关于干式空心并联电抗器烧损问题的研究

应用理论分析、计算机模拟和现场试验等方法，对干式空心并联电抗器连续烧损的事故原因进行了较为系统全面的研究，指出导致电抗器烧损事故频繁发生的主要原因是在设计接线和参数配合上存在问题。提出了用调整设备参数及加装并联氧化锌避雷器等技术措施限制并联电抗器匝间过电压的方法，从而解决了这一困扰电网安全运行的问题。     

A technique of parallel connections of pulsewidth-modulated NPC inverters by using current-sharing reactors

The neutral-point-clamped (NPC) PWM inverters have many advantages such as the ability to operate the motor with nearly sinusoidal current waveforms. For this reason, in larger-capacity inverter systems, NPC PWM inverters using the GTOs, etc., have also been put into practical use because of great advantages to large-capacity ac motor drives such as lower ripple currents and higher output voltages. With the spread of applications, still larger-capacity inverters also are expected. However, since the capacities of such switching devices are insufficient, a certain technique and controlling method are proposed for the parallel connections of NPC inverters. The output voltage waveforms of the proposed inverter have certain voltage levels, and thus it is anticipated that it will be difficult to analyze the output harmonics. For such waveforms of output voltage and current-sharing reactor, a frequency analysis approach is described whose results are verified by experiments.     

光孤子通信及其发展动态

介绍了光孤子的形成原理和光孤子通信系统，总结了光孤子通信发展动态，展望了光孤子通信技术发展前景。     

Polarized and non-polarized saturable reactors

Contents The present paper analyses the performance of the saturable core with and without external polarization. For the circuit without external control, positive and negative saturation are discussed; for the circuit with d. c. excitation three cases are pointed out: underexcitation; critical ecxitation and overexcitation. The various saturation and desaturation angles are computed and their physical meaning is discussed along with the relevant explanations pertaining to current amplification. Experimental results are quoted.

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Übersicht Die vorliegende arbeit untersucht die Wirkungsweise der gesättigten Drossel mit und ohne äußerer Gleichstromvormagnetisierung. Für die Grundschaltung ohne äußerer Polarisierung, wird die Wirkungsweise bei positiver und negativer Sättigung erklärt; für die Schaltung mit äußerem Gleichstrom werden die folgenden drei Fälle untersucht: nicht-kritische Erregung; kritische Erregung; überkritische Erregung. Die verschiedenen Sättigungs- und Entsättigungswinkel sind errechnet und deren physikalische Deutung ist erläutert. Ferner wird die Stromverstärkung untersucht und zum Schluß werden experimentelle Ergebnisse vorgelegt.

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Nomenclature A Cross section of core - C Integration constant - Mean value of load current - I _c Control current - I _cs Saturation control current - i _a Instantaneous load current - K _i Current amplification factor - L _a Power-coil self-inductivity - l Magnetic path length - N _a Number of power-coil turns - N _c Number of control-coil turns - R _L Load resistance - Supply voltage, maximum value - Saturation voltage - t Time - ₁ Positive saturation angle - ₂ Positive desaturation angle - ₁ Negative saturation angle - ₂ Negative desaturation angle - Dummy variable - Permeability - Relative voltage - Magnetic flux - _s Saturation magnetic flux - w Angular frequency of supply     

Ultrahigh-speed long-distance TDM and WDM soliton transmissiontechnologies

Recent progress on time-division multiplexed (TDM) and wavelength-division multiplexed (WDM) soliton transmission is described, in which dispersion management (DM) plays an important role in increasing the power margin and the dispersion tolerance. The characteristics of the DM soliton are compared with those of return-to-zero (RZ) and nonreturn-to-zero (NRZ) pulses. With a small dispersion swing, the system can still be described as an average soliton with a nonlinear Schrodinger equation (NLSE), whereas with a large dispersion swing, the soliton-like steady-state pulse becomes a chirped Gaussian pulse, in which the master equation is closer to a linear Schrodinger equation (LSE) with a parabolic potential well. An in-line modulation scheme up to 80 Gb/s per channel and its two-channel WDM transmission over 10000 km are described. A 640-Gb/s (40 Gb/s×16 channels) WDM soliton transmission over 1000 km is also reported with a DM single-mode fiber, without the use of in-line modulation. Finally, dark soliton transmission at 10 Gb/s over 1000 km is described as a different nonlinear pulse application     

Phase jitter in single-channel soliton systems with constantdispersion

The phase jitter of optical solitons in single-channel communication systems with constant dispersion and distributed amplification is studied in detail. The variational method is used to derive equations that model phase jitter caused by amplifier noise. These equations are solved analytically. Simple formulas are obtained for the phase variance of an ensemble of solitons, which together cover the entire range of practical transmission distances. These formulas are validated for parameters of current interest by numerical solutions of the nonlinear Schroedinger equation     

Linda and parallel computing-running efficiently on parallel time

Linda, a set of commands that can be added to an arbitrary programming language N to form the N-Linda parallel programming language, is described. Linda enables users to use parallelism efficiently for many applications on a wide range of machines. Linda helps parallel languages meet the following four goals: (1) to augment but not replace the (serial) programming language most suitable to solve the problem at hand; (2) to support both process creation and interprocess communication; (3) to be portable; and (4) to be easy to use     

Influences of polarization-mode dispersion on soliton transmissionsystems

In soliton transmission systems with polarization-mode dispersion (PMD), random birefringence causes solitons to generate dispersive waves, which degrade soliton transmission systems in two aspects. First, the dispersive waves cause solitons to continuously lose energy, thus induce pulse broadening. Second, the dispersive waves interact with other soliton pulses and cause distortion of a sequence of soliton pulses. Both of these effects induce performance degradation of soliton transmission systems. We study these effects of PMD on both conventional and dispersion-managed (DM) soliton transmission systems. We show that, for conventional soliton systems, although single pulse has robustness to PMD, the interplay between the dispersive waves and solitons would seriously distort a sequence of pulses and make soliton systems worse than linear systems if all other transmission impairments are neglected. We also show that DM solitons are more robust to PMD than both conventional solitons and linear systems due to the enhanced nonlinearity and less sensitivity of DM solitons to perturbations. We further point out that soliton collision-induced polarization scattering causes additional timing jitter and system performance penalty in WDM soliton systems     

电容器组串联电抗率优化选择模型和算法研究

在简要分析了电容器对谐波电流放大机理的基础上,面向整个电网研究了集中补偿电容器组串联电抗器电抗率的优化配置问题,建立了该问题的内、外双层优化数学模型.内层优化用于搜索给定电抗率配置方案下导致电网谐波畸变最严重的运行方式,外层优化用于确定电抗率的最优配置方案并利用内层优化的结果判断配置方案是否可行.针对内层优化模型中控制变量的二进制特性,提出了基于BPSO的优化算法,并给出了详细的算法流程.对IEEE14节点系统进行了算例分析,计算结果表明了所提模型及算法在抑制谐波放大方面的作用.     

电容器组串联电抗率优化选择模型和算法研究

在简要分析了电容器对谐波电流放大机理的基础上,面向整个电网研究了集中补偿电容器组串联电抗器电抗率的优化配置问题,建立了该问题的内、外双层优化数学模型。内层优化用于搜索给定电抗率配置方案下导致电网谐波畸变最严重的运行方式,外层优化用于确定电抗率的最优配置方案并利用内层优化的结果判断配置方案是否可行。针对内层优化模型中控制变量的二进制特性,提出了基于BPSO的优化算法,并给出了详细的算法流程。对IEEE14节点系统进行了算例分析,计算结果表明了所提模型及算法在抑制谐波放大方面的作用。     

Decomposition of benzene using alumina-hybrid and catalyst-hybridplasma reactors

In order to investigate the effects of alumina and metal ions in plasma discharge, plasma reactors packed with a mixture of BaTiO₃ pellets and porous Al₂O₃ pellets (alumina-hybrid reactor), and with a-mixture of BaTiO₃ pellets and metal-supported Al₂O₃ pellets (catalyst-hybrid reactor) were examined for oxidation of dilute benzene in air. It was found that the oxidative decomposition of benzene was enhanced by concentrating benzene on the Al₂O₃ pellets and the catalyst pellets. Furthermore, the selectivities to CO ₂ in the alumina-hybrid reactor and the catalyst-hybrid reactors were higher than those in the plasma reactor packed with BaTiO ₃ pellets alone. In particular, the selectivities to CO₂ in the catalyst-hybrid reactors using Ag, Co, Cu and Ni/Al₂ O₃ were higher than those from the alumina-hybrid reactor. In addition, the presence of the alumina and catalysts suppressed the formation of N₂O     

Multichannel soliton transmission and pulse shepherding inbit-parallel-wavelength optical fiber links

We study basic principles of the bit-parallel-wavelength (BPW) pulse transmission in multichannel single-mode optical fiber links for high-performance computer networks. We develop a theory of the pulse shepherding effect that allows simultaneous propagation of pulses in parallel bit slots by binding them into a multicomponent BPW soliton. We describe families of the BPW solitons and bifurcation cascades in a system of N incoherently coupled nonlinear Schrodinger equations that model the multichannel multiwavelength transmission in a single-mode optical fiber. We demonstrate high robustness of the composite BPW solitons, due to their underlying linear stability, to a moderate pulse walkoff     

并联电容器的谐波放大及对策

并联电容器是目前电网中普遍应用的无功补偿装置，用于提高功率因数，改善电能质量。由于电容器的阻抗呈容性，易与电力系统中的谐波产生相互影响，发生谐波的并联谐振和电容器对谐波电流的谐波放大，造成电容器和电气设备的损坏。通过实例分析了谐波对电容器的危害及并联电容器对谐波放大作用，应合理地配置电容器和电抗器，以避免电气参数匹配发生谐振，控制谐波电流放大。     

并联电抗器在超(特)高压电网中应用及发展

研究了超（特）高压输电线路在长线电容效应、不对称接地和突然甩负荷等各种工况下工频过电压的产生．提出了采用并联电抗器进行无功补偿限制工频电压升高的措施。分析了并联电抗器在超（特）高压输电线路单端供电与双端电源供电情况下抑制过电压的作用。分析比较了裂心式、磁饱和式及变压器式3种超（特）高压可控并联电抗器的基本工作原理、主要功能和特性．指出裂心式可控电抗器具有非线性伏安特性,兼具大幅度限制操作过电压功能：磁饱和式电抗器的伏安特性与普通电抗器相近,结构简单、控制方便,具有优良的技术经济综合指标：变压器式可控电抗器与磁饱和式可控电抗器相比。谐波电流更小、响应速度更快、功率损耗更小。同时指出了特高压并联电抗器与超高压并联电抗器相比的特殊性。     

Selecting ratings for capacitors and reactors in applicationsinvolving multiple single-tuned filters

This paper focuses on the selection of ratings for capacitors and air-core reactors used in multiple single-tuned harmonic filter configurations. Digital transient simulations of an example power system demonstrate the exceptionally high voltage and current stresses placed upon filter components in these configurations. Design guidelines for increasing the component ratings to account for the extra stresses are described. A comparison between traditional rating methods and the proposed methods are presented for the example system     

The compatibility of n-ports in parallel

A mathematical test for the compatibility of n-ports in parallel is given. It is shown that the well-known Brune tests are sufficient but not necessary.     

三极管并联使用的分析

从目前空调实际应用的角度,分析了ULN2003驱动电路两路并联运行时可能造成电流不均衡的各种因素。介绍了选择三极管并联运行的思路和原则,提出了保证三极管并联可靠运行的设计方法。     

空心电抗器计算机辅助设计系统的开发

在提出合理的空心电抗器计算机辅助设计模型的基础上，用VisualC 开发了Windows平台下空心电抗器计算机辅助设计系统。软件开发过程中采用了面向对象的设计方法，主体计算利用多线程技术实现，利用数据库技术实现资源共享和数据维护，图形绘制选用OpenGL(开放图形语言)。