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本文通过分析风力发电机遭受的年平均直击雷频率计算公式,指出其存在的缺陷,并通过对比两种接闪模型,根据雷击距的概念,为风力发电机提供了一个电气-几何模型,用于计算一个已知雷击大地密度区域可能遭受的雷击风险。以一个典型的风力发电机为例,计算被一个负地闪击中的概率,以便更好地对风力发电机的雷击风险进行评估,同时为风力发电场的选址提供一个科学的数据。 相似文献
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接闪器的雷闪接触点与防雷建筑之间保持足够的空气间隙距离,可以防止雷闪接触点的雷电位击穿该空气间隙,并减弱雷击电磁脉冲的影响,确保防雷建筑及其内部人员、设备的安全。 相似文献
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基于传统的接闪网网格尺寸面积及保护范围作假设模型,运用滚球法提出平行线—薄板模型,得到接闪网网格宽度与其保护范围的相关性。对模型修正后,提出了电流源散流模型。指出防雷建筑物接闪网网格宽度满足一定数值且合理设置引下线的情况下,网格长度可以无限延伸。 相似文献
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众所周知,建筑物防雷装置应由接闪器、引下线和接地装置3部份组成。将雷电流引至接地装置的接闪器,常见有避雷针或避雷带。笔者在北京航华科贸中心工程中,实施了一种少见的技术做法:利用建筑物自身的金属屋面板作防雷接闪器。 1.几种技术方案 该工程为建有6幢高层、超高层写字楼、高级公寓的建筑群,其中3幢为坡屋顶,采用钢结构框架,其上敷盖YB—W—5125型钢金属薄压型板,楼高度分别为83.6m、74.5m和74.5m。 由于屋面坡度较大,首次提出的坡 相似文献
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通常认为避雷针端部曲率半径越小,端部附近电场越强,雷击接闪效能越强;一些学者认为不同高度避雷针端部曲率半径对接闪效能的影响不同;还有学者则认为曲率半径对接闪效能没有影响。因此,研究避雷针端部曲率半径是否影响其雷击接闪效能对新型避雷针的设计研发和工程应用具有指导意义。论文开展了针–板间隙下不同曲率半径避雷针流注放电与先导放电模拟实验,结合实验室针–板间隙和避雷针–雷云超长间隙放电的空间电场计算,对曲率半径是否影响避雷针迎面流注和迎面先导接闪效能进行了分析。结果表明,不同曲率半径下避雷针流注放电起始时刻差异<0.22μs,发展速度差异<5%;当曲率半径小于临界半径时,避雷针连续稳定先导起始时刻差异<1.27μs,发展速度差异小于5%;自然雷电环境下,避雷针端部曲率半径的变化仅对端部附近区域电场产生影响。研究表明,避雷针端部曲率半径对其雷击接闪效能几乎不产生影响。 相似文献
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输电线路作为电力系统的关键组成部分,保持其安全稳定运行至关重要。据统计,由输电线路故障引起的电力系统事故占多数,做好输电线路的防雷工作对我国经济的持续发展具有重要意义。首先研究了雷电相关参数以及防雷计算的基本方法,对比各算法的优缺点,然后结合环境因素,提出了基于改进电气几何模型法的地区差异化防雷算法。针对不同地形条件,提出了线路绕击跳闸率的计算方法,并使用MATLAB图形用户界面,开发了一款差异化防雷辅助计算软件,可以实现不同电压等级和不同地区年雷击次数、击杆率、耐雷水平、绕击跳闸率、输电线路雷击跳闸率的快速准确计算。 相似文献
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基于响应面方法的汽轮机叶片静动频概率设计及敏感性分析 总被引:1,自引:0,他引:1
考虑随机因素的影响,对叶片的固有振动特性进行概率分析和设计是叶片动强度可靠性设计的基础。文中以某试验台用汽轮机等直叶片为研究对象,考虑几何参数(包括长度、宽度、厚度)、材料参数(弹性模量,密度)和转速的随机性,通过有限元参数化建模,将确定性有限元方法(FEM)、响应面方法(RSM)和Monte-Carlo模拟法相结合,从而获得了叶片静频、动频的统计特性和累积分布函数;同时考虑随机变量的梯度和离散范围对静、动频的影响,通过概率敏感性分析,定量地判断出叶片静、动频对随机输入变量的敏感性;通过绘制叶片静、动频与输入变量的散点图,定量地分析了如何改变随机变量以调整静、动频率的方法。计算结果表明,FEM-RSM-Monte Carlo方法计算量小,速度快,拟合精度高,是叶片动强度可靠性分析的可选方法。 相似文献
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Adaptive control of complex systems with unknown dynamics and input constraint: Applied to a chaotic elastic beam 下载免费PDF全文
Mohammad Pourmahmood Aghababa 《International Journal of Adaptive Control and Signal Processing》2018,32(2):213-228
Owing to the limitations of system identification and modeling techniques, there is usually some unknown dynamics in the mathematical models of the complex systems. In addition, external perturbations can affect the chaotic systems' responses and may destroy the desired control purpose. Consideration of such uncertain dynamics and external fluctuations in control applications is important in research and practice. On the other hand, because of the limited operation of control actuators, most of the practical implementations of control systems are forced with some input constraints. Therefore, this paper investigates the control problem of uncertain autonomous and/or nonautonomous complex chaotic systems in the presence of input saturation. The upper bounds of the unknown dynamics, modeling uncertainties, external perturbations, and the parameters of the saturation function are assumed to be unknown in advance. To make a fast control response, an adaptive nonsingular terminal variable structure controller is proposed to assure the finite‐time stability of the equilibrium states. Rigorous stability analysis is performed to prove the correct performance of the designed control algorithm. Numerical simulations on the unified system and a chaotic elastic beam model are developed to demonstrate the usefulness of the introduced adaptive control strategy. It is worth to notice that the derived adaptive nonsmooth sliding mode approach is general and it can be easily adopted for controlling of a wide class of uncertain MIMO nonlinear systems. 相似文献
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在分析电能计量装置的综合误差的基础上 ,提出了影响电能计费系统中电能计量精度的新因素 ,并提出了如何减少综合误差的方法 相似文献
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Chih‐Ju Chou Chun‐Yao Lee Chun‐Chi Chen 《IEEJ Transactions on Electrical and Electronic Engineering》2014,9(6):605-613
At first, this paper proceeds with a survey of a dam to help understand the defects of existing lightning protection within the reservoir, using an actual drilling method for geological exploration and research at the base. The soil samples acquired by the drilling, testing, analysis, and computation indicate the distribution of geological soil layers and earth resistivity. The average earth resistivity values, measured by the Wenner four‐pin method, are used as auxiliary data. The design values of the earth resistivity are decided by the comparison and analysis of both data given above. In this paper, the optimal objective function is based on the minimum total costs of the grounding system and may satisfy all constraints, including the safety evaluation of the grounding system as well as the planning of ground material. The particle swarm optimization (PSO) method is used in searching for the optimal solution for a grounding system. Finally, through a practical case of grounding system planning, we show that the PSO method is indeed better than the conventional planning and design (CPD) method. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
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《IEEJ Transactions on Electrical and Electronic Engineering》2017,12(4):536-545
Demand response (DR ), which is used to shave the peak demand for securing supply reliability in a power system, is one of the promising constitutions for the end users. In a commercial building (COB ), the most popular adjustable DR resource (DRR ) is the chiller system. More specifically, its power consumption can be reduced by thermal mass control (precooling) in a specified DR duration. On the other hand, installation of energy storage systems (ESSs ) is going on at an accelerated pace because of its high economic efficiency. ESSs have been used for peak‐shift operation under the time‐of‐use (TOU ) tariff. However, ESS can be also used as an attractive DRR because it can reduce the net load by discharging the ESS for a specified DR duration. Based on this background, this paper presents a method for determining the optimal DR capacity in a COB with a chiller system and ESS . In the proposed scheme, the optimal DR capacity (kW ) can be determined so that the total expected cost of a COB becomes minimum by using the chiller system and ESS while avoiding the DR penalty threat adopted in the Korean DR market. Uncertainty in the ambient temperature, the amount of reduction, and DR durations are considered as the scenarios. The estimation and economic evaluation of the proposed scheme is ascertained through case studies. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
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提出一种基于MonteCarlo仿真和静态电压稳定域方法的概率最大输电能力(TTC)分层计算模型,实现了综合考虑负荷、发电机出力和设备故障不确定性因素的概率TTC快速计算。针对设备故障引起的电压稳定域边界的改变,利用阻尼牛顿法从故障前稳定域边界点直接计算得到故障后稳定域边界点,用切平面描述故障后稳定域的局部从而快速得到该故障情况下的TTC。 相似文献