area control systems (WACSs) using wide-area or global signals can provide remote auxiliary control to local controllers such as automatic voltage regulators, power system stabilizers, etc. to damp out inter-area oscillations. This paper presents a design and real time implementation of a nonlinear neural network based optimal wide area controller using adaptive critic design (ACD). The real time implementation of a power system model is carried out on a real time digital simulator (RTDS). The performance of the WACS as a power system stability agent is studied using a two-area power system under different operating conditions and contingencies. The WACS shows improvement in the damping of inter-area mode with the use of supplementary excitation control. In addition, results show that the designed controller can provide robust performance under small communication delay in remote signal transmission.     

ZigBee与GPRS的远程数据采集系统设计

ZigBee技术虽然先进但网络覆盖范围较小,本文将GPRS广域无线通信技术引入ZigBee网络中,构建了一种远程ZigBee网络的数据采集与管理系统,并采用直观方便的嵌入式Web服务器提高管理效率。系统测试结果证明了该系统具有很好的有效性和可靠性。     

IrisNet: an architecture for a worldwide sensor Web

We discuss about the IrisNet (Internet-scale resource-intensive sensor network services) project at Intel Research, we design an architecture and build a system that enable easy deployment of such wide-area sensing services. We aim to provide the missing software components for realizing a worldwide sensor Web. Wide-area architectures for pervasive sensing enable a new generation of powerful distributed sensing services. A worldwide sensor Web, in which users can query, as a single unit, vast quantities of data from thousands or even millions of widely distributed, heterogeneous sensors. Internet-connected PCs that source sensor feeds and cooperate to answer users' queries will form the global sensor Web's backbone. Developers of wide-area sensing services (service authors) deploy the services on this distributed infrastructure.     

Programming environments for high-performance Grid computing: the Albatross project

The aim of the Albatross project is to study applications and programming environments for computational Grids. We focus on high-performance applications, running in parallel on multiple clusters or MPPs that are connected by wide-area networks (WANs). We briefly present three Grid programming environments developed in the context of the Albatross project: the MagPIe library for collective communication with MPI, the replicated method invocation (RepMI) mechanism for Java, and the Java-based Satin system for running divide-and-conquer programs on Grid platforms.A major challenge in investigating the performance of such applications is the actual WAN behavior. Typical wide-area links are just part of the Internet and thus shared among many applications, making runtime measurements irreproducible and thus scientifically hardly valuable. To overcome this problem, we developed a WAN emulator as part of Panda, our general-purpose communication substrate. The WAN emulator allows us to run parallel applications on a single (large) parallel machine with only the wide-area links being emulated. The Panda emulator is highly accurate and configurable at runtime. We present a case study in which Satin runs across various emulated WAN scenarios.     

供应链中控制多级存储的射频辨识Push/Pull混合策略设计与仿真

由于射频辨识(radio frequency identification,RFID)激励的电子看板系统能够从远端看见供应链节点企业库存的状况,使得广域分布的供应链多级存储能够实现RFID激励的Pull控制.本文根据供应链分销网络多级存储的结构特点,以及系统运作期间各阶段节点企业的功能,在不同阶段采用不同的控制策略.因此,设计了多种不同的RFID激励的Push/Pull混合控制策略.为了比较和验证各混合策略对多级存储的控制性能,建立了以总库存成本、总缺货损失、总运行成本和库存周转率作为评价策略性能的指标体系.由于供应链系统的动态性与随机性,难以进行数学建模和精确求解,因此基于离散事件系统仿真原理,设计并实现了仿真模型.通过对各策略下多种结构的供应链分销网络多级存储的仿真,验证并分析了制造商阶段采用Push控制,分销商和零售商阶段采用Pull控制的策略的有效性和最优性.     

GCSS: a global collaborative scheduling strategy for wide-area high-performance computing

Wide-area high-performance computing is widely used for large-scale parallel computing applications owing to its high computing and storage resources. However, the geographical distribution of computing and storage resources makes efficient task distribution and data placement more challenging. To achieve a higher system performance, this study proposes a two-level global collaborative scheduling strategy for wide-area high-performance computing environments. The collaborative scheduling strategy integrates lightweight solution selection, redundant data placement and task stealing mechanisms, optimizing task distribution and data placement to achieve efficient computing in wide-area environments. The experimental results indicate that compared with the state-of-the-art collaborative scheduling algorithm HPS+, the proposed scheduling strategy reduces the makespan by 23.24%, improves computing and storage resource utilization by 8.28% and 21.73% respectively, and achieves similar global data migration costs.