Induction Motor Control with Small DC-Link Capacitor Inverter fed by Three-Phase Diode Front-End Rectifiers

Transcription

1 Induction Motor Control with Small DC-Link Capacitor Invrtr fd by Thr-Pha Diod Front-End Rctifir SHwan Kim GwangRok Kim Anno Yoo Jul-Ki Sok Studnt Mmbr, IEEE Mmbr, IEEE Snior Mmbr, IEEE Powr Convrion Lab. Advancd Powr Elctronic Tam Powr Convrion Lab. Yungnam Univrity LS IS Co., Ltd Yungnam Univrity Gyongan, Kora Anyang, Kora Gyongan, Kora Abtract Thi papr prnt a mall film capacitor invrtr-bad induction motor control approach to nhanc with rliability and powr dnity of thr-pha variabl pd driv application. A robut hybrid motor controllr i dvlopd to prvnt prformanc dgradation caud by th lctrolytic capacitor-l invrtr fd by front-nd diod rctifir. Th tructur of th controllr combin a modlbad voltag controllr (MVC) and a hxagon voltag manipulating controllr (HVMC). Th MVC dtrmin th command output voltag with th intrction of th torqu and rotor flux linkag command. In HVMC mod, th command voltag vctor i dtrmind imply by th torqu command and th hxagon-hapd invrtr voltag boundary. Succful application of th control approach i corroboratd by a graphical and analytical man that naturally lad to a ingl voltag lction rul. Thi papr alo xamin th opration nitivity undr motor paramtr drift to dtrmin how to dcoupl it ffct uing a voltag diturbanc tat-filtr dign. Indx Trm-- Front-nd diod rctifir, hxagon voltag manipulating controllr (HVMC), modl-bad voltag controllr (MVC), mall film capacitor invrtr, thr-pha variabl pd driv. I. INTRODUCTION In low-cot thr-pha variabl pd driv application, uch a hating-vntilating-air-conditioning (HVAC) ytm, diod rctifir ar commonly ud a th front-nd circuit for non-rgnrativ ac-dc convrion bcau of thir lowr cot and highr rliability []. In th typ of lowcot ac driv ytm, aluminum lctrolytic capacitor ar commonly ud to balanc th diffrnc btwn th intantanou input and output powr a wll a uppr th voltag pik caud by lakag inductanc and witching opration, a hown in Fig. [-3]. On th othr hand, th dc-bu capacitor i not only bulky and havy but it i alo on of th lat rliabl componnt on variou powr lctronic topologi. Furthrmor, th paraitic lad inductanc can cau voltag pik, which ar a major factor in th failur of powr lctronic dvic. A failur urvy of witch mod powr uppli rportd that lctrolytic capacitor ar rponibl for mor than half of th brakdown of an invrtr [4]. Thrfor, thr i incraing intrt in th monitoring liftim of lctrolytic capacitor for rliabl and af opration [4-7]. On th othr hand, offlin monitoring tchniqu [4-5] rquir additional maurmnt a wll a a priori data for th rfrnc modl, which mak monitoring proc complicatd and difficult. A prviouly rportd onlin mthod [6] for timating th capacitanc cannot b applid to invrtr fd by diod rctifir. C dc V dc Fig.. Thr-pha diod rctifir and PWM invrtr for induction motor driv. In thi rgard, a rang of rgnrativ convrtr and control mthod hav bn propod in ordr to minimiz or rduc th paiv componnt on a dc-bu. Th focu of mot tudi ha bn on how to rduc th dc-bu capacitor of thr-pha PWM rctifir and ingl-pha diod rctifir [7-]. All prviou tudi wr quippd with a convntional clod-loop currnt controllr to rgulat th air-gap torqu and flux linkag of ac motor. Howvr, intantanou currnt control in a mall dc-bu capacitor invrtr with th diod rctifir front-nd i not traightforward bcau th dc-link voltag and output powr to th motor dcra priodically du to th abnc of nrgy torag. Thi rapid dc voltag rduction driv th motor to b opratd frquntly in th fild-wakning rgion blow a bad pd. Thrfor, th currnt control tratgy bcom mor complicatd undr voltag-limitd condition bcau multipl-objctiv ub-controllr, uch a fildwakning, anti-windup control, and ovr-modulation chm, hould b dignd carfully bad on th complx trad-off btwn th ub-control action and currnt control dynamic [-3]. Furthrmor, ralization of th maximum voltag utilization fail bcau a circular voltag limit i /4/$3. 4 IEEE 3584

2 conidrd an opration boundary intad of a hxagonal limit [8]. Thi papr prnt a poition norl vctor-controlld induction motor (IM) driv ytm intgratd into HVAC application. Th motor powr i upplid by a mall dc-link film capacitor invrtr fd by a thr-pha diod front-nd rctifir. A motor-currnt PI rgulator-fr control tratgy i propod to mt th aformntiond challng by combining a modl-bad voltag controllr (MVC) and a hxagon voltag manipulating controllr (HVMC). Th MVC find th command output voltag with th intrction of th torqu and rotor flux linkag command. In HVMC mod, th command voltag vctor can b dtrmind imply by th torqu command and th hxagon voltag boundary. Th MVC i prformd undr non-limitd condition and motor control i handd automatically ovr to th propod HVMC in th voltag hortag rgion. Th voltag lction rul allow for th choic of an objctiv voltag vctor in th abnc of PI control gain, ub-controllr, and obrvr for clod-loop control. Th control tratgy wa implmntd on a.5-kw IM driv that wa quippd with a μf film capacitor to confirm it faibility. II. MOTOR CONTROLLER DESIGN WITH SMALL DC-LINK CAPACITOR INVERTER A. Dign and Analyi of Motor Controllr Fig. how a block diagram of th propod control tratgy for an IM uing a complx vctor rprntation. Hr, v abc and v ar th tator voltag command in th abc-rfrnc fram and th ynchronou rfrnc fram, rpctivly, and V dc dnot th maurd dc-link voltag. Mod I Mod II Mod III 3 VF MVC HVMC v abc_vf v _MVC V v dc _MVC v V dc _MVC < 3 v _HVMC Fig.. Propod induction motor control tratgy for mall capacitor invrtr. Whn tarting (Mod I), th calar Volt/Hz or V/f opn-loop control i introducd to avoid th lack of obrvability of th motor back-emf voltag at low pd. Thi fatur prmit th driv ytm to atify th tarting pd rquirmnt of th back-emf tracking-bad poition norl opration, of which th thrhold bgin in th vicinity of % of th ratd pd. Th control authority i thn handd ovr to modl-bad voltag control (MVC, Mod II) or hxagon voltag manipulating control (HVMC, Mod III), dpnding on th amount of availabl dc-link voltag. Th motor tator voltag and flux linkag quation can b xprd uing a complx vctor rprntation: di v = R i σl JωσLi dt, () L dλ m dqr Lm J ωλ dqr Lr dt Lr whr i i th d-q axi tator currnt vctor in th ynchronou rfrnc fram, J =, R i th tator ritanc, ω i th ynchronou angular vlocity, σ L i th tator tranint lakag inductanc, and λ dqr rprnt th d-q axi tator and rotor flux linkag vctor. L m and L r rprnt th magntizing and rotor inductanc, rpctivly. At th tady-tat, th motor air-gap torqu and th rotor flux linkag of th rotor-flux orintd-controlld (RFO) IM can b xprd a 3 P Lm T = λ dr iq (a) L r dr Lmid λ (b) whr P i th numbr of pol. Th tator voltag quation can b alo implifid a vd vq R id ωσliq =. (3a) R iq ωlid =. (3b) By combining () and (3), th torqu and rotor flux linkag command can b obtaind a a function of th rotor pd: 3 P L = m vd Rid T λ dr. (4) L r ωσl vq R i q λ dr = Lm. (5) ωl Fig. 3 prnt a zoomd viw of th tator voltag olution btwn (4) and (5) in th ynchronouly rotating d- q volt plan. Th dird torqu of (4) form a lin in th complx d-q plan and i hown in blu. 3585

3 5 q - axi [V] 5 5 q - axi [V] 5 5 _ MVC v ω Th rotor flux linkag lin, which i hown in rd, hift downward along th q-axi dirction a th flux dcra at a crtain rotor pd or th rotor pd dcra for a givn flux. Whn th voltag olution rmain within V dc / 3 (circular voltag boundary), which i calld th MVC opration, thy bcom faibl voltag vctor at th nxt ampling tim. Th tator voltag command v _ MVC can b obtaind imply a T v d _ MVC = ωσl R i 3 P L d. (6a) m λdr Lr λ v dr q _ MVC = ωl R i q. (6b) Lm Th motor pd lvation or th dc-link voltag rduction driv d - axi[v] v _ MVC to approach V dc / 3. Onc v _ MVC nar th circular voltag boundary, th control witch to th propod HVMC that gnrat th dird air-gap torqu a cloly a poibl, whil imultanouly rgulating th flux linkag magnitud undr a fild-wakning opration. In practic, th MVC dominat th control action at low pd, whra th HVMC opration dominat at high pd. In thi n, it i raonabl to aum that th tator ritanc voltag drop can b ngligibl in HVMC mod, which do not jopardiz th motor control prformanc. Thrfor, in HVMC mod, th tator voltag quation can b implifid a vd ωσliq. (7) vq ωlid Fig. 3. Voltag command lction in th MVC mod d - axi[v] Combining (a) and (7) provid a command torqu quation with rpct to th d-q command voltag a follow: 3 P L = m v v d q T, (8) L ω r ωσl L whr th torqu command trajctory form a hyprbolic curv in th d-q volt plan. Fig. 4 giv a chmatic rprntation of th tator voltag olution btwn th torqu curv and rotating hxagon, which hrink with th invrtr dc-bu voltag. In th propod HVMC mthod, th intrction (markd a a black dot) of th torqu lin and th hrinking hxagon bcom th command voltag vctor at th nxt ampling intant. Th boundary of ach rotating hxagon ctor can b modld a a traight lin in th d-q volt plan a follow []: v q ( k) T = Mn vd ( k) Bn, (9) whr M n and Bn ar contant valu givn by th boundary of ach hxagon ctor. A lctd voltag vctor at th intrction can b xprd a Bn Bn 4Mn γ vd _ HVC = (a) Mn v q _ HVC = Mn vd _ HVC Bn (b) T whr γ =. Uign thi algorithm, th 3 P L m L r ωlσl motor torqu i rgulatd around a dird torqu lin in th prnc of rapid voltag variation. How th HVMC prform th fild-wakning opration during th invrtr voltag rduction priod hould b invtigatd. 3586

4 v v v 3 v 4 v q [V] ω ttd IM, a hown in Tabl I, at 6% of th ratd pd and 67% of th ratd torqu. Th tator ritanc rror ha littl impact on th currnt dviation at thi pd. In practical application, an onlin compnation for modl rror i blivd to b mor ffctiv in achiving accurat motor control. Thi papr propo a voltag diturbanc tat-filtr [4] to dcoupl th paramtr dpndncy of MVC and HVMC mod. v d [V] 5 L σl R 5 Δ i [%] Fig. 4.Voltag command lction in th HVMC mod. A hown in Fig. 4, th poibl voltag olution for a givn command torqu trajctory ar dtrmind on th rotating hxagon with th dc-link voltag fluctuation. Th voltag olution naturally mov to a downward q-axi dirction (from v to v 4 ) a th hxagon hrink. Th voltag vctor v 4 ha a lowr q-axi voltag componnt than that of v. It can b noticd from (7) that v 4 lad to th dcrad d-axi currnt which cau a lowr flux linkag at a givn rotor pd.. Thi uggt that an automatic fild-wakning opration and maximum voltag utilization can b achivd imultanouly without rquiring an xtra control function. In addition, a rapid mod tranition btwn MVC and HVMC i poibl without control manipulation bcau no intgrator ar involvd for motor air-gap torqu rgulation. Thi fatur i bnficial to mall capacitor invrtr application that ar ubjct to an unxpctd grid voltag dip and frqunt dc voltag fluctuation. B. Compnation of Effct of Paramtr Drift In practic, th rotor flux lvl i not maintaind proprly in th MVC and HVMC mod bcau th machinparamtr of (6) and () drift du to magntic aturation and initial rror. Th voltag rror of (6) and () alo rult in an incorrct actual tator currnt, which might rult in high coppr or iron lo for a givn torqu condition. In HVAC application, th main opration i prformd in th pd rang from 5% up to 9% of th ratd motor pd. Fig. 5 how th tator currnt dviation trajctori of a Paramtr rror [%] Fig. 5. Stator currnt dviation by motor paramtr p.u. of th ratd pd. Fig. 6 prnt a block diagram of th diturbanc voltag timation tratgy uing a complx vctor rprntation in th ynchronou rfrnc fram. A familiar PI-typ Lunbrgr-tyl modl-currnt obrvr controllr wa adoptd to timat th voltag diturbanc rulting from paramtr variation, whr th timatd output currnt î follow th tator currnt i. Bcau th command voltag vctor v i fd-forward to th obrvr, th voltag diturbanc rror Δ ˆv _ D can b timatd at th output of th obrvr controllr. Hr, th tator currnt ha a crtain amount of harmonic with ix tim th ynchronou and grid frquncy du to th manipulatd voltag on th hxagon boundary and fluctuating dc-bu voltag. A ronant-typ filtr i introducd to rjct th rippl componnt of i, which achiv normouly high gain at ronant frqunci of concrn. Thi tructur can timat and compnat for voltag dviation rulting from diturbanc and uncrtainti [4]. Th timatd diturbanc voltag and tator currnt in th -domain ar givn by 3587

5 Rˆ ˆ i σ ˆ i Jωσ ˆ i vˆ _D = m ˆ v m ˆ λ dqr J ωλ dqr r r ˆ i ˆ = i Δv G() _D (a) whr K p Ki K rωcut G() = ωcut ωh_6fg (b) K rωcut ωcut ωh_6f Δ.() whr K p and K i rprnt th PI gain. ω h _ 6fg, ω f _ 6f, ω cut, and K r rprnt th grid frquncy, concrnd ynchronou frquncy, 3dB cut-off frquncy, and ronant filtr gain, rpctivly. In thi papr, uprcript ^ rprnt th corrponding variabl ar timatd. i K p K i Krωcut ωcut ωh_6fg Krωcut ωcut ωh_6f v Jω dt dt σ ΔσL ΔL Δˆv _D _D Jωi m dˆ λdqr Jω ˆ λdqr r dt i Fig. 6. Stat-filtr dign for dcoupling th paramtr dpndncy. Jω Subtituting () into () yild TF () = Rˆ σ Jω ctr ( σ ) _D i m m λˆ ˆ dqr J ωλ dqr v r r Rˆ î,(3a) whr Rˆ σ ω σ TF () J ctr =. (3b) G() At th tady-tat ( ), th timatd d-q-axi diturbanc voltag can b obtaind by ubtituting () into (3a): Δ = Δ Δ m L vˆ m d_d Rid ω σliq ω λˆ qr λqr r Lr,(4) Δ = Δ Δ m L vˆ m q_d Riq ω σlid ω λˆ dr λdr r Lr whr Δ R = Rˆ R and Δ σl = σ σl. i λ dr i λ dr Paramtr Compnation Paramtr Compnation Tim [.5/div] (a) Paramtr Compnation Paramtr Compnation Tim [.5/div] (b) Fig. 7. Inductanc compnation rult. (a) 5% (b) 5% Δ L. For th RFO IM, (4) can b rwrittn a 5% ΔL Δ L. 5% ΔL d_d = ΔRid ωδσliq, (5) q_d = ΔRiq ωδlid Δ L = L. whr From (5), th inductanc valu ud in (6) and () can b idntifid by nglcting th tator ritanc voltag drop: 3588

6 d_d ΔσL ωiq. (6) q_d ΔL ωid Fig. 7 how th imulatd compnation rult of th paramtr variation ffct at 6% of th ba pd and 67% of th load torqu. In Fig. 7(a), L wa t to b 5% of it nominal valu and (6) wa dlivrd at t =. Aftr, th dviation of th tator currnt and rotor flux linkag wa rducd to almot zro. Th am tt wa rpatd at -5% of Δ L, a hown in Fig. 7(b). Th tt rult indicat that th tator currnt and rotor flux linkag wr controlld prcily againt paramtr mimatch bcau th propod compnation mthod provid a concurrnt timation of th magntic aturation and initial rror. Thrfor, thi dign can b ffctiv in accuratly timating and compnating for th MVC and HVMC mod whil rducing th computational complxity. Fig. 8 prnt an ovrall block diagram of th control ytm augmntd to includ th propod algorithm to compnat for th paramtr variation ffct in ral tim. A impl back-emf tracking-bad poition norl mthod wa mployd for a motor poition timation [5]. III. SIMULATION AND EXPERIMENTAL RESULTS Validation of th thortical dvlopmnt prntd abov wa prformd on a.5 kw IM driv with a μf film capacitor fd by a thr-pha diod rctifir through a imulation and ral tt. A 496 pul-pr-rvolution ncodr wa mountd to on V/f v _VF nd of th IM to monitor th rotor pd. Th othr nd of th haft wa coupld to a.5 kw dc gnrator to control th xtrnal load. Th algorithm wa implmntd in th invrtr with a contant PWM witching frquncy of 5 khz. Th nominal input lin-to-lin voltag wa t to V and th advnt of flux wakning occur at approximatly 5 r/min. Th onlin diturbanc tat-filtr wa prformd vry μ and th bandwidth of th tat-filtr and PI pd controllr wa t to 6 rad/. Th gain ( K r ) of th ronant controllr and 3-dB cut-off frquncy ( ω cut ) ar fixd to 3 and 5Hz, rpctivly. In all xprimntal tt, th running condition wr idntical to tho in th imulation. TABLE I Rating and Known Paramtr of IM undr tt Rating and Paramtr Valu Unit Ratd powr output.5 kw Ratd voltag V Ratd pd 5 r/min R / C.47 /.7 Ω L m / σ L 34 /.6 mh Fig. 9 prnt a imulatd rult in th motoring opration, whr th dc-link voltag, flag ignal, air-gap torqu, and rotor flux linkag ar illutratd from top to bottom. Th mod_hvmc i if th HVMC mod activat and othrwi (MVC mod). In thi tt, th IM ω rm PI Spd Controllr T SC MVC v _MVC Small Film Cap. v Invrtr v PWM IM Jω dt σl i HVMC v _HVMC L dλ m dqr Jω λdqr L r dt R θˆ ωˆ ωˆ rm Poition and Vlocity Etimator v i jθˆ jθˆ ΔL, ΔσL Stat-Filtr Fig. 8. Ovrall control block diagram. 3589

7 V dc [V] V dc_maur3 [V/div] mod_hvmc mod_hvmc.5 T.5 Tˆ [.5p.u./div].593 λ dr.59 [Wb].59 Tim [5m/div] λˆ dr.5 [.Wb/div] Tim[5m/div] q - axi[v] - v q [5V/div] d - axi[v] v d [5V/div] v [V] - v [5V/div] - Tim [m/div] Fig. 9. Simulatd rult of th propod control mthod. driv wa opratd with 9% of th ba pd whil th ratd load torqu wa applid. Th dc-link voltag fluctuat with ix tim th input grid voltag frquncy. Th wavform of th flag ignal and air-gap torqu how a mooth and rapid tranition occur btwn th MBC and HVMC opration. Fig. how th xprimntal rult in th am tt cnario, whr th maurd dc-link voltag, flag ignal, timatd air-gap torqu, and timatd rotor flux linkag ar rpctivly illutratd from top to bottom. Th dird torqu wa wll-rgulatd with th avrag valu bcau th propod tat-filtr provid a concurrnt compnation. Although a ufficint control voltag margin i ntial to th currnt rgulator-bad tratgy for fdback corrction, th propod mthod i immun to a lack of availabl voltag bcau it manipulat th output voltag intad of controlling th motor currnt. A clo match wa obrvd btwn imulation and tt rult. Th x-y locu how that th rulting controllr can achiv th maximum voltag utilization at th priodic voltag dropping rgion. 3 v ab [5V/div] 3 3 V dc [V/div] 5.9 ωˆ rpm [.6 p.u./div] λˆ dr [.4 p.u./div] Tim [m/div] Fig.. Tt rult of th propod control mthod. Tim [/div] Fig.. HVMC opration during th grid voltag tranint. Particular attntion hould b paid to th fild-wakning opration of th propod HVMC mod bcau a uddn 359

8 grid voltag drop forc th driv to ntr th fildwakning rgion. Fig. how th fild-wakning opration rult, whr th thr-pha ourc voltag uddnly drop by 5% of it nominal valu at 9% of th ratd pd. Th lin-to-lin grid voltag, maurd dc-bu voltag, th timatd rotor vlocity, and rotor flux linkag ar dpictd from top to bottom. In th wavform of th dc-bu voltag and th rotor flux, it can b noticd that an automatic and rapid tranition occur btwn non-limitd opration and fild-wakning mod without any ub-control function ud in th currnt control tratgy. Thi fatur i bnficial for achiving th ability to maintain th invrtr opration during th grid voltag tranint. Fig. how th tt rult at th ba pd, whra th xtrnal load wa incrad tpwi from % to th ratd valu. Thi load torqu tt can b thought to b a bing mor vr than would b ncountrd in practical ituation. Th timatd/controlld rotor pd, actual rotor pd for monitoring, maurd armatur currnt of th dc gnrator, and q-axi tator currnt of th ttd IM ar illutratd from top to bottom. Ditortion wr rarly found during th vlocity tranition of ach control mod. Th driv do not lo it control capability in th prnc of th full load torqu, which man that th motor gnrat th dird air-gap torqu with raonabl accuracy that i comparabl to that of commrcial ac driv ytm. With th propod algorithm, th invrtr rquirmnt of a long liftim, high rliability, and high powr dnity can b achivd without acrificing th ytm prformanc. 5 ωˆ rpm [5r/min/div] 5 ω rpm [5r/min/div] i A [.5A/div] 6 i q [4A/div] 6 Tim[/div] Fig.. Load tt rult of th propod mthod. IV. CONCLUSIONS Thi papr addr th controllr dign of a poition norl vctor-controlld IM driv ytm upplid from a mall dc-link film capacitor invrtr fd by a thr-pha diod front-nd rctifir. Th propod approach focu on th controllr prformanc whn ntring or laving th infaibl voltag domain. Th motor currnt PI rgulatorfr control tructur prnt a mooth tranition from th MBC undr th uncontraind voltag rgion to th HVMC whn th voltag limit i ncountrd. Th algorithm can provid adquat rult ovr a numbr of potntial condary upt found in th currnt rgulator-bad control tructur. Th opration nitivity undr motor paramtr drift i alo xamind to dcoupl it influnc uing a voltag diturbanc tat filtr. Th tt rult clarly how that th propod mthod can improv th invrtr rliability without acrificing th motor control prformanc. REFERENCES [] Altivar Ur Manual. Schnidr Elctric Indutri S.A.S., 6. [] K. W. L, M. Kim, J. Yoon, S. B. L, and J. Y. Yoo, Condition monitoring of dc-link lctrolytic capacitor in adjutabl-pd driv, IEEE Tran. Ind. Appl., vol. 44, no. 5, pp , Sp./Oct. 8. [3] M. L. Gapri, Lif prdiction modling of bu capacitor in AC variabl frquncy driv, IEEE Tran. Ind. Appl., vol. 4, no. 6, pp , Nov./Dc. 5. [4] A. Layhani, P. Vnt, G. Grllt, and P. J. Vivrg, Failur prdiction of lctrolytic capacitor during opration of a witchmod powr upply, IEEE Tran. Powr Elctron., vol. 3, no. 6, pp. 99 7, Nov [5] A. M. Imam, T. G. Habtlr, R. G. Harly, and D. M. Divan, Raltim condition monitoring of th lctrolytic capacitor for powr lctronic application, in Proc. IEEE APEC Conf., 7, pp [6] D. C. L, J. K. Sok, and J. W. Choi, Onlin capacitanc timation of DC-link lctrolytic capacitor for thr-pha AC/DC/AC PWM convrtr uing rcuriv lat quar mthod, Proc. Int. Elctr. Eng. Elctr. Powr Appl., vol. 5, no. 6, pp , Nov. 5. [7] L. Malani, L. Rotto, P. Tnti, and P. Tomain, AC/DC/AC PWM convrtr with rducd nrgy torag in th DC link, IEEE Tran. Ind. Appl., vol. 3, no., pp. 87 9, Mar./Apr [8] A. Yoo, S. K. Sul, H. Kim, and K. S. Kim, Flux-wakning tratgy of an induction machin drivn by an lctrolytic-capacitor-l invrtr, IEEE Tran. Ind. Appl., vol. 47, no. 3, pp , May/Jun. [9] K. Inazuma, H. Utugi, K. Ohihi, and H. Haga, High-powr-factor ingl-pha diod rctifir drivn by rptitivly controlld IPM motor, IEEE Tran. Ind. Elctron., vol. 6, no., pp , Oct. 3. [] H. S. Jung, S. J. Ch, S. K. Sul, Y. J. Park, H. S. Park, and W. K. Kim, Control of thr pha invrtr for AC motor driv with mall DC-link capacitor fd by ingl pha AC ourc, Proc. of IEEE ECCE Conf.,, pp [] W. J. L, Y. Son, and J. I. Ha, Singl-pha activ powr filtring mthod uing diod-rctifir-fd motor driv, Proc. of IEEE ECCE Conf., 3, pp [] C. H. Choi, J. K. Sok, and R. D. Lornz, Wid-pd dirct torqu and flux control for intrior PM ynchronou motor oprating at voltag and currnt limit, IEEE Tran. Ind. Appl., vol. 49, no., Jan./Fb. 3. [3] S. H. Kim and J. K. Sok, Finit-ttling tp dirct torqu and flux control (FSS-DTFC) for torqu-controlld intrior PM motor at voltag limit, IEEE Tran. Ind. Appl., to b publihd. [4] S. H. Kim, C. H. Choi, and J. K. Sok, Voltag diturbanc tat-filtr dign for prci torqu-controlld intrior prmannt magnt ynchronou motor, in Proc. IEEE ECCE,, pp [5] Hyunba Kim, M. C. Hark, and R. D. Lornz, Snorl control of intrior prmannt-magnt machin driv with zro-pha lag poition timation, IEEE Tran. Ind. Appl., vol. 39, pp , Nov./Dc