有源电力滤波器控制时延的研究

针对有源电力滤波器(APF)系统存在的延时情况,分析了延时对APF补偿效果的影响并提出了解决的办法.通过建立APF系统的网络阻抗传递函数,利用pade近似式对其进行简化分析,得到了不同时滞情况下该网络频率响应特性.由此分析时延对系统性能的影响并说明在控制中不能忽略延时的存在.由于固有时延只能减小不能根除,只能从消除时延对补偿效果影响的角度出发,提出了一种利用谐波的周期性特点来延迟补偿谐波输出的方法提高补偿效果.仿真结果表明了该方法的正确性和有效性.     

油中局部放电脉冲波形的测量与特性分析

设计了具有较宽频率响应范围的紧凑型测试电路,结合高速数字示波器ＴＤＳ７５４Ｃ对油中的局部放电脉冲波形进行了测量。为了验证测试电路具有足够的频率响应范围,利用高速脉冲发生器产生的陡脉冲对检测阻抗进行了检验。结果表明测量系统可以满足要求,利用该系统对３种缺陷模型进行了测量,结果表明油中局部放电脉冲均有振荡成分存在,特别是对某些类型的局部放电,当放电比较剧烈时,会有放电脉冲群的出现,这种情况要求传统的测     

五軸組合机床无触点程序控制系統

指命发生器及逻辑控制部件,常常是工业无触点程序控制系统(或静止开关控制系统)中的主要组成部分.通过工业试验的验证,本文介绍了利用无触点元件设计这两个部件的方法,并且提出了一些工业实用的新线路.     

MOBILE ENVIRONMENTAL INFORMATION SYSTEMS

This paper presents the foundations for building mobile environmental information systems (MEISs) requiring an interdisciplinary approach. MEISs require expertise from the disciplines of environmental biology, geography, and mobile technology. MEISs show great promise for the acquisition of environmental information using different mobile devices. Automatic mobile acquisition enables the forwarding of the information to central databases for storage, further processing, and transmission to the mobile devices in a form that is useful to the users. Furthermore, these systems have the potential to be used both in the protection of nature, as well as in recreational use in a way that takes the constraints of nature into account. In this paper we describe the preliminary results of the MINNE project and the prototypes currently under research in the project.     

Multi-point matching along vertical lines in SPOT images

Abstract

Digital elevation models(DEMs) are measured in SPOT images with a digital matching technique. A multi-point matching method developed by the author in earlier work is reformulated from epipolar geometry with the stereoparallaxes in one of the images used as unknowns, to SPOT geometry with the elevations as unknowns. Constraints minimizingthe curvature and the slope of the Computed DEM are investigated, as well as the use of data snooping, low-pass filtering and an alternative logarithmic grey level function. The investigatedimage pair was a stereo SPOT pair from Stockholm, with a rather poor base-to-height ratio of 0·29. All 2073 investigated points were compared with heights obtained from the official Swedish maps, scale 1:10000, with a 5 m contour interval. The results point towards a r.m.s. matching accuracy around 0·15-0·20 pixels in this image material.     

Nanoparticles from a Gold Complex with Sulfite Ion as Ligand: Preparation and Characterization

ABSTRACT

Gold colloidal nanoparticles (GNPs) were prepared by reducing a complex of Au⁺. Na₃Au(SO₃)₂ with sodium citrate. The procedure provides control of the dimension of nanoparticles produced, which is a function of reaction time and concentration of reactants. The nanoparticles were separated by centrifugation and their characteristics and dimensions were studied using UV-Vis and IR spectroscopy and transmission electronic microscopy (TEM).     

Eliminating limit cycles in interconnected systems via describing series

Unlike the customary describing functions, the describing series proposed by Teodorescu (1970, 1971) allow one to compute the equivalent gain vector n of any symmetric non-linearity (non-linearity vector z) by means of a linear transformation n = Hz, where H is a constant matrix, i.e. independent of the non-linearity shape. The inverse transformation z = H ^-1 n is useful for computing non-linear systems with desired steady-state and/or transient properties. Such transformations with constant matrices H, H ^-1 can be combined with a recently proposed criterion for the non-existence of limit cycles in interconnected systems (Skar et al. 1981 a, b) to yield a straightforward design technique.     

A Riccati-like equation arising in suboptimal control

An explicit Formula for the suboptimal control of linear plants has been derived by Teodorescu (1985). Based on this result, the present paper proves that the suboptimal control and trajectory can be obtained by solving a matrix equation of the form XLX + XH + E = 0, where L, H, E are some constant, parameter-dependent matrices. The equation is easier to solve in comparison with the customary Riccati equation. An example is worked out to illustrate the steps of the procedure.     

GITT studies on oxide cathode LiNi1/3Co1/3Mn1/3O2 synthesized by citric acid assisted high-energy ball milling

Layered LiNi_1/3Co_1/3Mn_1/3O₂ was synthesized by a citric acid assisted solid-state method. The structure and electrochemical properties of the LiNi_1/3Co_1/3Mn_1/3O₂ materials were investigated. XRD analysis indicated the as-synthesized LiNi_1/3Co_1/3Mn_1/3O₂ was with the layered α-NaFeO₂ structure. The discharge capacity was about 154 m·Ahg^???1 at 0·1 °C rate in the range of 2·0–4·5 V. The kinetics of the LiNi_1/3Co_1/3Mn_1/3O₂ materials was investigated by the galvanostatic intermittent titration technique (GITT) method. The lithium ion diffusion coefficient of the LiNi_1/3Co_1/3Mn_1/3O₂ was determined in the range of 10^???8??? 10^???9 cm²· s^???1 as a function of voltage of 3·7?4·5 V.     

大规模新能源接入电网连锁故障预防控制策略研究

本文着眼于大规模新能源接入的电网连锁故障预防控制策略研究,在深入分析大规模新能源接入对电网连锁故障影响机理的基础上,提出了适应含大规模新能源的电网连锁故障预防控制策略。该控制策略采用直流灵敏度法甄选出高危线路,并计算出发电功率转移分布系数矩阵,继而采用反向等量配对法,根据发电功率转移分布系数调整发电机组的出力,使得高危线路的负载率得到有效下降,同时保证其他线路负载率维持在重载阈值以下,改善潮流分布,起到预防连锁故障发生的作用。最后通过甘肃酒泉地区电网的仿真分析,进一步揭示了大规模新能源接入对电网连锁故障的影响机理;验证了本文提出的连锁故障控制策略的有效性。