共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
电机定子结构及其绝缘介电常数的频率特性对定子绕组电容值的影响 总被引:2,自引:3,他引:2
确定电机定子线棒的高频参数对于研究局部放电信号在电机绕组中的传播特性及研究PWM逆变器驱动的交流电机的定子绕组电压分布有重要意义。文中对大型汽轮发电机定子线棒的电容做了比较详细的研究,内容包括:对电机定子线棒复合绝缘等值介电常数的频率特性的测试研究、采用数值计算方法计算出用铝箔纸裹住的电机定子线棒的多导体传输线模型的单位长度电容、线棒股线间薄绝缘对电容的影响、对铁心硅钢片叠片间隙对电容的影响等。其数值计算结果与之前测量得到的电容值比较吻合,这也证明了通过测量开路阻抗、短路阻抗来得到电机定子线棒分布参数的试验方法是有效的。 相似文献
3.
This paper proposes a novel scheme for detecting and classifying faults in stator windings of a synchronous
generator (SG). The proposed scheme employs a new method for fault detection and classification based on
Support Vector Machine (SVM). Two SVM classifiers are proposed. SVM1 is used to identify the fault occurrence in
the system and SVM2 is used to determine whether the fault, if any, is internal or external. In this method, the
detection and classification of faults are not affected by the fault type and location, pre-fault power, fault resistance
or fault inception time. The proposed method increases the ability of detecting the ground faults near the neutral
terminal of the stator windings for generators with high impedance grounding neutral point. The proposed
scheme is compared with ANN-based method and gives faster response and better reliability for fault classification. 相似文献
4.
Power transformer insulation systems are subjected to many stresses during normal operation due to lightning and switching.If the spectrum of incoming surge voltage matches the winding one,the corresponding resonance will be excited.Therefore external transients occurring in power systems might trigger internal overvoltages with large maximum value in transformer windings.Overvoltages having such characteristic have been the root cause of many power transformer failures.The paper presents an approach to the identification of sensitive zones in the transformer windings based on the measurements of overvoltages inside windings and frequency dependences of admittance of the power transformer.The frequency characteristic of the transformer winding may determine those regions in the frequency spectrum.The presented approach might be used both for design optimization and diagnostics of distribution and power transformers. 相似文献
5.
Integration of electric vehicles (EVs), demand response and renewable energy will bring multiple opportunities for
low carbon power system. A promising integration will be EV battery swapping station (BSS) bundled with PV
(photovoltaic) power. Optimizing the configuration and operation of BSS is the key problem to maximize benefit of
this integration. The main objective of this paper is to solve infrastructure configuration of BSS. The principle
challenge of such an objective is to enhance the swapping ability and save corresponding investment and
operation cost under uncertainties of PV generation and swapping demand. Consequently this paper mainly
concentrates on combining operation optimization with optimal investment strategies for BSS considering multiscenarios
PV power generation and swapping demand. A stochastic programming model is developed by using
state flow method to express different states of batteries and its objective is to maximize the station’s net profit.
The model is formulated as a mixed-integer linear program to guarantee the efficiency and stability of the
optimization. Case studies validate the effectiveness of the proposed approach and demonstrate that ignoring the
uncertainties of PV generation and swapping demand may lead to an inappropriate batteries, chargers and
swapping robots configuration for BSS. 相似文献
6.
V. I. Mishin N. T. Lut S. S. Makarevich R. N. Chuenko 《Russian Electrical Engineering》2016,87(12):653-660
The disadvantages of three-phase asynchronous motors with short-circuited rotors, which are widely used in practice, are discussed. It is determined that the most significant disadvantage is consumption of two types of electric energy from a network: active energy for conversion into mechanical energy accompanied by inevitable heat losses and reactive energy that is not converted into other types of energy, but is expended on generation of the magnetic field required for electromechanical conversion of energy in an electrical machine. It is suggested to use internal capacitive compensation of reactive power to improve the technical and economic indices of asynchronous machines of both motors and generators. In addition, each phase winding of the asynchronous machine stator is divided into two parts equal in number of turns spatially shifted between each other in the core slots by an angle of 30°. These parts are connected according to the scheme of the rotary autotransformer to the electrical capacity at its output. The change of the spatial position of the stator windings leads to a change in time of the action of the phase angles of their electromotive force and, therefore, of currents and voltages without changing the introduced reactive impedances. Thus, the spatial coordinate of the electrical value is converted into the time coordinate in the electromagnetic circuit with a rotating magnetic field. The combination of this property of the stator windings in accordance with the rotary autotransformer with the action of the electrical capacity at its output creates the effect of internal capacitive compensation of reactive power in an asynchronous machine. The ability to use internal capacitive compensation of reactive power in single-phase asynchronous machines is considered. A method of calculation of the characteristics of compensated asynchronous machines taking into account the change of the magnetizing contour resistance is presented. The advantages of compensated asynchronous motors and compensated asynchronous generators are determined. Recommendations as to their effective practical use are given. 相似文献
7.
等距笼型转子无刷双馈电机的有限元分析 总被引:1,自引:0,他引:1
针对笼型无刷双馈电机的效率较低的问题进行研究,电机效率与转子磁场极数转换效率和转子漏阻抗参数相关,对转子结构进行优化设计是提高电机性能的根本途径。在分析现有笼型转子的特性基础上,提出等距笼型的新转子结构。新转子具有公共端环和独立叠式转子导体回路,每个转子导体回路的节距相等。利用ANSYS软件对不同笼型转子结构的磁场进行有限元分析,计算出转子磁动势谐波含量和转子漏阻抗参数。结果表明,新转子结构无刷双馈电机的转子电阻和漏电抗小,与定子功率绕组和控制绕组极数相对应的转子谐波磁场含量高,其他高次谐波磁场含量低。 相似文献
8.
Changzheng Zhang Qiaofu Chen Youbin Zhao Dayi Li Yali Xiong 《Power Delivery, IEEE Transactions on》2007,22(2):911-918
In this paper, a novel principle of an active power filter based on the harmonic impedance control of a transformer is proposed for high-voltage power distribution systems application. A linear transformer with multiple secondary windings is adopted. The primary winding is shunted with harmonic-producing loads, while the secondary windings are connected with inverters. The primary harmonic current is detected and then tracked by the inverters with fixed compensation coefficient. When the harmonic current compensation condition is satisfied, the transformer can really exhibit nearly zero impedance to harmonic current and primary self-impedance to fundamental current. As a result, the harmonic currents in power systems can be led to flow into the transformer branch. The operation principle, the control scheme, and the harmonic current detection method are discussed in detail. Finally, simulated waveforms and experimental results are presented to verify the effectiveness of the active power filter 相似文献
9.
研究了感应加热电源拓扑结构,基于全桥变流电路结构分析了电源的工作状态和输出波形,提出了一种减小损耗的有效途径,即新型定频移相控制技术(FFP),应用电磁感应理论,对感应加热电路的负载,即线圈部分的阻抗计算和优化进行了分析,得到了减小负载线圈损耗的方法。软开关仿真及实验结果验证了上述观点。 相似文献
10.
11.
This paper presents a method of how to obtain both terminal and internal high frequency models of power transformers using FEM. The model is established from construction information and the approach implements frequency-dependent phenomena on a physical basis. Eddy current effects are represented accurately even with a relatively coarse mesh by using a frequency-dependent complex permeability representation for the core and windings. The model can be employed in EMTP-like programs for a variety of applications, such as analysis for FRA, internal/terminal stresses and transformer network interaction. Analyses of internal stresses are elucidated in this paper. 相似文献
12.
13.
本文提出了新型混合励磁发电系统,它由混合励磁发电机、无刷励磁机和旋转整流器构成,其中混合励磁发电机转子由结构上独立的两部分——永磁体和电励磁组成,定子铁心沿轴向分为三段:永磁部分定子铁心、电励磁部分定子铁心以及中间部分定子铁心,其中中间部分定子铁心采用非导磁材料。新型混合励磁系统具有永磁电机高效、高功率密度的优点。本文仅针对新型混合励磁发电系统中的无刷励磁机进行分析,无刷励磁机结构与绕线式异步电机结构相似,定、转子均采用三相绕组,无刷励磁机的转子与混合励磁发电机转子同轴,转子绕组经固定在同发电机转轴上的二极管整流将交流变为直流,供给混合励磁发电机励磁。同时本文采用电磁场有限元法对无刷励磁运行机理和电磁性能进行分析,其中包括供电电源类型、定子电流特性和转矩特性等。本研究成果对掌握无刷励磁机运行特性具有重要作用。 相似文献
14.
为了方便和准确地计算双馈风电机组(DFIG)接入系统的短路电流分布,提出了投撬棒后DFIG的工频和转频序网等值电路,并给出了利用该等值电路计算系统短路电流的方法。通过求解投撬棒后DFIG磁链的状态微分方程,得到其工频分量和转频分量的解析表达式。在此基础上,将DFIG的电压空间矢量方程按转频和工频分量进行分解,并根据空间矢量与相量间的关系,分别形成了转频和工频序网等值电路。其中,转频正序、负序等值电路分别为带内阻抗的电势和无源阻抗,而工频正序、负序等值电路均为无源阻抗。利用该等值电路只需已知DFIG的电机参数和故障初值条件而无需仿真即可求得DFIG接入系统各处的短路电流。以某DFIG接入系统为例,通过PSCAD仿真验证了该等值电路和短路计算方法在不同故障条件下的有效性。 相似文献
15.
16.
ABSTRACT A steady state heat transfer model applicable to rotating electrical machines with non salient poles is presented. Several cooling options are accounted for, ranging from the totally enclosed machine running in a high vacuum to the open ventilated one with axial and radial ducts. Sophisticated cooling systems, such as gas or water cooled windings, are not considered. The model includes such unusual levels of detail as radiation heat exchanges and prediction of the actual hot spot temperatures of the iron and windings. Peripheral results are the temperatures at other representative points and complete maps of the conduction, convection and radiation heat exchanges. The resultant computer program may be used either to check the temperature rise constraints for a given design, or as a tool to analyze the performance of the cooling system of an actual machine or proposed design. Parametric studies can be easily performed, showing the sensitivity of the temperature rises and heat exchanges to variations of a particular dimension, loss, flow rate or material property. 相似文献
17.
18.
阻抗可控的并联混合型有源电力滤波器 总被引:3,自引:0,他引:3
针对高压交流电力系统,提出一种基于阻抗可控的并联混合型有源电力滤波器新原理。通过电力电子变换器的控制,使得并联变压器呈现可控的阻抗。它始终对谐波呈现近似为零的低阻抗,从而输导系统中的谐波电流,流入并联变压器支路;同时对基波呈现连续无级可调的电抗,与无源电力滤波器相结合,实时补偿系统的无功功率。为满足有源电力滤波器大容量的工程需要,并联变压器采用二次侧多补偿绕组的结构。提出一种适合该滤波原理的指令电流运算方法。仿真结果表明此滤波新方案具有良好的谐波抑制和无功功率补偿的性能。 相似文献
19.
20.
《Electric Power Systems Research》1999,49(1):37-44
In this paper, the effects of various power system parameters on the critical clearing time are presented. The various parameters for which the analysis is presented include the machine parameters, i.e. damping, inertia constant and transient reactance, and system parameters, i.e. line impedance, transformer impedance and fault impedance. Various configurations of faults are also investigated. The simplest single machine infinite bus power system was simulated. Plots and relationships for each parameter are presented and conclusions are drawn from their behavior. The paper is a comprehensive treatment of the time domain method to the single machine system and is particularly helpful to the utility power engineers and researchers in the electric machines area to comprehend the system behavior for various system parameters. The results can be generalized to the large scale multimachine power systems as well. 相似文献