Three-Phase to Single-Phase Matrix Converters: New Topology Based on New Control Method

Transcription

1 Three-Phase t Sngle-Phase Matrx Cnerters: New Tplgy Based n New Cntrl Methd. Babae S. H. Hssen G. B. Gharehpetan 3 Asscate Prfessr, Faculty f lectrcal and Cmputer ngneerng, Unersty f Tabrz, Tabrz, Iran e-babae@tabrzu.ac.r Prfessr, Faculty f lectrcal and Cmputer ngneerng, Unersty f Tabrz, Tabrz, Iran hssen@tabrzu.ac.r 3 Prfessr, lectrcal ngneerng Department, Amrkabr Unersty f Technlgy, Tehran, Iran grptan@aut.ac.r Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3 Abstract: In ths paper, a new tplgy s prpsed fr three-phase t sngle-phase matrx cnerters, where mre ltage leels are prduced n the utput n cmparsn wth the cnentnal tplges. In addtn, a new cntrl methd based n mnmum errr between the generated and the desred utput ltages s prpsed fr three-phase t sngle-phase matrx cnerters. In the prpsed cntrl methd, the utput ltage s generated by the mxture f dfferent peces f the nput ltages. In ther wrds, by applyng ths methd, the matrx cnerter perates lke a multleel cnerter wthut requrng t any extra elements. Due t the prpsed cntrl methd, the desred utput ltage can be generated wth an acceptable accuracy een wth unbalanced and sgnfcantly dstrted nput ltage waefrms. The ther adantage f the prpsed cntrl methd s reductn f number f swtchng whch allws lw speed semcnductrs applcatn n the structure f bdrectnal swtches requred by matrx cnerters and als reductn n swtchng lsses. Usng ths strategy, the d / dt stresses n lad are sgnfcantly reduced. As a result, the electrmagnetc nterference (MI s cnsderably decreased n cmparsn wth the ther cnentnal cntrl methds. Smulatn results n PSCAD/MTDC sftware and expermental results shw that the prpsed cntrl methd perates crrectly and cnfrm the perfect perfrmance f the prpsed tplgy. Keywrds: Matrx cnerter, Three-phase t sngle-phase cnerter, Mnmum errr, Bdrectnal swtch. Submssn date: May 9 Cndtnal acceptance date: 9 Oct. Acceptance date: Oct. Crrespndng authr: brahm Babae Crrespndng authr s address: Faculty f lectrcal and Cmputer ngneerng, Unersty f Tabrz, Tabrz, Iran

2 . Intrductn Matrx cnerters are drect ac/ac cnerters whch cnert nput lne ltages nt arable ltage wth unrestrcted frequency wthut usng any ntermedate dc lnk crcut []. In recent years, the matrx cnerters hae receed cnsderable attentn because they may becme a gd alternate t ltage surce nerter pulse wdth mdulatn (PWM tplgy. Ths s because f the fact that the matrx cnerter prdes bdrectnal pwer flw and nearly snusdal nput/utput waefrms. Furthermre, the matrx cnerter allws a cmpact desgn due t the elmnatn f dc lnk capactrs. On the ther hand, the cmplexty f the matrx cnerter tplgy makes the study and the determnatn f sutable mdulatn strateges a dffcult task []. Seeral slutns based n dfferent mathematcal appraches hae been presented n the past. ach f them shws dfferent features n terms f the number f swtches cmmutatns n a cycle perd and full utlzatn f the nput ltages. Alesna and Venturn prpsed the prncples f matrx cnerter cntrl n 98 (AV methd [3]. In the rgnal thery, the utput/nput ltage transfer rat was lmted t.5, but t was shwn later that, by means f thrd harmnc njectn technques (ptmum AV methd, the maxmum utput/nput ltage transfer rat culd be ncreased up t.866, a alue whch represents an ntrnsc lmtatn f the three-phase matrx cnerters wth balanced supply ltages [4]. The scalar cntrl mdulatn algrthm presented n [5], althugh based n a dfferent apprach, leads t perfrmance smlar t that btaned usng the ptmum AV methd. A sensble ncrease f the maxmum ltage transfer rat up t.53 s a feature f the fcttus dc lnk algrthm, presented n [6]. Ths strategy cnsders the mdulatn as a tw-step prcess, namely, rectfcatn and nersn. The hgher ltage transfer rat s acheed n spte f lw frequency dstrtn n the nput and utput arables []. The space-ectr mdulatn apprach was ntally presented n [7] t cntrl nly the utput ltages. Ths methd has been successely deelped n [] and [8] n rder t explt the pssblty f matrx cnerters n cntrllng nput pwer factr regardless f the utput pwer factr, t fully utlze the nput ltages and t reduce the number f swtch cmmutatns n each cycle perd. The abe mdulatn methds are the basc mdulatn technques and the ther presented methds mstly try t elmnate weak pnts f the preus methds [9-]. The preus methds are generally based n PWM technque and cntan sme lmtatns. One f them s lw ltage transfer rat. In addtn, f the nput ltages are sgnfcantly dstrted then these methds can nt prduce the desred utput ltage. It s mprtant t nte that the matrx cnerters are drect 38 cnerters and any dstrbutns and unbalances n the nput sdes are mmedately reflected t the utput sde. The abe-mentned cntrl methds are generally related t three-phase t three-phase matrx cnerters. In sme applcatns, t s necessary t feed the sngle-phase lads frm the three-phase netwrk wth a dfferent frequency and ampltude. Fr such cnersns, three-phase t sngle-phase cnerters are necessary. The generally used methd n ndustry fr such cnersn s dc lnk based cnerters. The ac/ac cnerters wth dc lnks are the mst cmmn type f cnerters fr ac/ac cnersn. These cnerters are tw-stage cnerters whse nstantaneus peratn s decupled by an energy strage element (a capactr r an nductrr. In ths type f cnerters, frstly, the ac nput ltage s rectfed t dc ltage and then ts nerted nt an ac ltage wth changeable frequency and ampltude. They need bulky capactr banks whch results n a slw dynamc respnse. Due t the cnsderaby hgh prce and sze f the energy strng elements, these certers are bulky and expense and dffcult t cntrl the stred energy n case f faults. Cyclcnerters are anther cmmn methd fr three-phase t sngle-phase cnersn. Cyclcnerters are drect frequency cnerters that cnert the ac nput wth a frequency t the ac utput wth anther frequency wthut usng an ntermdte stage cnerter. They are used n hgh pwer mtr dres and slp energy regeneratn. In redr t hae a hgh effecency, the utput frequency s lmted t a thrd f the nput frequency. Mre cmplex cyclcnertrs t ncrease the frequency range whch use frced cmmutatn and lad cmmutatn technques hae been presented. Due t need fr a lad wth specfc characterstcs, ntrnsc cmplexty and the ecnmcal cnsderatns, ths type f cyclcnerters hae nt been wdely used n ndustry. The three-phase t sngle-phase matrx cnerters are anther pssble methd fr three-phase t snglephase cnersn. Matrx cnerters d nt need energy strng elements. Accrdng t the authrs studes, lmted number f cntrl prcedures fr threephase t sngle-phase matrx cnerters hae been presented n the lterature. These cntrl methds are based n PWM technques. When the swtchng frequency s hgh, due t ntrnsc characterstc f these technques, lw rder harmncs wll be absent n the utput sde but nput and utput ttal harmnc dstrtn (THD wll be cnsderably hgh. In addtn, because f the hgh swtchng frequency, the effcency f the cnerter s lw. Hgh d / dt wll result n hgh MI and hgh stress n swtches [3-]. In ths paper, a new tplgy fr three-phase t sngle-phase matrx cnerters s prpsed whch cnsderably reduces the befre-mentned ptfalls. In addtn, a new cntrl methd based n mnmum errr between the measured and desred utput ltages s prpsed. The perfrmance f bth tplgy and the cntrl methd s erfed by smulatn (usng PSCAD/MTDC sftware and expermental results Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3

3 Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3. Cnentnal Three-Phase t Sngle- Phase Matrx Cnerters A matrx cnerter cnssts f n pwer swtches and n can create numbers f n and ff states (mdes. The fllwng tw basc rules shuld be cnsdered fr the crrect peratn f the cnerter: Shrt-crcut ccurrence amng pwer supples must be aded (er current cnstrant, Open crcut n the lads wth nducte prpertes must be aded (er ltage cnstrant... Three-Phase t Sngle-Phase Matrx Cnerter wth Three Bdrectnal Pwer Swtches The structure f a three-phase t sngle-phase matrx cnerter wth 3 bdrectnal swtches s llustrated n Fg.. The nput ltages f the cnerter are, and 3 and the currents thrugh them are, and, respectely. The utput ltage and current f the 3 cnerter are and, respectely. The nput ltages f the cnerter under balanced cndtn are cnsdered as fllws: ( t = V 3 m ( t = V m ( t = V m sn( ω t sn( ω t sn( ω t + where V m and ω are the ampltude and angular frequency f the nput ltage, respectely. The fundamental cmpnent f the desred utput ltage s cnsdered as fllws: (,Desred ( ( t = V sn( ω (, Desred m t where V m and ω are s the ampltude and angular frequency f the desred utput ltage, respectely. Generally, any arbtrary phase can be cnsdered fr utput ltage. The relatnshp between V and V can be expressed n terms f ltage transfer rat m (q as fllws: Vm q = (3 Vm As mentned, the matrx cnerters requre bdrectnal swtches fr pwer transmssn. Seeral methds exst t make bdrectnal swtches [-3]. In ths paper, the cmmn emtter cnfguratn has been used. Ths cnfguratn cnssts f tw nsulated gate bplar transstrs (IGBT and tw reerse parallel ddes as shwn n Fg.. m The matrx cnerter wth three pwer swtches can prduce eght mdes whle just three mdes f them are acceptable cnsderng tw mentned rules n sectn. In Table, the permtted mdes are presented. As ndcated, the maxmum nstantaneus utput ltage ampltude s lmted t maxmum nput ltage ampltude. Accrdng t Table, three dfferent ltages (, and 3 can be generated at the utput f ths cnerter. Fg. : Three-phase t sngle-phase matrx cnerter wth three swtches Table : Permtted mdes fr a three-phase t snglephase matrx cnerter wth three swtches Mde On Swtch 3 S S S 3, Mde 3, Mde.. Three-Phase t Sngle-Phase Matrx Cnerter wth Sx Bdrectnal Pwer Swtches The pwer crcut f three-phase t sngle-phase matrx cnerter wth sx pwer swtches s shwn n Fg.. Ths crcut has sx pwer swtches that are S, S, S, S, S 3 and S 3 whch ttally prduce 6 = 64 mdes but cnsderng tw explaned rules, the numbers f usable mdes are restrcted t seen mdes that are summarzed n Table. As shwn n ths table, at the utput f ths cnerter, seen dfferent ltage leels can be prduced (cnsderng pste, negate and zer alues. In the case f strngly capacte lad cnnectn t the matrx cnerter, the seenth mde shuld be gnred. As ths table llustrates, the maxmum nstantaneus utput ltage ampltude s lmted t 3 tmes f the maxmum nput ltage ampltude. Cnsderng the ncreased the number f mdes, the capablty f ths crcut ercmes the preus crcut and can prduce the utput waefrm wth fewer addte steps n cmparsn wth the preus crcut. As a result, t can prduce the utput ltage wth hgher qualty S S S 3 + 3

4 preus crcuts. As a result, t can prduce the utput ltage waefrm wth hgher qualty. S S S S S S 3 3 S3 S3 S S Fg. : Three-phase t sngle-phase matrx cnerter wth sx swtches + 3 S N Table : Permtted mdes fr three-phase t sngle-phase matrx cnerter wth sx swtches Mde On Swtches, Mde, Mde S P 3 S3 S3 + Fg. 3: Prpsed tplgy fr three-phase t sngle-phase matrx cnerter S & S S & S 3 S & S S & S 3 S & S 3 S & S 3 ( S ( & S ( S 3 & S3 S & r S r = = 3 = = 3 = 3 = 3 3. Prpsed Tplgy fr Three-Phase t Sngle-Phase Matrx Cnerter In rder t ncrease the number f mdes f threephase t sngle-phase matrx cnerters n cmparsn wth the preusly dscussed tw cnerters, a threephase t sngle-phase matrx cnerter wth eght bdrectnal pwer swtches s prpsed as shwn n Fg. 3. Ths cnerter has tw mre swtches f S and S N n cmparsn wth the matrx cnerters wth sx swtches. The cnerter wth eght swtches generates 8 = 56 mdes but takng the tw mentned rules nt accunt, thrteen permtted mdes can be created accrdng t Table 3. In the case f strngly capacte lad cnnectn t the matrx cnerter, the thrteenth mde shuld be gnred. As ths table llustrates, the maxmum nstantaneus utput ltage ampltude s lmted t 3 tmes f the maxmum nput ltage ampltude. Cnsderng the ncreased number f mdes, the capablty f ths crcut ercmes the preus tplges and can prduce the utput ltage wth less addte steps than P 4 Table 3: Permtted mdes fr the prpsed tplgy Mde On Swtches S & S S & S 3 S & S S & S 3 S & S 3 S & S 3 S P S P S P S N S N S N & S & S & S 3 & S & S & S 3 ( S ( & S ( 3 & S3 ( S P & S N S & r S r S r, Mde , Mde = = 3 = = 3 = 3 = Relatn between Output Vltage and Current The relatnshp between the utput ltage and current n three-phase t sngle-phase cnerters fr R L lad can be expressed as fllws: d ( t ( t = R ( t + L (4 dt Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3

5 Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3 Cnsderng (, the fundamental cmpnent f the utput current can be calculated as: Vm Lω ( t = sn ωt tan (5 ( Lω + R R 5. Prpsed Cntrl Methd The majrty f the presented cntrl methds fr cntrllng the matrx cnerters need balanced nput ltages and f an unbalance whether n ampltude r n phase angle ccurs n the nput ltages, these cntrl methds usually fal t perate prperly. In addtn, the cnentnal cntrl methds are generally based n PWM technques. In these technques, the swtchng frequency s chsen s hgh that des nt affect the lad. There are seeral methds t generate PWM pulses. Wth these technques, the THD f the utput ltages ncreases but n return the resultng harmncs are generated arund the swtchng frequency. Althugh the PWM technque has partcular adantages, but t has sme dsadantages as fllws: The cntrl technques based n PWM, need hgh swtchng frequences up t seeral khz t mantan ther adantages. Ths factr causes an ncrease n cmmutatn frequency. It shuld be mentned that the cmmutatn prblem s ne f the factrs that preents matrx cnerters frm fndng ther specfc place n ndustry. Due t hgh swtchng frequency f PWM based technques, the applcatn f semcnductr based nstruments wth hgh cnnectn and dscnnectn frequency are requred. It s clear that hgh pwer and the hgh cnnect/dscnnect frequency semcnductr nstruments are t expense. As a result, the ttal cst f cnerter s ncreased. Because f applyng hgh frequency swtchng methd, the PWM technques hae hgh swtchng lsses whch cause declne n effcency f the cnerter. Due t ntrnsc ptfalls f these technques, the utput ltage usually wuld be lke a tran f square pulses. Because f great dfference between lw leel ltage and hgh leel ltage, these technques generate hgh d / dt stress n the lad. As a result, the MI effect s ncreased. The applcatn f PWM technques generates harmncs t far frm the fundamental frequency arund the swtchng frequency. Therefre the sze f passe cmpnents s reduced t reme harmncs. Hweer, these technques generally hae a ery hgh THD. Generally, applyng PWM technques, the ltage transfer rat f matrx cnerters becme lwer than unty that s cnsdered as ne f the man dsadantages f these methds and lmts ther applcatn. In ths paper, a new cntrl methd s prpsed fr three-phase t sngle-phase matrx cnerters whch s based n dfferent technque frm PWM technques. In the wrld f ntellgent systems, there are seeral methds t explan a scentfc subject. Maybe ne f these methds s applyng natural language that s usually called IF-THN rule: IF prmse THN cnclusn In the prpsed cntrl methd, the generated utput ltage s cmpared wth the desred utput ltage n arus peratn mdes f cnerter. In ther wrds, n dfferent peratn mdes f matrx cnerter, the errr between the desred and generated utput ltages s explaned as fllws: j ( t =, Desred ( t, Mde, j ( t j =,, L (6 In ths equatn, j s the errr f ltage and, Mde, j s the generated utput ltage durng j th mde. Ths cntrl methd s based n the mnmum errr between the desred and generated utput ltages. In ther wrds: IF (mn(, THN The swtches n Mde wll be ON IF (mn(, THN The swtches n Mde wll be ON IF (mn(,, L,, L,, L, k k k == == M == THN The swtches n Mde k wll be ON K (7 Fg. 4 shws the blck dagram f the prpsed cntrl methd. Dependng n the selected tplgy fr the matrx cnerter (Fgs., and 3, the crrespndng swtchng table (tables, and 3 s saed n the Lk-up table (n the memry f a mcrprcessr n practce. In ther wrds, the Lkup table seres the functn f sang dfferent ON/OFF swtchng mdes n dfferent peratng cndtns. Decsn Unt cmpares the measured ltage n cnerter s utput wth the desred ltage (accrdng t the prpsed algrthm n (7. In each samplng tme nteral, ths blck recgnzes the mde that n whch mnmum errr ccurs and then the swtches must be turned n are selected frm the Lkup table and the crrespndng cmmands are sent t gate drer crcuts blck. The pwer swtch trgger sgnals are generated and appled t the swtches. Dependng n the selected mde by Decsn Unt blck, the utput ltage wth mnmum errr n regards t the desred ltage s generated. Ths prcedure s repeated n all samplng nterals []. 4

6 ( t ( t ( t 3 Three Phase t Sngle Phase Matrx Cnerter ( Based n Fgs.,, 3 Gate Sgnals Gate Drer Crcuts ON Swtches Lk Up Table (t L a d ± % f errr s between q =. 85 and q =.. Als n ths cnerter, fr ltage transfer rat lwer than.7 and mre than., the waefrm f utput ltage remans cnstant and ndependent f the ltage transfer rat. The percentage f ltage errr fr the cnerter wth sx pwer swtches has greatly mpred n cmparsn wth the matrx cnerter wth three pwer swtches. In ths cnerter, acceptng ± % errr, the range f ltage transfer rat s between q =. and q =. 9. In ths cnerter, fr ltage transfer rat lwer than.85 and mre than.9, the waefrm f utput ltage s ndependent f the ltage transfer rat and remans cnstant. Fg. 4: Blck dagram f the prpsed cntrl methd In the prpsed cntrl methd, the matrx cnerters perate as a multleel cnerter. As the smulatn and expermental results wll shw, ne f the mst mprtant adantages f ths cntrl methd s that een fr unbalanced and sgnfcantly dstrted nput ltages, the desred utput ltage can be acceptably prduced wth mnmum errr. The man dsadantage f ths methd s that, fr lttle changes n ltage transfer rat, there mght nt be ntceable changes n the waefrm f the utput ltage f the cnerter. In addtn, t des nt guarantee that the ampltude f fundamental cmpnent f the measured utput ltage exactly equals t the desred utput ltage. Therefre, wth ths cntrl methd, there s an errr n the ampltude f fundamental cmpnent. T nestgate ths subject, a cncept named as percentage f ltage errr s cnsdered fr matrx cnerters, whch presents the percentage f errr between generated ltage and the expected utput ltage. The percentage f ltage errr fr matrx cnerters s defned as fllws []: Vm Vm, Fun % rrr = (8 V m Decsn Unt, Desred where V m, Fun s the ampltude f fundamental cmpnent f the generated utput ltage. The pste ltage errr shws that the ampltude f the generated utput ltage shuld be ncreased n rder t achee the desred utput ltage. Als, the negate ltage errr shws that the ampltude f the utput ltage shuld be decreased t achee the expected utput ltage. Fg. 5 shws the percentage f ltage errr fr three three-phase t sngle-phase matrx cnerters. As ths fgure shws, fr cnerter wth three pwer swtches, the percentage f ltage errr s t hgh and nt acceptable. The maxmum range f ltage transfer rat f permtted ltage wth maxmum 4 In the prpsed three-phase t sngle-phase matrx cnerter, n addtn t a ntceable reductn n ltage errr, the range f ltage transfer rat s sgnfcantly ncreased s that takng maxmum ± % errr nt cnsderatn, the acceptable range s between q =. 65 and q =. 9. In ths cnerter, fr a ltage transfer rat lwer than.3 and mre than.9, the waefrm f utput ltage, becmes ndependent f the ltage transfer rat and remans cnstant. As the smulatn and expermental results wll shw, takng nt accunt the adantages and seeral capabltes f the prpsed tplgy and cntrl methd, the exstence f maxmum % errr can be neglected partcularly fr lads nsenste t ampltude f ltage. %rrr suggested wth 3 swtches -3 wth 6 swtches q Fg. 5: The percent f ltage errr ersus ltage transfer rat 6. Smulatn and xpermental Results In rder t erfy the theretcal analyss f the prpsed swtchng strategy, three labratry prttypes f the three-phase t sngle-phase matrx cnerters accrdng t Fgs. -3 were mplemented and tested wth a passe R L lad. The cnerters are fed by a ltage transfrmer wth arable turns rat t adjust the nput ltage. The man parameters f the matrx cnerters are lsted n Table Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3

7 Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3 Table 4. Man parameters f the matrx cnerters Parameter Value V V m V 4V m f f L R f s 5Hz Hz 55mH 4Ω Hz ach bdrectnal swtch can be dren wth respect t the cmmn pnt,.e. the cmmn emtter can be cnsdered as a lcal grund fr a bdrectnal swtch. On the ther hand, n rder t ensure a crrect peratn, each bdrectnal swtch requres an slated pwer supply. Fg. 6 shws the slatr and drer crcut f each bdrectnal swtch. Ths crcut cnssts f an ptslatr, a schmt trgger and a buffer. As mentned, each bdrectnal swtch n the matrx cnerters requres an slated drer crcut. The slatn can be prded usng ether pulse transfrmers r ptslatrs. Opt-slatrs can perate n a wde range f nput sgnal pulse wdth but a separate slated pwer supply s requred fr each swtchng dece. The ptslatr based n the gate drer crcut s used n the prttypes. The square safe peratng area f the IGBT fr swtch mde peratn mnmzes the need fr snubber crcuts n mst applcatns such as the ltage surce nerter. Hweer, t s necessary t use a snubber crcut n the matrx cnerters due t the absence f freewheelng paths. In the matrx cnerters, the lad current s always cmmutated frm ne cntrlled swtch t anther. In these cnerters, a tme delay can be easly ntrduced between dre sgnals fr cmplementary deces n rder t ad smultaneus cnductn. Durng ths delay tme, the nducte lad current s taken er by a snubber crcut []. In these cnerters, a small R C turn-ff snubber crcut as depcted n Fg. 6 s cnnected acrss each bdrectnal swtch t lmt the dece ltage t an apprprate leel. It s mprtant t mentn that the man fcus f ths paper s t deelp the swtchng strateges and therefre the prblem f ptmzed snubber crcut desgn s nt pursued further. The alues f R and C n the snubber crcut are Ω and.µf, respectely. The 89C5 mcrcntrller by ATML Cmpany has been used t generate the swtchng patterns accrdng t the prpsed swtchng strateges. The IGBTs are the type BUP36D wth nternal ant-parallel ddes. T examne the perfrmance f the prpsed cnerter and cntrl methd n the generatn f a desred utput ltage waefrm, the matrx cnerters shwn n Fgs. -3 are smulated by PSCAD sftware In addtn, t cnfrm the smulatn results, three prttypes are mplemented based n the tplges shwn n Fgs. -3. The smulatn and expermental results fr each tplgy f three-phase t sngle-phase matrx cnerters wll be presented n the next parts. Input Sgnal Opt slatr Gate Drer Schmt Trgger Buffer Fg. 6: Gate drer crcut f bdrectnal swtch 6.. Smulatn and xpermental Results fr Balanced Inputs In the frst experment, the nput and utput ltages are cnsdered as ( and (, respectely. Fg. 7 shws the smulatn and expermental results fr utput ltage. As shwn n ths fgure, the utput ltage cnssts f sme peces f nput ltages. The waefrm f the utput ltage n the prpsed cnerter s ery clse t the expected utput waefrm. In addtn, d / dt aratns n the utput ltage are lwer and decreasng the MI. It shuld be ntced that d / dt aratns n the prpsed tplgy are fewer than the cnentnal tplges. It s necessary t mentn that the expermental results are exactly smlar t the smulatn results. Fg. 8 shws the smulatn and expermental results fr the utput current. As ths fgure shws, the current waefrm n the prpsed cnerter s ery smlar t snusdal waefrm because the utput ltage s smlar t snusdal waefrm. Fg. 9 shws the spectrums f ltages and currents fr the three cnerters. Snce the lad f the cnerters ( R L s almst a lw pass flter, the utput current cntans less hgh-rder harmncs than the utput ltage. Ths fgure shws that the ampltude f the fundamental cmpnent f the utput ltage n the prpsed cnerter has less errr than the cnentnal cnerters. In addtn, n the prpsed tplgy the generated harmncs are much fewer than ther tplges. The percentage f errr fr three-phase t sngle-phase cnerters wth three, sx and eght pwer swtches are equal t %5.4, 7% and %3.5, respectely, and exactly cmples wth the results f Fg. 5. As the waefrms f the utput ltages shw, the cnerters can generate the desred utput ltages wth mnmum number f swtchng. The maxmum 43 R C

8 number f swtchng amng the cnerters belngs t the prpsed cnerter (the tplgy shwn n Fg. 3. Hweer, een n the prpsed cnerter, applyng the prpsed cntrl methd, the number f swtchng s cnsderably reduce n cmparsn wth that f the PWM based methds. In rder t ndcate ths, the n/ff cmmands f the swtches f the prpsed cnerter are shwn n Fg.. As ths fgure shws, the desred utput ltage s generated wth lwer number f swtchng that leads t reductn n swtchng lsses. In addtn, t s pssble t apply lw speed semcnductr n the structure f matrx cnerters. As a result, the cst f cnerter s sgnfcantly reduced. Table 5 shws the THDs f the utput ltage and utput current based n smulatns fr three cnerters wth ampltude f up t the 63 th harmnc. Reductn f THD s acheed by the prpsed tplgy. As ths table shws, the THD n the prpsed methd s much less than PWM methd. Mreer the amunt f THD n the prpsed tplgy s lwer than ther tplges that shws the gd qualty f the prpsed cnerter Phase t Sngle-Phase wth 3-Swtch (BIBO I Phase t Sngle-Phase wth 6-Swtch (BIBO I (a Wth three pwer swtches (b Wth sx swtches Phase t Sngle-Phase wth 8-Swtch (BIBO I c prpsed tplgy Fg. 8: Output current under balanced peratn (a Wth three pwer swtches 3-Phase t Sngle-Phase wth 3-Swtch (BIBO V,Desred V,Measured Phase t Sngle-Phase wth 6-Swtch (BIBO V_Desred (a Wth three pwer swtches V_Measured Phase t Sngle-Phase wth 8-Swtch (BIBO V,Desred (b Wth sx pwer swtches V,Measured (c Prpsed tplgy Fg. 7: Output ltage under balanced peratn (Left clumn: Smulatn; Rght clumn: xpermental 44 (b Wth sx pwer swtches (c Prpsed tplgy Fg. 9: FFTs f utput ltage and current under balanced peratn (Left clumn: Output ltage; Rght clumn: Output current Table 5: THDs f utput ltage and current Wth three Wth sx swtches swtches THD f utput ltage THD f utput current Prpsed tplgy %4.7 %33.44 %. %. %.3 % Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3

9 S S S S S3 S3 SN knd f the fgure f wae shape. The qualty f utput waefrm n the prpsed cnerter s better than the cnentnal cnerters Phase t Sngle-Phase wth 3-Swtch (BIUO V,Desred V,Measured (a Wth three pwer swtches 3-Phase t Sngle-Phase wth 6-Swtch (BIUO V,Desred V,Measured Phase t Sngle-Phase wth 8-Swtch (BIUO V,Desred (b Wth sx pwer swtches V,Measured (c Prpsed tplgy Fg. : Output ltage under dstrted peratn (Left clumn: Smulatn; Rght clumn: xpermental Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3... SP..5. Tme [sec] Fg. : Cmmands f swtches fr the prpsed tplgy 6.. Smulatn and xpermental Results fr Unsnusdal Output In the prpsed cntrl methd, the expected dstrted utput ltage can be generated frm balanced nputs. T shw ths capablty, the desred utput ltage s cnsdered as fllws: ( t =.V m sn ω t +.4Vm sn 3ω t +.Vm cs(5ω t (9 Fg. shws the smulatn and expermental results f utput ltage fr each three cnerters. As these results shw, the prpsed cntrl methd s able t generate the desred utput ltage regardless f the Smulatn Results fr Unbalanced and Dstrted Inputs In rder t shw mre capabltes f the prpsed cntrl methd, assume that the nput ltages are unbalanced and sgnfcantly dstrted as fllws: ( t =.V A ( t =.5V B ( t =.8V C m m sn( ω t V m sn( ω t V sn( ω t 7 +.V m m cs(ω t m cs(3ω t cs(5ω t ( The waefrm f utput ltage s cnsdered as (. Fg. shws the smulatn results fr the utput ltage f cnerter under the unbalanced and dstrted cndtn. It s ery nterestng t nte that the prpsed cntrl methd s ne f the partcular cntrl methds that can generate the desred utput ltage wth mnmum errr frm unbalanced and sgnfcantly dstrted nput ltages. As Fg. shws, the qualty f the utput waefrm n the prpsed cnerter s better than the cnentnal cnerters. 45

10 Phase t Sngle-Phase wth 3-Swtch (UIBO V,Desred V,Measured (a Wth three pwer swtches 3-Phase t Sngle-Phase wth 6-Swtch (UIBO V,Desred V,Measured (a Wth three pwer swtches (b Wth sx pwer swtches (b Wth sx pwer swtches Phase t Sngle-Phase wth 8-Swtch (UIBO V,Desred V,Measured (c Prpsed tplgy Fg. : Output ltage under dstrted peratn 6.4. Smulatn Results fr Unbalanced and Dstrted Inputs and Unsnusdal Output It s nterestng t nte that usng the prpsed cntrl methd the unsnusdal utput ltage can be generated usng unbalanced and sgnfcantly dstrted nput ltages. In rder t shw ths capablty, the nput ltages and utput ltage are cnsdered as ( and (9, respectely. Fg. 3 shws the smulatn results fr utput ltage f cnerters under ths peratn. As the smulatn results shw, the prpsed cntrl methd can prperly prduce the expected utput ltage wth acceptable accuracy. It shuld be ntced that the cntrl methd wth such peratn and capablty has nt been presented s far. 46 (c Prpsed tplgy Fg. 3: Output ltage under dstrted cndtns 6.5. Smulatn Results fr Output Vltage wth Dfferent Output Frequences In ths sectn, the am s t shw that the prpsed cntrl methd can generate the dfferent frequences at the utput ltage. In rder t reach ths am, the nput ltages are cnsdered as balanced accrdng t ( and the utput ltage s cnsdered as balanced as (. Fg. 4 shws the smulatn results wth tw dfferent frequences f f = 6Hz and f = 35Hz fr the prpsed cnerter. Ntce that, the same results can be btaned fr cnentnal cnerters. As these results shw, the prpsed cntrl methd des nt lmt the generated utput frequency. Ths result s true een f the nput ltages are cnsdered unbalanced and sgnfcantly dstrted Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3

11 Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter V,Desred V,Measured (a f = 35Hz V,Desred V,Measured (b f = 6Hz Fg. 4: Output ltage f prpsed tplgy fr dfferent utput frequences 7. Cmparsn wth Cnentnal Cntrl Methd In rder t cmpare the prpsed cnerter and cntrl methd wth a cnentnal three-phase t sngle-phase ac/dc/ac cnerter wth SPWM cntrl methd, the cnentnal ac/dc/ac cnerter has been smulated. T achee hgh alue f the dc ltage, the full-wae three-phase rectfer crcut has been used at the nput sde f ac/dc/ac cnerter. It s mprtant t nte that n half-wae and full-wae three-phase rectfers the aerage utput ltages are.87v m.654v m, respectely [4]. The used capactr n dc lnk s cnsdered large. S, the ltage f dc lnk can be assumed cnstant. The sngle-phase H-brdge nerter s used at the utput sde f ac/dc/ac cnerter. In ths nerter, the maxmum acheable ampltude at the utput s lmted t the alue f dc lnk ltage. The same data gen n Table 4 s used fr smulatn. Fg. 5(a shws the utput ltage and Fg. 5(b shws the utput current. Obusly the ltage and current cntan hgh rder harmncs. Fgs. 6(a and 6(b shw the spectrum f the utput ltage and current respectely. Cmparng these fgures wth that f the prpsed cnerter shwn n Fg. 9(c, t can be cncluded that the harmncs f the prpsed cnerter wth the prpsed cntrl methd s lwer. Als, the THD f the utput ltage and ltage and current s 86.55% and 6.4%, respectely. Cnsderng Table 5, ltage and current THD f the prpsed cnerter are much lwer than these alues V (a I (b Fg. 5: Smulatn results fr a three-phase t snglephase ac/dc/ac cnerter, (a utput ltage, (b utput current 5 V [V ] 5 Frequency 3 (khz 4 5 (a 3.5 I [ A].5.5 Frequency 3 (khz 4 5 (b Fg. 6: (a spectrum f the utput ltage, (b spectrum f the utput current 8. Cnclusn In ths paper, a new cntrl methd s prpsed thrugh whch multleel matrx cnerter can be easly made wth n requrement t any extra element. Ths cntrl methd s based n the mnmum errr between the expected and generated utput ltages. In ths methd, the swtchng frequency f the cnerters s drastcally decreased whch leads t reductn n the swtchng lsses and cnsequently ncreases the effcency f the cnerters. Als lw speed semcnductr deces can be used t make swtches whse adantage s ntceable decrease the cst f the 47

12 cnerters. In addtn, fr hgher capablty f multleel matrx cnerters, a new tplgy by addng tw swtches t the cnerter s prpsed whch permts ncreasng the mdes f matrx cnerters drastcally. The prpsed cntrl methd and tplgy has the ablty t generate the desred utput ltage frm any knd f three-phase system regardless f the degree f unbalance and amunt f dstrtn. It shuld be remnded that althugh a lttle errr exsts n prduced ampltude f ltage, n a lt f applcatns where the cnsumer s nt senste t ampltude f ltage, ths errr des nt make any prblem. In return, the prpsed methd has partcular capabltes and adantages that are ery aluable n the engneerng wrld. In the prpsed methd, because f remarkable decrease f d / dt n utput ltage, ther stresses n the lad s extremely decreased. As a result, MI decreases cnsderably. References [] S. Sunter, Slp energy recery f a rtr-sde feld rented cntrlled wund rtr nductn mtr fed by matrx cnerter, lseer Jurnal f the Frankln Insttute, l. 345, n. 4, pp , July 8. [] D. Casade, G. Serra, A. Tan, and L. Zarr, Matrx cnerter mdulatn strateges: A new general apprach based n space-ectr representatn f the swtch state, I Trans. Ind. lectrn., l. 49, n., pp , Aprl. [3] A. Alesna and M. Venturn, Sld-state pwer cnersn: A Furer analyss apprach t generalzed transfrmer synthess, I Trans. Crcuts Syst., l. CAS-8, pp , Aprl 98. [4] M.J. Maytum and D. Clman, The mplementatn and future ptental f the Venturn cnerter, n Prc. Dres, Mtrs Cntrls, 983, pp [5] G. Ry and G.. Aprl, Cyclcnerter peratn under a new scalar cntrl algrthm, n Prc. PSC, Mlwaukee, WI, 989, pp [6] P.D. Zgas, S.I. Khan, and M.H. Rashd, Analyss and desgn f frced cmmutated cyclcnerter structures wth mpred transfer characterstcs, I Trans. Ind. lectrn., l. -33, pp. 7-8, August 986. [7] L. Huber and D. Brjec, Space ectr mdulatr fr frced cmmutated cyclcnerters, n Prc. Cnf. Rec. I-IAS Annu. Meetng, l., 989, pp [8] D. Casade, G. Serra, and A. Tan, Reductn f the nput current harmnc cntent n matrx cnerters under nput/utput unbalance, I Trans. Ind. lectrn., l. 45, pp. 4-4, June 998. [9] R.T. Shener, V.K. Kryaz, and A.I. Kalygn, Crdnate PWM cntrl strategy f the tw-stage drect frequency cnerter, I 3, pp [] M. Imayaaramban, K. Latha, and G. Uma, Analyss f dfferent schemes f matrx cnerter wth maxmum ltage cnersn rat, n Prc. MLCON, 4, Crata, l. 3, pp []. Babae, Mdelng and desgn f nel cntrl methds f matrx cnerters, Ph.D. Thess, Faculty f lectrcal and Cmputer ngneerng, Unersty f Tabrz, Iran, Aprl [] S. Kawak, Indrect matrx cnerter dres fr unty dsplacement factr and mnmum swtchng lsses, lseer Jurnal f lectrc Pwer Systems Research, l. 77, n. 5-6, pp , Aprl 7. [3] S. Sunter, A ectr cntrlled matrx cnerter nductn mtr dre, Ph.D. Thess, Unersty f Nttngham, July 995. [4]. Babae and A. Aghabeg, A new cntrl methd fr three-phase t sngle-phase matrx cnerters, n Prc. PSC, 8, Tehran, Iran (n Persan. [5]. Babae and A. Aghabeg Hers, PWM-based cntrl strategy fr frced cmmutated cyclcnerters, n Prc. ISIA, 9, Kuala Lumpur, Malaysa, l., pp [6]. Babae, Cntrl f drect three-phase t snglephase cnerters under balanced and unbalanced peratns, lseer Jurnal f nergy Cnersn and Management, l. 5, n., pp , Jan.. [7] S.I. Khan, M.H. Rashd, P.D. Zgas, Analyss and desgn f mpred three t sngle phase cyclcnerter, n Prc. ICON, 988, l. 3, pp [8] T.F. Pdlesak, J..B. Tuttle, P. W. Wheeler; and L. mprngham, Matrx cnerter usng MOS turn-ff thyrstrs, n Prc. Twenty-Furth Internatnal Pwer Mdulatr Sympsum,, pp. 7-. [9]. Babae, A. Aghaglzadeh, S.H. Hssen, and S. Khanmhammad, A new structure fr three-phase t sngle-phase ac/ac matrx cnerters, n Prc. ICCS, 3, Sharjah, Unted Arab mrates (U.A.., l. I, pp [] S. Khanmhammad, A. Aghaglzadeh, S.H. Hssen, and. Babae, A new algrthm fr threephase t sngle-phase ac/ac matrx cnerters, n Prc. ICCS, 3, Sharjah, Unted Arab mrates (U.A.., l. III, pp. -4. " [] - " 39 []. Babae, S. H. Hssen, G. B. Gharehpetan, M. Tarafdar Haque, and M. Sabah, Reductn f dc ltage surces and swtches n asymmetrcal multleel cnerters usng a nel tplgy, lseer Jurnal f lectrc Pwer Systems Research, l. 77, n. 8, pp , Jun. 7. [3] C. Klumpner and F. Blaabjerg, Usng reerse blckng IGBTs n pwer cnerters fr adjustable speed dres, I Trans. Ind. Appl., l. 4, n. 3, pp , May/Jun. 6. [4] M.H. Rashd, Pwer lectrncs Handbk, Academc Press, Jurnal f Iranan Asscatn f lectrcal and lectrncs ngneers - Vl.- N.- Fall & Wnter 3