Fast Electromagnetic Transient Simulations of Power Systems Utilizing Single‐Phase Phasor‐Based Modeling of Remote Systems

Electromagnetic transient (EMT) simulations of relatively large power systems have become quite common, for instance, in the case where simulations of HVDC converters are carried out with large ac power systems connected to the converters. Thus, the increase in computation time is a serious concern. To reduce computation time, this paper proposes a method to reduce computational demand of a remote power system which is located far from the source of a transient event to be simulated. In the proposed method, the remote power system, which is supposed to be represented by a three‐phase EMT‐based model, is reduced to a single‐phase phasor‐based model, and the size of the circuit to be simulated is thus reduced and the dynamics calculations of inductors and capacitors included in the remote power system are neglected. The calculation algorithm of generator models included in the remote power system is also simplified. The proposed method has been applied to EMT simulations of the WEST 10 benchmark power system prepared by the IEEJ, and it has been shown that the computation time is remarkably reduced without significant loss of accuracy if the portion assumed to be the remote power system is sufficiently far from the source of a transient event.     

基于状态变量分析的有源配电网电磁暂态仿真自动建模方法

状态变量分析法是电力系统电磁暂态仿真中的一类重要方法,但复杂的建模过程限制了其在实际研究中的应用,对于配电网等大规模系统而言必须考虑易于程序实现的一般性建模方法。提出了一种面向有源配电系统电磁暂态仿真的状态空间自动建模方法,与传统方法相比充分考虑了当前配电网络的实际结构特点与元件特性,并通过选取适当的状态变量保证了模型规模较小、模型性质满足分析需要,同时特别易于算法的程序自动实现,为各种基于状态变量分析的电力系统电磁暂态仿真、分析、计算方法的研究奠定了基础。     

A TLM‐Based Surge Analysis of Grounding Electrodes

In this paper, representations of a perfectly conducting thin wire and an imperfectly conducting medium in the transmission line modeling (TLM) calculation are briefly explained. Then, the method is applied to analyzing surge responses of a vertical parallelepiped grounding electrode and a square‐loop grounding electrode. Surge responses calculated using the TLM method agree reasonably well with the corresponding responses measured and calculated using the finite‐difference time‐domain method. It is probably the first time that surge responses of grounding electrodes have been analyzed reasonably accurately using the TLM method.     

电力系统移频电磁暂态仿真原理及应用综述

高效、精确的电磁暂态仿真是支撑电力系统运行和控制的关键技术.为了解决传统电磁暂态仿真中速度和精度之间的矛盾,提出了移频电磁暂态仿真方法.文中对移频电磁暂态仿真理论的关键技术进行梳理并对其中存在的部分问题进行分析.首先,介绍移频电磁暂态仿真的原理.然后,依次对移频电磁暂态仿真中的3个关键点进行分析,包括复数信号的构造方法...     

架空传输线在电偶极子激励下的瞬态电磁响应

利用电磁拓扑学,将电偶极子产生的电磁场与架空传输线的电磁耦合问题进行拓扑分解,推导出用于同时求解传输线瞬态电压响应和空间电场的BLT方程.推导过程中引入电场的分量形式以解决入射场的方向性,考虑了传输线中差模电流和共模电流的辐射,并计及了由传输线初始状态引起的零输入响应.利用本文结果可有效地计算外部电磁场与传输线的耦合问题.     

非均匀传输线中电磁暂态过程的新型时域算法

为了精确高效地计算非均匀传输线中的电磁暂态过程,提出了一种称为任意差分精细积分法的新型时域计算方法来计算非均匀传输线中的电磁暂态过程,该方法是空间域任意差分法和时间域精细积分法的结合,既能根据非均匀传输线的特性来任意地构建差分方程,同时又能够消除时间稳定性条件(CFL)的限制。采用该方法计算垂直导体中的电磁暂态过程,并与有限差分法和EMTP方法所得的结果比较。结果表明,由于该方法能够实现局部点加密,同时时间步长的选取不受稳定性条件的限制,该方法在相同的计算精度下具有更高的效率。     

基于分段平均化模型的微电网快速电磁暂态仿真方法

针对微电网的详细电磁暂态（EMT）仿真模型效率较低的问题,提出了一种基于分段平均化模型的微电网快速电磁暂态仿真方法,记作EMTPAM。该方法将分布式电源（DG）和分布式储能元件（DS）以分段平均化模型（PAM）来处理,并将PAM集成到微电网EMT仿真程序中。对带有两个光伏元件（PV）和一个电池储能系统（BESS）的微电网系统分别进行PSCAD/EMTDC和EMTPAM仿真,两者结果的一致性验证了所提方法的有效性;但后者的速度更快,表明所提的分段平均化模型具有更高的效率。     

电磁脉冲模拟器仿真与实验研究

为了获得电磁脉冲模拟器工作区间内瞬态电磁场的分布情况并用时域有限差分法对自建的电磁脉冲模拟器进行了建模和数值仿真,并用三维瞬态电场测量系统和瞬态磁场测量系统实际测量了模拟器工作区间内的瞬态电磁场。仿真和测量结果表明,该电磁脉冲模拟器可产生上升沿为20~30ns的强电磁脉冲,且二者吻合较好。基于建立的模型得到了有界波电磁脉冲模拟器工作区间内瞬态电磁场的分布规律:电磁脉冲强度由工作区间中心向两侧逐渐减小,随高度的增加,电磁脉冲强度逐渐增大。基于上述模型通过数值仿真可检验电磁干扰和电磁防护实验结果的准确性。     

基于双模调频分解的低压配电网同期线损率预测模型

为了高精度评价电力系统运行方式合理性以及电力企业运营状况,研究基于双模调频分解的低压配电网同期线损率预测模型,利用高精度的线损率预测结果提升电网运营管理性能。采集低压配电网电能传输信号,通过双模调频分解方法利用双模调频基函数分解信号,去除无用信号;利用分层式节点识别策略在分解后的配电信号中划分低压配电网的负荷节点,获取各负荷节点的注入电流;利用支持向量机方法建立同期线损率预测模型,将所获取的注入电流输入到模型中,输出线损率预测优化结果。试验结果表明,该预测模型的预测结果与实际结果极为吻合,平均绝对误差和均方根误差均不超过0.09%,证明该模型可有效预测低压配电网同期线损率,预测精度高,可为智能配电网运营管理提供有效依据。     

传输线残余电荷放电响应模型的研究

残余电荷放电机制研究对开关操作中快速暂态过电压和电磁干扰研究有着重要意义。基于传输线电荷密度与电压之间的关系,建立了以传输线电荷密度和沿线电流为变量的新传输线模型;结合传输线终端条件,给出了端接负载时域有限差分公式,对该差分公式进行修改获得了终端开路和短路时的差分公式。运用时域有限差分法和无损传输线理论,验证了新传输线模型的正确性,比较了新模型与传统模型在分析残余电荷放电时电压响应中的各自特点。从分析结果发现,无论空间和时间离散步长是否满足Courant条件的等式关系,残余电荷释放产生的响应均发生了振荡现象。对比电荷均匀分布和不均分布传输线电压响应可以看出:电荷不均匀分布对电压幅值和传输时延有很大的影响。     

基于平均化理论的PWM变流器电磁暂态快速仿真方法：（一）PWM变流器分段平均模型的建立

为提高分布式发电系统和微电网电磁暂态仿真的效率,基于非线性动态系统的平均化理论,提出了脉宽调制(PWM)变流器的分段平均模型。该模型在开关周期内对PWM变流器的状态方程进行局部平均化,将脉冲形式的开关函数转化为分段常数函数,从而可以采用更大的积分步长进行仿真以提高效率。进一步,文中给出了PWM变流器分段平均模型的误差估计定理及状态变量纹波的近似表达式。最后,通过三相PWM AC-DC变流器算例验证了所述分段平均模型的有效性。     

Use of lossless transmission‐line segments and shunt resistors for TLM diffusion modelling

In diffusion modelling by means of the transmission‐line matrix (TLM) method, a nodal arrangement of using lossless transmission‐line segments and series resistors is almost exclusively adopted and is currently considered as a standard approach. In this paper, the use of shunt resistors instead of series resistors is shown to represent an equally valid configuration. As a starting point, we have derived the telegrapher's equation in its most general form for TLM modelling of diffusion processes. A general algorithm based on the shunt‐resistor TLM model for implementing a numerical solution of the diffusion equation in multiple dimensions is given. Fundamental analysis and calculated examples confirm that the alternative shunt‐resistor configuration does not exhibit the unwanted absorption effects suggested by a recent paper (Internat. J. Numerical Model.: Electronic Networks, Devices and Fields 2002; 15 :261). Copyright © 2003 John Wiley & Sons, Ltd.     

基于准稳态模型的特高压半波长交流输电系统稳态特性与暂态稳定研究

特高压半波长交流输电是一项很有吸引力和前瞻性的远距离大容量输电技术,其稳态特性和暂态稳定研究是其可行性应用研究的基础。首先根据传输线和二端口理论推导出可用于潮流和稳定工程计算的特高压半波长交流线路的准稳态模型;然后在潮流计算的基础上,得出半波长线路的稳态运行特性,并从入、反射波与无功需求2个方面对其电压分布特性进行深入分析。在大量暂态稳定工程计算的基础上,提出特高压半波长交流输电系统的暂态稳定极限和输电能力,并研究最严重故障点和频率变化对系统暂态稳定极限的影响。研究成果对特高压半波长交流输电系统的可行性研究和未来试验工程的实施提供了有力的技术支撑。     

Transmission‐line matrix models for solving transient problems of diffusion with recombination

Starting from the general telegrapher's equation, we investigate two nodal network constructions for modelling diffusion with recombination by means of the transmission‐line matrix (TLM) method. The diffusion effect is modelled by the series and shunt capacitance in one approach, and by the series inductance and shunt resistance in the other. Both approaches use the series and shunt resistances to model the recombination effect. The constraint of using both TLM networks for solving transient problems of diffusion with recombination is found to be identical in terms of the physics behind the numerical routines. A practical way of determining the spatial resolution and iteration time step for accurate TLM numerical computations is suggested based on a simple frequency analysis. Copyright © 2003 John Wiley & Sons, Ltd.     

Time‐domain sensitivity analysis of planar structures using first‐order one‐way wave‐equation boundaries

An efficient adjoint variable method technique is developed for time‐domain sensitivity analysis of planar structures with transmission‐line modeling complemented by a first‐order one‐way wave‐equation absorbing boundaries. A backward‐running adjoint simulation is derived and solved. The validity of the technique is illustrated through three microstrip circuits. The examples demonstrate the efficiency and accuracy of the technique in comparison with the classical finite‐difference approaches to the estimation of the response sensitivities. Copyright © 2007 John Wiley & Sons, Ltd.     

基于可靠性理论的特高压送电线路杆塔设计风速确定方法

特高压送电线路杆塔设计中,设计风速的合理取值关乎其结构安全。参照现行110～500kV送电线路风速取值及设计方法,提出了基于可靠性理论确定特高压送电线路杆塔设计风速的方法。首先确定目标可靠指标,然后确定设计风速相关参数,综合考虑可靠指标及经济指标后,确定设计风速最优参数。2条特高压送电线路杆塔设计风速的应用实例验证了该方法的有效性。     

Sparse approximate inverse preconditioning of deflated block‐GMRES algorithm for the fast monostatic RCS calculation

A sparse approximate inverse (SAI) preconditioning of deflated block‐generalized minimal residual (GMRES) algorithm is proposed to solve large dense linear systems with multiple right‐hand sides arising from monostatic radar cross section (RCS) calculations. The multilevel fast multipole method (MLFMM) is used to accelerate the matrix–vector product operations, and the SAI preconditioning technique is employed to speed up the convergence rate of block‐GMRES (BGMRES) iterations. The main purpose of this study is to show that the convergence rate of the SAI preconditioned BGMRES method can be significantly improved by deflating a few smallest eigenvalues. Numerical experiments indicate that the combined effect of the SAI preconditioning technique that clusters most of eigenvalues to one, coupled with the deflation technique that shifts the rest of the smallest eigenvalues in the spectrum, can be very beneficial in the MLFMM, thus reducing the overall simulation time substantially. Copyright © 2008 John Wiley & Sons, Ltd.     

基于MMC的多端直流输电系统直流侧故障控制保护策略

基于模块化多电平换流器(MMC)的多端直流(MTDC)输电技术,兼具MMC技术和多端柔性直流输电技术的优势,具有广阔的应用前景。文中分析了MMC的拓扑结构和运行机理,设计了基于电压裕度的多点直流电压控制策略,并对控制器进行了设计。在此基础上,分析了直流侧单极接地故障、极间短路故障、断线故障对基于MMC的MTDC系统的影响,并进一步提出了相应的控制保护策略与保护时序。利用电磁暂态仿真软件PSCAD/EMTDC对以上几种直流侧故障及控制保护策略进行了仿真,结果表明所提出的控制保护策略能够实现系统故障后的快速恢复,有效提高多端系统的可靠性和可用率。     

500kV郓城～泰安紧凑型输电线路潜供电流限制及单重时间配合研究

针对500kV郓城—泰安紧凑型(部分同塔双回)输电工程的设计,研究了该线路的潜供电流限制及单重时间配合问题。通过仿真计算,讨论了该紧凑型(包括同塔双回)输电线路采用不同高抗时,潜供电流、恢复电压、中性点工频过电压随高抗中性点小电抗值变化的趋势,得出高抗和中性点小电抗的选择要综合考虑限制潜供电流和各种工频过电压的幅值。并在工程投运时的系统调试过程中实测了潜供电流暂态波形和系统恢复电压暂态过程以验证工程前期的计算和潜供电流限制措施,讨论了断路器单重分合时间与潜供电流计算值如何配合的问题,说明单重整定时间取0.8s以上能保证该线路单相重合闸成功。     

基于暂态分量的配电网单相接地故障测距的研究

在对配电网单相接地故障零序电流分析的基础上,提出了基于暂态分量的配电网单相接地故障测距方法,利用小波包重构系数形成各频段的能量值,构造出测距的特征向量,并引入支持向量机映射该特征向量与故障距离之间的对应关系.仿真结果证明该算法是有效的.