A Generalized Design Framework for Neutral Point Voltage Balance of Three Phase Vienna Rectifiers

Transcription

1 1 A Generalzed Degn Framework for Netral Pont Voltage Balance of hree Phae Venna Rectfer Xng L Jan Han Yao Sn Member EEE Me S Janheng Ln Shmng Xe Shodao Hang Ser Member EEE 1 Abtract h tdy propoe a generalzed degn framework for three phae Venna rectfer to handle the netral pont voltage balance e. On the ba of the degn framework t convenent to contrct varo netral pont voltage balancng method wth the garantee of tablty. A demontraton three repreentatve netral pont voltage balance approache are preented by choong dfferent zero eqence voltage. A comprehenve comparon among the three approache are gven n the apect of npt crrent qalty capactor voltage flctaton and ytem effcency. he comparon relt provde a gdance for contrctng the mot approprate approach baed on the pecfc reqrement. Fnally mlaton and epermental relt verfy the correctne and effectvene of the preented approache and the related performance analy. nde erm Venna converter carrer-baed PWM netral pont voltage balance.. NRODUCON hree phae Venna rectfer ha attracted mch attenton de to t advantage of low cot low crrent total harmonc dtorton (HD) low devce voltage tre hgh power denty and hgh effcency [1]-[3]. h t wdely ed n telecommncaton ytem arcraft and wnd trbne ytem and other area [1] [4]-[7]. he Venna rectfer eentally a n-regeneratve three level boot converter. n recent year the related reearch manly nvolve control method and modlaton tratege. here have been a lot of control cheme for the Venna rectfer. n [1] a hytere crrent control method propoed to reglate the npt crrent of Venna rectfer. he advantage of the hytere control are that t robt and the complcated modlaton trategy can be omtted. n [8] proportonal-ntegral (P) controller are ed baed on the Mancrpt receved Agt 18; reved November 8 18; accepted for pblcaton December 18. h work wa pported by Natonal Natral Scence Fondaton of Chna nder Grant and the Natonal Key Reearch and Development Program of Chna nder Grant 16YFF34 the Project of nvaton-drven Plan n Central Soth Unverty nder Grant 19CX3 Fndamental Reearch Fnd for the Central Unverte and Chna Scholarhp Concl Fnd.(Correpondng athor: Yao Sn) X. L J. Han and S. Hang are wth the College of Electrcal and nformaton Engneerng Hnan Unverty Changha 418 Chna (E-mal: lhn@hn.ed.cn @qq.com hd196@hn.ed.cn). Y. Sn M. S J. Ln and S. Xe are wth the School of nformaton Scence and Engneerng Central Soth Unverty Changha 4183 Chna (e-mal: yaonc@gmal.com mec@c.ed.cn @qq.com hmnge@c.ed.cn). average d-q model of the Venna rectfer and a new mltple-npt mltple-otpt lnear control cheme propoed n [9] baed on the mall gnal model of Venna rectfer. o mprove dynamc performance a bac one cycle control (OCC) trategy propoed n [1]. However the tlzaton rato of the -lnk voltage low. hen an mproved OCC control cheme preented whch mprove the -lnk voltage tlzaton and effcency [11]. o redce the cot a voltage enor-le control ntrodced for the Venna rectfer [1] n whch the grd voltage etmated by an oberver. On the other hand a crrent enor-le control cheme preented n [13]. Bede a drect power control cheme baed on ldng mode control propoed to mprove the dynamc repone and robtne [14]. n the cae of nbalanced power pple a control cheme baed on potve and negatve eqence decompoton ntrodced whch elmnate the -lnk voltage rpple [15]-[16]. Adonally varo modlaton method have been propoed for Venna rectfer. hey can manly be dvded nto two categore: pace vector modlaton (SVM) and carrer-baed ple wh modlaton (PWM) method. n [17]-[18] the bac SVM approache for the three phae Venna rectfer are nvetgated and a dcont SVM method propoed n [19] to redce power loe. Accordng to [] there alway et a carrer-baed PWM that eqvalent to t correpondng SVM n three phae voltage orce nverter. he eqvalence of SVM and carrer-baed PWM tded n detal for the Venna rectfer [1]. On the ba of the eqvalence a carrer-baed PWM algorthm propoed n []. o enhance effcency and accommodate varable power factor operaton a dcont carrer-baed PWM method preented [3]-[4]. De to the charactertc of three-level power converter netral pont voltage balance control very eental n Venna rectfer. Unbalanced netral pont voltage wll change the voltage tre on the wtchng devce and degrade the ytem performance. n SVM the netral pont voltage balance ally realzed by adjtng the dwell tme of the redndant hort vector [1]-[] [5]. he dwell tme rato of the redndant vector determned by a P or proportonal controller. However the degn and tablty of the netral pont voltage balance controller t ntrodced n detal. On the other hand the netral pont voltage balance realzed by reglatng the zero eqence gnal [1]-[] n carrer baed-pwm cheme. he prncple to mantan the netral pont voltage balance n the framework of carrer baed-pwm dced ntenvely [8]. And the method cold effectvely

2 elmnate netral pont voltage flctaton. Baed on the ame prncple a hybrd control propoed to ppre the thrd-harmonc component n the netral pont voltage [6]. On the ba of the eqvalence of SVM and carrer-baed PWM a carrer-baed PWM method wth netral pont voltage balance preented n []. A dcont carrer-baed PWM wth netral pont voltage balance propoed and the performance evalaton carred ot n [3] [7]. Bede there are ome other netral pont voltage balance method. For ntance n the hytere control [1] [8] a zero eqence crrent generated by a P controller added to the npt crrent reference for netral pont voltage balance. Recently a fnte et model pretve control for Venna rectfer preented n [9]. he netral pont voltage balance realzed by mpong the capactor voltage error nto the cot fncton. hogh many netral pont voltage balance method have been propoed mot of them lack the ytematc degn and n-depth tablty analy. n th tdy a generalzed degn framework preented to mantan netral pont voltage balance for Venna rectfer. he other contrbton of th tdy nclde: 1) baed on the degn framework varo netral pont voltage balancng method can be contrcted convenently; ) a demontraton three repreentatve netral pont balance approache are preented nder the propoed degn framework; 3) the performance of the three approache are analyzed and compared n term of npt crrent qalty capactor voltage flctaton and operatng effcency; 4) the tablty of the three approache have been proven and t fond that approach table n the common ene approach and are table n the average ene whle the tablty of approach belong to npt-to-tate tablty; 5) netral pont voltage elf-balancng can be acheved wthot addng etra feedback control acton nder the propoed approache. he remander of th paper organzed a follow. Secton preent the ytem model of the three-phae Venna rectfer. hen the carrer-baed PWM trategy decrbed n Secton. n Secton V the propoed degn framework for netral pont voltage balance ntrodced n detal a well a the three approache derved from the framework. n Secton V the performance analy among thee approache decrbed. n Secton V the mlaton and epermental relt are preented and dced and fnally the man pont of th paper are mmarzed n Secton V. n. MODELNG OF HREE-PHASE VENNA RECFER a b c a b c a Fg. 1 Crct topology of the three-phae Venna rectfer. b c a b c + C + C1 o z C + C Fg. 1 how the crct confgraton of three-phae Venna rectfer whch compoed of a three-phae dode brdge and three bdrectonal wtche connectng the npt phae to the -lnk netral pont. Bede two plt capactor are located at RL the -lnk. Accordng to Fg. 1 an eqvalent crct of the three-phae Venna rectfer hown n Fg.. n a b c a b c ao a + b + c + bo Fg. Eqvalent crct of the three-phae Venna rectfer. co + C + C1 o z C + C Dete S a the wtchng tate of the bdrectonal wtch n Fg. 1 and { abc } S = mean the wtch off. R L. S = 1 mean the wtch on; he npt crrent dynamc are gven a d a L = a db L = b L = c where L the flter ndctance. and are the orce voltage and phae crrent repectvely. n are the npt voltage (referred to the ac netral pont n) whch cold be an = ao bn = bo () cn = co n () the zero eqence voltage and o are em-controllable voltage (referred to the -lnk netral pont o). De to the trctral charactertc of the Venna rectfer o determned t only by the tat of the bdrectonal wtch bt alo by the npt crrent drecton. h t called the em-controllable voltage. For convenence o cold be epreed precely n ch a compact way a: gn( a ) 1 gn( a ) 1 ao ( 1 Sa ) Ha ( 1 S ) + a C1 = = + C gn( b ) 1 gn( b ) 1 bo ( 1 Sb ) Hb ( 1 Sb ) + C1 = = + C gn( c ) + 1 gn( c ) 1 co ( 1 Sc ) Hc ( 1 Sc ) C1 = = + C where gn() the gn fncton that ed to dtngh the npt crrent drecton. C1 and C repreent the related voltage acro the pper and lower capactor repectvely. Note that o n (3) refer to the actal capactor voltage rather than the amed capactor voltage that eqal to the half of the -lnk voltage. he dynamc eqaton of the two capactor can be gven a an bn cn d C1 + C = dc C = (1) (3) (4)

3 3 where C repreent the capactance of the two capactor and the load crrent. + and are the crrent throgh the potve and negatve -b whch can be formlated a gn( ) + 1 {( 1 ) } = gn( ) 1 {( 1 ) } + = S a b c = S = a b c. CARRER-BASED MODULAON SRAEGY FOR HE VENNA RECFER Ame that the orce voltage and npt crrent are balanced and nodal. hen n and n the teady tate cold be epreed a an = Um n ( ωt ) bn = Um n ( ωt 3 ) (6) cn = Um n ( ωt + 3 ) ( ωt ϕ ) a = m n + b = m n ( ωt 3 + ϕ ) (7) c = m n ( ωt + ϕ 3 + ) where ω the npt anglar freqency; m the magntde of ; ϕ the dplacement angle between n and whch dfferent from the npt power factor angle ϕ de to the npt flterng ndctor L. U m the magntde of n whch can be determned by the kwn and L. ake the average of both de of (3) over a wtchng perod and then combne () the y cycle d of the bdrectonal wtche can be gven drectly a da = 1 db = 1 = 1 an + Ha bn + Hb cn + Hc Wth the H n (3) the y cycle calclaton n (8) wll e the actal capactor voltage. n carrer-baed PWM method t eental to chooe a proper zero eqence voltage for enhancng -lnk voltage tlzaton. Frt the feable range of cold be determned. Accordng to () the followng neqalte can be obtaned. where = = = aomn an ao an aoma an bomn bn bo bn boma bn comn cn co cn coma cn gn( ) + 1 oma = C1 gn( ) 1 omn = C. and { abc } (5) (8) (9) hen the feable range of epreed a follow. (1) mn ma where C gn( a ) C gn( b ) C gn( c ) C mn = + ma ( an bn cn) C 1 gn( a ) C1 gn( b ) C1 gn( c ) C1 ma = + mn ( an bn cn). Clearly the feable range of related to the npt crrent drecton and capactor voltage whch are tme-varyng. However f mn ma there wll alway et a zero-eqence voltage that make the modlaton trategy feable. V. PROPOSED DESGN FRAMEWORK FOR NEURAL PON VOLAGE BALANCE Combne (4) and (5) and then conder the wtchng perod average method t lead to d% + C = = d d d a a b b c c (11) where % the error between capactor voltage C1 and C. After btttng (6)-(8) nto (11) and performng ome mplfcaton (11) can then be formlated a where d% = αf ( t % ) = α ( J + N ) K % (1) α= ; ( % ) C = a bc ( n ) J = ; N = ; = abc = abc ( ) K =. n n (1) the -lnk voltage. Ually > th 3 K = U co mm ϕ. Snce ϕ N >. K can be rewrtten a ( ) confned wthn 6 6 K alway a potve contant. f % mall relatve to then α >. C Accordng to (1) the electon of crtcal to determne whether % can converge to zero leadng to netral pont voltage balance. n th tdy a generalzed degn framework for netral pont voltage balance wll be ntrodced whch manly nvolve the electon of. Let be dvded nto two part epreed a n (13) = + (13) repreent a feed-forward term and ( = k% ) a feedback term where k an adjtable coeffcent. Note that f k = the feedback term wll be nll.

4 4 Sbtttng (13) nto (1) t yeld d% = αf ( t % ) = α ( J + N ) + ( Nk K ) % (14) o verfy the convergence of (14) the average theory [3] f t and condered. Accordng to the averagng theory let ( ) t partal dervatve be cont and bonded for t t D & = εf t ( ε a ( ) ) then for the ytem ( ) mall potve vale and f ( t ) -pero n t ) the olton ( t ) can be appromated by the olton of an "averaged ytem" & = εf ( ) where av av 1 ( ) ( ) f = f t (15) Ame that ha been well reglated by a voltage controller. By nmercal calclaton t eay to verfy that both J and N n (14) are -pero fncton n t where ( ) ω = the power orce perod. h wth a proper electon of f t % n (14) can be een a a -pero fncton. A the potve parameter α relatvely mall the averagng theory cold be appled to (14). hen the related "averaged ytem" can be derved a the ( ) ( ) ( ) d% 1 = α J + N + Nk K % (16) where % the averaged voltage error and repreent the olton of the "averaged ytem" and N the average vale of N a formlated n (17). 1 6m N (17) N = = Oberve (16) to garantee the aymptotc tablty k hold meet the followng con. ( ) and 1 J N + = (18) Nk K < Moreover baed on the carrer-baed modlaton prncple hold be wthn the range mn ma. However f the capactance are large egh the feedback term wll be neglgble or even be zero n the teady tate. hen t practcal to jt enre the feed-forward term tay n the range. A a relt a generalzed degn framework for netral voltage pont balance can be mmarzed a follow: ( ) 1 J + N = mn ma Nk K < (19) Wth the propoed degn framework t convenent to contrct varo netral pont voltage balance method. Alo t by electng proper and k. Sch degn framework combne the control ytem tablty and carrer-baed modlaton prncple o both the dynamc and teady tate performance are taken nto accont. t worth tng that the electon of and k have dfferent fncton. More pecfcally the coeffcent k that contaned n the feedback term manly determne the convergence rate of voltage error dynamc; whle the feed-forward term concern the teady-tate operatng performance. Wth a qalfed k hold jt meet Nk K <. n partclar f k = (16) can be mplfed to d% = αk% () A een () aymptotcally table and the convergence rate of % determned by α K whch related to the ytem parameter and can barely be adjted. n other word the netral pont voltage can be elf-balanced depte the lack of feedback control acton. However to peed p the convergence rate or enhance the netral pont voltage balance capablty a proper k of le than zero wll be more table. So far only the deal cae condered where there are n-ymmetrc otpt crrent n the Venna rectfer. n the preence of permanent n-ymmetrc otpt crrent the feedback term n (13) hold be reved a = kp% + k % to mantan netral pont voltage balance whch the otpt of a P controller. o enre the tablty both k p and k are le than zero. Wth a proper k the electon of hold be pad more attenton. Becae t embode the mot eental featre of netral pont voltage balancng method. n the followng becton three approache to electng wll be preented from dfferent apect. A. Approach n approach let J + N = then J = = N ( n ) = abc = abc (1) n th cae the orgnal voltage error dynamc (14) can be condered rather than the averaged ytem (16). Sbtttng (1) nto (14) t lead to d% = α ( K Nk ) % () where the actal voltage error % can drectly converge to zero wth a proper k. From the vewpont of modlaton hold be wthn mn ma to enre the vald carrer-baed PWM. By

5 5 mn ma analy can trctly atfy only at ϕ = ; whle n other con wll be otde the range at certan tme pont. Sch featre may affect npt crrent qalty whch wll be dced n the net ecton. Note that th approach mlar to the feed-forward qantty of the control cheme n [8]. However t amed C1 = C n [8] when modelng the ytem and feedback control mt be ed. B. Approach n approach can take the ntermedate vale of the range (1) whch where the ( mn ma ) 1 + = (3) n (3) wll be alway wthn t feable range. However n (3) wll fal to enre the netral pont voltage balance when a large devaton occr between the two capactor voltage at k =. hen a modfed electon for degned n approach baed on (3) a epreed n (4). c c ( ) 1 mn ma = + (4) where c C gn( a ) C gn( b ) C gn( c ) C mn = + ma ( an bn cn) c C gn( a ) C gn( b ) C gn( c ) C ma = + mn ( an bn cn) ( ) = +. 1 C C1 C Compare (3) wth (4) the dfference le n that a fctto C n (4) ed to replace C1 and C and t eqal to the average of the two. When the capactor voltage are balanced there wll be lttle dfference between (3) and (4). By nmercal calclaton t can be verfed that -pero and ( ) 1 J + N = (5) Sbtttng (5) nto the averaged ytem (16) t lead to d% = α ( K Nk ) % (6) A een the averaged form of (6) very mlar to (). Here the netral pont voltage balance n the average ene can be garanteed wth. C. Approach n adon to the cont modlaton dcont carrer-baed PWM trategy ha the advantage of redcng wtchng lo whch can alo be ed n the three-phae Venna rectfer. n approach degned by choong t bondary vale of the range whch c mn = c c c mn f mn ma c c c ma f mn < ma c ma (7) where and are the ame a n (4). n adon to (7) can alo be degned n other form of dcont PWM ch a n (8). = c c c ma f mn ma c c c mn f mn < ma (8) After ome manplaton wth (7) or (8) t can be verfed that the average vale of J N + are zero. Conder the averagng theory the averaged ytem n approach the ame a (6) by whch the related tablty can be verfed wth. However by ng (7) or (8) one of the bdrectonal wtche can retan on or off-tate for one modlaton perod only f the two capactor voltage are trctly dentcal n the teady tate. However the averagng theory-baed tablty crtera can only enre that the two capactor voltage have the ame average vale rather than the actal vale. h t dffclt to keep one of the wtche beng on or off for the entre wtchng perod. n that cae the dcont carrer-baed PWM cant be flly accomplhed. herefore n actal mplementaton proce n (7) and (8) wll be reved to (9) and (3) repectvely. r r c c c c mn f mn ma and mn mn > β c c c mn f mn ma and mn mn β = (9) c c c c ma f mn < ma andma ma > β c c c ma f mn < ma andma ma β c c c c ma f mn ma and mn mn > β c c c ma f mn ma and mn mn β = (3) c c c c mn f mn < ma andma ma > β c c c mn f mn < ma andma ma β where β a mall potve vale and related to the capactor voltage dfference n the teady tate. By comparon t clear that β. Snce the average vale of can lead to ( ) r J N d% 1 = α ( K Nk ) % + α K Nk % + β = + and + are zero t (31)

6 6 A β relatvely mall the "averaged ytem" (31) cold tll prove to be bonded table. hen the appromate netral pont voltage balance can alo be garanteed. r By ng when the averaged ytem enter teady tate the actal bondary vale of wll be ed. herefore the actal dcont PWM can be realzed whch favorable to mprove the operatng effcency. From approach t fond that the electon of n the propoed degn framework can be frther relaed to: 1 ( ) J + N β where β a mall potve vale. n mmary from the vewpont of tablty approach can tay table n the common ene; approach and are table n the average ene; whle the tablty of approach belong to npt-to-tate tablty. n adon to the above approache there are tll other way to contrct. f the contrcted method atfe the generalzed degn framework above t mt be effectve to mantan netral pont voltage balance. V. PERFORMANCE ANALYSS FOR HE APPROACHES For the above three approache the related teady-tate performance wll be dced n th ecton. A. Netral Pont Voltage Balance Performance n approach the capactor voltage error governed by the orgnal dynamc ytem (). Clearly the actal voltage error wll converge to zero a tme tend to nfnty. n other word the two capactor voltage can concde well wth each other. Unlke approach both approach and deal wth the averaged voltage error relyng on the "averaged ytem" (6). hogh the average voltage error converge to zero they cant gve all the nformaton of the actal capactor voltage. Frthermore the actal capactor voltage error n approach and are dfferent. o evalate the netral pont voltage balance performance the tandard devaton of capactor voltage error are calclated for the three approache. Conder (1) the followng formlaton n (3) can be ed to appromate the tandard devaton. 1 1 ( ) σ = J + N (3) condered here and n the followng ecton. t can be nferred that approach wll obtan the bet netral pont voltage balance performance and approach the wort one. B. npt Crrent Qalty Bede the netral pont voltage balance performance npt crrent qalty alo an mportant nde to evalate the three approache. n ch apect t better for lyng n the feable range. From (1) t can be nferred that the feable range of actally related wth npt power factor. n order to tet f the elected atfy mn ma n the three approache ome nmercal analy are gven n th becton. At nty npt power factor Fg. 4 how the correpondng teady-tate waveform of mn ma n approach and repectvely. Note that all the voltage qantte are rmalzed by the -lnk voltage. A een the neqalty hold. Moreover both and r mn ma le n the feable range at any tme. However wthn mn ma of are otde the feable range. only n mot of tme and ome pont Fg. 3 dagram n approach and : (a) the appromated tandard devaton of % ; (b) the waveform of %. he relt n Fg. 3(a) nate that σ > σ > σ =. Accordngly the capactor voltage error how dfferent varaton range n the teady tate a hown n Fg. 3(b). o avod repettve work only the frt form (7) of approach Fg. 4 Waveform of mn ma n the three approache at nty npt power factor ( ϕ = ). At lower npt power factor Fg. 5 how the related r waveform n the three approache. A een are tll wthn the feable range at any tme; whle more pont of are otde the range. n fact can completely be wthn the range only at ϕ = whch mean that the operatng range of approach relatvely narrow. hat the hortcomng of approach. Becae of th approach prone to the npt crrent

7 7 dtorton epecally at lower power factor whch however t too obvo at nty npt power factor. n adon both approach and belong to cont PWM; whle approach e the dcont PWM. Accordng to [31] the crrent qalty n dcont PWM ally wore than that n cont PWM even n lnear modlaton regon. approache dffer from the electon of zero eqence voltage that wll be added n the y cycle calclaton. ABLE. lt the parameter nvolved n the mlaton and eperment. ABLE. Parameter ed n the mlaton and eperment A. Smlaton Relt n th becton ome nmercal mlaton have been carred ot n the MALAB/Smlnk platform. o tet the netral pont voltage balance capablty an nbalanced taton contrcted by connectng a retor of 8 Ω n parallel wth the pper capactor drng the tme nterval [.3.31]. he Venna rectfer work wth nty npt power factor and the dered -lnk voltage et to 36V. Fg. 7(a)-(c) how the capactor voltage waveform when the three approache to electng k =. are ed wth Fg. 5 Waveform of mn ma n the three approache at lower npt power factor ( ϕ = ). 18 Baed on the above analy approach wll ha the bet npt crrent qalty of the three approache. Frther the npt crrent qalty of approach may be wore than the other two approache at nty npt power factor. Bt wth the decreae of npt power factor the npt crrent dtorton of approach wll be more ero than that of approach. V. SMULAON AND EXPERMEN RESULS θ dq Approach (1) ref q abc PLL C1 + + abc C abc dq Approach (4) Approach (9) + q θ L P Sa Sb Sc Swtchng Arrangement da db Dty cycle Calclaton (8) an bn cn abc dq θ ref P + + Fg. 6. Control block dagram for three phae Venna rectfer. C1 C ref d P + o valdate the propoed degn framework and related performance analy ome mlaton and eperment have been carred ot. Fg. 6 how the control block dagram for the three-phae Venna rectfer where the -lnk voltage and npt crrent are reglated by P controller. he three RL d Fg. 7 Smlaton relt wth k = and n (a) approach ; (b) approach ; (c) approach. A een all the capactor voltage can retrn to balance pont gradally. Moreover the balancng rate of capactor voltage are almot the ame becae they are all determned by α K. Bede t teworthy that the capactor voltage waveform are dfferent n the three approache. he capactor voltage n approach are relatvely mooth; whle they are platng wth dfferent degree n approach and. t clear that the platon n approach more ero than that n

8 8 approach. hee relt agree well wth the related performance analy mentoned before. Fg. 8(a)-(c) how the capactor voltage waveform n approach and when the feedback term added and k = 3. A een the voltage devaton are maller than thoe n Fg. 7 and the nbalanced capactor voltage trn nto balance more rapdly. Clearly the feedback term wll help to mprove netral pont voltage balance capablty. Bede the capactor voltage waveform alo ehbt dfferent charactertc n the three approache mlar to the relt n Fg. 7. Fg. 9 npt voltage and crrent waveform at nty npt power factor n (a) approach ; (b) approach ; (c) approach. o valdate the analy abot npt crrent qalty two taton wth dfferent npt power factor are teted. Fg. 9(a)-(c) how a-phae orce voltage and npt crrent waveform of the three approache wth nty npt power factor. A een all the npt crrent are well controlled. he HD of npt crrent are 3.98% 3.84% and 4.9% n approach and repectvely. Fg. 8 Smlaton relt wth k = 3 and n (a) approach ; (b) approach ; (c) approach. Fg. 1 npt voltage and crrent waveform at ϕ = 18 n (a) approach ; (b) approach ; (c) approach. Fg. 1 (a)-(c) how the correpondng waveform of the three approache wth the npt power factor angle ϕ =. A 18 een all the npt crrent lead the related npt voltage. However the crrent waveform are a lttle dfferent n thee approache. By comparon approach can acqre the bet npt crrent qalty (HD =4.1%) approach come net (HD =6.18%) then followed by approach (HD =8.3%). Clearly the mlaton relt n Fg. 9 and Fg. 1 are n good agreement wth the analy n Secton V. B. Epermental Relt Fg. 11 Prototype of the three-phae Venna rectfer.

9 9 A prototype of three-phae Venna rectfer wth the pecfcaton gven n ABLE. ha been blt n the laboratory a hown n Fg.11. he bdrectonal wtche are made p of two nlated gate bpolar trantor (GB) KW3N65EL5 (65V/3A nfneon) wth common emtter. he three phae dode brdge crct employ fat recovery dode DW4E65D1 (65V/4A nfneon). Bede the control platform baed on a floatng-pont dgtal gnal proceor (DSP) MS3F8335. crrent trn nto nodal qckly and the capactor voltage become half of the dered -lnk voltage. he npt crrent are n phae wth the npt voltage whch mean that nty npt power factor ha been obtaned. Bede t can be nferred from the voltage error waveform that the control ytem wth the cae of k = 3 ha fater convergence peed than that wth k = whch agree well wth the theoretc analy. Fg. 1 Epermental relt of approach when the control ytem tart p n: (a) cae of k = ; (b) cae of k = 3. Fg. 14 Epermental relt of approach when the control ytem tart p n: (a) cae of k = ; (b) cae of k = 3. Fg. 13 Epermental relt of approach when the control ytem tart p n: (a) cae of k = ; (b) cae of k = 3. Frt conder nty npt power factor and the dered -lnk voltage et to 3V. Fg. 1(a) how the epermental relt of approach wth k = before and after the control ytem tart p whch contan the waveform of a-phae orce voltage and npt crrent two capactor voltage and the voltage error between them. Fg. 1(b) how the epermental relt of approach wth k = 3. A een after the control ytem tart p both the npt Fg. 15 Epermental relt at nty npt power factor n (a) approach ; (b) approach ; (c) approach.

10 1 Smlarly Fg. 13(a)-(b) how the related epermental relt of approach ; whle Fg. 14(a)-(b) how the epermental relt of approach. A een the control ytem wth k = 3 tll come nto teady tate more rapdly than that wth k = regardle of whch approach t take. Bede by comparon among the relt n Fg the capactor voltage n approach and are platng wth dfferent level; whle they are very mooth n approach. hee relt are n lne wth the theoretc analy and the related mlaton relt. For npt crrent qalty analy Fg. 15(a)-(c) how the related epermental relt of approach and wth nty npt power factor repectvely. n ch eperment the dered -lnk voltage change from 3V to 36V. By comparon among thee relt thee are obvo dfference n the crrent waveform. At npt power factor angle of ϕ = 18 Fg. 16(a)-(c) how the correpondng epermental relt of approach and repectvely wth the ame con n the mlaton. A een the mlaton and epermental waveform how ecellent agreement. Moreover the pectrm analy relt of the npt crrent are demontrated n Fg. 17(a)-(c) ccevely. From the pectrm graph t fond that when the npt crrent dtorton relatvely ero lke n Fg. 16(a) low order harmonc ch a 5th and/or 7th harmonc wll et. Bede the npt crrent HD the lowet n approach and the hghet n approach wth approach lyng omewhere n between. n adon Fg. 18(a)-(b) lltrate the calclated and meared effcency crve of the three phae Venna rectfer n the three approache repectvely. A een all the calclated effcence are relatvely hgher than the meared one regardle of whchever approach ha been ed. Frther the (ether calclated or meared) effcency n approach alway hgher than thoe n the other two approache de to the redced wtchng lo; whle they are of lttle dfference approach and. Fg. 16 Epermental relt at ϕ = n (a) approach ; (b) approach ; (c) 18 approach. Fg. 18 he crve of the (a) calclated and (b) meared effcency wth regard to actve power n the three approache. ABLE. Performance comparon n three approache Fg. 17 Spectrm analy relt of npt crrent at ϕ = n (a) approach 18 (HD=9.1%); (b) approach (HD=4.35%) ; (c) approach (HD= 6.37%).

11 11 Generally the performance comparon among the three approache are demontrated n ABLE.. V. CONCLUSON n th paper a generalzed degn framework propoed for the three phae Venna rectfer to addre the e of netral pont voltage mbalance. Baed on the propoed framework t convenent to contrct dfferent netral pont voltage balance approache and the related tablty can be garanteed baed on the averagng theory. hrogh proper contrcton netral pont voltage elf-balance can be acheved wthot addng etra feedback control acton. A demontraton three repreentatve approache are preented ccevely whch ehbt dfferent performance charactertc. Moreover when the three approache are ed n the Venna rectfer the related performance are analyzed and compared n term of npt crrent qalty capactor voltage flctaton and operatng effcency. Comparatvely approach can garantee two capactor voltage of great concdence bt the npt crrent qalty the wort of the three at lower power factor. Approach can obtan the bet npt crrent qalty bt the teady capactor voltage have mall flctaton. n approach the degree of capactor voltage flctaton even larger than that n approach bt the operatng effcency hgher than that n the other approache. n other word each approach ha t own trength and weakne whch can be appled a the related performance reqred. herefore t can be nferred that new netral pont voltage balance method can be ctomzed throgh the propoed degn framework accordng to pecfc operatng performance reqrement. REFERENCES [1] J. W. Kolar F. C. Zach "A vel three-phae tlty nterface mnmzng lne crrent harmonc of hgh-power telecommncaton rectfer modle" EEE ran. nd. Electron. vol pp Ag [] L. Hang M. Zhang L. M. olbert and Z. L Dgtzed feedforward compenaton method for hgh-power-denty three-phae Venna PFC converter EEE ran. nd. Electron. vol pp Apr. 13. [3]. B. Soero and J. W. Kolar "Analy of hgh-effcency three-phae two-and three-level ndrectonal hybrd rectfer" EEE ran. nd. Electron. vol pp Sept. 13. [4] M. Hartmann S. D. Rond H. Ertl and J. W. Kolar Dgtal crrent controller for a 1 MHz 1 kw three-phae VENNA rectfer EEE ran. Power Electron. vol pp Nov. 9. [5] M. Hartmann J. Mnboeck H. Ertl and J. W. Kolar "A three-phae delta wtch rectfer for e n modern arcraft" EEE ran. nd. Electron. vol pp Sept. 1. [6] A. Rajae M. Mtafa and A. Y. Varjan "Venna-rectfer-baed drect torqe control of PMSG for wnd energy applcaton" EEE ran. nd. Electron. vol pp Jl. 13. [7] H. Chen and D. C. Alprant Analy of qrrel-cage ndcton generator wth VENNA rectfer for wnd energy converon ytem EEE ran. Energy Conver. vol pp Sept. 11. [8] R. La F. Wang R. Brgo D. Boroyevch D. Jang and D. Zhang "Average modelng and control degn for VENNA-type rectfer conderng the DC-lnk voltage balance" EEE ran. Power Electron. vol pp Nov. 9. [9] N. B. H. Yoef K. Al-Haddad H. Y. Kanaan "mplementaton of a new lnear control technqe baed on epermentally valdated mall-gnal model of three-phae three-level boot-type Venna rectfer" EEE ran. nd. Electron. vol pp Apr. 8. [1] C. Qao and K. M. Smedley "hree-phae nty-power-factor tar-connected wtch (VENNA) rectfer wth nfed contant-freqency ntegraton control" EEE ran. Power Electron. vol pp Jl. 3. [11] Z. We J. Chen X. Chen C. Y. Gong and Y. Fan "Modfed one-cycle-controlled three-phae ple-wh modlaton rectfer nder low-otpt DC voltage con" E Power Electronc vol pp Mar. 14. [1] D. Mkherjee and D. Katha. "Voltage enorle control of the three-level three-wtch Venna rectfer wth programmable npt power factor" E Power Electronc vol pp Jl. 15. [13] B. Wang G. Venkataramanan A. Bendre Unty power factor control for three-phae three-level rectfer wthot crrent enor" EEE ran. nd. Appl. vol pp Sept. 7. [14] H. Ma Y. Xe and Z. Sh "mproved drect power control for Venna-type rectfer baed on ldng mode control" E Power Electronc vol pp Mar. 16. [15] L. Hang H. Zhang S. L X. Xe C. Zhao and S. L A vel control trategy baed on natral frame for Venna-type rectfer nder lght nbalanced-grd con EEE ran. Power Electron. vol pp Mar. 15. [16] S. L L. Hang and M. Zhang "Natral frame-baed trategy for Venna-type rectfer wth lght nbalanced npt voltage" E Power Electronc vol pp Ag. 13. [17]. Vtanen and H. a Space vector modlaton and control of a ndrectonal three-phae/level/wtch Venna rectfer wth LCL-type AC flter n Proc. EEE PESC 3 Jn. 3 vol. 3 pp [18] L. Hang M. Zhang B. L L. Hang and S. L Space vector modlaton trategy for VENNA rectfer and load nbalanced ablty E Power Electron. vol pp Ag. 13. [19] L. Daleandro S. D. Rond U. Drofenk and J. W. Kolar Dcont pace-vector modlaton for three-level PWM rectfer EEE ran. Power Electron. vol. 3. pp Mar. 8. [] K. Zho D. 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12 1 [31] J. Preto M. Jone F. Barrero E. Lev S. oral "Comparatve analy of dcont and cont PWM technqe n VS-fed fve-phae ndcton motor" EEE ran. nd. Electron. vol pp Dec. 11. Xng L wa born n Hnan Chna n She receved the B.S. and Ph.D. degree from the School of nformaton Scence and Engneerng Central Soth Unverty Changha Chna n 9 and 14 repectvely. She crrently an Aocate Profeor wth the College of Electrcal and nformaton Engneerng Hnan Unverty Chna. Her reearch nteret nclde power electronc converter and wnd energy converon ytem. Shodao Hang (SM 14) wa born n Hnan Chna n 196. He receved the B.S. and Ph.D. degree from the College of Electrcal and nformaton Engneerng Hnan Unverty Changha Chna n 1983 and 5 repectvely. He crrently a Fll Profeor wth the College of Electrcal and nformatonn Engneerng Hnan Unverty Chna. H reearch nteret nclde motor degn and control power electronc ytem and control and wnd energy converon ytem. Jan Han wa born n Hbe Chna n He receved the B.S. degree n electronc engneerng from Chna hree Gorge Unverty Ychang Chna n 15. He crrently workng toward the Ph.D. degree n electronc engneerng at the Hnan Unverty Changha. H reearch nteret nclde matr converter and FAC. Yao Sn (M 13) wa born n Hnan chna n He receved the B.S. M.S. and Ph.D. degree from the School of nformaton Scence and Engneerng Central Soth Unverty Changha Chna n 4 7 and 1 repectvely. He ha been a Fll Profeor wth the School of nformaton Scence and Engneerng Central Soth Unverty Chna. H reearch nteret nclde matr converter mcro-grd and wnd energy converon ytem. Me S wa born n Hnan Chna n She receved the B.S. M.S. and Ph.D. degree from the School of nformaton Scence and Engneerng Central Soth Unverty Changha Chna n and 5 repectvely. Snce 6 he ha been a Fll Profeor wth the School of nformaton Scence and Engneerng Central Soth Unverty. Her reearch nteret nclde matr converter adjtable peed drve and wnd energy converon ytem. Janheng Ln wa born n Fjan Chna n He receved the B.S. degree n electronc engneerng from Jme Unverty Xamen Chna n 16. He crrently workng toward the Ph.D. degree n control cence and engneerng at the Central Soth Unverty Changha. H reearch nteret nclde lnear tme pero ytem analy and matr converter. ShmngXe wa born n Fjan Chna n He receved the B.S. degree n electronc engneerng from Central Soth Unverty Changha Chna n 17 where he crrently workng toward the M.S. degree. H reearch nteret nclde matr converter and DC/DC converter.