电压暂降毕业论文

摘要I摘要随着现代电力电子设备的广泛应用，电压暂降已经日益成为电力部门和电力用户所关注的电能质量问题。准确的电压暂降扰动源辨识对于协调电力用户与供电企业间的矛盾和对电能质量进行治理具有重要的意义。引起电压暂降的原因主要有短路故障、感应电动机启动、变压器激磁。本文在分析这三种原因基础上，通过理论分析，并结合MATLAB/SIMULINK仿真实验结果，研究并总结了三种原因造成电压暂降的特征。通过小波理论分析、分解波形，对电压暂降事件进行分类，以电压基波的有效值波形的跳变点位置、突变大小和方向，以及缓变信息为特征指标来描述电压暂降事件，并通过三层小波分解来获取特征指标，最后利用小波变换准确区分电压暂降的扰动原因。仿真结果表明：提取的特征指标能反映电压暂降事件本质和特征；不同干扰源所引起的电压暂降波形及其特征是不相同的，而且这些特征在电压基波有效值波形上显得尤为突出，凭此可以实现电压暂降事件的描述、辨识及评估。并且通过仿真实验验证了本文中关于电压暂降扰动原因识别的方法的可行性。关键词:电压暂降；扰动原因；小波理论；识别燕山大学本科生毕业设计（论文）IIAbstractWiththewideapplicationofmodernpowerelectronicsequipment，moreandmoreattentionfrombothelectricalengineersandcustomersisincreasinglypaidtothevoltagesagsasoneofthepowerqualityproblems.Thereisgreatdealofsignificanceonchangingtherelationshipbetweenthecustomersandutilitiestogetherwithimprovingpowerqualitytoidentifythesourcesofvoltagesagaccurately.Inthispaper，thecharacteristicsofvoltagesagsaregeneralizedbasedonanalysisofthethreecauseswhichareshortcircuitfaults，inductionmotorstartingtransformersaturation.WiththetheoreticalanalysisandthesimulationresultsMATLAB/SIMULINK，researchesandsummarizesthecharacteristicsofthethreereasonsofvoltagesag.Thenanalysisanddisintegrationthewave，accordingtothecharacteristicsofvoltagesageventswillinterferencesourceisdividedintofaultclasses，suchasswitchingoftransformer.Usingjumppointlocation，size，anddirectionoftheeffectivevaluevoltagewaveformofbasewaveandthegradedinformationtodescribethevoltagesagevents，characteristicindexcanbeobtainedbythreelayerwaveletdecompositionwavelettransform.Howtousewavelettransformtoaccuratelydistinguishvoltagesaginterferencesourceanditsdirectionareanalyzedindetail.Resultsshowthat:voltagesagwaveformsandeventcharacteristicswhichcausedbydifferentdisturbancesourcesaredifferent，thesefeaturesareparticularlyevidentonthevalidvalueoffundamental-wave.Therefore，thedescription，identificationandevaluationofvoltaicsadeventscanbeachievedbyusingthesefeatures.KeywordsVoltageSag;CausesofvoltageSag;Wavelettheory;DistinguishIII目录摘要.......................................................................................................................IAbstract................................................................................................................II第1章绪论........................................................................................................11.1本课题提出的背景................................................................................11.2关于本课题的研究现状........................................................................21.3本文的主要工作....................................................................................6第2章电压暂降................................................................................................72.1电压暂降的定义....................................................................................72.1.1暂降幅值........................................................................................72.1.2电压暂降持续时间........................................................................82.2电压暂降的起因....................................................................................92.3不同原因引起的电压暂降的幅值特征..............................................102.3.1短路故障引起的电压暂降..........................................................102.3.2感应电动机启动引起的电压暂降..............................................122.3.3变压器激磁引起的电压暂降.......................................................132.4本章小结..............................................................................................14第3章小波分析的基本理论及应用..............................................................153.1傅立叶分析..........................................................................................153.1.1傅立叶变换...................................................................................153.1.2离散傅立叶变换...........................................................................173.1.3快速傅立叶变换...........................................................................183.1.4短时傅立叶变换...........................................................................183.2小波变换基本理论..............................................................................193.2.1连续小波变换...............................................................................193.2.2离散小波变换...............................................................................203.2.3多分辨率分析...............................................................................213.2.4Mallat算法..................................................................................223.2.5信号的奇异性检测和小波变换模极大值理论...........................233.3傅立叶分析与小波分析的比较..........................................................25IV3.4小波变换在电力系统中的应用..........................................................263.5本章小结..............................................................................................28第4章电压暂降扰动原因的识别..................................................................294.1造成电压暂降的原因..........................................................................294.2仿真验证...................................................