Input DC Voltages of Three-level Neutral Point Clamped Voltage Source Inverter Balancing Using a New Kind of Clamping Bridge

Transcription

1 nternatonal Journal of Computer an Eletral Engneerng, ol., No. 5, Otoer, 00 nput DC oltages of Three-level Neutral Pont Clampe oltage oure nverter Balanng Usng a New Kn of Clampng Brge R. Chan, E.M. Berkouk an M.. Bouhert Astrat A serous onstrant n multlevel nverters s the apator voltage-alanng prolem. The unalane of the fferent DC voltage soures of the three-level Neutral Pont Clampng oltage oure nverter (NPC-) onsttute the major lmtaton for the use of ths power onverter. To remey to ths prolem, a new ontrol soluton to ompensate the unalane DC voltages for the three-level NPC s presente. t proves a fast an flexle ontrol of the nverter apator voltages, leas to a smpler mplementaton, an present hgh equalzaton effeny. mulaton results show the effetveness of our methos. nex Terms Clampng rge, Multlevel nverter, NPC, lng moe ontrol.. NTRODUCTON One mportant prolem assoate wth the NPC threelevel nverter s ts Neutral Pont (NP) varaton [], the DC lnk NP potental an sgnfantly flutuate or ontnuously rft to unaeptale levels. The auses of NP potental rft an e non unform swthng eve or DC lnk apator haratersts or flutuaton ue to the rregular an unpretale hargng an shargng n eah apator [] [3] [4]. The voltage aross the apator may grow or eay so that the NP voltage fals to keep the half of the DC lnk voltage. Therefore, an exessve hgh voltage may e apple to the swthng eves of DC lnk apators an ths affets the onverter performane ue to the generaton of unharaterst harmons an the presene of overvoltages aross the semonutor swthes. Therefore, the hoe of approprate moulaton tehnques an the evelopment of avane neutral pont potental ontrol tehnques s neessary to overome the NP potental prolems. ome solutons have een propose, whh are ase on reunant swthng onfguratons [], [5]-[] or on the Manusrpt reeve August 5th 009. R. CHBAN s wth the Proess Control Laoratory of the Natonal Polytehn hool of Algers, 0, Rue Hassen BAD. ELHarrah BP8 Algers ALGERA (orresponng author to prove; fax: ; e-mal: reha9@yahoo.fr). EM BERKOUK, s wth the Proess Control Laoratory of the Natonal Polytehn hool of Algers, 0, Rue Hassen BAD. ELHarrah BP8 Algers ALGERA ( fax: ; e-mal: emerkouk@yahoo.fr). M.. BOUCHERT s wth the Proess Control Laoratory of the Natonal Polytehn hool of Algers, 0, Rue Hassen BAD. ELHarrah BP8 Algers ALGERA ( fax: ; e-mal: ms_bouhert@yahoo.fr). 879 aton of zero-sequene voltage omponents to the output voltage [6]. However, all these methos seem to e not always useful n no-loa or low-loa operatons, when the supple urrent tens to zero. n real systems, no-loa ontons etermne almost always the loss of DC-lnk apators voltages alane, owng to onverter non ealty. Unfortunately, these methos mofy the output voltage waveform. As the numer of nverter-levels nreases, the prolem of apator alanng eomes more omplex an the soluton very rast. The unalane DC voltage prolem an also e solve y separate DC soures [3] or y ang eletron rutry. n [3] an [4], lampng rges ase on transstors an resstors are propose as a soluton to ths prolem. Dsavantages of ths metho are the requrement for large power sspatng resstors, hgh urrent swthes, an thermal management requrements. Ths metho s est sute for systems that are harge often wth small urrents. Ths paper eals ntroues a new lampng rge for the DC apator voltage equalsaton has een propose to ompensate DC-lnk apators voltages flutuatons n a NPC that permts to aheve a orret apators voltages sharng, when onventonal alanng methos fal. The organzaton of ths paper s as follows. eton evelops the mathematal moellng of the DC-AC onverter (three-level NPC-) an ts Pulse Wth Moulaton ontrol strategy (PWM) usng two polar arrers. eton 3, proves the spee ontrol of a Permanent Magnet ynhronous Mahne ase on slng moe. The ontrol of the three-level PWM urrent retfer y slng moe usng feeak loops to regulate the average value of DC voltages an the network urrents are susse n seton 4. Therefore, a lampng rge ontrol s ntroue to mprove the performane of voltage alane strategy n seton 5. Fnally, n the seton 6, smulaton wll e mplemente to present a stuy of the phenomenon, to emonstrate the propose metho an to report the effetveness of ths soluton.. THREE-LEEL CACADE We frstly propose a knowlege moel of the three-phase three-level NPC- nverter an evelop a PWM strategy to ontrol t (two polar arrers). The gloal sheme of the asae s gven on the fg.. A. Three-level NPC- moellng The general struture of the three-phase three-level NPC

2 nternatonal Journal of Computer an Eletral Engneerng, ol., No. 5, Otoer, 00 voltage soure nverter s shown on the fg.. t s ompose y pars transstor-oe. Every leg of ths nverter nlues four pars (two on the upper half leg an two on the lower one) an two oes. Fg. General struture of the three-phase three-level NPC. Fg. truture of the three-level asae. The optmal ontrol law s gven elow: B B k k 4 B B k k 3 () B s the ontrol sgnal of TD. TD represent every par transstor-oe y one -retonal swth. The voltage of the three phases A, B, C relatvely to the mle pont M an usng the half leg onneton funtons F are gven y XM wth x pont A, B or C. km AM CM F. U F0. U BM F. U F0. U F () 3. U F30. U The nput urrents of the three phases three-level nverter usng the loa urrents are gven y the followng relatons: F F F F0. + F0. + F30. 3 (3) B. Control strategy of the nverter Ths strategy uses two polar arrers ( U, p U ). t s p haraterse y two parameters m the nex moulaton an r the moulaton rate. The algorthm of ths strategy an e summarse as follows: tep : Determnaton of the ntermeate voltages f U U refk p k refk < U p k refk U p k 0 refk < U p k 0 f 0 f 0 (4) f U tep : Determnaton of the output voltage + (5) km k k 0. PERMANENT MAGNET YNCHRONOU MACHNE MODELLNG n ths part, we present the PMM moellng an ts spee ontrol y slng moe. The moel of PMM wthout amper wnng has een evelope on rotor referene frame as follows [3] [4] [5] [6]: s Rs + L s pω. Lq 0. + (6) qs pω. L Rs + Lqs q pφ f.ω The eletr torque s state as: C p. Φ. + ( L L ).. (7) em f q J.( sω ) Cem Cr F. Ω (8) Control of PM motors s performe usng fel orente ontrol for the operaton of synhronous motor as a DC motor. For the PM synhronous mahne use, we evelop the algorthm 0 (Fg.3). When the axs urrent s equal to zero, the lok agram of the q axs eomes smlar to that of a DC mahne an the spee an e ontrolle y usng a slng moe ontroller whh generates the q axs voltage. We use a urrent regulator for the an q axes [7] [8]. Fg.3 Permanent Magnet ynhronous Mahne spee ontrol sheme ase on slng moe. THREE-LEEL PWM CURRENT RECTFER The ontrol of the three-level PWM urrent retfer y slng moe usng feeak loops to regulate the average value of the two DC voltages an the network urrents are q q 880

3 nternatonal Journal of Computer an Eletral Engneerng, ol., No. 5, Otoer, 00 gven. The general struture of the three-level PWM urrent retfer s gven on the fg.4. re 3. r. e (). U We efne the next values as follows: U h U + U + (3) + h h re h + We want to regulate the voltage U of the retfer. For that, we hoose for slng surfae: Fg.4 truture of the three-level PWM urrent retfer A. oltage feeak ontrol For eah phase k (k, or 3) of the three-phase network feeng, the retfer onsere an e represente y a R,L rut. resk s the voltage of one phase k of the three-phase network an k s the voltage of the leg k of the retfer. The voltage loop mposes the effetve value of the referene urrent of the network orresponng to the power exhange etween the network an the ontnue loa (Fg.5). Fg.5 Control algorthm of the output DC voltage of the three-level PWM urrent retfer. For the voltage loop moellng, we use the nstantaneous power onservaton prnple. n ths prnple, P n s the nput power of the retfer an P out the output one. 3 resk P n ( resk. resk R. resk L. ) (9) t k P U.( + ) + U.( + ) (0) out h h ts ervatve s: U U ref (4) U (5) ( re h) U (6) C f we replae () n (6), we otan: 3. r. e U ( h ) / C. U (7) The onton. < 0 nsures the attratlty of the trajetory towars the slng surfae. For that, we hoose: k. sgn( ) k. (8) The output of the slng moe ontroller gave: e [ C.( k. sgn ( U U ref ). U (9) + k.( U U ref )) h ]. 3. r B. Current feeak ontrol We ontrol the network urrent of the phase an y a slng moe regulator. The algorthm of ths urrent loop s gven on the fg.6. n ths sheme, the transfer funton H (s) s expresse as follows: resk H( s) (0) R + L. s f we suppose the snusoal urrents of the network n phase wth the orresponng voltages resk an we neglet the retfer losses an the Joule effet n the network resstors R, we an wrte: Then P 3... U. () r e re 88 Fg.6 Control algorthm of the network urrent resk of the three-level PWM retfer. From the network equatons we have:

4 nternatonal Journal of Computer an Eletral Engneerng, ol., No. 5, Otoer, 00 res A R. res + L. res res B R. res + L. res () N. U B A g g N. U () We hoose the followng slng surfaes res ref res ref (3) To satsfy the attratlty onton, we hoose: k. sgn( ) k. k. sgn( ) k. (4) waveform. Also, as the numer of nverter-levels nreases, the prolem of apator alanng eomes more omplex an the soluton very rast. By usng a separate supply for eah DC-lnk level, the alanng ssues are solve [3]. However, ths soluton s expensve espeally for more then three-level. Another soluton onssts of ang eletron rutry. n [3] an [4], lampng rges ase on transstors an resstors are propose as a soluton to ths prolem. Avantages are low ost an low omplexty. Dsavantages are hgh energy losses, hgh urrent swthes an ostly esgn thermal management requrements for large values. Ths metho s est sute for systems that are harge often wth small urrents. n orer to remey to the unalane prolem, we suggest a soluton whh onssts n estalsh a rge alanng etween the retfer an the ntermeate flter (fg.7). The am of ths use s to lmt an stalse varatons of the nput DC voltages of the nverter..( ). π k k resk. ω. e.os( ω. t ) (5) 3 wth k,, 3 N Lk N Lk We otan: g g [ ( ( res res [ res res R. ref R. ref res ) res ) + L. k. sgn( e res ref. L. ω..os( ωt)]/. U + Lk.. sgn( e res ref ) + ) +. L. ω..os( ωt π / 3)]/. U. CLAMPNG BRDGE (6) n ths seton, a lampng rge ontrol s ntroue to alane the two DC nput voltages, avo NP potental rft an mprove the performanes of the spee ontrol of the permanent magnet synhronous mahne. everal pulatons have susse ways to solve ths alanng prolem n three-level NPC- [5-4]. The multtue of proposals (seleton of approprate voltage vetors) mplemente to ensure DC voltage alanng an e roaly ve nto two ategores. n the frst ategory ase on spae vetor realzaton, reunant swthng states of the onverter are use whle n the seon ategory usng arrer-ase pulse wth moulaton (PWM) sheme, a zero sequene voltage sgnal s ae to the moulaton sgnals. n some shemes usng zero sequene voltage to alane DC apator voltages, knowlege of loa power fator (or reton of nstantaneous power flow) s requre whh s ffult to mplement uner transent ontons, an n others, measurements of oth apator voltages an loa urrents (magntues or polartes) are requre. Unfortunately, these methos mofy the output voltage 88 Fg. 7 truture of the lampng rge The apator voltage equalzaton lampng rge sheme has many avantages suh as hgher equalzaton effeny an a moular esgn approah. The alanng algorthms searh to effently remove energy from a strong apator an transfer that energy nto a weak one untl the apator voltage s equalze aross all apators. Every swth T x (x,,3,4) represent a par transstoroe. A. wth ontrol strategy of the lampng rge tep : Deuton of the sgn of the fferenes. We use the followng equatons: ( U U ) C. ( L ) t tep : Deuton of the omman of the transstors U > U T ; T 0 U > U T 0; T. MULATON REULT (7) (8) n orer to valate the soluton propose prevously, we present smulaton results for the three-level PWM urrent retfer three-level NPC- PMM asae. n the frst ase, the lampng rge wll not e use n orer to show the nstalty prolem of the two nput DC voltages.

5 nternatonal Journal of Computer an Eletral Engneerng, ol., No. 5, Otoer, 00 n the seon one, the soluton propose s ntroue to mprove the performanes of DC voltages an PMM. Fg. Harmon spetrum of A Fg.8 Referene voltages an polar arrers Fg. oltage U an ts referene Fg.9 oltage AM Fg.3 res, res an ts referene ref Fg.0 : Output voltage A Fg.4 oltage U 883

6 nternatonal Journal of Computer an Eletral Engneerng, ol., No. 5, Otoer, 00 Fg.5 oltage U Fg.9 q axs urrent ( q ) Fg.6 pee an ts referene Fg.0 oltages U an U Fg.7 Eletromagnet torque Fg. pee an ts referene Fg.8 axs urrent ( ) Fg. Eletromagnet torque 884

7 nternatonal Journal of Computer an Eletral Engneerng, ol., No. 5, Otoer, 00 performanes (pee (fg.), Torque (fg.) an urrents (fg.3) an q (fg.4)) of the PMM sappear an those performanes are mprove y usng the Clampng rge. Fg.3 axs urrent ( ) Fg.4 q axs urrent ( q ). REULT AND DCUON Fgure 8 shows the referene voltages an the two arrers use for ths strategy. We an see on ths fgure that the voltage AM has three levels (fg.9). Fg.0 show the output voltage A an ts harmon spetrum for m (fg.). We note that the harmons gather y famles entre aroun frequenes multple of.m.f. Fg. shows the voltage U an ts referene otane y ontrollng the three-level PWM retfer ontrolle y slng moe. Ths voltage follows perfetly ts referene (00). The network urrent res s n phase wth the network voltage res.(fg.3) We show perfetly the prolem of the unalane of the two DC voltages of the ntermeate apators rge. The voltage U (fg.4) s nreasng an the voltage U (fg.5) s ereasng. The haratersts of the rve of the PM synhronous mahne (pee (fg.6), torque(fg.7) an fferent urrents (fg.8 an fg.9)) fe y a three-level PWM urrent retfer three-level NPC asae show that the unulatons of the urrents, q an the eletromagnet torque are very mportant. These results show the mportane of the stalty of the nput DC voltages of the nverter to have goo performanes for the spee ontrol of the PM synhronous mahne. Fg.0 to 4 show the fferent nput DC voltages otane y usng the stalsaton rge. We an see that the output voltages of the retfer (U an U (fg.0) stalse aroun 00. By usng ths tehnque of stalsaton, we an remark that the unulatons on the. CONCLUON The present ontruton ntens to emonstrate that permanent magnet synhronous mahne ontrol ase on slng moe ontrol when apple wth a three-level PWM urrent retfer Three-level PWM NPC- may ontrute oth for funtonal performanes mprovement an attenuaton of some tehnologal lmtatons. Wth a hgh numer of sem-onutng eves, urrent an voltage qualty are mprove an weght reue y avong heavy flters. The nput DC voltages are generate y a three-level PWM urrent retfer ontrolle y slng moe ontrol. By ths stuy, we have partularly shown the prolem of the stalty an ts effets on the spee ontrol of PMM an the nput DC voltages soures of the nverter. n the last part of ths paper, we propose a smple soluton to stalse the two DC voltages y usng a lampng rge ompose y two swthes (par transstor-oe) an one nutane. Ths tehnque permt an eonom an smple eletron mplementaton, whereas n the spae vetor moulaton ontrol the omputatonal uren, the omplexty of the algorthms an the numer of nstrutons are rast espeally when the numer of levels of the nverter s greater than three. B : Control sgnal of TD : Par transstor-oe F km U, p U p ref, ref APPENDX TD. : Conneton funton of a half arm : The two polar arrers, ref 3 : The three referene voltages m : nex moulaton r : Moulaton rate L, L q : self nutane of the an q armatures equvalent wnng. R : resstane of an armature wnng. s ω : angular spee. s : Laplae operator. J : nerta of the set mahne-loa C r : Loa torque. e : Error varale : urfae varale resk : Network voltage of one phase k k : oltage of the leg k of the retfer. R : Network resstane L : Network nutane * The parameters of the PM synhronous mahne are: L L q 3. mh ; R s Ω ; p3 ; Φ f 0.3N.m/A ; J6.0-4 kg.m² ; F 9, N.m.s/ra 885

8 nternatonal Journal of Computer an Eletral Engneerng, ol., No. 5, Otoer, 00 * The parameters of the apators are: C C 0mF * The parameters of the Clampng rge are: L mh * The parameters of the net are: R0.5Ω ; L0mH REFERENCE [].Ogasawara, H.Akag, Analyss of varaton of neutral pont potental n neutral pont lampe voltage soure PWM nverters, Conferene reor EEE-A Annual Meetng, Toronto, Canaa, 993, pp [] H.L.Lu, N..Cho, G.H.Cho, DP ase spae vetor PWM for three-level nverter wth DC-lnk voltage alanng, Proeeng of EEE-ECON, Koe, Japan, Otoer 99, pp [3] H.Menzes, P.temer, J.K tenke, Fve-level GTO nverters for large nuton motor rves, Conferene reor EEE-A Annual Meetng, Toronto, Canaa, 993, pp [4] D.H.Lee,.R.Lee, Fre.C.Lee, An analyss of mpont alane for the neutral-pont-lampe three-level, Proeengs of EEE- PEC 98, Fukuoka, Japan, 998, pp [5] M. Koyama, T. Fuj, R. Uha, T. Kawaata, pae voltage vetor ase new PWM metho for large apaty three-level GTO nverter, Proeeng of EEE ECON, an Dego, CA, UA, Novemer 99, pp [6] N. Celanov, D. Borojev, A omprehensve stuy of neutral pont voltage alanng prolem n three-level neutral-pont-lampe voltage soure PWM nverters, EEE Transatons on Power Eletrons, vol. 5, Marh 000, pp [7] M. Fraha, T. Ghara, M. Marheson, M. Mazzuhell, Optmze moulaton tehnques for the generalze n-level onverter, PEC 99 Conferene Reor, Toleo, pan, June/July 99, pp [8] P.Purkat, R..ramakavaham A new generalze spae vetor moulaton algorthm for Neutral-pont-lampe Multlevel onverters, Progress n Eletromagnets Researh ymposum 006, Camrge, UA, Marh.6-9, pp [9] A.Benre,.Krst, J.aner Meer, G enkataramanan, Comparatve evaluaton of moulaton algorthms for Neutral-Pont- Clampe onverters, EEE Transatons on nustry Applatons, ol.4, N, Marh/Aprl 005, pp [0] Z.Pan, F.Z.Peng, K.A.Corzne,.R.tefanov, J.M.Leuthen,.Gatar, oltage alanng ontrol of Doe Clampe Multlevel Retfer/nverter systems, EEE Transatons on nustry applatons, ol 4, N 6, Novemer/Deemer 005, pp [] A.Benre, G enkataramanan, D.Rosene,.rnvasan, Moellng an esgn of Neutral-Pont voltage regulator for a three-level Doe Clampe nverter usng multple-arrer moulaton, EEE Transatons on nustral Eletrons, ol 53, N 3, June 006, pp []. enkateshmarhu, B.P.Mun, A.D Rajkumar, J.Praveen, Dret Power Control strateges for multlevel nverter ase ustom power eves, Proeeng of the Worl Aaemy of ene, Engneerng an Tehnology, ol 9, May 008, pp [3] R. Chan, E.M. Berkouk, Fve-level PWM urrent retfer Fvelevel NPC Permanent magnet synhronous mahne asae, European Physal Journal-Apple Physs, n 30, May 005, pp [4] R.Chan, E.M. Berkouk, M..Bouhert, Lyapunov ontrol of three-level PWM retfers to equlrate nput DC voltages of fvelevel NPC-, nternatonal Revew of Eletral Engneerng, ol, n, January- Feruary 007, pp [5] Krause PC: Analyss of eletr mahnery (MGraw Hll, New York, 986, BN: ). [6] P. Pllay an R. Krshnan, Moellng, smulaton an analyss of permanent magnet motor rves.. The permanent-magnet synhronous motor rve, EEE Transatons on nustry Applatons, vol. 5, pp , Mar./Apr [7] R. anhs, H. Njmejer, "lng Controller-lng Oserver Desgn for Nonlnear ystems," European Journal of Control, no. 4, pp , 998. [8] M. Kelemen, O. Akhrf, A. Kaour, "Lnear Roust Control of a ynhronous Motor, Expermental Comparson wth Nonlnear Control," nternatonal Journal of Control, ol. 73, n. 7, pp , 000. CHBAN Réha was orn n Algers, Algera, n 970. He reeve the Engneer egree n 993 from the Natonal hool of engneers an tehnans of Algera, the Magster egree n eletral engneerng n 999 an the Dotorate n 007 from Natonal Polytehn hool of Algers, Algera. Hs urrent researh nterests are n the area of eletral rves, power eletrons an proess ontrol. BERKOUK El Maj was orn n Béjaïa Algera, n 968. He reeve the Engneer egree n 99 n eletral engneerng from the Polytehn Natonal hool of Algers, Algera. n 993 an 995, he otane respetvely the Master of ene n ENEEHT (Toulouse) an PhD n CNAM (Pars). From 993 to 996, he was teahng at unversty of Pars X. ne 996, he was wth Natonal Polytehn hool Natonal of Algers as assoate Professor. Hs urrent researh nterests are n power eletrons an eletral rves. BOUCHERT Mohame eghr was orn n 954 n Algers. He reeve the Engneer egree n Eletrotehns, the Magster egree an the Dotorat Etat (PhD) n eletral engneerng, from the Natonal Polytehn hool of Algers, Algera, n 980, 988 an 995 respetvely. Upon grauaton, he jone the Eletral Engneerng Department of Polytehn Natonal hool. He s a Professor, memer of Proess Control Laoratory an hs researh nterests are n the area of eletral rves an proess ontrol. 886