K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 1Phn 1. Gii thiu v bin tn a bc 1.1B nghch lu: Bnghchlucnhimvchuyninnglngtnguninmtchiukhngi sang dng nng lng in xoay chiu cung cp cho ti xoay chiu. i lng c iu khin ng ra l in p hoc dng in. Nu i lng c iu khin ng ra l in p th b nghch lu c gi l b nghch lu p, ngc li gi l b nghch lu dng. Ngun mt chiu cung cp cho b nghch lu p c tnh cht ngun p, v ngun mt chiu cung cp cho b nghch lu dng c tnh cht ngun dng. Cc b nghch lu tng ng c gi l b nghch lu p ngun p v b nghch lu dng ngun dng hoc gi tt l b nghch lu p v b nghch lu dng. Trong trng hp ngun in u vo v i lng ng ra khc nhau, b nghch lu cung cp dng in xoay chiu t ngun in p mt chiu, ta gi chng l b nghch lu dng ngun p. B nghch lu l thnh phn ch yu trong b bin tn. ng dng ca chng kh quan trng v tng i rng ri, ch yu nhm vo lnh vc truyn ng in ng c xoay chiu vi chnh xc cao. Trong lnh vc tn s cao, b nghch lu c dng trong cc thit b l cm ng trung tn, thit b hn trung tn... B nghch lu cn c dng lm ngun in xoay chiu cho cc nhu cu trong gia nh, lm ngun in lin tc UPS, iu khin chiu sng v cn c ng dng trong lnh vc b nhuyn cng sut phn khng. K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 21.2B nghch lu p a bc: 1.2.1Khi nim: B nghch lu p l mt b nghch lu c ngun mt chiu cung cp l ngun p v i tng iu khin ng ra l in p. B nghch lu dng l b nghch lu c ngun mt chiu cung cp l ngun dng v i tng iu khin ng ra l ngun dng. Trn thc t ngun mt chiu l ngun p v i tng nghin cu l b nghch lu p. B nghch lu p cung cp v iu khin in p xoay chiu ng ra, ngun in p mt chiu c th l: pin in, c quy, in p mt chiu c chnh lu t in p xoay chiu c lc phng Cc ti xoay chiu thng mang tnh cht cm khng (ng c xoay chiu, l cm ng), dng in qua cc linh kin khng th ng ngt bng qu trnh chuyn mch t nhin. Do , linh kin trong b nghch lu p phi c kh nng kch ng, ngt dng qua n. Trong cc ng dng vi cng sut nh v va th c th s dng transitor BJT, MOSFET, IGBT. Trong phm vi cng sut ln c th dng GTO, IGCT hoc SCR kt hp vi b chuyn mch. Vi ti tng qut, mi linh kin cn mc thm mt diode i song hn ch in p pht sinh khi kch ngt linh kin. 1.2.2Phn loi: B nghch lu p c nhiu loi v nhiu phng php iu khin khc nhau: -Theo s pha in p u ra: nghch lu p mt pha, ba pha. -Theo s cp gi tr in p gia mt u pha ti n mt im in th chun trn mch: hai bc (two level), a bc (multilevel). Khi nim b bin tn hai bc xut pht t in p mt u pha ti (pha A, B, C) vi im chun (v tr ni t) trn mch DC thay i gia hai bc khc nhau (Vdc v 0). B nghch lu p hai bc c nhc im l to in p cung cp cho cun dy ng c dv/dt kh ln v gy ra hin tng in p common-mode (VNO khc 0) rt nghim trng. B nghch lu p a bc c pht trin gii quyt cc vn gy ra nu trn ca b nghch lu p hai bc v thng c s dng cho cc ng dng in p co v cng sut ln. u im ca b nghch lu p a bc l cng sut ca b nghch lu tng ln, in p t ln cc linh kin gim xung nn cng sut tn hao do qu trnh ng ngt ca linh kin cng K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 3gim theo; vi cng tn s ng ngt, cc thnh phn sng hi bc cao ca in p ra gim nh hn so vi b nghch lu p hai bc. -Theo cu hnh b nghch lu: dng Cascade, dng nghch lu cha cp diode kp NPC. Cc phng php iu khin b nghch lu p: -Phng php iu rng -Phng php iu bin -Phng php iu ch rng xung (SH PWM ) -Phng php iu ch rng xung ci bin (Modified PWM) -Phng php iu ch vector khng gian (SVPWM Carrier Based PWM) K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 4Phn 2. K thut iu ch sng mang PWM K thut iu ch sng mang PWM:T p ti 3 pha yu cu Vtj, c th s dng s sau xc inh Vj0: Theo s trn ta tnh c tn hiu iu khin cho cc cp linh kin: Vj0 = Vjt + V0 (V0 l in p offset) in p V0 c th chn gi tr bt k trong gii hn V0min:V0max ca n: V0min V0 V0max Vi :V0min = nVd Max V0max = - mVd Min(ty theo cc b nghch lu m chn ch s m,n cho ph hp) Min = min(Vt1, Vt2, Vt3)Max = max(Vt1, Vt2, Vt3) Cc trng hp c bit: ) min) maxa Vo Vob Vo Vo= `=)iu ch gin on (discontinueous PWM)

min max)2Vo Voc Vo+= space vector modulation (SVPWM)So snh tn hiu iu khin Vj0 vi sng mang Vcarrier ta tnh ton c tn hiu iu ch danh nh j K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 5Phn 3. Tnh ton v m phng Matlab A.B bin tn a bc dng Cascade A.1Cu trc b nghch lu dng Cascade: S dng cc ngun DC ring, thch hp trong trng hp s dng ngun DC c sn, v d di dng acquy, battery. Cascade inverter gm nhiu b nghch lu p cu mt pha ghp ni tip, cc b nghch lu p dng cu mt pha ny c cc ngun DC ring. Bng cch kch ng cc linh kin trong mi b nghch lu p mt pha, ba mc in p (-U,0,U) c to thnh. S kt hp hot ng ca n b nghch lu p trn mt nhnh pha ti s to nn n kh nng mc in p theo chiu m, n kh nng mc in p theo chiu dng v mc in p 0. Nh vy, b nghch lu p dng Cascade gm n b nghch lu p mt pha trn mi nhnh s to thnh b nghch lu 2n+1 bc. B bin tn 5 bc dng H-Brige Cascade Tn s ng ngt trong mi module ca dng mch ny c th gim i n ln v dvdt cng gim i n ln. in p p t ln cc linh kin gim i 0,57 ln, cho php s dng IJBT in p thp. K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 6Ngoi dng mch gm cc b nghch lu p mt pha, mch nghch lu p a bc cncdngghptngracaccbnghchlupbapha.Cutrcnychophp gim dvdt v tn s ng ngt cn 13. Mch cho php s dng cc cu hnh nghch lu p 3 pha chun. Mch nghch lu t c s cn bng in p cc ngun DC, khng tntidngcnbnggiaccmodule.Tuynhincutomchihisdngcc my bin p ng ra. B nghch lu c kho st y l b nghch lu 5 bc dng Cascade, v di y l gin vector khng gian vi y cc trng thi redundant state ca n.

Gin vector khng gian in p ca b cascade 5 bc. Vi cu to nh trn th in p trn mt pha c biu din nh sau:

0 1 2 3 4( )j dV V = + ;j= A, B, C 0 1i s s , vi1, 6 i =K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 7

Thit lp bng 1: Bng phn tch cc tn hiu iu khin : Mc in p nghch lu 0 AvCc trng thi ng ngt tng ng Trng thi ng ngt cacc cp linh kin Sj=(s1,s2,s3,s4) 2Vd(Vd,0,Vd,0)(1,0,1,0) Vd(Vd,0,0,0);( 0,0,Vd,0)(1,0,0,0) 0(0,0,0,0);(Vd,0 ,0,Vd);( 0,Vd,Vd,0)(0,0,0,0) -Vd(0,0,0,Vd);(0,Vd,0,0)(0,0,0,1) -2Vd(0,Vd,0,Vd)(0,1,0,1) Vj0(V10,V20,V30,V40)1234 - 2VdsVj0 s-Vd (0,Vd,0,Vd) (0,0,0,Vd) 0 d 0dV VjV 01 - VdsVj0 s0 (0,0,0,Vd) (0,0,0,0) 000 0dVjV 0 sVj0 sVd (0,0,0,0) (Vd,0,0,0) 0dVjV 000 VdsVj0 s2Vd (Vd,0,0,0) (Vd,0,Vd,0) 10 d+ 0dV VjV 0 K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 8 B nghch lu 3pha 5 bc dng Cascade. A.1.1Cc tham s B nghch lu Cascade 7 bc s dng linh kin l tng.in p dy ng ra Vd = 2300 V Cng sut ng ra S = 2MVA in p ngun dc b nghch lu khng thay i. Ti3phacnbngvicosu=0.9,tnsp50Hz.Vigitrxcnhcati,gi nguynthamskhixthotngcabnghchlucctnsvchsiuch khc nhau. K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 9A.1.2Tnh ton Vi in p dy ti Vd = 2300 V v ch s m = 1, ta c th xc nh in p Vdc max ax3383, 336 6 3t tmdcdcV Vm V Vm V= = = tdtpU 2300U = = 1327,91 (V)3 3=tptpSI =502,04A3U=P Scos 1,8MW; = =2 2QS- P0,87 MVAr = = 2tpL 2tpPR =2,383IQX= 1,153I= O= OLXL 0,0037 H2 f= ~ K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 10A.2Kt qu m phng: a) fo= 50Hz, m= 0.9, fsw= 720Hz in p offset, udk v in p pha vAO. in p H-Bridge, p nghch lu p ti K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 11 Sng in p vH1, v phn tch ph FFT tng ng. Sng in p vH2, v phn tch ph FFT tng ng. K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 12 p dy ti v ph FFT tng ng. Dng ti v ph FFT tng ng. K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 13b) fo= 50Hz, fsw= 4320Hz, m=0.9

Thit lp bng 1: Bng phn tch cc tn hiu iu khin : Mc in p nghch lu 0 AvCc trng thi ng ngt tng ng Trng thi ng ngt cacc cp linh kin Sj=(s1,s2,s3,s4) 2Vd(Vd,0,Vd,0)(1,0,1,0) Vd(Vd,0,0,0);( 0,0,Vd,0)(0,0,1,0) 0(0,0,0,0);(Vd,0 ,0,Vd);( 0,Vd,Vd,0)(0,1,1,0) -Vd(0,0,0,Vd);(0,Vd,0,0)(0,1,0,0) -2Vd(0,Vd,0,Vd)(0,1,0,1) Vj0(V10,V20,V30,V40)1234 - 2VdsVj0 s-Vd (0,Vd,0,Vd) (0,Vd,0,0) 010 d 0dV VjV - VdsVj0 s0 (0,Vd,0,0) (0,Vd,Vd,0) 01 1 0dVjV + 0 0 sVj0 sVd (0,Vd,Vd,0) (0,0,Vd,0) 0 1 0dVjV 10 VdsVj0 s2Vd (0,0,Vd,0) (Vd,0,Vd,0) d+ 0dV VjV 010 K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 14Kt qu m phng: in p offset, udk v in p pha vAO. in p H-Bridge, p nghch lu p ti K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 15 Sng in p vH1 v phn tch ph FFT tng ng. Sng in p vH2 v phn tch ph FFT tng ng. K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 16 p dy ti v ph FFT tng ng. Dng ti v ph FFT tng ng. K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 17Nhn xt: Ging nhau: Dng p v dng ti 2 kt qu trn tng i ging nhau. Khc nhau : Do tn s sng so snh th nghim b) cao hn phn a), dn n kt qu dng sng th nghim b) c dng hnh sin mn hn. THD th nghim b) thp hn so vi th nghim a). K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 18C. B bin tn a bc dng NPC C.1Gii thiu: S dng thch hp khi cc ngun DC to nn t h thng in AC. B nghch lu a bc cha cc cp diode kp c mt mch ngun DC c phn chia thnh mt s in p nh hn nh chui cc t in mc ni tip. GisnhnhmchDCgmnngunclnbngnhaumcnitip.inppha-ngunDCcthtc(n+1)gitrkhcnhauvtbnghchlucgilb nghch lu p (n+1) bc.Vd,chnmcinth0cuidingun,ccmcinpcthtcgm (0,U,2U,3U,,nU). in p t mt pha ti thng n mt v tr bt k trn nh cp diode kp ti im . in p pha-ngun DC t c mc in p nu trn (Ua0=U), tt c cc linh kin b kp gia 2 diode gm n linh kin mc ni tip lin tc k nhau, phi c kch ng, cc linh kin cn li phai c kha theo nguyn tc kch i nghch. B nghch lu p a bc dng diode kp ci tin dng sng in p ti v gim shock in p trn linh kin n ln. Vi b nghch lu 3 bc, dvdt trn linh kin v tn s ng ct gim i mt na. Tuy nhin vi n >3, mc chu gai p trn cc diode s khc nhau. Ngoi ra, cn bng in p gia cc ngun DC (p trn t) tr nn kh khn. K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 19 B nghch lu 3 bc dng NPC. Gin vector khng gian ca b nghch lu NPC 3 bc . C.1.1Cc tham s B nghch lu Cascade 7 bc s dng linh kin l tng.in p dy ng ra Vd = 6600 V Cng sut ng ra S = 5 MVA in p ngun dc b nghch lu khng thay i. Ti 3 pha cn bng vi cosu = 0.9, tn s p 50Hz. K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 20C.1.2Tnh ton Vi in p dy ti Vd = 2300 V v ch s m = 1, ta c th xc nh in p Vdc max ax366003t tmdcdcV Vm V Vm V= = = tdtpU 6600U = = 3810,5 (V)3 3=tptpSI =437,38A3U=P Scos 4, 5MW; = =2 2QS- P2,18 MVAr = = 2tpL 2tpPR =7,843IQX= 3,83I= O= OLXL 0,012 H2f= ~ M hnh m phng b nghch lu NPC 3 bc (nhiu sng iu khin). K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 21 Kt qu m phng a)fo= 50Hz, fsw= 900Hz, m=0.9 Dng sng xung kch ca cc cp linh kin. p pha tm ngun vAO, p dy vAB K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 22 FFT p Ti VAN FFT p Dy VAB K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 23 FFT p pha tm ngun vAO K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 24b)fo= 50Hz, fsw= 900Hz, m=0.3 Dng sng xung kch ca cc cp linh kin. p pha tm ngun vAO, p dy vAB K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 25 FFT p Ti VAN FFT p Dy VAB K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 26 FFT p pha tm ngun vAO K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 27 M hnh m phng b nghch lu NPC 3 bc (1 sng so snh). Kt qu m phng a)fo= 50Hz, fsw= 900Hz, m=0.9 Dng sng xung kch ca cc cp linh kin. K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 28 p pha tm ngun vAO, p dy vAB FFT p ti VAN K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 29 FFT p dy VAB FFT p pha VA0 K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 30b)fo= 20Hz, fsw= 0.9, m=0.3 Dng sng xung kch ca cc cp linh kin. p pha tm ngun vAO, p dy vAB K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 31 FFT p ti VAN FFT p dy VAB K THUT PWM CHO B NGHCH LU A BC HV : PHM HONG ANH 32 FFT p pha VA0