SIMPLE AND NOVEL HYBRID RANDOM PWM ALGORITHM FOR DTC-INDUCTION MOTOR DRIVE FOR REDUCED ACOUSTICAL NOISE

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1 Acta Elctrotchnica t Informatica, ol. 1, No. 4, 01, 69 75, DOI: /v x 69 SIMPLE AND NOEL HYBRID RANDOM PWM ALGORIHM FOR DC-INDUCION MOOR DRIE FOR REDUCED ACOUSICAL NOISE P. NAGASEKHARA REDDY, J. AMARNAH, P. LINGA REDDY E.E.E. Dpartmnt, M.G.I.., Hydrabad, Andhra Pradh, India, -mail: pnrddy04@gmail.com E.E.E. Dpartmnt, J.N.. Univrity, Hydrabad, Andhra Pradh, India, -mail: amarnathjinka@rdiffmail.com E.E.E. Dpartmnt, K.L. Univrity, Guntur, Andhra Pradh, India ABSRAC A impl and novl hybrid random PWM algorithm for dirct torqu controlld induction motor driv for rducd acoutical noi and harmonic ditortion i prntd in thi papr to rduc th complxity of th claical pac vctor approach. h propod algorithm i dvlopd by uing th imaginary witching tim, which do not rquir angl and ctor information. In ordr to gt th randomization ffct, th propod algorithm u dicontinuou pulwidth modulation maximum (DPWMMAX) algorithm in conjunction with th pac vctor pulwidth modulation (SPWM) algorithm. h harmonic analyi of th two witching qunc i carrid out and by comparing ach othr in ach ampling tim intrval, th propod algorithm lct a uitabl witching qunc. In th propod algorithm by changing th factor, th witching qunc of SPWM and DPWMMAX algorithm ar gnratd. h propod PWM algorithm u 017 and 71 qunc whn valu tak 0.5 and 0 rpctivly. A th zro tat tim i varid randomly according to th oprating qunc, randomization ffct will occur, which rult in rducd dominating harmonic and hnc giv rducd acoutical noi. o validat th propod PWM algorithm, th numrical imulation tudi hav bn carrid out and rult ar prntd and compard. h imulation rult confirm th ffctivn of th propod algorithm. Kyword: DC, imaginary witching tim, random PWM, tator flux rippl, SPWM 1. INRODUCION Aftr th invntion of fild orintd control (FOC) [1] algorithm, th induction motor driv ar bcoming popular in many indutrial application. But, th FOC i mor complx du to th uag of rfrnc fram tranformation. o rduc th complxity of FOC, a impl control tchniqu known a dirct torqu control (DC) i invntd by akahahi in 1980 []. hough th oprating principl of FOC and DC ar diffrnt, both tchniqu giv ffctiv control of flux and torqu. h two control tratgi hav bn implmntd in many indutrial application uccfully. h dtaild comparion btwn FOC and DC i givn in [3]. Du to th abnc of rfrnc fram tranformation, DC i impl whn compard with th FOC. hough DC giv uprior torqu prformanc, it giv variabl witching frquncy of th invrtr and larg tady tat rippl in torqu, currnt and flux. o improv th torqu and currnt rippl, vral pulwidth modulation (PWM) algorithm hav bn dvlopd by vral rarchr. A dtaild urvy of th PWM algorithm i givn in [4]. h PWM algorithm can b claifid into two catgori uch a triangular comparion approach and pac vctor approach. Howvr, th pac vctor approach i mor popular a it offr mor advantag whn compard with th triangular comparion approach [5]-[6]. Hnc, th pac vctor PWM (SPWM) algorithm i attracting many rarchr nowaday. hough th SPWM algorithm bad DC giv rducd harmonic ditortion whn compard with th convntional DC, it giv dominating harmonic around th witching frquncy. Hnc, th acoutical noi of th motor i mor. o rduc th acoutical noi of th driv, rcntly, random PWM (RPWM) algorithm ar bcoming popular. ariou typ of RPWM algorithm hav bn dicud in [7]- [10]. h RPWM algorithm randomiz th pul pattrn or witching frquncy by uing a random numbr gnrator. h tandard SPWM algorithm ditribut th zro tat tim qually among th two poibl zro voltag vctor. By utilizing th frdom in zro tat tim ditribution variou PWM algorithm can b gnratd a xplaind in [11]-[19]. In many application an fficint PWM algorithm i rquird, which giv l harmonic ditortion and acoutical noi. Hnc, in rcnt yar many rarchr hav bn concntratd on th harmonic analyi of PWM algorithm. o calculat th harmonic analyi of th algorithm a tim domain analyi ha bn givn in [11]-[16], [18]-[19] by uing th notion of tator flux rippl and currnt rippl. Howvr, th PWM algorithm, which ar dicud o far, u th angl and ctor information, which incra th complxity involvd in th algorithm. o rduc th complxity, a novl approach i prntd in [17]-[19] by uing th concpt of imaginary witching tim. hi papr prnt a implifid hybrid random PWM algorithm, which u two witching qunc and lct on qunc in ach ampling tim priod that rult in rducd harmonic ditortion.. PROPOSED SWIHCING SEQUENCES o rduc th complxity involvd in th SPWM, th propod witching qunc ar dvlopd by uing th concpt imaginary witching tim. h imaginary witching tim ar proportional to th intantanou valu of th ampld rfrnc pha voltag. h can b calculatd a. an an ; bn bn ; cn cn (1)

2 70 Simpl and Novl Hybrid Random PWM Algorithm for DC-Induction Motor Driv for Rducd Acoutical Noi o calculat th witching tim of th activ and zro voltag vctor, in vry ampling tim priod maximum ( Max ( an, bn, cn) ), minimum ( Min ( an, bn, cn ) ) and middl valu ( Mid ( an, bn, cn ) ) of imaginary witching tim ar valuatd. hn th activ voltag vctor and zro voltag vctor witching tim can b givn a in ()- (4). [18] 1 max mid () 0, 7 r0, q r7 r r7 r0 rf r1 1 r r1 mid min z 1 hu, th activ tat and zro tat tim can b calculatd in a impl by uing imaginary witching tim. Howvr, th SPWM algorithm ditribut th zro tat tim qually in vry ampling tim priod. By utilizing th unqual ditribution of zro voltag vctor witching tim, variou PWM algorithm can b gnratd. o gnrat th propod witching qunc, th zro tat tim duration can b modifid a 0 z for 0 voltag vctor and 7 (1 )z for 7 voltag vctor. By varying th valu btwn 0 and 1, variou PWM algorithm can b gnratd. h SPWM and DPWMMAX algorithm can b gnratd for =0.5 and 0 rpctivly. h algorithm u and qunc in th firt ctor and o on. In ach ampling tim intrval, th SPWM algorithm ha thr numbr of witching and whra for th DPWMMAX algorithm i two. Hnc, to gt th am avrag witching frquncy of th invrtr, a ampling tim intrval i takn a for th SPWM algorithm, 3 for th DPWMMAX algorithm. whil 3. PROPOSED HYBRID RPWM ALGORIHM 3.1. Analyi of Harmonic Ditortion h total harmonic ditortion (HD) of th lin currnt i a widly ud maur for th quality of currnt wavform. h quality of th lin currnt wavform can b dirctly dtrmind in tim domain by intgrating th rippl voltag. hi mthod of analyi can b applid for any PWM witching qunc. In th pac vctor approach, th rfrnc voltag vctor i contructd in an avrag mannr but not in an intantanou mannr. h actual valu of th tator voltag diffr from th applid voltag. Hnc, thr i alway an intantanou rror voltag vctor. h rror voltag vctor i dfind a givn in (6) rip k rf, k 0,1,...7 (5) whr k i th k th voltag vctor. h activ voltag vctor ( 1,,... 6 ) can b dfind a j( k 1) 3 k. 3 h rippl voltag vctor and trajctory of th tator flux rippl can b rprntd in a complx plan a hown in Fig. 1. (3) (4) d Fig. 1 Rippl voltag vctor and trajctory of tator flux rippl h tator flux rippl vctor corrponding to th voltag rippl vctor ar givn by [19] r1 in 1 j co 3 3 rf 1 (6) o r in 60 3 j co 3 r j rf 0 0 o 60 rf r 7 j rf 7 (9) h abov tator flux rippl vctor ar normalizd to b for furthr implification. h final flux rippl vctor xprion can b obtaind in trm of imaginary witching tim and modulation indx a givn in (10) (13). 1 ( 1 1 ) r1 j M i 1 6 3M i 18M i (10) r 1 ( 1 ) j M i 6 3M i 18M i r 0 jm i 0 (7) (8) (11) (1) r 7 jm i 7 (13) hn th rm tator flux rippl ovr a ampling tim priod can b calculatd a (rm) whr 1 1 r dt M i (14) (15) ( 0 ) 1 1 ( ) (16)

3 Acta Elctrotchnica t Informatica, ol. 1, No. 4, ( 0 1 ) 7 ( 0 ) 1 13 M i 01 7 ( 0 1 ) (17) By mploying (14), th modulation indx and angl dpndnt man quar tator flux rippl of SPWM and DPWMMAX algorithm can b aily computd and graphically illutratd a hown in Fig. Fig. 4. Fig. ariation of tator flux rippl for SPWM (continuou lin) and DPWMMAX (dottd lin) algorithm ovr th firt ctor at M i Propod Hybrid RPWM Algorithm From th tator flux rippl charactritic, it can b obrvd that at lowr modulation indic, th SPWM algorithm giv uprior prformanc whra at highr modulation indic th DPWMMAX algorithm giv uprior prformanc. o minimiz th harmonic ditortion in th lin currnt, th rm tator flux rippl ovr vry ampling tim priod hould b rducd. h dvlopmnt of propod PWM tchniqu for rducd harmonic ditortion involv dtrmination of uprior prformanc for ach qunc. h zon of uprior prformanc for a givn qunc i th patial zon within a ctor whr th givn qunc rult in l man quar tator flux rippl than th othr qunc conidrd. In th propod PWM algorithm, in vry ampling tim priod th rm tator flux rippl ar compard with ach othr and th qunc, which ha l rm tator flux rippl i applid to minimiz th total harmonic ditortion (HD). A th propod PWM algorithm randomiz th tim duration of zro tat tim, it giv prad pctra and giv rducd amplitud for dominating harmonic around witching frqunci. Hnc, th acoutical noi of th induction motor alo can b rducd. hu, th propod PWM algorithm u th DPWM algorithm in conjunction with SPWM algorithm. 4. PROPOSED HYBRID RPWM BASED DC Fig. 3 ariation of tator flux rippl for SPWM (continuou lin) and DPWMMAX (dottd lin) algorithm ovr th firt ctor at M i 0. 7 h block diagram of th propod hybrid RPWM algorithm bad DC i a hown in Fig. 5. In th propod mthod, th d-axi and q-axi componnt of th rfrnc voltag vctor can b obtaind a follow: Rfrnc valu of th d-axi and q- axi tator flux and actual valu of th d-axi and q-axi tator flux ar compard in th rfrnc voltag vctor calculator block and hnc th rror in th d-axi and q-axi tator flux vctor ar obtaind a in (18) (19). d d d (18) q q q (19) Fig. 4 ariation of tator flux rippl for SPWM (continuou lin) and DPWMMAX (dottd lin) algorithm ovr th firt ctor at M i Fig. 4 compar th rm harmonic flux charactritic of th two witching qunc at diffrnt modulation indic. From th figur, it can b obrvd that th SPWM provid uprior prformanc in th low modulation rang and a th modulation indx incra, th prformanc of DPWMMAX mthod ignificantly improvd. h knowldg of flux rror and tator ohmic drop allow th dtrmination of appropriat rfrnc voltag pac vctor a givn in (0)-(1). d q R i R i d q d q (0) (1) whr, i th duration of ubcycl or ampling priod and it i a half of priod of th witching frquncy. h d-q componnt of th rfrnc voltag vctor ar fd to th PWM block. In PWM block, th two-pha voltag thn convrtr into thr-pha voltag. hn, th witching tim ar calculatd.

4 7 Simpl and Novl Hybrid Random PWM Algorithm for DC-Induction Motor Driv for Rducd Acoutical Noi Rf pd PI PI + + _ + + _ Actual Spd l r Rfrnc oltag ctor Calculator d q R P W M d, q Calculation orqu, pd and flux timation 3 IM Fig. 5 Block diagram of propod PWM bad DC 5. SIMULAION RESULS AND DISCUSSION o vrify th propod hybrid RPWM algorithm, th numrical imulation tudi hav bn carrid out uing MALAB. For th imulation tudi, th avrag witching frquncy of th invrtr i takn a 5 khz. h induction motor ud in thi ca tudy i a 4 kw, 400, 1470 rpm, 4-pol, 50 Hz, 3-pha induction motor having th following paramtr: R = 1.57Ω, R r = 1.1Ω, L = 0.17H, L r = 0.17H, L m = H and J = Kg.m. h tady tat plot of convntional DC mthod ar hown in Fig. 6 and corrponding lin currnt harmonic pctra i hown in Fig. 7. From Fig. 6 7, it can b obrvd that th convntional DC giv larg rippl in torqu, flux and currnt. Morovr, th harmonic ditortion i alo high. o ovrcom th drawback, SPWM algorithm i ud for DC. h tady tat plot of SPWM algorithm bad DC ar givn in Fig. 8 and th harmonic pctra of lin currnt i givn in Fig. 9. From th harmonic pctra, it can b obrvd that th SPWM algorithm giv conidrabl amplitud of dominating harmonic around witching frquncy. Hnc, th SPWM algorithm giv mor acoutical noi/lctromagntic intrfrnc. Hnc, to rduc th acoutical noi and harmonic ditortion, a implifid hybrid RPWM algorithm i propod in thi papr. h imulation rult at variou condition uch a tarting, tady tat, tp chang in load chang and pd rvral for propod hybrid RPWM algorithm bad DC ar hown from Fig. 10 to Fig. 14. From th imulation rult, it can b obrvd that th propod PWM algorithm giv good prformanc whn compard with th SPWM algorithm. Morovr, th propod hybrid RPWM algorithm giv wid prad harmonic pctrum and giv rducd amplitud of dominating harmonic. Hnc, th propod PWM algorithm giv rducd acoutical noi and rducd harmonic ditortion whn compard with th SPWM algorithm. Fig. 6 Stady tat plot of convntional DC Fig. 7 Harmonic pctra of lin currnt of convntional DC

5 Acta Elctrotchnica t Informatica, ol. 1, No. 4, Fig. 8 Stady tat plot of SPWM algorithm bad DC Fig. 11 Stady tat plot of propod PWM algorithm bad DC Fig. 9 Harmonic pctra of lin currnt of SPWM bad DC Fig. 1 Harmonic pctra of lin currnt of propod PWM bad DC Fig. 10 tarting tranint propod PWM algorithm bad DC Fig. 13 ranint during tp chang in load for propod PWM bad DC (a load torqu of 10 N-m i applid at 0.75 and rmovd at 0.85)

6 74 Simpl and Novl Hybrid Random PWM Algorithm for DC-Induction Motor Driv for Rducd Acoutical Noi Fig. 14 ranint during pd rvral opration of propod PWM bad DC (a load torqu of 10 N-m i applid at 0.75 and rmovd at 0.85) 6. CONCLUSIONS In arlir day to rduc th drawback of convntional DC tchniqu, SPWM algorithm i ud. A th SPWM algorithm giv conidrabl dominating harmonic around witching frquncy, it gnrat mor acoutical noi and giv mor harmonic ditortion. Hnc, to rduc th acoutical noi and harmonic ditortion, a implifid hybrid RPWM algorithm i prntd in thi papr for dirct torqu controlld induction motor driv. h propod PWM algorithm lct uitabl witching qunc bad on th tator flux rippl valu. hu, th propod PWM algorithm giv randomization of zro tat tim. Hnc, th propod PWM algorithm giv prad pctra and giv rducd amplitud of dominating harmonic whn compard with th SPWM algorithm. h imulation rult confirm th upriority of propod PWM algorithm whn compard with th SPWM algorithm. REFERENCES [1] BLASCHKE, F.: h principl of fild orintation a applid to th nw tranvctor clod loop control ytm for rotating-fild machin, Simn Rviw, 197, pp [] AKAHASHI, I. NOGUCHI,.: A nw quickrpon and high-fficincy control tratgy of an induction motor, IEEE ran. Ind. Appl., ol. IA-, No.5, Sp./Oct. 1986, pp [3] CASADEI, D. PROFUMO, F. SERRA, G. ANI, A.: FOC and DC: wo iabl Schm for Induction Motor orqu Control, IEEE ran. Powr Elctron., ol. 17, No. 5, Sp. 00, pp [4] HOLZ, J.: Pulwidth modulation A urvy, IEEE ran. Ind. Elctron., ol. 39, No. 5, Dc. 199, pp [5] van dr BROECK, H. W. SKUDELNY, H.-Ch. SANKE, G..: Analyi and ralization of a pulwidth modulator bad on voltag pac vctor, IEEE ran. Ind. Applicat., ol. 4, No. 1, Jan./Fb. 1988, pp [6] NARAYANAN, G. RANGANAHAN,..: riangl comparion and pac vctor approach to pulwidth modulation in invrtr fd driv, Journal of Indian Intitut of Scinc, Spt./Oct. 000, pp [7] RZYNADLOWSKI, A. M. BLAABJERG, F. PEDERSEN, J. K. KIRLIN, R. L. LEGOWSKI, S.: Random pul width modulation tchniqu for convrtr-fd driv ytm-a rviw, IEEE ran. Ind. Appl., ol. 30, No. 5, 1994, pp [8] BECH, M. M. BLAABJERG, F. PEDERSEN, J. K.: Random modulation tchniqu with fixd witching frquncy for thr-pha powr convrtr, IEEE ran. Powr Elctron., ol. 15, No. 4, pp , July, 000. [9] NA, S.-H. JUNG, Y.-G. LIM, Y.-C. YANG, S.-H.: Rduction of audibl witching noi in induction motor driv uing random poition pac vctor PWM, IEE Proc. Elctr. Powr Appl., ol. 149, No. 3, pp , May, 00. [10] RZYNADLOWSKI, A. M. BORISO, K. YUAN LI LING QIN: A novl random PWM tchniqu with low computational ovrhad and contant ampling frquncy for high-volum, lowcot application, IEEE ran. Powr Elctron., ol. 0, No. 1, pp , Jan [11] HAA, A. M. KERKMAN, R. J. LIPO,.A.: Simpl analytical and graphical mthod for carrir-bad PWM-SI driv, IEEE ran. Powr Elctron., ol. 14, No. 1, Jan. 1999, pp [1] BLASKO,.: Analyi of a hybrid PWM bad on modifid pac-vctor and triangl-comparion mthod, IEEE ran. Ind. Applicat., ol. 33, No. 3, May/Jun 1997, pp [13] NARAYANAN, G. RANGANAHAN,..: Analytical valuation of harmonic ditortion in PWM AC driv uing th notion of tator flux rippl, IEEE ran. Powr Elctron., ol. 0, No., March 005, pp [14] DI ZHAO PAAN KUMAR HARI,. S. S. NARAYANAN, G.: Spac ctor Bad Hybrid Pul Width Modulation chniqu for Rducd Harmonic Ditortion and Switching Lo, IEEE ranaction on Powr Elctron., ol. 5, Iu 4, March 010, pp [15] CASADEI, D. SERRA, G. ANI, A. ZARRI, L.: hortical and xprimntal analyi for th RMS currnt rippl minimization in induction motor driv controlld by SM tchniqu, IEEE

7 Acta Elctrotchnica t Informatica, ol. 1, No. 4, ran. Ind. Elctron., ol. 51, No. 5, Oct. 004, pp [16] BASU, K. SIA PRASAD, J. S. NARAYANAN, G.: Minimization of torqu rippl in PWM ac driv, IEEE ran. Ind. Elctron., ol. 56, No., pp , Fb [17] DAE-WOONG CHUNG JOOHN-SHEOK KIM SEUNG-KI SUL: Unifid voltag modulation tchniqu for ral-tim thr-pha powr convrion, IEEE ran. Ind. Applicat., ol. 34, No., Mar./Apr. 1998, pp [18] BRAHMANANDA REDDY,. AMARNAH, J. SUBBARAYUDU, D.: Improvmnt of DC prformanc by uing hybrid pac vctor Pulwidth modulation algorithm: Intrnational Rviw of Elctrical Enginring, ol., No. 1, July Aug. 007, pp [19] RAISANKAR REDDY, N. BRAHMANANDA REDDY,. AMARNAH, J. SUBBA RAYUDU, D.: Hybrid PWM Algorithm for ctor Controlld Induction Motor Driv without Angl Etimation for Rducd Currnt Rippl, ICGS- ACSE journal, ol. 9, Iu 3, pp , Dc. 009, ASME BPC-I-004, Boilr and Prur l Cod, Sction 1 Powr Boilr. Rcivd May 5, 01, accptd Dcmbr 17, 01 BIOGRAPHIES P. Nagakhar Rddy graduatd from Bangalor Univrity, Bangalor in th yar 000. H rcivd M.ch dgr from Jawaharlal Nhru tchnological Univrity, Hydrabad, India in 005. H i prntly working a Sr. Aitant Profor, MGI, Hydrabad. Alo, h i puruing hi Ph.D in Jawaharlal Nhru tchnological Univrity, Hydrabad, India. H prntd 14 rarch papr in variou national and intrnational confrnc and journal. Hi rarch intrt includ PWM tchniqu and control of lctrical driv. J. Amarnath graduatd from Omania Univrity in th yar 198, M.E from Andhra Univrity in th yar 1984 and Ph.D from J.N.. Univrity, Hydrabad in th yar 001. H i prntly Profor in Elctrical and Elctronic Enginring Dpartmnt, JNU Collg of Enginring, Hydrabad and alo h i th Chairman, Board of tudi in Elctrical and Elctronic Enginring, JNU Collg of Enginring, Hydrabad. H prntd mor than 100 rarch papr in variou national and intrnational confrnc and journal. Hi rarch ara includ Ga Inulatd Subtation, High oltag Enginring, Powr Sytm and Elctrical Driv. P. Linga Rddy rcivd M.E from Andhra Univrity, iakhapatnam in 1965 and Ph.D dgr from Indian Intitut of chnology, Dlhi in H i prntly working a Profor at K.L. Univrity, Guntur, India. H i having mor than 45 yar xprinc in taching. H publihd mor than 15 papr in variou national and intrnational journal and confrnc. Hi rarch intrt includ control ytm and control of lctrical driv.