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1、附录AResearchofParameterAdjustableHarmonicSignalGeneratorBasedonDDSLIWeiCollegeofComputerandInformationEngineeringHohaiUniversityChangzhou,213022,Chinaliwei_2142@163.comZHANGJinboCollegeofComputerandInformationEngineeringHohaiUniversityChangzhou,213022,Chinazhangjb@hhuc.edu.cnAbstr
2、actHarmonicsignalgeneratorwhosefrequency,phaseandharmonicproportionareadjustableisdesignedforthedetectingequipmentofpowersystem.TheprincipleofDDSandthedesignrequirementareintroduced.ThenthealgorithmofROMcompressionbasedonthesymmetryofsinewaveisexpounded.Finally,usingAlteraFPGA,th
3、edetaildesignofthewholesystemispresentedandtestwaveformsaregiven.Testresultsindicatethatthesystemfulfilsthedesignrequirements.1.IntroductionAnidealpowersystemsuppliespowerwithsinewave,butthepracticalwaveformofpowersupplyoftenhasmanyharmoniccomponents.Thebasicreasonofharmonicistha
4、tthepowersystemsuppliespowertotheelectricalequipmentwithnonlinearcharacteristic.Thesenonlinearloadsfeedhigherharmonicbacktothepowersupply,andmakethewaveformofcurrentandvoltageinpowersystemproduceseriousdistortion.Inthedetectionfieldofpowersystem,standardsignalgeneratorswhichcansi
5、mulatethepowerharmonicarehighlyneededtocalibratethepowerdetectingequipment,suchasphasedetector,PDdetector,andsoon.Sotheresearchofparameteradjustableharmonicsignalgeneratorprovidestheexactbasisforthestableoperationofpowerdetectingequipment,andhasgreateconomicbenefitandsocialvalue.
6、2.PrincipleofdirectdigitalsynthesisDirectdigitalsynthesis(DDS)isanewfrequencysynthesistechnologywhichdirectlysynthesizeswaveformonthebasisofphase.Usingtherelationshipbetweenphaseandamplitude,thephaseofwaveformissegmentedandassignedrelevantaddresses.Ineachclockperiod,theseaddresse
7、sareextractedandtherelevantamplitudesaresampled.Theenvelopeofthesesampledamplitudesistheexpectedwaveform.Iftheclockfrequencyisconstant,thefrequencyofoutputsignalisadjustablewithdifferentextractedstepsofaddresses.DDSiscomposedofphaseaccumulator,ROMtable,DACandLPF.Ineachclockperiod
8、,theoutputofphaseaccumulatorisaccumulate
