Front solution program for transmission tower analysis

A simpler version of the frontal solution technique suitable for solving structures with large number of members is described here. The facilities of the program are brought out with regard to the re-solution and re-design of a large structural problem. It is used here to solve a transmission tower problem and the resulting stress distribution in the main members are discussed.     

基于复频特性分析的输电线路故障监测方法

为了实现对输电线路的状态监测与故障诊断,提出了基于复频特性分析的输电线路故障监测方法。给定了分段传递函数及其模值的相对偏差的定义,针对输电线路故障的在线监测,建立了基于分段传递函数的故障分析方法,该分析方法的核心是以文中所定义的相对偏差作为反映输电线路状态的故障特征量。运用此方法对单条10kV架空输电线路进行了接地短路故障的仿真研究。仿真实验结果验证了该分析方法在输电线路故障监测中的有效性。     

一对多无线电能传输理论分析研究

磁耦合谐振式无线电能传输具有距离较远、功率大、穿透性强等优点,近年来一对多无线电能传输技术成为无线充电领域的热门研究方向。基于磁耦合谐振式无线电能传输的理论来对一对多无线电能传输系统进行研究,建立电路仿真模型,计算出系统谐振状态下的发射端电流、接收端电流、输出平均功率、电源内阻消耗平均功率、接收端平均功率以及传输效率等数学表达式,并利用MATLAB对模型进行仿真分析。仿真模型通过修改每个接收端回路的耦合系数的比例和另外两个接收端线圈自感的乘积来调节该接收端的功率,可以实现多个接收端的功率分配,并使电能传输效率可达90%以上。     

输电线路杆塔纵向不平衡载荷动态预测模型研究

为了提高输电线路杆塔纵向不平衡载荷控制性能和抗波动冲击能力,提出一种基于耦合波动抑制和机构运动力学分析的输电线路杆塔纵向不平衡载荷预测模型,构建输电线路杆塔的耦合波动载荷测量模型,采用传感器进行输电线路杆塔的力学参数采集,构建输电线路杆塔纵向不平衡耦合动力学模型,运用封闭矢量法建立输电线路杆塔的纵向波动力学控制模型,采用二自由度离散控制方法进行输电线路杆塔的欠驱动机构模型设计,采用双连杆柔性空间力学分配方法,实现输电线路杆塔纵向不平衡载荷动态预测和未知载荷的质量参数辨识,结合相关性耦合波动控制方法,获得载荷的质量参数,实现输电线路杆塔的运动力学分析和动态载荷预测。仿真结果表明,采用该方法进行输电线路杆塔纵向不平衡载荷动态预测的准确性较高,可靠性较好,动态收敛性较强。     

Automatic time series analysis for electric load forecasting via support vector regression

In this work, a strategy for automatic lag selection in time series analysis is proposed. The method extends the ideas of feature selection with support vector regression, a powerful machine learning tool that can identify nonlinear patterns effectively thanks to the introduction of a kernel function. The proposed approach follows a backward variable elimination procedure based on gradient descent optimisation, iteratively adjusting the widths of an anisotropic Gaussian kernel. Experiments on four electricity demand forecasting datasets demonstrate the virtues of the proposed approach in terms of predictive performance and correct identification of relevant lags and seasonal patterns, compared to well-known strategies for time series analysis designed for energy load forecasting and state-of-the-art strategies for automatic model selection.     

Transient analysis and simulation of nonuniform lossy transmission lines

A new formulation of equations of the nonuniform lossy transmission line, in the form of integral equations based on the method of characteristics, has been introduced. Two methods of solution of these equations are presented, the first based on discretization of the integrals and, the second, a method of successive approximations, are presented and the results are compared. The presented integral equations of the line have interesting circuit representations and exhibit wave processes such as reflection, distortion, and attenuation. © 1992 John Wiley & Sons, Inc.     

高压输电线电场检测与距离估计方法设计

针对无人机在有高压输电线的环境中飞行时发生事故的问题,提出了一种远距离电场检测方法。介绍了球型感应式电场传感器的测量原理,并制作电场测量系统。将设计的电场检测系统装载至无人机,在某高压输电线路附近进行电场的测量。测量结果表明:设计电场检测系统能够检测高压输电线附近的电场强度,且电场强度能够反映与高压塔的距离关系。     

A hybrid robust system considering outliers for electric load series forecasting

Electric load forecasting has become crucial to the safe operation of power grids and cost reduction in the production of power. Although numerous electric load forecasting models have been proposed, most of them are still limited by poor effectiveness in the model training and a sensitivity to outliers. The limitations of current methods may lead to extra operational costs of a power system or even disrupt its power distribution and network safety. To this end, we propose a new hybrid load-forecasting model, which is based on a robust extreme-learning machine and an improved whale optimization algorithm. Specifically, Huber loss, which is insensitive to outliers, is proposed as the objective function in extreme learning machine (ELM) training. In addition, an improved whale optimization algorithm is designed for the robust ELM training, in which a cellular automaton mechanism is used to enhance the local search. To verify our improved whale optimization algorithm, some experiments were then conducted based on seven benchmark test functions. Due to the enhancement of the local search, the improved optimizer was around 7% superior to the basic. Finally, our proposed hybrid forecasting model was validated by two real electric load datasets (Nanjing and New South Wales), and the experimental results confirmed that the proposed hybrid load-forecasting model could achieve satisfying improvements in both datasets.

     

电力系统短期负荷预测的一种模糊建模方法

预测问题在科学技术领域有着广泛的应用背景。本文介绍了一种短期负荷预测的模糊建模方法，基于三角形隶属函数和卡尔曼滤波器，辨识出电力系统的动态模型，并把辨识模型的仿真结果与系统实测值相比较，以检验模糊模型的可靠性。仿真结果表明，这种新的模糊建模方法具有较高的精度，为高度复杂的非线性电力系统模型化提供了一条新途经。此方法利用河北省某一地区具体的数据进行检验．得到了满意的结果。     

A new microcomputer-based approach for pilot differential protection of transmission lines

This paper presents a theoretical and experimental study of a new technique for pilot differential protection of transmission lines. The difference currents obtained from post- and pre-fault line currents, adjusted by calculated charging currents, are used to minimize the desensitizing effect of load and line charging currents. The experimental results are from a laboratory 16-bit microcomputer-based relay that was developed to test some of the features of this new approach. Off-line test results for various types of faults on a lumped parameter long transmission line model and real-time test results for a short transmission line model are presented.     

基于MATHEMATICA的因次分析程序

因次分析是一种重要的数学建模方法,广泛应用于化工原理中与湍流有关的物理现象的无因次数群关联式的建立。经典化工原理在因次分析过程中采用手算法进行符号运算,非常烦琐；本文基于MATHEMATICA软件强大的符号运算功能,给出了一个因次分析程序,用来进行因次分析中的这些烦琐而重复的计算。本文还给出了该程序的若干应用实例。     

纵轴式掘进机截割头载荷影响因素的仿真分析

针对现有掘进机截割头载荷特性研究方法采用单一影响因素不能全面反映截割头载荷及其波动变化规律的问题,通过分析截割头瞬时载荷,确定了纵轴式掘进机在水平截割工况下截割头载荷的主要影响因素有截割岩石特性、截割头掏槽深度、截割头吃刀深度、截割头转速和截割臂摆速。针对某纵轴式掘进机水平截割工况,采用Matlab对影响截割头载荷的多种因素进行仿真分析,得到了各向载荷及其波动随各因素的变化规律:截割头载荷随着岩壁普氏系数的增大而增加,其中横向阻力增加尤为明显,横向阻力波动程度高于其他方向载荷,且随着岩壁普氏系数的增大呈减小趋势;随着截割头掏槽深度的增加,截割头各向载荷近似呈线性增加,其中升力增加幅度最大,各向载荷波动则随着截割头掏槽深度的增大而减小;随着吃刀深度的增加,截割头载荷总体呈增大趋势,载荷波动程度则随之减小;在截割头转速一定的情况下,截割头载荷均随着截割臂摆速的增加而增大,在同一摆速下,截割头载荷随着截割头转速的减小而增大,横向阻力波动明显高于升力和推进阻力波动,横向阻力和推进阻力波动按截割头载荷规律变化,升力波动则与之相反。截割头载荷波动变化规律与截割头载荷变化规律不尽一致,有时甚至相互冲突。因此,掘进机作业过程中应合理选择截割头掏槽深度、吃刀深度等操作参数和截割头转速、截割臂摆速等运动参数,使各参数相互匹配,以减小掘进机振动,延长使用寿命。     

A novel coupled transmission lines method for easy CAD of image guides

In this article, a novel coupled transmission lines method has been developed for the systematic and easy computer-aided design (CAD) of image guides. The method is based on a two-dimensional transverse resonance technique, which includes new mode designations involving LSE and LSM modes. The numerical performances are very attractive; that is, considerably less computer time and fewer memory requirements, and very good agreement with the referenced results. Moreover, the formulation of the problem is easier, more compact, and elegant. © 1997 John Wiley & Sons, Inc. Int J Microwave Millimeter-Wave CAE 7 : 272–277, 1997.     

基于优化模拟电荷法的直流输电线路电场特性计算

为了提高模拟电荷法计算电场的精度并降低其计算复杂度,采用黄金分割法对模拟电荷法进行优化,提出了一种精度高且易实现的模拟电荷设置方法.应用该模拟电荷法计算了直流输电线路导线表面电场,采用化曲为直法绘制了电场线轨迹.在此基础上,基于通量线法对比分析了分裂导线表面最大场强在不同取值方法下求解合成电场和离子流密度时带来的计...     

Algorithm for the design of overhead transmission lines

A dynamic programming algorithm which chooses types, heights and sites of towers along a given transmission line route is described. On the basis of estimated data for the ground strength along the line path, and the criterion of minimum construction costs, a set of consecutive cheapest solutions of the problem is determined (ie the optimal and the required number of suboptimal solutions). It is proposed to submit the obtained set of solutions for further analysis based on some additional criteria and a more accurate survey of ground strength in tower locations already known. The analysis may prove that one of the suboptimal solutions is most advantageous. Some specific features of the computer program and the results of experimental calculations are presented.     

电动负载模拟器的重复控制器的设计

通过分析电动负载模拟器的基本结构和工作原理,建立数学模型并且分析了多余力矩产生的机理,提出一种重复控制和PID控制相结合的复合控制策略,利用重复控制改善系统的稳态特性,利用PID控制改善系统的动态特性.仿真结果表明,所采用的方控制方法能够有效地抑制多余力矩,提高了系统的稳态精度和动态性能.     

A hybrid system for forecasting 24-h power load profile for Polish electric grid

We present a method of forecasting 24-h power load profile in state-wide power system in Poland. The presented method is based on a hybrid artificial intelligence system. It employs actual temperature forecasts prepared by Interdisciplinary Centre for Mathematical and Computational Modelling of Warsaw University. The machine learning part of the system consists of 24 instances of Hierarchical Estimator: a machine learning method that divides the problem into non-exclusive subproblems with the help of fuzzy clustering and combines results of fairly simple neural networks trained on those subproblems into one, possibly more accurate solution. The presented system also includes a part responsible for dealing with days that have distinct power load patterns, such as additional state holidays. That latter part uses 30 (or 33) appropriately arranged linear regressions.The proposed approach was tested on historical load data from Poland and a few other countries. The achieved MAPE varied from 1.08% to 2.26% in dependence on the country. Such errors are among the lowest achieved by the published methods.     

A new approach to the calculations of the limit load of steel structure supports of electric overhead lines of the highest tensions

Starting from the Lagrange equations the generalized algebraic eigenproblem has been obtained. The notions of the statical compression measure density matrix as well as the coefficient α of the statical compression measure density (α-N) of the bar finite element have been introduced. On the basis of the above formulae the limit load P of the two steel structure supports of 110 kV electric lines has been calculated using the author's own CAD system named SLEN. After solving the generalized algebraic eigenproblem, the lowest eigenvalue α₁ < 1 for all cases has been calculated. The average value of the α₁, was about 0.7. Then the calculated limit load P was about 30% lower than the real limit load P_o. For the technical conformity of the limit loads, calculated (P) and measured at the trial station (P_o), the following has been proposed:

• 1.(1) assumption of the statical compression measure density coefficient α ≠ 1,
• 2.(2) assumption of the relation α = α₁,
• 3.(3) calculation of the coefficient α₁ by the statistical identification process.