电力系统非线性自适应励磁控制设计

考虑了发电机参数的不确定性,根据滤波后的线性参数化模型,通过使参数更新的方向与关于参数的预测误差平方的梯度方向相反,提出了一种在线自适应参数估计非线性励磁控制方法。数字仿真试验表明,设计的非线性自适应控制律具有较强的参数自适应能力,控制器以发电机端电压为输出,保证了系统内动态的稳定。     

Die Erhöhung des Nutzerkomforts von Fußgängerbrücken mit Massendämpfern am Beispiel des August‐Wilhelm‐Stegs in Oranienburg

Aufgrund ihrer schlanken Bauweise gelten viele Fußgängerbrücken bei personeninduzierten Belastungen als schwingungsanfällig. Die eventuelle Ausstattung einer Brücke mit zusätzlichen Dämpfungsmaßnahmen sollte bereits in der Planungsphase berücksichtigt werden, damit bei Gewissheit, dass Maßnahmen notwendig sind, die Fertigstellung und Eröffnung der Brücke nicht verzögert wird. Im vorliegenden Beitrag wird am Beispiel des August‐Wilhelm‐Stegs in Oranienburg das Vorgehen zwischen Erkennen einer möglichen Schwingungsanfälligkeit, Prüfung der Erforderlichkeit schwingungsdämpfender Maßnahmen, Auslegung und Einbau sowie Überprüfung der Wirksamkeit erläutert. Dabei werden insbesondere die praktischen Aspekte bei der Auslegung der Massendämpfer erläutert. The increasing comfort of footbridges with mass dampers is exemplary shown with the August‐Wilhelm‐Steg in Oranienburg, Germany. Many footbridges are susceptible to pedestrian induced vibrations due to their slender design. Hence, an equipment with additional damping devices on demand should be considered already in the preliminary design phase to avoid unnecessary delays of the erection and opening, if the damping devices are required. In this article the procedure of identifying a potential vibration susceptibility, checking the necessity of damping devices, design and installation as well as checking the working efficiency of them are explained using the example of the August‐Wilhelm‐Steg in Oranienburg. Particular emphasis is laid on the practical aspects when designing tuned mass dampers.     

基于虚拟同步发电机的微网逆变器控制策略研究

本文研究了一种基于虚拟同步发电机算法的微网逆变器控制策略。根据同步发电机的本体数学模型、一次调频及无功电压调节特性,分别设计了虚拟同步发电机算法、虚拟原动机调节及励磁电流调节模块,同时通过电压电流双环控制,使逆变器输出的电压幅值和频率具有良好的下垂特性、可调的转动惯量及较好的跟踪性能,从而提高了系统的稳定性和可靠性。此外在并网系统中要求频率控制精度高及实时响应的情况下,本文还对虚拟原动机调节模块进行了改进,实现了频率的无误差控制,提高了频率控制的精度和响应速度。最后在matlab/simulink中进行了模型的搭建和仿真,逆变器输出电压很好的模拟了同步发电机的外特性,单相电压的畸变率仅为0.2%,引入改进原动机调节模块后,输出频率不随负荷的变化发生偏移。最终稳定在49.98Hz,验证了本文理论分析的正确性和可行性。     

Plasma-assisted ignition and combustion

The use of a thermal equilibrium plasma for combustion control dates back more than a hundred years to the advent of internal combustion (IC) engines and spark ignition systems. The same principles are still applied today to achieve high efficiency in various applications. Recently, the potential use of nonequilibrium plasma for ignition and combustion control has garnered increasing interest due to the possibility of plasma-assisted approaches for ignition and flame stabilization. During the past decade, significant progress has been made toward understanding the mechanisms of plasma–chemistry interactions, energy redistribution and the nonequilibrium initiation of combustion. In addition, a wide variety of fuels have been examined using various types of discharge plasmas. Plasma application has been shown to provide additional combustion control, which is necessary for ultra-lean flames, high-speed flows, cold low-pressure conditions of high-altitude gas turbine engine (GTE) relight, detonation initiation in pulsed detonation engines (PDE) and distributed ignition control in homogeneous charge-compression ignition (HCCI) engines, among others. The present paper describes the current understanding of the nonequilibrium excitation of combustible mixtures by electrical discharges and plasma-assisted ignition and combustion.     

一起空压机未遂事故原因解析与对策

分析解决了空气压缩机因直连拖动同步电动机投励时间滞后引起的启动失败故障,以及设备制造、安装质量造成的运行安全隐患,提出了空压机电气设计、安装与运行安全对策措施。     

汽轮发电机与工厂电网中的无功补偿

汽轮发电机是工厂中常见的利用余热发电的设备,它对工厂电网无功功率的调节有非常重要的意义.文章对无功功率的概念、作用、负面影响和补偿方法进行了简要描述.重点介绍了工厂中汽轮发电机对无功功率调节的原理和方式,并分析了无功功率异常与发电机励磁故障之间的联系.     

60Hz与50Hz中小型汽轮发电机之比较

阐述了中小型60 Hz空冷汽轮发电机的方案设计,针对30 MW以下的中小型机组,从设计角度与国内50 H z同等容量的产品进行比较,探讨两种频率发电机主要电气性能参数及结构特点的异同。     

千兆瓦静态励磁发电机高频轴电流调谐滤波器研究

在大型发电机广泛应用的静态励磁系统晶闸管换相引发幅值较高的高频轴电压脉冲,使得轴电压成为影响大型发电机安全可靠运行的主要问题之一。文章在现场实测1 000 MW发电机轴电压的基础上,建立了基于Matlab Simulink Power System的大型静态励磁发电机轴电压仿真模型,分析得出静态励磁系统输出共模电压基频及其奇次高频谐波轴电压应为大型汽轮发电机轴电压的防治重点,研究提出了一种选择滤除千兆瓦静态励磁发电机高频轴电流的调谐滤波器,仿真表明该滤波器对所选择的高频轴电流滤除效果良好。     

Identification of stiffness and periodic excitation forces of a transverse switching crack in a Laval rotor

This work involves model‐based identification of rotor crack. A Laval rotor with a transverse surface crack and disc unbalance is studied. Viscous damping, disc eccentricity and additive stiffness due to crack are the parameters considered for identification. The linear system equations of motion together with the switching crack excitation function are used for developing the identification algorithm. Furthermore, the algorithm is extended for a novel attempt of estimating the coefficients of switching crack excitation function, which constitute the crack excitation force. This estimation could be used to provide valuable information on the actual opening/closing profile of the switching crack. The proposed algorithms are illustrated through numerical examples. They are tested against measurement noise and found to be reasonably robust.     

Intranuclear cascade model for 50-MeV-region (p,p′x) reactions over a wide target mass range

In our previous study, the applicable range of the intranuclear cascade model was successfully extended to lower incident energy (p, p′x) reactions by introducing trajectory deflections and low-energy-loss process due to collective excitations. However, the model's validity was confirmed only for a ⁵⁶Fe target. In the present work we widen the applicable range of masses of the target nucleus. First, we derive an expression for the response function, which gives the probability of collective excitation strengths, to fit the distorted-wave Born approximation results as a function of the target mass number and the beam energy. Second, the barrier transmission coefficient was investigated. An expression with a modified Gamow penetration factor was chosen from four phenomenological forms of one-dimensional barrier transmission coefficients. Calculations with the proposed model followed by a generalized evaporation model were carried out for double-differential cross sections of (p, p′x) reactions at 30–60 MeV. Although the response function and the transmission coefficient were only parameterized approximately, the proposed model showed good agreements with experimental observations for a variety of nuclear targets from ¹²C to ²⁰⁹Bi.