Analysing a power transformer’s internal response to system transients using a hybrid modelling methodology

This article presents a novel approach to analysing a power transformer’s internal response to system transients. In this approach a hybrid modelling methodology is adopted which leverages the distinct advantages offered by both Black and Grey Box modelling techniques. The Black Box model of the transformer is used within the EMTP system study environment in order to take advantage of its mathematical flexibility and modelling accuracy. Transients derived from network switching operations within the study can then be used for injection tests within the Grey Box modelling environment. The Grey Box model, which is based upon the physical structure of the transformer, will facilitate analysis of the transformer’s internal voltage response to the external stimulus. A fundamental difference between the approach described in this paper and more traditional approaches is that it does not require prior knowledge of the internal geometry of the transformer. All of the modelling parameters are derived from external tests, nameplate details and an intrinsic understanding of common transformer design principles. This can be a distinct advantage since in most cases a transformer’s design specifications are not readily available outside of the laboratory due to the manufacturer’s intellectual property restrictions. A study of a gas insulated substation within a hydroelectric power plant in Brazil is used to demonstrate the proposed technique.     

用于移动变电站的三相隔离变压器的降阶模型研究

三相隔离变压器是移动变电站的关键一次设备,为在实验室环境下快速模拟该变压器的输入/输出特性,应用Arnoldi算法建立了其降阶模型.根据电磁感应定律和安培定律,搭建了三相隔离变压器的高精度电磁等效电路,得到了输入电压、电流与磁通量变化率之间的定量关系.应用分块近似方法将变压器磁芯等效为多组环形回路,得到了铁芯的磁路等效...     

Voltage-dependent model for teaching transformer core nonlinearity

A voltage-dependent model for transformer core nonlinearity suitable for undergraduate instruction is proposed. The model is based on Fourier series representation of the excitation current, and its parameters are determined with the aid of computer software and measured data. Laboratory experiments are performed to determine the model and verify its validity. The experiment shed light on transformer nonlinearity when used as part of the classical experiment on transformer saturation in the undergraduate energy conversion/power systems laboratory course     

Total compensation of line-side switching harmonics inconverter-fed AC locomotives

PWM controlled line-side power converters of modern AC traction locomotives inject harmonic currents into the feeding overhead line. This causes problems of electromagnetic interference. Passive or active filters are usually provided for a partial reduction of the line harmonics. A novel and superior approach employs a switched electronic compensator. It generates an exact replica of the harmonic current, feeding it to the high-voltage transformer to produce a harmonic counter MMF. The transformer main flux is then forced to be sinusoidal, and so is the induced voltage in the primary. The line current, being low-pass filtered by the transformer leakage inductance, assumes a pure sinusoidal waveform. The compensator operates in the low switching frequency range of the main power converters. Its installed power is only 1% of the traction power. Operation, control, and design considerations are described. Results from laboratory tests at full power level are presented     

推挽DC／DC变换电路中高频变压器的设计

高频变压器的设计是功率变换电路设计的核心技术。详细介绍了1100W／55kHz推挽DC／DC变换电路中高频变压器的设计过程,包括变压器磁芯选取及型号的确定、绕组设计及变压器的绕制。给出了变压器原、副边电压实验波形,实验结果表明所设计的变压器工作稳定可靠,满足电路设计要求。     

高频变压器分布参数分析

随着单端反激电源工作频率的提高,高频变压器分布参数的影响不可忽视,但在实际设计中一般考虑漏感而忽略了分布电容的影响。高频变压器分布电容可分为绕组匝间电容、绕组层间电容、绕组间电容。文章给出了高频变压器数学模型及各类分布电容的理论计算方法,并分析了不同绕制方法和空间布局对高频变压器分布电容的影响,最后通过实验验证了理论分析的正确性。     

Sensitivity Analysis on Ladder Network Equivalent Circuit Parameters of Power Transformer

In this article, novel methods and ideas are introduced, which altogether lead to an accurate model of power transformer windings. First, by the determination of non-dominant (hidden) resonances from frequency-response tests, a ladder model is proposed. Next, it is improved by assigning different values for similar elements of each section of the model. The parameters are obtained by minimizing the error function via a genetic algorithm. Sensitivity analysis is then applied to the obtained model to achieve further examinations and tests. Measurements have been driven from the windings of a 20/0.4-kV, 1600-kVA transformer. Modeling, methodologies, and sensitivity analysis in this article can be very useful for future research aiming to find internal faults of the transformer with the frequency response analysis.     

Analysis of three-phase transformer no-load characteristics

The traditional laboratory experiment on three-phase transformer connections consists of a qualitative observation of current and phase voltage waveforms by means of an oscilloscope, with emphasis placed on the dominant third harmonic component. Some recorded waveshapes, however, cannot be explained in simple terms without considering other harmonic components and the quality of power supply. This paper outlines an improved lecture/experiment that quantitatively analyzes the waveforms of various transformer connections under steady-state no-load conditions while taking into account the nonideal voltage supply. The experimental data obtained with the aid of a harmonic analyzer are then compared to the qualitative predictions and the discrepancies are discussed     

采用穿心式电流互感器电源设计的三遥实验分析

根据电流互感器的工作原理,建立了电流互感器取电的负载模型;参考变压器磁化曲线,选择电流互感器的工作范围,并通过实验数据得出取电互感器的设计参数.电路电源部分采用MCU智能管理,通过负载控制的方法使二次电流和功率得到控制,最终实现电流互感器取电电源在15～500 A范围内可稳定输出功率.     

开关电源传导EMI的模型分析与应用

从分布电容的角度出发，分析变压器及散热片产生EMI的方式及其特征，建立了开关电源共模传导发射的分析模型，并据此提出了降低反激式开关电源EMI共模发射源水平的解决方案及设计方法，通过实验验证了各设计方法的有效性。     

The minimization of voltage sag effect for specially connected transformers with a sensitive load and distributed generation systems

This paper improves the voltage sag for a distributed generation (DG) system with three-phase to two-phase connected transformers. The proposed connection system is compared with the systems designed by Scott and Le Blanc. A particle swarm optimization method with nonlinear time-varying evolution (PSO-NTVE) is used to determine the design values. This analysis considers sensitive loads and the coordination of over-current relays. The model uses a node admittance matrix for voltage sag calculation, in order to calculate the severity of system sag after single or two-phase faults. The analytical equations are useful in the mathematical optimal planning method. The PSO-NTVE is then used to derive suitable transformer impedances and relay time multiplier parameter values. The search for a global optimal solution for the voltage sag problems involves tests on the Scott and Le Blanc connected transformer power systems, in order to verify the effectiveness of the proposed method. Finally, the results show that the severity of the voltage sag is reduced by tuning the transformer impedances and relay settings.     

基于变压器突发短路试验探讨提高抗短路能力

电力系统中不可避免的短路事故层出不穷,为提高变压器抗短路能力设计,根据变压器短路试验的基本情况、数学模型和受力情况,分析了变压器短路试验过程中出现的各种故障前兆及其原理。最后,根据试验结果情况提出了关于提高变压器抗短路能力的措施和建议,对变压器抗短路能力设计有一定的指导意义。     

超导储能功率脉冲电源中脉冲变压器的研制

利用脉冲变压器模式的超导储能功率脉冲电源能有效地提升输出电流,针对这种模式,笔者重点介绍了降压升流型脉冲变压器的一种设计方法.文中先建立了脉冲变压器的等效电路模型,给出了脉冲变压器的技术要求和结构参数设计.通过理论分析和参数计算研制了一台脉冲变压器,对研制好的脉冲变压器进行仿真和实验测试,结果表明:实验输出波形与仿真波...     

基于电路-磁路耦合的感应型滤波换流变压器仿真与验证

感应型滤波换流变压器是一种利用变压器耦合绕组的安匝平衡作为滤波机理的变压器,为了研究其内部磁通链的耦合关系,建立电路-磁路模型很有必要。以绕组的连接方式为基础,建立了电路和电磁感应模型,以铁芯和绕组的空间几何结构为基础,考虑铁磁材料中的涡流效应,建立了磁路模型。铁芯的非线性磁阻用集总参数模型表示,并用微粒群优化(PSO)算法进行优化,最后以感应型滤波换流变压器的实际设计参数为依据,对感应型滤波换流变压器的滤波绕组接入滤波器前后的一次绕组电流和励磁电流进行了仿真对比。动模实验验证了所建模型的正确性与准确性。所建模型为感应型滤波换流变压器的阻抗设计提供了理论依据,并对正确分析感应型滤波换流变压器的运行性能具有重要意义。     

基于数字控制的MHz频率单脉冲电源设计

介绍了一种基于DSP数字控制的MHz级单脉冲电源设计方案。采用DSP作为信号源,产生三路相同的PWM信号,通过驱动电路放大后驱动三个并联的MOSFET,经变压器感应叠加后,在负载上输出频率为MHz脉冲。文中详细介绍了主电路、驱动电路以及变压器感应叠加的设计方法,并给出了各主要节点的实验波形。最后对研制的脉冲电源进行测试,证明该电源已达到设计要求。     

基于电流相位估计的三相不平衡条件下配变损耗计算

在配电网节能改造中因地制宜地更换高损耗配电变压器尤为重要,计算实际负荷条件下的配变损耗是变压器选型技术经济的关键之一。在低压三相四线制系统中,负荷不平衡往往造成了配变三相电流不对称。文中首先讨论了三相不平衡条件下变压器损耗计算模型,然后面向现有配变低压侧用采系统数据缺失电流相位的情况,提出了变压器低压侧电流相位估算方法,从而建立了三相不平衡条件下基于配变电流相位估算的损耗计算模型,解决了实际工程中因缺失相位数据而无法计算的难题。最后,通过仿真和试验分别对Yyn0和Dyn11这2种常用配变的电流相位估算和损耗计算模型进行了验证。     

采用统一磁路及空载试验的变压器饱和模型

为了精确地对变压器饱和进行仿真并建立变压器饱和模型,提出了一种基于统一磁路(UMEC)模型及空载试验的变压器饱和新模型.该模型利用UMEC来表示磁路中各个磁导之间的关系,并采用变压器空载试验获得电压、电流有效值曲线和功率损耗曲线,通过分段线性化方法得到变压器励磁磁导与电流之间的关系而近似表示磁路的饱和.该模型充分利用了...     

Optimal design of single-phase shell-type distribution transformers based on a multiple design method validated by measurements

This paper presents a method for the design of shell-type, single-phase distribution transformers to obtain the manufacturing specifications. The method is simple, efficient and accurate. By an exhaustive analysis, it is concluded that the obtained solution is the global optimum. The following constraints are imposed: excitation current, no-load losses, total losses, impedance and efficiency. The methodology of this paper requires only six input data: transformer rating, low voltage, high voltage, connection of low-voltage coil, connection of high-voltage coil, and frequency. These data are included in the transformer nameplate. In this paper, the minimization of the following four objective functions is considered: total owing cost, mass, total losses and material cost. The consideration of these four objective functions is implemented automatically by running the optimization algorithm four times without intervention of a designer. Consequently, transformer manufacturers save design man-hours and increase capacity. A design example on a 25 kVA transformer is presented for illustration. The optimized solutions of transformer design are validated with laboratory and process measurements.     

Modeling and simulation of the power transformer faults and relatedprotective relay behavior

The modeling of power transformer faults and its application to performance evaluation of a commercial digital power transformer relay are the objectives of this study. A new method to build an EMTP/ATP power transformer model is proposed in this paper. Detailed modeling of the transformer relay is also discussed. The transient waveforms generated by ATP under different operating conditions are utilized to evaluate the performance of the transformer relay. The computer simulation results presented in this paper are consistent with the laboratory test results obtained using an analog power system model     

基于MATLAB的BPNN在变压器故障诊断中的仿真参数研究

首先简要介绍了基于油中溶解气体DGA( Dissolved Gas - in - oil Analysis)的变压器故障诊断机理,然后介绍了反向传播神经网络BPNN( Back - propagation Neural Network)的网络结构、学习算法和训练流程,并结合变压器故障实际特点,分析了输入输出模式的确定、隐含层设计、传递函数和训练函数的选择对于整个网络设计的重要性,通过在MATLAB中神经网络工具箱平台上的仿真比较找出合理的参数,从而建立基于BPNN的变压器故障诊断模型,最后通过对验证样本的仿真诊断结果对比,说明了该模型在实际应用中的有效性.