TD-LTE-A信道估计DFT算法研究

TDLTE-A信道估计的经典算法有最小平方（LS）算法,线性最小均方误差（LMMSE）算法以及基于变换域的离散傅里叶变换（DFT）算法.LS算法不需要知道信道的先验信息,但是对噪声没有做任何处理.LMMSE算法利用了信道的自相关矩阵,估计性能比LS要优良,但是计算较为复杂,不利于在实际系统中实现.DFT算法则是在LS算法估计结果的基础上,进行变换域处理.但是DFT算法存在较为明显的“地板效应”.然而,提出通过改进TD-LTE-A系统的参数配置,可以有效地改善DFT算法的估计性能,使其性能接近于理想信道估计,并且通过仿真比较了DFT估计与其他信道估计算法在信道响应值的均方误差和信道冲击响应值的差异.     

A novel variable‐length sliding window blockwise least‐squares algorithm for on‐line estimation of time‐varying parameters

Motivated by the advances in computer technology and the fact that the batch/block least‐squares (LS) produces more accurate parameter estimates than its recursive counterparts, several important issues associated with the block LS have been re‐examined in the framework of on‐line identification of systems with abrupt/gradual change parameters in this paper. It is no surprise that the standard block LS performs unsatisfactorily in such a situation. To overcome this deficiency, a novel variable‐length sliding window‐based LS algorithm, known as variable‐length sliding window blockwise least squares, is developed. The algorithm consists of a change detection scheme and a data window with adjustable length. The window length adjustment is triggered by the change detection scheme. Whenever a change in system parameters is detected, the window is shortened to discount ‘old’ data and place more weight on the latest measurements. Several strategies for window length adjustment have been considered. The performance of the proposed algorithm has been evaluated through numerical studies. In comparison with the recursive least squares (RLS) with forgetting factors, superior results have been obtained consistently for the proposed algorithm. Robustness analysis of the algorithm to measurement noise have also been carried out. The significance of the work reported herein is that this algorithm offers a viable alternative to traditional RLS for on‐line parameter estimation by trading off the computational complexity of block LS for improved performance over RLS, because the computational complexity becomes less and less an issue with the rapid advance in computer technologies. Copyright © 2004 John Wiley & Sons, Ltd.     

Rough set and fuzzy wavelet neural network integrated with least square weighted fusion algorithm based fault diagnosis research for power transformers

In this paper, a rough set (RS) and fuzzy wavelet neural network (FWNN), integrated with least square weighted fusion algorithm based fault diagnosis for power transformers, using dissolved gas analysis (DGA) is proposed. This approach takes advantage of the knowledge reduction ability of rough set and good classified diagnosis ability of FWNN, integrated with least square (LS) weighted fusion algorithm. The rough set is used as a front of FWNN, integrated with LS weighted fusion algorithm to simplify the input of FWNN and mine the rules whose “confidence” and “support” satisfy a preset criteria. The mined rules are used as a diagnosis knowledge base to offer fault diagnosis service for power transformers. FWNN, integrated with LS weighted fusion algorithm, is used to diagnose the case that cannot be diagnosed by mined rules by rough set. The FWNN input is simplified by rough set reduction, and its learning rate is improved greatly. FWNN, integrated with LS weighted fusion algorithm, on one side, can much better improve the diagnosis accuracy, when the output vector of single FWNN has the similar element. On the other hand, its diagnosis accuracy cannot be limited by the neural network hidden layer number and correlated training parameter. The mechanism has good classified diagnosis ability. The advantages and effectiveness of this method are verified by testing.     

Systematic Characterization of Integrated Circuit Standard Components as Stimulated by Scanning Laser Beam

Laser stimulation (LS) has become a common technique of failure localization in integrated circuits (ICs). In optical-beam-induced resistivity change, thermally induced voltage alteration, Seebeck effect imaging, soft defect localization, etc., device modules with special passive and active device properties are the subject of stimulation effects. This paper investigates in detail the behavior and equivalent circuit models of most commonly used IC components, passives such as metal and polysilicon interconnect resistors and thermoelectric junctions, and actives like p-n diodes and field-effect transistors under illumination from both chip frontside and backside. The systematic characterization of the results improves the evaluation of LS analysis in failing circuits.     

基于混合算法的短期负荷预测模糊建模

结合最小二乘（LS）辨识以及一种基于进化规划（EP）和粒子群优化（PSO）的混合进化算法EPPSO,针对对温度比较敏感的夏季负荷,提出一种3阶段短期负荷预测（STLF）算法。在第1阶段,应用LS设计模糊基函数网络（FBFN）完成STLF模糊空间划分;第2阶段,首先拓展FBFN成一阶Sugeno模糊模型,然后应用EPPSO调节其前件参数同时训练后件参数,最后将前述模型用于STLF得出的预测误差看做一个新的时间序列,并仅用气象因素对其进行辨识,可以用回归模型表示该辨识模型,进而应用LS进行辨识。文中提出的STLF模糊建模策略主要贡献于受气象因素影响较大的夏季负荷。仿真部分对浙江省电力公司的实际负荷进行了预测,与其他方法的比较结果证明该方法具有良好的预测性能。     

Finite‐model adaptive control using an LS‐like algorithm

Adaptive control problem of a class of discrete‐time nonlinear uncertain systems, of which the internal uncertainty can be characterized by a finite set of functions, is formulated and studied by using an least squares (LS)‐like algorithm to design the feedback control law. For the finite‐model adaptive control problem, this algorithm is proposed as an extension of counterpart of traditional LS algorithm. Stability in sense of pth mean for the closed‐loop system is proved under a so‐called linear growth assumption, which is shown to be necessary in general by a counter‐example constructed in this paper. The main results have been also applied to parametric cases, which demonstrate how to bridge the non‐parametric case and parametric case. Copyright © 2006 John Wiley & Sons, Ltd.     

On some parameter estimation algorithms for the nonlinear exponential autoregressive model

Modeling an exponential autoregressive (ExpAR) time series is the basis of solving the corresponding prediction and control problems. This paper investigates the hierarchical parameter estimation methods for the ExpAR model. By the hierarchical identification principle, the original nonlinear optimization problem is transformed into the combination of a linear and nonlinear optimization problem, and then, we derive a hierarchical least squares and stochastic gradient (LS‐SG) algorithm. Given the difficulty of determining the step‐size in the hierarchical LS‐SG algorithm, an approach is proposed to obtain the optimal step‐size. To improve the parameter estimation accuracy, the multi‐innovation identification theory is employed to develop a hierarchical least squares and multi‐innovation stochastic gradient algorithm for the ExpAR model. Two simulation examples are provided to test the effectiveness of the proposed algorithms.     

单载波频域均衡系统的信道估计技术

介绍了基于IEEE802．16a标准的单载波频域均衡(SC-FDE)系统的原理和频域均衡的过程，并采用LS算法对信道估计进行了简单仿真。     

并网逆变器用LCL滤波器新型有源阻尼控制

针对并网逆变器用LCL输出滤波器的不稳定性,在分析LCL滤波器无源阻尼控制算法的基础上,提出了一种基于电容电流估计的三闭环LCL滤波器有源阻尼控制算法.算法引入电容电流内环以抑制系统不稳定的现象,电容电流信号通过估计过程得到.定性分析了提出算法的稳定性.因省去了以往无源阻尼控制算法中用以抑制系统谐振而增加的阻尼电阻,而...     

Phasor Estimation in the Presence of DC Offset and CT Saturation

A hybrid algorithm for phasor estimation is proposed that is immune to DC offset and current transformer (CT) saturation problems. The algorithm utilizes partial sum (PS)-based and multistage least-squares (MLS)-based methods before and after CT saturation is detected, respectively. The MLS-based method is initiated when the third difference of the secondary current detects the start point of the first saturation period. The determination of each saturation period is based on the sum of the secondary current from the start point of the first saturation period. A least-squares (LS) technique estimates the DC offset parameters from the single-cycle difference of the secondary current in the unsaturated periods. Removal of DC offset from the secondary current yields the sinusoidal waveform portion. Finally, the LS technique is used once again to estimate the phasor from the sinusoidal waveform portion. The performance of the algorithm was evaluated for a-g faults on a 345-kV 100-km overhead transmission line. The electromagnetic transient program was used to generate fault current signals for different fault angles and remanent fluxes. The performance evaluation shows that the proposed algorithm accurately estimates the phasor of a current signal regardless of DC offset and CT saturation. The paper concludes by describing the hardware implementation of the algorithm on a prototype unit based on a digital signal processor.     

基于时频双域迫零的增强OFDM移动信道估计方法

本文主要研究移动环境中的OFDM信道估计技术,通过在多普勒域将带限频率以外部分迫零,在多径域将噪声抽头迫零,传统的最小二乘（LS）算法的性能可以得到进一步的提高。本文提出一种基于速度自适应的重要抽头选择算法,能够有效减少传统选择多径时的误选漏选概率。仿真结果表明,本文所提出的自适应时频双域迫零降噪算法可以有效提高移动无线信道的估计精度,进而提高OFDM系统的性能。     

遥测速变参数自适应谱估计方法研究

针对靶场遥测速变信号处理对高分辨谱及非平稳信号处理的要求,在高分辨谱估计方法基础上,研究了最小均方准则(LMS)和最小二乘准则(LS)的自适应格型滤波算法,实现了LMS自适应格型滤波最大熵谱估计和LS自适应格型滤波ARMA谱估计.利用本研究方法对仿真数据和试验数据进行了大量的实验研究,并与经典周期图法、Burg最大熵法、Yule-Walker自回归法获得的谱估计进行对比.实验表明该方法适用于遥测速变信号的处理和分析,在改善谱分辨率的同时提高了算法的效率,为非平稳信号分析提供了时变谱估计方法,为深入研究导弹飞行振动特性、性能评估或故障诊断提供了新的分析工具.     

Exact initialization of the recursive least‐squares algorithm

We present an initialization procedure for the recursive least‐squares (RLS) algorithm that has almost the same form as the RLS algorithm itself and which is exact in the sense that the so‐initialized RLS estimate coincides with the batch LS estimate as soon as the latter exists. Copyright © 2002 John Wiley & Sons, Ltd.     

Estimating Of Steady State Voltage And Frequency Of Power Systems From Digitized Bus Voltage Samples

ABSTRACT

This paper presents a new efficient technique for estimating the voltage and frequency of power systems from digitized bus voltage samples. The new algorithm is based on the least absolute value error (LAV) approximation technique. The proposed algorithm is superior to the well-known least error squares technique (LS) used in Ref. 1, when the voltage samples contain bad data or noise in instrumentation and telemetry. The algorithm was tested on off-line simulated data. Results of the comparison between the least error squares technique and the new proposed algorithm are reported in this paper.     

谐波和间谐波三参数识别的SSI-LS方法

为精确检测谐波和间谐波的三参数,提出了基于随机子空间辨识（Stochastic Subspace Identification, SSI）与最小二乘（Least Square）法的谐波和间谐波三参数检测方法。运用奇异值差值法确定SSI-LS算法的阶数;利用SSI算法直接对原始含噪信号精确检测出各谐波和间谐波分量的频率;当信噪比大于20 dB时,应用最小二乘法对各谐波和间谐波分量进行幅值和相位的估计,从而实现了谐波和间谐波的三参数识别。分别针对含有噪声和直流分量的谐波和间谐波数值仿真信号和频率相近且幅值相差百倍的谐波和间谐波信号作谐波和间谐波的三参数识别。仿真分析表明该方法抗噪声能力强、检测精度高、计算速度快,尤其是对信号中各谐波和间谐波分量的相位检测精度高、对频率相近且幅值相差百倍的谐波和间谐波信号具有较高的分辨率,为电力系统谐波和间谐波的精确检测提供了新的思路与方法。     

改进的主动频率偏移孤岛检测算法

针对被动孤岛检测存在检测盲区以及传统主动频率偏移(AFD)孤岛检测算法会带来有功电流波动的不足,提出一种改进的AFD孤岛检测算法。该算法通过控制无功电流的大小来实现电流频率偏移,从而实现孤岛状态下接入点电压频率的正反馈,进而检测出孤岛。为了减小无功电流对电力系统的污染,需将该AFD算法与传统的被动孤岛检测算法结合使用。仿真和实验结果表明,该孤岛检测算法不仅消除了被动孤岛检测算法在负载功率和逆变器功率匹配时存在的检测盲区,而且克服了传统AFD算法有功电流波动的缺点,提高了直流母线电压的稳定性。     

基于改进遗传算法的无源滤波器设计

利用遗传算法对无源滤波器电路参数进行全局优化并对算法进行改进。在标准遗传算法的基础上,引入了自适应的遗传操作和最优保存策略。相对于经典滤波器设计方法,可不依赖先验知识而获得近似最优解,自动化程度高。仿真结果表明改进后的算法性能良好。     

基于Spark平台的推荐算法研究

传统的推荐系统无论是在处理效率还是推荐准确度上都有一些不足之处,Spark作为新一代的数据处理的分布式框架,在数据处理效率上相较于hadoop有飞速的提升。主要针对Spark平台上的主流推荐算法ALS算法只考虑隐含信息而忽略了相似度信息的缺点展开研究,目的是进一步提高ALS算法的推荐精确度。通过将用户的相似度信息加权到ALS算法评分预测的公式中对ALS算法进行改进,并在Spark平台上使用MovieLens数据集验证改进前后的ALS算法的均方根误差(RMSE)值。实验证明,改进后的ALS算法的RMSE值更小,推荐的精度更高。     

Improved average consensus algorithm based distributed cost optimization for loading shedding of autonomous microgrids

This paper addresses a new distributed cost optimization (DCO) method for load shedding (LS) of an islanded microgrid considering cost. A two-layer improved average consensus algorithm (IACA) of multi-agent system (MAS) is proposed, and the consensus characteristic of which is analyzed in detail. With the global information discovered in the first layer of the IACA, the DCO of LS can be solved by using the synchronization processing of the IACA in the second layer. PSCAD/EMTDC-based simulation models are built to study the value settings of consensus constants and the performances of the proposed DCO method. Simulation results verified the convergence improvement of the IACA and the effectiveness of the proposed DCO.     

无线测向定位算法及实现系统

随着无线通信技术和卫星导航技术的发展,无源定位技术成为电子对抗领域的热点问题。主要对无源定位技术方法进行了分析,重点分析了无源测向定位相关理论,并提出了测向定位与几何联立的新算法。通过地面探测系统进行该算法的验证,得到目标辐射源的绝对误差在经度上为1.16°×10~(-4),纬度上为1.04°×10~(-4),其相对误差在经度上为9.77×10~(-7),纬度上为3.23×10~(-6)。实际误差距离通过MATLAB计算得出为26.67 m。通过实验验证与结果分析,对于不定时目标辐射源,该算法具有很好的有效性与可行性。