1、Power ElectronicsChapter 7 PWM TechniquesPowerElectronics2Pulse Width Modulation(PWM)(Chopping control)DC/DCAC/ACDC/ACAC/DCPowerElectronics3PowerElectronics4PowerElectronics5PowerElectronics6PowerElectronics7PowerElectronics8ControlsignalCarrier图6-4MudulationCarrierUd+V1V2V3V4VD1VD2VD3VD4uoRLurucPow
2、erElectronics9ControlsignalCarrier图6-4MudulationCarrierUd+V1V2V3V4VD1VD2VD3VD4uoRLurucPowerElectronics10PowerElectronics11PowerElectronics12 PowerElectronics13PowerElectronics141002+-1234+-02+-4+-01+-3+-5+-Magnitude(%)(nc+kr)0.20.40.60.81.01.21.4kna=1.0a=0.8a=0.5a=0PowerElectronics15100 2+-1234+-0 2
3、+-4+-0 1+-3+-5+-Magnitude(%)0.20.40.60.81.01.2kna=1.0a=0.8a=0.5a=0(nc+kr)PowerElectronics16PowerElectronics17图6-18ucur1uOturur1uOtur3图 6-1 9ucur U 1ur V 1ur W 1uuU N Ud-UdOtOur Uur Vur WucOtOOOOtttttuV N uW N uU Vu1-11-1-0.5uP2Ud2UdPowerElectronics18PowerElectronics19acbabbccaabbcca1 1 1T Phase vari
4、ables(a,b and c)produceline-to-line variables(ab,bc and ca)in plane-Line-to-line variables(ab,bc and ca)do not have-component in-coordinate systemVector Space of 3-phase Line-to-Line VariablesPowerElectronics20wherecabcababcvvvTvv/232302121132/abcTabbccavv Space vectorjev22vvvv1tanIf Vm is the ampli
5、tude of balanced,symmetrical,three-phase line-to-linevoltages,then mV23vPowerElectronics21idcvabVdcsascsb010000000000011111111111icibib+ic0iaia+icia+ibia+ib+icSwitching statepnnppnnpnnppnnppnppppnnnvcavbcVdcVdcVdcVdcVdc-Vdc-Vdc-Vdc-Vdc-Vdc-Vdc000000000000iaibicvavcvbsasbscpnVdcidcPowerElectronics22/
6、11312222033310222abdcdcpnnabcbcpnncadcdcpnnvVVvVTvvvVVj1pnneVVdcV230vv1tanab,bccavv1VPowerElectronics23dcdcdcppncabcababcppnppnVVVvvvTvvV200232302121132/j2ppneVVdcV290vv1tanab,bccav2VPowerElectronics2400000232302121132/pppcabcababcppppppvvvTvvV0VV0pppab,bcca0VPowerElectronics25dcV23015090-90-1500-30
7、00()pnnV1ppnV2npnV3nppV4nnpV5pnpV6pppV0nnnV0Sector IIVIIIIIVVIat center pointab,bccapnnV1ppnV2npnV3nppV4nnpV5pnpV6nnnpppV0PowerElectronics26ab,bccavvjrefrefevvVm22V23vvtvv1tanwhereIn general,120tV120tVtVvvvmmmrefcabcabcoscoscosAssume)()()(tjmrefetV23tVpnnV1pnpV6ppnV2npnV3nppV4nnpV5at center pointnnn
8、pppV0refVPowerElectronics27SiiiT0iT0refTTdtVdtViS,Vref()V1()V2()T1T2T0TStTotal area of=Area of211S211STTTTTT02T01T0refdtVdtVdtVdtVFor examplevPowerElectronics28ab,bccavvpnnV1pnpV6ppnV2npnV3nppV4nnpV5nnnpppV0refV iaibicvavcvbsasbscpnVdcidcabc101010IIVIIIIIVVI2V0V1V11Vd22VdrefVPowerElectronics29211S21
9、1STTTTTT02T01T0refdtVdtVdtVdtV2211SrefTVTVTV2211ST6060VT01VTsincossincos)sin(60V32dTT11S1sin22S2V32dTT210dd1dFrom HF synthesis definition,Assume is constant in TS,where30refV2V0V1V11Vd22VdrefVPowerElectronics30PowerElectronics31PowerElectronics32PowerElectronics33图6-26Filter+-uu*u2Ud2UdPowerElectronics34PowerElectronics35PowerElectronics36PowerElectronics37图6-31PI+-LoadTriangular-wavesin(t+2k/3)(k=0,1,2)cos(t+2k/3)(k=0,1,2)u*dud+-+-+iduRuLXLRuA,B,CudRLua,ub,ucPowerElectronics38Direct current control
