利用有限资源实现高速Viterbi解码

文中提供一种分组方法简单，兼顾连线复杂性与存储空间有限性的Viterbi解码方法，并提出三种处理方法，可以依据实际情况选定所需的处理结构。     

Simulation and visualization of the Viterbi decoder using a spreadsheet

This paper demonstrates that a spreadsheet is an excellent tool for the simulation of the Viterbi decoder for educational purposes. Spreadsheet programming is streamlined by using complex number representations for metrics computation, allowing two values associated with each state at each time to be stored in a cell, thus providing a one-to-one correspondence between the spreadsheet cells and the nodes in the trellis diagram. The decoded path is plotted in a trellis diagram on the same spreadsheet so that the results can be readily visualized and examined. Either soft-decision or hard-decision decoding can be performed. A simple convolutional code of rate 1/2 and constraint length 3 is used for illustration, but the spreadsheet program is structured in such a way that it can be readily modified to simulate other codes.     

维特比译码器实现中的关键技术

本文针对维特比译码算法中的两个关键问题,即路径寄存器溢出与幸存路径存储问题,分别提出了可行的解决方案,并应用该方案在XilinxSpartanIIFPGA上实现了速率为64Kb/s的软判决译码器。     

基于Dijkstra算法的电网故障行波定位方法

为避免电网故障行波定位方法中环网的复杂解网运算,提出了一种基于Dijkstra算法的电网故障行波定位新方法。该方法在电网中某条输电线路故障后,在所有变电站检测记录初始行波到达时间。然后,利用Dijkstra算法计算最短路径,建立最短路径距离矩阵,并利用最短路径矩阵和初始行波到达时间计算故障距离,建立故障距离矩阵。最后,对故障距离矩阵中的元素进行有效性识别,并综合所有有效故障距离得到精确的故障点位置。仿真结果表明该方法无需复杂环网的解网运算,可有效提高网络定位的可靠性与准确度。     

一种基于线路相关集的大电网继电保护隐藏故障算法

世界各国频繁发生的大停电事故表明,当某条线路因故需要退出运行时,后备保护中的隐藏故障造成保护发生不必要的动作是造成大停电事故发生的重要因素。提出了线路相关集的概念,详细介绍了基于最短路径算法的线路相关集求解过程,推导了多条支路同时开断时线路相关集及相关因子的求解方法。在此基础上对假想事故后的潮流转移进行快速计算,准确地判断出后备保护的隐藏故障并快速进行消除,有效防止连锁跳闸事故的发生。用CEPRI36节点系统进行了仿真验证,证明了所提方法的正确性和有效性。     

一种基于线路相关集的事故预警系统

对近年来世界各国发生的大停电事故进行分析,指出在输电网络中某条线路因故退出运行而引起的潮流转移是导致后备保护连锁跳闸事故发生或发展的重要原因。提出了线路相关集的概念并进行严格定义,用来限定潮流影响的范围,节省潮流计算的时间。将线路相关集的搜索归纳为最短路径的求解问题,利用k最短路径算法求解线路相关集。分析了多条支路同时断开时线路相关集的搜索办法。另外,定义了线路相关因子,用于估算某条线路或多条线路断开时其他各线路承担的潮流转移分配。利用直流潮流法对线路相关因子进行求解。在此基础上提出了一套事故预警系统,对预想事故后的潮流转移进行快速计算,准确地判断出过负荷线路,有效地进行事故预警。用CEPRI36节点系统进行了仿真验证,证明了所提方法的正确性和有效性。     

A novel PDWC‐UCO algorithm‐based buffer placement in FPGA architecture

Clock distribution networks consume a significant amount of the whole chip power budget. Therefore, reduction in the power consumption of the clock networks is a significant objective in high‐performance Integrated Circuit (IC) designs. This paper presents a novel Particle Distance Weighted Clustering (PDWC)‐Unity Clustering Optimization (UCO) algorithm for the placement of clock buffers in the Field Programmable Gate Array (FPGA) architecture. A novel PDWC algorithm is applied for clustering the logical components based on the minimum distance between components. A UCO algorithm is developed to determine the location for the placement of the buffers. This clustering technique reduces the delay rate of the architecture because of the minimum number of logical components. The overall area and power consumption of the FPGA architecture are reduced because of the placement of the buffers and latches. Our proposed PDWC‐UCO algorithm achieves lower delay, power consumption, wire length, latency and skew than the existing Flip‐Flop (FF) merging and register clustering algorithms. Copyright © 2016 John Wiley & Sons, Ltd.     

改进QAM调制技术在电力通信中的应用研究

论述了电力通信中QAM调制技术及其不足,提出了改进QAM调制下的编、译码结构及译码算法.解决了宽带利用率和传输速率之间的矛盾,提高了抗干扰性和纠错能力,在电力线通信中具有较好的应用前景.     

基于拥塞感知的ASON路由算法

针对网络中瞬间涌现的大量并发数据流导致网络拥塞的问题,提出了一种改进的拥塞感知路由算法。该算法可实时根据节点和邻居节点到目的节点的路径长度及拥塞状况选择路径,以自动交换光网络(Automatically Switched Optical Network, ASON)网数据包拥塞指标为链路代价值,根据网络实际的信息包传输状况,对各节点链路进行加权计算。该算法能够动态感知网络拥塞状态,是一种可自适应调节的路由算法。仿真实验表明,相比传统最短路径路由算法,所提算法能够有效提高ASON网动态选路的合理性及传输网数据的传输效率,优化网络资源利用率。     

基于时间差定位法的电力系统扰动源定位

在大规模互联电网中系统频率动态具有时空分布特性,且传播速度远低于光速。借助电网频率动态的传播特性及不同节点处频率响应的时间差对电网的扰动源进行定位,首先利用Floyd算法计算各节点之间的最短传播路径,根据传播路径的物理参数确定传播速度,然后借助时间差定位法（TDOA）对电网的扰动源进行定位,最后将所提方法应用于3机9节点系统和某实际电网,分析结果表明该方法能够有效地对电网的扰动源进行定位。     

一种改善LDPC译码性能的新方法

由于LDPC码可以逼近香农限,近年来在国内外编码研究与应用中受到广泛关注,然而,LDPC码迭代译码存在误码平底,限制了LDPC码的进一步应用.陷阱集是导致LDPC码误码平底的主要因素,为了消除陷阱集的影响,提出一种基于陷阱集变量节点消息重置译码方法.当译码器进入陷阱状态后,重新计算陷阱集变量点消息,使译码器在后续迭代过...     

基于全球定位系统和锁相环技术的同步相量测量装置的实现

电网实时相量监测系统对于电力系统的状态估计、稳定监控具有重要意义。着重介绍电网实时相量监测系统中的基本功能单元——同步相量测量装置的原理和实现方法。该装置将全球定位系统和锁相环技术相结合,既保证了不同测量点被测相量的同步采样,又保证了各测量点对被测相量信号的采样频率能自适应地跟踪电网频率变化,使相量测量精度进一步提高。介绍基于离散傅里叶变换的电压相角计算方法,给出了发电机功角的计算公式。该装置可对电网重要节点的电压(幅值、相角)以及发电机的功角进行实时同步测量,并将测量结果实时送往监测中心,实现全网运行状态的实时监测。     

Redundancy‐bandwidth scalable techniques for signal‐independent element transition rates in high‐speed current‐steering DACs

This paper presents redundancy‐bandwidth scalable techniques to deal with the intersymbol interference distortions for current‐steering digital‐to‐analog converters in high‐speed applications. A switching strategy that explores the use of redundant current sources is proposed to realize a signal‐independent element transition rate, ie, the number of switching activities during the transition of successive sampling clock cycles. With a certain number of redundant current sources, this strategy significantly reduces the intersymbol interference distortions without oversampling operation or causing signal attenuation, which makes it appealing for high‐speed applications. As analyzed in this paper, the number of required redundant current sources is scalable for different bandwidth requirement in specific applications, leading to 3 redundancy‐bandwidth scalable trade‐offs between the cost from redundant current sources and the high‐dynamic‐range bandwidth. In implementation, we propose a custom‐designed decoder, named as the overlap‐controlled data‐weighted averaging (OC‐DWA). Compared with the existing similar‐purpose designs, the proposed OC‐DWA decoder realizes the current sources selection with a simple barrel rotator, which is of much lower hardware complexity and energy consumption. Simulations of a digital‐to‐analog converter with this decoder exhibit an enhanced dynamic range over the entire Nyquist band, which verifies the redundancy‐bandwidth scalability of the proposed techniques.     

基于模糊聚类和最短路径的关键输电断面确定新方法

针对因支路故障或过载被切除之后的潮流转移关键输电断面如何正确快速确定问题,提出了基于模糊聚类和最短路径的潮流转移关键输电断面快速搜索新方法。该方法首先采用具有自适应选择最佳分类数的随机聚类方法,对所有线路功率构成进行分类,获得故障或过载支路的并行支路集构成初始输电断面,以避免由于人为给定分类数的不恰当所产生的多选及漏选问题;然后对初始输电断面中的每一支路,依次从故障或过载支路的一端开始搜索包括相应支路的到故障或过载支路另一端的最短路径,在该路径上所有与故障或过载支路潮流方向相同的支路,均为关键输电断面中的候选支路,以补充单纯由聚类方法确定的候选支路可能的漏选;候选支路再经简单的分布因子校核即可确定是否为关键输电断面中的支路。该方法实现了基于支路功率聚类关键输电断面选择方法和最短路径关键输电断面选择方法的有机融合和优势互补,提高了辨识精度。多个算例证实了文中方法的有效性。     

A fast and efficient load flow technique for unbalanced distribution system

This paper presents a fast and efficient load flow technique for unbalanced distribution system. The proposed load flow technique is derived by promulgating the concept of conventional backward forward sweep (BFS) technique of power flow study for distribution system. The proposed technique employs a novel load-impedance matrix (LIM) to calculate the bus voltages in a single step unlike the conventional BFS approach which involves two separate steps (backward sweep and forward sweep) to perform the same and this improvement is claimed as the novelty of this work. This distinctive feature makes the proposed algorithm faster in operation. Nodal voltages, at any iteration, may be calculated, directly, from the values obtained in the previous iteration by utilizing LIM. A simple concept of set theory is adopted here to construct the LIM. Special treatments are also included in this method to analyze weakly meshed systems. The proposed technique is flexible enough to accommodate any sort of changes in the existing network topology through LIM. It is tested on different three-phase balanced and unbalanced radial distribution systems as well as weakly meshed networks for load flow study. A separate case study is also presented to check the validity of the proposed load flow technique for various transformer connections. The obtained results demonstrate the effectiveness of the proposed technique. Furthermore, performance comparison reveals that the proposed algorithm is, computationally, faster and robust than the conventional power flow techniques reported in the recent state-of-the-art literatures.     

基于因子隐马尔可夫模型的负荷分解方法及灵敏度分析

负荷分解是智能电网的关键技术,对负荷预测、需求侧管理及电网安全有重要意义。传统负荷分解方法的准确率受限于负荷特征的维度、采样频率和负荷的稳定性。文中提出了基于因子隐马尔可夫模型的负荷分解方法,利用该模型对负荷进行建模,对Viterbi算法进行了扩展并求解负荷状态,进而基于整数规划实现对总负荷的最优分配。该方法对负荷数据的稳定性和采样频率不敏感,可适用于家居和工业电力用户。同时,深入研究了Viterbi算法求解最优状态与观测扰动之间的影响关系,并进一步得到最优状态对于当前观测的允许扰动范围,这对负荷分解最优状态的可靠性评估有重要意义。     

基于业务调用认证登录接口的电网信息防泄漏技术

为提高电网信息的安全性,提出基于业务调用认证登录接口的电网信息防泄漏技术。构建信息流传递路径模型,模拟信号攻击过程,将马尔科夫链方法引入到电网稳态中,量化电网信息泄露风险,设计终端主动免疫结构。仿真结果表明,所提方法能够减少信息泄露次数,提高信息加密效率与吞吐量,具有预防信息泄漏的效果。     

基于路径搜索的多节点低压电力线信道建模方法

为进一步实现多节点网络通信环境的精确仿真与模拟,本文从传输线理论出发,提出了一种基于低压电力网络拓扑的多节点电力线信道响应的生成方法。依据电力网络拓扑,通过最短路径搜索算法获取主干路径,并采用基于广度优先的搜索算法得到分支线路的父子节点关系表,由深至浅地对节点等效阻抗逐一更新,最后通过网络级联获取传输参量矩阵,求取信道频率响应。该方法原理清晰简明,适用于对任意给定拓扑结构的低压配电网络与室内电力网络等环境。仿真与实验结果表明该方法在给定的电力网络拓扑下能够有效地对低压电力网络中多个节点间信道进行模拟。     

基于业务调用认证登录接口的电网信息防泄漏技术

为提高电网信息的安全性，提出基于业务调用认证登录接口的电网信息防泄漏技术。构建信息流传递路径模型，模拟信号攻击过程，将马尔科夫链方法引入到电网稳态中，量化电网信息泄露风险，设计终端主动免疫结构。仿真结果表明，所提方法能够减少信息泄露次数，提高信息加密效率与吞吐量，具有预防信息泄漏的效果。     

A novel low power and high speed double edge explicit pulse triggered level converter flip‐flop

One of the effective ways to reduce power consumption is using clustered voltage scaling technique. The level converter flip‐flop is needed to control static current when the block with Low Supply Voltage (VDDL) drives the block with High Supply Voltage (VDDH). One of the big challenges of design is that level converter flip‐flop has low power and high speed. In this paper, pulse triggered level converter flip‐flop and double edge pulse generator were proposed. This level converter flip‐flop used conditional data mapping technique for reducing power consumption. An explicit double edge pulse generator could be shared among several level converter flip‐flops so that power consumption would be reduced. Also, the number of stack transistor was reduced in the discharging path that causes delay decrease. The simulation results showed that the proposed flip‐flop reduced 20% of power consumption and 17% of delay in comparison with other flip‐flops at 50% data switching activity. Copyright © 2013 John Wiley & Sons, Ltd.