基于级联H桥拓扑的SVG及其调制策略研究-(1)

申请上海交通大学全日制专业硕士学位论文基于级联H桥拓扑的SVG及其调制策略研究学校：上海交通大学院系：电子信息与电气工程学院学科专业：电气工程作者姓名：隋龙弟导师姓名：郑益慧教授上海交通大学电子信息与电气工程学院2013年12月AThesisSubmittedtoShanghaiJiaoTongUniversityfortheDegreeofMasterResearchofSVGbasedonCascadeH-bridgeTopologyandModulationStrategyAuthor:LongdiSUISpecialty:ElectricalEngineeringAdvisor:YihuiZHENGSchoolofElectronicInformationandElectricalEngineeringShanghaiJiaoTongUniversityShanghai,P.R.ChinaDecember,2013上海交通大学全日制专业硕士学位论文摘要第I页基于级联H桥拓扑的SVG及其调制策略研究摘要静止同步补偿器SVG能够有效补偿系统无功，维持系统电压稳定，提高电能质量，提高系统的功率因数。相比于传统的无功补偿器具有明显优势，代表了动态无功补偿装置的发展方向。而级联拓扑结构能够增加装置的容量，提高输出电压等级，使其在中高压无功补偿领域的应用成为可能。为了降低开关损耗，本文采用级联H桥拓扑结构，设计基频优化PAM调制策略。各H桥都工作于基频开关频率下，降低了开关损耗。同时，各H桥输出电压叠加构成阶梯波以逼近正弦波，通过面积等效原理求得开关角度初值，经迭代计算后得到各H桥最优的开关角度，使输出谐波畸变率最小。再通过脉冲轮换策略使直流侧电压在平均意义上保持平衡。然后采用电流间接控制方法，通过控制功角来调节无功的输出，简单有效。最后，在基频优化PAM方法的基础下加入逆系统PI控制方法使得装置的响应速度加快。仿真结果证明了上述方法的有效性。在上述基频优化PAM调制方法基础上，为了进一步改善了输出波形的质量，本文提出了PAM+PWM混合调制策略。通过增加PWM单元，采用单极倍频PWM调制实现电流直接控制，提高了控制精度和响应速度。PWM单元能够有效的对PAM单元输出阶梯波中的谐波进行补偿，同时增加了谐波自补偿环节，进一步改善了输上海交通大学全日制专业硕士学位论文摘要第II页出波形的质量，降低了输出谐波畸变率。最后通过在MATLAB/Simulink中建立级联SVG仿真模型，验证了所提方法的有效性。关键字：SVG，级联H桥拓扑，基频优化PAM调制，混合调制，电流控制方法上海交通大学全日制专业硕士学位论文ABSTRACT第III页RESEARCHOFSVGBASEDONCASCADEH-BRIDGETOPOLOGYANDMODULATIONSTRATEGYABSTRACTStaticVarGeneratorSVGcancompensatereactivepowereffectively,maintainthesystemvoltagestability,improvepowerquality,improvesystempowerfactor.Comparedwiththetraditionalreactivepowercompensationdevice,SVGhasobviousadvantages,representsthedevelopmentdirectionofdynamicreactivepowercompensationdevice.CascadedtopologyofSVGincreasesthecapacityandtheoutputvoltagelevel,whichmakestheapplicationofSVGpossibleinmiddleandhighvoltagesystems.Inordertoreduceswitchinglosses,thefundamentalfrequencyoptimizationPAMmodulationstrategyisusedoncascadeH-bridgetopologyinthepaper.EachH-bridgeareworkingonthefundamentalswitchingfrequency,reducingtheswitchinglosses.MeanwhiletheoutputvoltageofeachH-bridgeissuperimposedasstepwavetoapproximatethesinewave.Theinitialswitchinganglesaregettingbytheareaequivalenttheory,aftertheiterativecalculationtheoptimalswitchinganglesareobtained,makingtheharmonicdistortionleast.Thepulsecycle上海交通大学全日制专业硕士学位论文ABSTRACT第IV页transpositionisusedontheDCside,makingthembalanceintheaveragemeaning.Thecurrentindirectcontrolmethodisusedbyadjustingpowerangletocontroltheoutputreactivepowersimplyandeffectively,inversesystemPIcontrolmethodisaddedtomakethedeviceresponsespeedfaster.Simulationresultsshowtheeffectivenessofthemethodabove.BasedonthefundamentalfrequencyoptimizationPAMtoimprovethequalityoftheoutputwaveformfurther,thehybridmodulationmethodofPAM+PWMisintroducedinthispaper.ByaddingthePWMunit,theunipolar-frequencydoublingSPWMmodulationisappliedtoachievecurrentdirectcontrol,whichimprovesthecontrolaccuracyandresponsespeedofthedevice.ThePWMunitcancompensatetheoutputharmonicofthestepwaveeffectively,meanwhiletheharmonicself-compensatingmethodisintroduced,whichimprovesthequalityoftheoutputwaveformfurther,reducetheoutputharmonicdistortionfactor.ThemodelofcascadeSVGisbuiltinMatlab/Simulink,theresultprovesthevalidityofthismethod.KEYWORDS:SVG,cascadeH-bridgetopology,fundamentalfrequencyoptimizationPAM,hybridmodulation,currentcontrolmethod上海交通大学全日制专业硕士学位论文目录第V页目录摘要............................................................................................................................IABSTRACT...............................................................................................................III第1章绪论.................................................................................................................11.1无功补偿的研究背景及意义.........................................................................11.2无功补偿的发展历程.....................................................................................21.3SVG的研究现状.............................................................................................31.3.1拓扑结构的研究现状...........................................................................41.3.2调制策略的研究现状...........................................................................51.4文章主要研究内容和结构安排.....................................................................8第2章级联SVG的基本理论................................................................................102.1传统SVG的结构和基本原理.....................................................................102.2级联SVG的结构和基本原理.....................................................................122.2.1级联SVG基本拓扑结构...................................................................122.2.2级联SVG的数学模型.......................................................................132.2.3级联SVG的稳定性分析...................................................................162.3级联SVG系统参数选择.............................................................................182.3.1直流侧电容值.....................................................................................182.3.2并网电抗器及等效电阻.....................................................................202.4无功电流的检测方法...................................................................................