EMTP在变压器励磁电流仿真计算中的应用

利用电磁暂态程序 ( EMTP)对变压器在稳态和暂态情况下的励磁电流进行了仿真计算与分析。结果表明 ,使用EMTP对变压器的励磁电流进行仿真 ,所得的电流波形与理论波形相吻合     

A systematic method for the development of a three‐phase transformer non‐linear model

In this work, a novel three‐phase transformer non‐linear model is developed. The proposed model takes into account the magnetic core topology and the windings connections. The non‐linear characteristic curve of the core material is introduced by its magnetization curve or by its hysteresis loop using the mathematical hysteresis model proposed by Tellinen or the macroscopic hysteresis model proposed by Jiles–Atherton. The eddy currents effects are included through non‐linear resistors using Bertotti's work. The proposed model presents several advantages. An incremental linear circuit, having the same topology with the magnetic circuit of the core, is used in order to directly write the differential equations of the magnetic part of the transformer. The matrix L _d that describes the coupling between the windings of the transformer is systematically derived. The electrical equations of the transformer can be easily written for any possible connection of the primary and secondary windings using the unconnected windings equations and transformation matrices. The proposed methods for the calculation of the coupling between the windings, the representation of the eddy currents and the inclusion of the core material characteristic curve can be used to develop a transformer model appropriate for the EMTP/ATP‐type programs. Copyright © 2009 John Wiley & Sons, Ltd.     

基于Carson理论和EMTP的220 kV多回电缆线路电气参数及不平衡度分析

为分析珠澳电网220 kV电缆线路电磁不平衡问题,应用理论计算(Carson理论)与仿真(EMTP)相结合的方法。首先,对"导线—大地"回路与Carson线路理论得到的线路阻抗矩阵与EMTP仿真得到的线路阻抗矩阵进行对比。然后,利用EMTP搭建的完整实际线路模型,分析了不同因素对线路电气参数的影响程度。最后根据电磁不平衡度理论计算了相间距离、护套交联方式及相序排列3个因素对电缆线路的影响。结果表明:Carson线路模型在分析线路阻抗时误差很小与EMTP基本吻合;电缆金属护套交联和接地电阻对电缆序阻抗有一定影响;相间距离和金属护套交联影响线路负序不平衡度;在研究的这条珠澳电缆线路里,当采取ABC/CBA相序排布时线路的电磁不平衡度可以达到最低。     

小波模糊神经网络应用于配电网输电线的故障测距

在小电流接地系统单相接地故障特征分析的基础上，提出了一种基于故障后稳态及暂态电气量的小波模糊神经网络的故障测距方法。单相接地故障时的暂态分量故障特征非常明显，且故障暂态高频分量受故障前负荷的影响较少，故可以采用故障暂态分量描述故障模式特征并进行故障定位，鉴于已有的小波神经网络模型不适合于故障测距，作者从广义的小波神经网络概念出发，结合模糊控制理论，提出了适合于电力系统故障暂态和稳态信号分析的小波模糊神经网络方法，并将该方法应用于小电流接地系统直配输电线路的故障测距。理论分析及大量的EMTP仿真结果表明：本文所提出的小波模糊神经网络理论，模型及算法具有较好的故障测距性能，并可应用于电力系统的故障分析。     

Transient modeling of electromechanical relays

An electromechanical, plunger type 50 relay is modelled in EMTP/ATP using TACS. Mechanical, magnetic, and electrical characteristics are represented in the form of simple mathematical models that can provide a useful tool for studying the dynamic responses of the Type 50 devices and incorporating them into a power system transient analysis. This paper is the second part of a summary report by Rensselaer Polytechnic Institute (RPI) of work on relay modeling sponsored by the Bonneville Power Administration. (BPA). It presents the Electro-Magnetic Transient Program/Alternative Transient Program (EMTP/ATP) model for plunger type 50 instantaneous overcurrent relays that compare with actual tests performed on the devices on a power system simulator     

电力变压器励磁涌流和故障电流仿真研究

在研究电力变压器励磁涌流和故障电流特性的基础上 ,应用电磁暂态程序 (EMTP) ,采用不同的模型和方法对变压器励磁涌流和故障电流进行了全面系统的仿真计算和分析。结果表明 ,EMTP能够根据不同的条件和要求有效地实现对变压器励磁涌流和故障电流的仿真     

Transient modeling of electromechanical relays. Part I: armaturetype overcurrent relay

An electromechanical, armature type 50 relay is modelled in EMTP/ATP using TACS. Mechanical, magnetic, and electrical characteristics are represented in the form of simple mathematical models that can provide a useful tool for studying the dynamic responses of the armature type 50 devices and incorporating them into a power system transient analysis. This paper is the first part of a summary report by the Rensselaer Polytechnic Institute (RPI) of work on relay modeling sponsored by the Bonneville Power Administration (BPA). It presents the Electro-Magnetic Transient Program/Alternative Transient Program (EMTP/ATP) model for armature type 50 instantaneous overcurrent relays that compares with actual tests performed on the devices on a power system simulator (PSS)     

冻结磁导率先进技术及其在高性能电机研发中的应用

如何考虑磁场饱和的影响是当前电机设计中一个亟待解决的重要问题。近年来提出的冻结磁导率技术越来越多地被应用到电机负载电磁性能和参数计算中。本文详细阐述了冻结磁导率的原理及其在各种电机中的应用现状。研究表明,冻结磁导率技术可以用来精确分离各种电机负载状态下的电磁分量,如磁场、磁链、电感、转矩、转矩波动、反电势和端电压、弱磁性能以及径向力等均可以用冻结磁导率技术预测,并用来辅助电机及其驱动控制系统的设计。因此,冻结磁导率技术为高性能电机的研发提供了一个全新的方法。     

New combined power-conditioning system for superconducting magnetic energy storage

This paper proposes a new combined power-conditioning system for large-scale superconducting magnetic energy storage; it consists of a DC chopper and a PWM (pulse-width modulation) voltage-source converter. The proposed system can independently control the active and reactive power of the utility network by regulating the chopper duty cycle and the converter firing angle. The operational concept was verified through mathematical analyses using an equivalent circuit. The dynamic interaction was analyzed using a simulation model with EMTP (Electromagnetic Transients Program). The analysis results show that the new system is feasible for development with commercially available components and technologies.     

Reduced‐cost microwave component modeling using space mapping‐enhanced electromagnetic‐based kriging surrogates

We present a versatile technique for constructing fast microwave component models at a low computational cost. Our modeling procedure consists of two stages: (i) kriging interpolation of coarsely discretized electromagnetic simulation data of the device under consideration and (ii) enhancing the kriging model by using space mapping and a limited amount of high‐fidelity electromagnetic simulation data. The use of coarse discretization data allows for low‐cost model generation, whereas space mapping is a convenient way of ensuring its accuracy. Our approach can be applied to almost any type of microwave device; it can also work with other types of nonsmooth or costly low‐fidelity models. The operation and performance of our methodology is demonstrated using a variety of microwave components, including a microstrip filter, a planar ultrawideband antenna, and a microstrip‐to‐coplanar waveguide transition. Copyright © 2012 John Wiley & Sons, Ltd.     

恒定干扰磁场下电磁继电器静态特性的有限元分析

电磁继电器作为控制元件被广泛应用于各种电子设备和系统。保证电磁继电器之间及其与系统中其它组件之间的电磁兼容性是系统可靠运行的重要环节之一。该文针对以往电磁继电器生产厂家一直没有给出继电器产品的电磁兼容性指标问题,建立了电磁继电器在不同方向恒定磁场干扰下的矢量磁位有限元数学模型,并采用ANSYS软件分析给出了电磁继电器对空间磁干扰的最敏感方向,研究了该敏感方向下恒定干扰磁场B的大小与继电器静态特性的配合关系的影响规律,研究了干扰磁场对继电器吸合电压、释放电压以及继电器衔铁所受力矩等静态特性参数的影响。为分析和评估电磁继电器及其控制系统耐磁干扰能力,确定电磁继电器的电磁兼容性指标奠定了理论基础。     

Synchronized solution of power electronics system equations usingflexible MODELS component connected to the EMTP

The oscillations from the trapezoidal rule of integration following discontinuity and the one-time-step error from separate EMTP and TACS (or MODELS) simulations are the numerical stability and accuracy problems found in the transient study of power electronics systems using EMTP. This paper presents the technique of the synchronized solution of power electronics system equations. The proposed technique implements efficient and numerically stable approaches to model the switching circuit and control system as a MODELS component. This MODELS component is connected directly to the EMTP to avoid the one-time-step delay. Therefore, the numerical oscillations and one-time-step error in standard EMTP simulation can be eliminated     

New digital filter for unbalance distorted current and voltage estimation in power systems

This paper presents a novel algorithm for identifying and measuring the symmetrical components of distorted three phase voltage or current waveforms in electrical power systems. The proposed algorithm is capable of estimating the symmetrical components as well as the harmonic contents of a given unbalanced distorted signal. The proposed technique is based on stochastic estimation theorem. The problem is formulated as an estimation problem and presented in state space form. The proposed algorithm used to estimate the positive, negative and zero components of unsymmetrical waveforms as well as the harmonic content of a given distorted signal. Application of the proposed algorithm has been conducted on various test cases. Among which a practical simulated power system has been implemented using EMTP. Various scenarios are carried out to simulate realistic situations of unsymmetrical waveforms. Effects of bad data on the solution accuracy are also studied. The speed of convergence is examined by changing the estimator initial conditions. Results obtained show that the proposed technique can estimate and track the symmetrical components of non-stationary three phase unbalance voltage or current waveforms in noisy environments. Fast accurate solutions are guaranteed regardless of the initial conditions. It is also shown that bad measurements have no effects on the final accuracy of the estimation.     

A generalized method for Lagrangian modeling of power conversion circuit with integrated magnetic components

A generalized Lagrangian is proposed to enable systematic analysis of integrated magnetic components. Although a few conventional theories are known that handle magnetic circuit, they cause difficulties in modeling or analysis, especially when applied to a highly integrated core. These difficulties are avoided in the proposed theory, as its Lagrangian is configurable directly from the physical core structure. As an example, the Lagrangian of the trans‐linked three‐phase boost converter is presented. Along with the Lagrangian, two types of circuit analysis are also presented: one is to obtain the state‐space model of the converter; the other is to translate the integrated magnetic component into an equivalent circuit of basic components such as transformers and inductors. The analyses show the usefulness of the proposed method in practical applications. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

新型定子永磁式容错电机的工作原理和性能分析

为满足电机驱动系统在多种高可靠性领域的应用,提出一种新型的定子永磁式容错电机结构--双凸极容错(doubly salient fault tolerant,DSFT)电机。DSFT电机在结构上集中了开关磁阻电机和转子永磁式容错电机的特点,具有结构简单、可靠性高、功率密度高等优点。以一台四相8/10极DSFT电机为例,分析其结构特点、容错齿作用和运行原理。在此基础上,研究DSFT电机在正常和短路时的磁场特性,计算磁链、自感、互感等电磁特性,从理论上分析DSFT电机的容错性能。运用电路、磁路瞬态联合仿真的方法,建立DSFT电机驱动系统的场路耦合分析模型,分别对电机在正常和缺相运行状态下的转矩输出性能进行计算分析。研究结果表明,DSFT电机相与相间的独立性好,具有较强的带故障运行能力,适用于一些工作环境恶劣且要求高可靠性、高能量密度的场合。     

A distribution line model for lightning overvoltage studies

Recently, the focus of lightning protection measures for distribution lines has moved from a nearby lightning stroke to a direct lightning stroke. Studies of direct lightning stroke countermeasures are generally carried out by digital simulations using the EMTP (Electro‐Magnetic Transients Program). Thus, components of a distribution line must be modeled appropriately in the EMTP for accurate simulations. The authors have previously clarified the surge response of a distribution line by pulse tests using a reduced‐scale distribution line model. In this paper, first, the results of the pulse tests are simulated in the EMTP using a conventional model which represents a distribution pole by a single lossless distributed‐parameter line model, and comparisons with the test results show that transient overvoltages generated at the insulators cannot accurately be reproduced by the conventional model. This indicates that a special treatment is required to represent the transient response of a distribution pole and wires. Then, this paper proposes new EMTP models of the pole and wires which can reproduce the transient overvoltages at the insulators. The parameter values of the proposed models can be determined based on a pulse test result. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(1): 11–23, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.21001     

A comprehensive circuit model for partial discharge activities in cable insulation due to electrical treeing

A new comprehensive circuit model is proposed for electrical trees in cable insulation to be used in partial discharge (PD) analyses. Simple relations are presented for each of circuit components. The effect of tree’s constructional parameters (such as length, growth angle and type), cable and insulation dimension (such as conductor radius and insulation thickness), needle dimension, temperature and insulation aging are considered in the proposed model. The patterns (pulse sequences, φ–q–n and φ–n) extracted from the proposed model are in a good agreement with the published experimental patterns under different conditions. Moreover, the model is fully compatible with the software packages, such as EMTP, that can simulate pulse propagation along cable networks.     

A busbar protection technique and its performance during CTsaturation and CT ratio-mismatch

This paper describes a digital technique for protecting busbars. The technique uses positive- and negative-sequence models of the power system in a fault-detection algorithm. While phase voltages and currents are used to detect faults, parameters of the power system are not used. An analysis of the performance of the proposed technique during CT saturation and ratio-mismatch conditions is presented. The performance of the technique was investigated for a variety of operating conditions and for several busbar configurations. Data generated by EMTP simulations of model power systems were used in the investigations. The results indicate that the proposed technique is stable during CT saturation and ratio-mismatch conditions     

Revolving-field polygon technique for performance prediction of single-phase induction motors

This paper presents a new analytical technique for improving the performance prediction of single-phase induction motors, especially capacitor motors. The technique uses the split-phase motor electrical equivalent circuit analysis together with electrical and magnetic parameters whose variation is computed from the equivalent balanced polyphase motor, so that the same magnetic circuit analysis can be used for both. (The term split-phase is used to cover motors operating from a single-phase supply but with the phase windings split into two orthogonal windings, one of which may have a capacitor in series with it during running or starting.) The technique accounts for the elliptical envelope of the magnetizing field vector and results in improved precision, since the three-phase electromagnetic model is considered to be more precise than the normal split-phase motor analysis. An important result is the computation of vector polygons of flux density for each section of the magnetic circuit, providing a better basis for core loss prediction. The double-frequency torque ripple is also obtained from the stator magnetomotive force and flux-density polygons. Three different electrical equivalent circuit methods for the split-phase motor (based respectively on the cross-field theory, forward- and backward-revolving fields, and symmetrical components) are evaluated to determine the method best suited for incorporating the variation of the circuit parameters from the polyphase magnetic circuit analysis, and it is discussed how the core losses can be included in these circuits to obtain the best overall performance prediction.     

A power transformer protection technique with stability duringcurrent transformer saturation and ratio-mismatch conditions

This paper describes a digital technique for protecting power transformers. The technique uses positive- and negative-sequence models of the power system in a fault-detection algorithm. While phase voltages and currents at the transformer terminals are used to detect a fault, no information concerning parameters of the transformer and power system is required. The performance of the proposed technique was studied for a variety of operating conditions using data generated by EMTP simulations. The impact of ratio-mismatch and saturation of current transformers on the performance of the technique was also examined. Results indicate that the proposed technique is stable during these conditions