Frequency‐dependent modeling of transmission lines using bergeron cells

This paper proposes using Bergeron's equivalent circuit with traveling time equal to the simulation time step as an element for frequency‐dependent modeling of transmission lines for electromagnetic transient (EMT) simulations of power systems. According to the simulation time step used, a transmission line is divided into aforementioned Bergeron's equivalents, each of which is called a ‘Bergeron cell’ in this paper. In this way, the traveling‐wave nature of a line is represented by the cascaded Bergeron cells. Then, the frequency‐dependent loss nature of the line is represented by a matrix partial fraction expansion, and this is inserted at each connection point of the Bergeron cells in the form of a multiphase Norton equivalent. Since the frequency‐dependent loss is modeled in the dimension of impedance, the change of the line length is easily taken into account by a simple multiplication. This methodology thus allows variable‐length modeling and completely avoids modal decomposition in both model identification and EMT simulation stages. The proposed methodology is applied to the frequency‐dependent modeling of overhead and submarine‐cable transmission lines, and its accuracy is assessed.     

Unsymmetrical opening of mutually coupled transmission lines

The aim of this paper is to present a systematic approach of solving unsymmetrical faults due to unsymmetrical opening of mutually coupled transmission lines. Opening a transmission line is equivalent to adding, in parallel with it, another transmission line but having the negative impedance of the same line. This is straightforward if the line is not mutually coupled with other lines in the system. Mutual coupling between parallel and adjacent lines exist due to proximity. Such mutual coupling must be taken into consideration when modifying the bus impedance matrix for the purpose of fault studies due to the opening of mutually coupled transmission lines. In this paper, a systematic approach to applying the bus impedance matrix method for faults involving the switching of mutually coupled lines is presented. The approach is applied to several cases of simulation of symmetrical and unsymmetrical switching of mutually coupled transmission lines.     

单相整流负荷谐波功率需求建模分析

单相整流负荷作为典型的谐波源会对电网产生谐波污染,引起附加的谐波功率损耗。基于单相整流负荷工作原理,分析其各次谐波有功和无功功率流向特点,分别建立单相不控和相控整流负荷的功率需求模型。该模型计及整流器端电压和电流各次谐波分量之间的耦合关系,实现了整流负荷谐波功率的精确计算。利用仿真分析验证了该模型推导的正确性,并进一步定义了谐波有功和无功功率导纳矩阵。通过分析矩阵元素物理意义和幅值变化规律,确定单相整流负荷端电压各谐波分量对谐波功率的贡献程度。     

双回并行直流输电谐波不稳定判据研究及改进

现代电网往往是大规模的交直流混联系统,当直流系统与弱交流系统连接时,可能引发谐波不稳定等一系列问题。在现有双回并行直流输电线路谐波不稳定判据的基础上,引入了直流偏磁系数和双回直流线路的阻抗矢量差异,提出新的判断双回直流系统谐波不稳定的工程判据。在不同网络参数下,将所提判据与现有判据的判断结果进行对比分析,结果证明了所提判据的正确性。     

钢管组合大跨越输电塔导地线耦合效应研究

利用ANSYS软件建立了跨越珠江铁桩水道的220kV钢管组合大跨越输电塔线体系的空间数值分析模型。通过对实际工程进行环境振动测试,识别出输电塔耦合导地线的振动模态,验证了输电塔线体系有限元模型和理论计算的正确性。从动力特性和地震反应方面研究了单塔和塔线体系的动力特性和地震响应特点,分析得到关于输电塔导地线耦合效应的初步认识,进一步揭示了导地线对输电塔的耦合作用规律。研究表明,悬挂的导地线不仅具有质量效应,同时在线路的纵向和侧向还施加了一定的刚度效应。地震反应分析中可知导地线对输电塔具有一定的减震效应,并指出导地线的减震效应是否具有普遍性,还需要进一步研究。上述研究对类似输电塔的抗震、抗风设计有一定参考意义。     

Fault location of untransposed double-circuit transmission lines based on an improved Karrenbauer matrix and the QPSO algorithm

Some double-circuit transmission lines are untransposed, which results in complex coupling relations between the parameters of the transmission lines. If the traditional modal transformation matrix is directly used to decouple the parameters, it can lead to large errors in the decoupled modal parameter, errors which will be amplifed in the fault location equation. Consequently, it makes the fault location results of the untransposed double-circuit transmission lines less accurate. Therefore, a new modal transformation method is needed to decouple the parameter matrix of untransposed double-circuit transmission lines and realize the fault location according to the decoupled modal parameter. By improving the basis of the Karrenbauer matrix, a modal transformation matrix suitable for decoupling parameters of untransposed double-circuit transmission lines is obtained. To address the diffculties in solving the fault location equation of untransposed double-circuit transmission lines, a new fault location method based on an improved Karrenbauer matrix and the quantum-behaved particle swarm optimization (QPSO) algorithm is proposed. Firstly, the line parameter matrix is decomposed into identical and inverse sequence components using the identical-inverse sequence component transformation. The Karrenbauer matrix is then transformed to obtain the improved Karrenbauer matrix for untransposed double-circuit transmission lines and applied to identical and inverse sequence components to solve the decoupled modal parameter. Secondly, based on the principle that voltage magnitudes at both ends are equal, the fault location equation is expressed using sequence components at each end, and the QPSO algorithm is introduced to solve the equation. Finally, the feasibility and accuracy of the proposed method are verifed by PSCAD simulation. The simulation results fully demonstrate that the innovative improvement on the basis of the traditional modal transformation matrix in this paper can realize the modal transformation of the complex coupling parameters of the untransposed double-circuit transmission lines. It causes almost no errors in the decoupling process. The QPSO algorithm can also solve the fault location equation more accurately. The new fault location method can realize the accurate fault location of untransposed double-circuit transmission lines.     

基于双曲正切函数相位特性的高压长线路故障测距新算法

提出一种基于双曲正切函数相位特性高压长线路故障测距新算法,其在将故障位置作为已知条件看待并引入参考点与之匹配的思想基础上,构建了一个和双曲正切函数具有相同相位特性的测距函数。根据所取参考点与故障点相匹配时测距函数相位等于零这一特征进行定位。该方法理论上不存在伪根,所需运算量远小于传统方法的运算量,能有效克服传统方法存在的测距精度和测距速度此消彼长的矛盾。EMTDC仿真结果表明,该方法不受过渡电阻、故障位置和故障发生角等因素的影响,在线路参数严重不均匀情况下依然保持较高的测距精度,具有较好的鲁棒性。     

考虑交直流多谐波耦合的模块化多电平换流器矩阵建模

谐波耦合矩阵模型可为电力系统线路和元件的谐波稳定性研究提供有效支撑。但对于内部结构复杂的模块化多电平换流器(MMC),已有研究中的矩阵模型不能描述其交、直流侧谐波间耦合关系或只能对特定次数谐波的耦合关系进行讨论。故考虑MMC开关函数可描述换流器的特定次数谐波间耦合关系,但其本身为周期时变的特点,以及谐波状态空间理论(HSS)可以将周期时变模型定常化,同时描述各量全部次数谐波间耦合关系的优点,将两者结合以搭建了可同时描述MMC交、直流侧各电气量的全部次数谐波间关系的谐波耦合矩阵模型。将加入谐波扰动后的MMC谐波耦合矩阵模型的理论计算结果与PSCAD电磁仿真模型仿真结果对比,证明了该模型对MMC谐波耦合特性描述的准确性。     

分频输电系统模块化多电平矩阵变换器谐波特性分析

模块化多电平矩阵变换器(M3C)是构建分频输电系统(FFTS)的核心装备,但是M3C在进行交-交变换时,会导致两侧不同频率交流系统电气量在M3C内直接耦合,引起系统复杂的谐波分布。为分析M3C谐波特性,首先基于M3C工作原理推导得到子模块电容纹波电压解析式,在此基础上推导9个桥臂考虑子模块电容电压全部4种频率分量耦合的桥臂谐波电流解析式,进而分析多种频率桥臂谐波电流与系统电流的关系以及影响纹波电压/谐波电流幅值的关键因素。结果表明,在稳态下,分频侧频率ω₁和工频侧频率ω₂的电流分量以正序基波电流性质流入对应系统;频率为3ω₁和3ω₂的电流分量以零序谐波电流性质流入两侧交流系统;其他频率谐波分量在变换器内部环流。文中针对M3C提出一种零序电流抑制控制策略,并在Matlab/Simulink中进行仿真,验证了谐波理论分析的准确性以及控制策略的有效性。     

A new approach of fast fault detection in HV-B transmission lines based on Detail Spectrum Energy analysis using oscillographic data

The main focus of this research is to develop an accurate real-time method for fault detection and analysis of HVB (High Voltage Class-B) transmission lines. The current and voltage signals of oscillographic records are acquired by the distance protections relays with minimum impedance GE D60-1 installed in the electrical network of SONELGAZ (Algerian Company of Electricity and GAS). This method deals on the evaluation of the Detail Spectrum Energy (DSE) calculated from the Discrete Wavelet Transform (DWT) applied on the current phases by moving data windows with length equivalent to one cycle of the fundamental power frequency. The fault detection algorithm is processed at first scale superimposed in the fault current signals (phases and ground) by the sharp variation of (DSE). Most of the existing methods treat the disturbances and faults simultaneously exist in transmission line as a single type. The proposed method has the ability to discriminate between the disturbances and the faults. This study is compared with the “Powerful Analysis of all Protection Fault Records” SIGRA software for determining the start fault inception and it’s clearing time. The performance of this method was tested and evaluated on a real data records and can accurately detect the fault within only half a cycle from the instant of fault occurrence.     

带散射体的电力系统多级传输线高频耦合模型

高频电磁场会与架空输电线路产生耦合,一旦高频电磁场的波长小于传输线的高度,经典传输线理论就不再适用。传统的全波数值算法虽然可以解决这一问题,但它的求解效率不高,需要消耗大量的时间与计算资源。此外,电力系统输电线路往往有多个垂直端,线路布局复杂。为了解决这些问题,本文提出了一种理论有效的方法来解决有损耗地面上方带有散射体的电力系统多级传输线的高频电磁场耦合问题。采用计算效率高的渐近法,并在渐近法中引入散射体的概念,以考虑更复杂的电路结构。最后用数值算例验证了该方法的准确性和有效性。     

基于电磁-热耦合场的架空输电线路载流量分析与计算

架空输电线路的允许载流量是保证其安全运行的重要参数之一。根据架空输电线路产热和散热的特点,建立了架空导线的磁场-温度场耦合二维有限元分析模型,确定电磁-热耦合场分析的边界条件,求解得到了架空输电导线内部电磁场分布。将得到的焦耳热损耗作为热源耦合至热场模型进行计算,并采用数值迭代法求解得到架空输电导线的允许载流量。此外,基于该仿真模型通过仿真分析得出了不同外部环境因素对架空输电线路载流量的影响规律。该研究成果可以为架空输电线路的热分析和载流量计算提供一定的参考。     

基于潮流数据的输电线路谐波模型和电磁暂态模型研究

通过推导考虑分布参数效应的任意频率下的等效π模型参数和用于电磁暂态仿真的Bergeron模型参数,从理论上证明了只要已知输电线路的潮流数据,就能直接导出用于谐波分析的分布参数模型和用于电磁暂态仿真的Bergeron模型及Dommel模型,而与线路的真实长度无关,通过PSCAD程序对结论进行了验证.     

输配电线路施工仿真培训系统的设计与实现

分析和使用了面向对象的软件设计和开发方法、Browser/Server网络结构体系,基于C#语言的平台技术,结合传统的仿真数学建模,设计了输配电线路施工仿真培训系统。介绍该系统的配置、功能、构成和特点,并且阐明该系统的设计思想和技术。该系统是集计算机、通信、多媒体的高新技术产物,系统采用Browser/Serve架构,符合当前计算机和网络的发展趋势。系统的设计突出了实用性、技术先进性和功能完备性,达到较高的应用水平。施工操作人员通过在该仿真培训系统上的演练,有利于快速掌握输配电线路施工的工艺流程,积累施工操作经验,对保证输配电线路施工的安全具有重要意义。     

超高压输电线工频电场计算的矩量法和表面电荷混合法

结合矩量法和表面电荷法各自的优点,提出一种用矩量法—表面电荷法相结合的混合算法来计算复杂场景下超高压输电线工频电场的分布,通过综合考虑输电线路的弧垂、分裂导线等因素,建立了复杂场景下超高压输电线的三维模型,并进行了相应的计算。结果表明:该混合法具有提高计算速度,减少占用内存和避免模拟点电荷设置等优点。对于所述的树状物模型,树状物对其下方离地1.5 m处工频电场起屏蔽作用。树状物尺寸参数的变化对其下工频电场分布影响明显,树冠半径越大其屏蔽范围越大,树干高度越高其屏蔽强度越弱。相间距和输电线高度的变化对电场值基本无影响。混合法可为高压输电线路在复杂场景下工频电场分析提供重要的参考。     

基于随机矩阵理论的交直流输电通道线损大数据关联特性分析

基于随机矩阵理论对西电东送交直流输电通道线损率的关联特性进行分析。首先,利用线损大数据构建出实验矩阵数据源与对比矩阵数据源,并通过滑动窗口分别对这2类数据源进行滑动取样;其次,将平均谱半径作为关联特性的量化指标,计算出实验矩阵与对比矩阵的平均谱半径以量化线损率之间的关联特性;最后,对南方电网"八交八直"输电通道的线损大数据进行分析,结果表明所提方法能定量描述线损率与状态量及不同通道的线损率之间的关联特性。     

The hyperpolarization‐activated current regulates synchronization of gap–junction‐coupled dopaminergic neurons in the midbrain—a combined approach between computational modeling and electrophysiological recording

To examine the functional role of hyperpolarization‐activated and cyclic nucleotide‐gated (HCN) current observed in mesencephalic dopaminergic neurons, we constructed a conductance‐based model that can mimic the electrical properties obtained in electrophysiological recordings of rat brain slices. In the model, blocking the HCN current resulted in a reduction of spontaneous firing rate and a change in the properties of autonomous pacemaking. In addition, reduced one‐dimensional phase equations and their coupled oscillators were analyzed. The analysis indicated that HCN channels can regulate the extent of synchronization of coupled dopaminergic neurons through gap–junction connections. Thus, the HCN current can effectively shape the autonomous and cooperative firing of dopaminergic neurons in the midbrain. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.