Three-Phase Isolaed High-Power-Facor Recifier Using Sof-Swiched Two-Swich Forward Converer Yungaek Jang, David L. Dillman, and Milan M. Jovanović Power Elecronics Laboraory Dela Producs Corporaion P.O. Box 12173, 5101 Davis Drive Research Triangle Park, NC 27709 Absrac A hree-phase, high-power-facor (HPF), sofswiched isolaed recifier is inroduced. The proposed circui employs a disconinuous-volage-mode (DVM) resonan inpu recifier followed by a wo-swich forward converer. In addiion o achieving HPF recificaion, he circui also offers sof swiching of he forward converer swiches. The operaion and performance of he proposed opology were verified on a 3- kw prooype operaing from a hree-phase line-o-line volage of 220 V ± 10%. The experimenal resuls show ha he inpucurren-shaping using he proposed recifier can be performed wih a THD less han 6% over he enire line range and in he load range from full load down o less han 10% of full load. The measured efficiency of he experimenal prooype a full load and nominal line was approximaely 90%. I. INTRODUCTION A hree-phase six-swich recifier followed by an isolaed dc-dc converer is ypically used in hree-phase applicaions ha require high-power-facor (HPF) and galvanic isolaion beween he inpu and oupu [1] [2]. While his approach offers excellen performance, is major drawback is a relaively high cos due o he high number of swiches and complex conrol ha is required o achieve a low inpucurren harmonic recificaion. In cos sensiive applicaions, circuis wih a fewer number of swiches and simpler conrol are preferred. In he pas, several non-isolaed hree-phase single-swich HPF recifiers were inroduced [2]-[10]. Generally, hese single-swich circuis eiher employ a disconinuous-currenmode (DCM) pulse-widh-modulaion (PWM) boos recifier opology [4]-[8], or muli-resonan buck opology [9]-[10]. Whereas he boos recifier implemenaions offer a low componen coun and exhibi high efficiencies, he singleswich muli-resonan non-isolaed buck recifier seem more aracive a high power levels because i exhibis a low THD wih coninuous inpu and oupu currens. The major drawback of he muli-resonan buck converer recifier is he volage sress on he swiching devices. As a resul, he use of his circui has been limied o applicaions wih a relaively low line volage, specifically, o rms line-oline volages 380 V and below [10]. In his paper, he muli-resonan HPF recifier combined wih wo-swich forward converer opology is inroduced. Because he swich volage in he wo-swich forward converer is clamped, his opology exhibis minimal volage sress across semiconducor swiches. For example, for his converer operaing from a 220-V ±10% hree-phase line, he swich volage sress is limied o less han 700 V. In addiion, he converer offers zero-curren swiching (ZCS) of he swiches, which is he preferred operaing mode for IGBT devices. Because all recifiers operae wih zero-volage urn off, he proposed converer exhibis excellen elecromagneic compaibiliy (EMC) performance. I should also be noed ha since he proposed hree-phase HPF fron end provides galvanic isolaion, a downsream regulaor could be a simple non-isolaed buck converer. Finally, since in his variable-frequency conrolled HPF isolaed recifier he oupu power is direcly proporional o he swiching frequency, he pracical minimum swiching frequency imposes a lower limi on he oupu power variaion a a given inpu volage. A echnique ha significanly reduces he swiching frequency range over he enire inpu and load range is also described in his paper. II. 3-φ ISOLATED HPF MULTI-RESONANT ZCS TWO-SWITCH FORWARD RECTIFIER A. Principle of Operaion The circui diagram of he proposed 3-kW, isolaed, HPF, muli-resonan, ZCS wo-swich forward recifier is shown in Fig.1. The primary side consiss of inpu filer inducors L A, L B, and L C, inpu side resonan capaciors C 1 -C 3, inpu V AN L A L B V BN C 2 L C N C 1 C 3 D 1 D 2 D 3 D C1 sandby power supply D 4 D 5 D 6 D C3 TR D C2 C C L R C D D F L F + C F R V D O D Fig. 1. Proposed isolaed hree-phase HPF muli-resonan recifiers employing wo-swich forward converer. 1-4244-0714-1/07/$20.00 2007 IEEE. 809
D 1 D 2 D 3 D C1 D C3 V S S1 1 D F C Y1 C Y2 1 2 i PRI TR L R V DF i LM V B V PRI N 1 L M N 2 D C D D C2 D D i DD C Y3 3 D 4 D 5 D 6 (a) [T -T ] 0 1 Fig. 2. Simplified circui diagram of proposed converer wih reference direcions of volages and currens. recifiers D 1 hrough D 6, swiches and, and he primary winding of ransformer TR. I should be noed ha swich volages are clamped by clamp diodes D C1 -D C3 and clamp capacior C C. The volage across clamp capacior C C is uilized as boh he ransformer rese volage and a dc source for he housekeeping power supply. The oupu side of he circui consiss of he secondary winding of ransformer TR, resonan inducor L R, secondaryside resonan capacior C D, forward diode D F, oupu recifier D D, and oupu filer L F wih C F conneced across load R L. To faciliae he explanaion of he circui operaion, Fig. 2 shows a simplified circui diagram of he circui in Fig. 1. In he simplified circui, -conneced inpu side resonan capaciors C 1 -C 3 in Fig. 1 are convered o a Y-connecion, which is more convenien o describe he operaion. The Y- conneced inpu side resonan capaciors are denoed as C Y1, C Y2, and C Y3 as shown in Fig. 2. Moreover, clamp capacior C C is modeled by volage source, assuming ha he value of capacior C C is large enough ha he volage ripples across he capacior are small compared o is dc volage. Inpu filer inducors L A, L B, and L C are modeled by curren sources,, and, respecively. Also, oupu filer inducor L F is modeled by curren source. Because he inducance of he inpu and oupu filer inducors are large, he curren ripples in he inducors are small compared o heir dc or line frequency currens. In addiion, isolaion ransformer TR is modeled by magneizing inducance L M and an ideal ransformer wih urns raio n=n 1 /N 2, where N 1 is he number of urns for he primary winding and N 2 is he number of urns for he secondary winding. The leakage inducance of ransformer TR is negleced in he model since resonan inducor L R, whose inducance is much larger han he leakage inducance, is conneced in series. Finally in his analysis i is also assumed ha all semiconducor componens have zero impedance in he on sae and infinie impedance in he off sae. To furher faciliae he analysis of operaion, Fig. 3 shows he opological sages of he circui in Fig. 1 during a swiching cycle, whereas Fig. 4 shows is key waveforms. I (b) [T -T ] 1 2 (c) [T -T ] 2 3 (d) [T -T ] 3 4 (e) [T -T ] 4 5 (f) [T -T ] 5 6 Fig. 3(a)-(f). Topological sages of proposed circui. 810
(g) [T -T ] 6 7 (h) [T -T ] 7 8 I should be noed ha he peak volages of inpu resonan capaciors C Y1 -C Y3 a =T 1 are proporional o inpu currens,, and. Because inpu resonan capaciors C Y1 -C Y3 operae very close o he coninuous/disconinuous-volagemode boundary (CVM/DVM), heir average volages are proporional o inpu currens,, and. Since he average volage of each inpu resonan capacior is equal o he phase inpu volage, he average volage across inpu inducors L A-C is proporional o he inpu volage. As a resul, he average inducor curren is proporional o he inpu curren and a HPF is achieved. Afer swiches and are closed a =T 1, inpu resonan capaciors C Y1 and C Y2 sar o resonae wih resonan inducor L R hrough ransformer TR as shown in Fig. 3(b). This period ends a =T 2 when he curren of resonan inducor L R reaches oupu curren. During he [T 1 T 3 ] inerval, inpu resonan capaciors C Y1 and C Y2 are discharged by he resonance while inpu resonan capaciors C Y3 is sill linearly charged by inpu curren because diode D 6 is Gae of V S1 T ON T S T OFF (i) [T -T ] 8 9 1 2 3 1 3 Fig. 3(g)-(i). Topological sages of proposed circui. 2 V B should be noed ha he operaion shown in Figs. 3 and 4 is wihin he period when >- >-. The reference direcions of currens and volages ploed in Fig. 4 are shown in Fig. 2. As can be seen from he iming diagram of he conrol signals for swiches and shown in Fig. 4, swiches and of he proposed circui are simulaneously urned on and off. I should be noed ha swich on-ime T ON is consan, whereas, swich off-ime T OFF is modulaed by he conrol circui, leading o a variable swiching frequency. During he ime inerval when swiches and are open, inpu currens,, and flow hrough inpu resonan capaciors C Y1 -C Y3, respecively, as shown in Fig. 3(a). Assuming ha a =T 0, ransformer TR is compleely rese, i.e., magneizing curren i LM (=T 0 )=0, no oher curren is flowing in he circui during he ime inerval from =T 0 unil swiches and are urned on a =T 1. Since inpu currens,, and are consan, he volages across inpu resonan capaciors C Y1 -C Y3 are linearly changed during he [T 0 T 1 ] inerval, as shown in Fig. 4. The slopes of he volage variaions are as follows, dvc1 IAN dvc2 dvc3 ICN =, =, and =. (1) d C d C d C Y1 Y2 Y3 V S1 V PRI D i DD - 0 1 2 3 4 5 6 7 8 9 Fig. 4. Key waveforms of proposed circui. 811
reverse biased. When capacior volage 2 reaches volage 3 a =T 3, as shown in Fig. 4, inpu resonan capacior C Y3 also resonaes wih resonan inducor L R, as shown Fig. 3(d). Volage V B across he dc side of he inpu bridge recifier is he difference beween resonan capacior volages 1 and 2, as shown in Fig. 4. Afer inpu resonan capaciors C Y1 - C Y3 are compleely discharged a =T 4, resonan inducor curren flows hrough inpu bridge diodes D 1 -D 6, as shown in Fig. 3(e). When he curren of resonan inducor L R reaches zero a =T 5, forward diode D F becomes reverse biased. Afer =T 5, small magneizing curren i LM flows hrough inpu bridge diodes D 1 and D 5 while he majoriy of inpu currens,, and begins charging inpu resonan capaciors C Y1 -C Y3, as shown in Fig. 3(f). A =T 6, swiches and are simulaneously open so ha he magneizing curren flows hrough clamp diodes D C2 and D C3 and sars o rese ransformer TR by clamp volage, as shown in Fig. 3(g). During he [T 6 T 7 ] inerval, swich volage is equal o clamp volage because clamp diode D C2 conducs. I should be noed ha swiches and are urned off when heir curren is only magneizing curren i LM, which is a negligible amoun compared o he resonan curren. During he [T 5 T 7 ] inerval, oupu side resonan capacior C D delivers oupu curren, hence is volage linearly decreases as shown in Fig. 4. When he volage of resonan capacior C D reaches zero a =T 7, oupu diode D D is forward biased and delivers oupu curren. Transformer TR is compleely rese a =T 8, as illusraed in Fig. 4. The volages across inpu resonan capaciors C Y1 -C Y3 are linearly charged during he [T 5 T 9 ] inerval, as shown in Fig. 4. The nex swiching cycle is iniiaed a =T 9 when swiches and are urned on again. B. Normalized Conrol Characerisics To simplify he hree-phase inpu and single-ended oupu circui shown in Fig. 2, one operaing poin a he ime π/2 of he angular line frequency is chosen as described in [9]. A his momen, phase volage V AN is a is peak value, whereas phase volages V BN and N are boh negaive and equal in magniude o one-half of V AN. The simplified single inpu single oupu circui model is derived, as shown in Fig. 5. Diodes D 1 and D 2 of Fig. 5 represen he hree phase inpu bridge diodes. The relaions beween he hree phase inpu circui and normalized quaniies are described approximaely by: (a) C X = C Y 2/3, where resonan capaciors C Y1 -C Y3 have he same values and are represened as C Y, (b) I g = peak phase curren -PEAK, (c) V g = 3/2 imes peak phase volage V AN-PEAK, (d) inpu power P IN = V g I g = 3/2 (V AN-PEAK -PEAK ). The normalizing base quaniies nv O, /n, R O, and f O are defined as: nv O base volage, I B = nv O /R O base curren, I g C X X D 2 n nd C D n 2 D D 2 D 1 S n 2 L R Fig. 5. Simplified single inpu and single oupu circui model of proposed circui in Fig. 3. R O = n L R CX characerisic impedance, f O = π 2 1 2 n L RC X base frequency, where V O is he oupu volage of he recifier. Therefore, he normalized values of he inpu and oupu quaniies are: normalized inpu volage M g = V g /(nv O ), normalized inpu curren J g = I g R O /(nv O ), normalized oupu curren J O = R O /(n 2 V O ) = M g J g. Figure 6 shows he inpu characerisic of he converer, i.e., normalized inpu curren J g vs. normalized inpu volage M g, for normalized swiching frequency F = f S /f O as a parameer, as derived in [9] and [10]. Figure 6 is indispensable in deermining he converer s seady-sae operaing poin and design parameers. The shaded area in Fig. 6 is he operaing area for he experimenal 3 kw converer. C. Resonan Componen Design A 3-kW HPF recifier is required o deliver an isolaed 400 V DC oupu from a 3-φ 220 V L-L ±10% inpu. Because he inpu line-o-line volage is 220 V, effecive inpu volage 3 3 220 2 V g-nom = VAN PEAK = = 269.4V, herefore, 2 2 3 normalized nominal inpu volage M g(nom) = V g-nom /(nv O )= 269.4/200 = 1.34 when urns raio n=0.5. From Fig. 6, normalized nominal inpu curren J g(nom) is chosen o be 0.72 for he maximum oupu power of 3 kw so ha he selecion of J g(max) =0.8 a low line allows for over a 30% margin from he zero-curren-swiching (ZCS) boundary (J g(zcs) 1.2), ensuring ZCS over he enire inpu-volage range including some ransien condiion. Since a maximum oupu power M g(nom) = 1.34 and J g(nom) = 0.72, normalized full-load frequency F FL-NOM is deermined as F FL-NOM = 0.89, as shown in Fig. 6. Furhermore, because oupu curren = P O /V O = 7.5 A, characerisic impedance is R O = M g(nom) J g(nom) n 2 V O / = 9.5 Ω. If he swiching frequency a full load and nominal line is chosen o be f S(NOM) = 70 khz, hen resonan frequency f O can be calculaed as f O = f S(NOM) /F FL = 70/0.92 = 76 khz. I should be noed ha he maximum swiching frequency is approximaely 75 khz a full load and low line. n 812
Mg = Vg/nVo 2.0 1.75 1.5 1.47 1.25 1.2 0.14 0.23 0.44 0.37 0.5 HL, LL LL, LL 0.61 0.75 0.84 0.96 1.1 HL, FL Mg (MAX) M g (NOM) LL, FL M g (MIN) F = 1.3 zero curren swiching boundary f S F = f O 1.0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Jg = IgRo/nVo Fig. 6. The normalized inpu characerisic of proposed circui in Fig. 6. The normalized frequency F is defined as he raio of he swiching frequency f S and he resonan frequency f O. The shaded area is he operaing area for he experimenal 3 kw converer. The operaing region for his design is indicaed as he shaded area in Fig. 6. Three salien poins which define he operaing region are high-line full-load (HL, FL), nominalline full-load (NL, FL), low-line full-load (LL, FL). The maximum normalized inpu volage M g(max) is 1.47 a inpuvolage of 220 V L-L + 10% and he minimum normalized inpu volage M g(min) is 1.2 a an inpu-volage of 220 V L-L - 10%. The calculaed effecive capaciance C X is C x = 1 (2πR OfO ) = 220 nf, whereas he resonan 2 inducance is L R = R O (2πf On ) = 80 uh. Therefore, inpu-side -conneced resonan capaciors C 1 -C 3 = C X /2 = 110 nf and he value of oupu-side resonan capacior C D is chosen o be C X n 2 = C d = 55 nf. This choice leads o a good compromise beween low volage sress and low inpucurren harmonics. Due o he wide inpu-volage and load ranges, he closedloop conrol of he prooype recifier is implemened by a combinaion of variable- and consan-frequency conrol. The circui frequency is conrolled in he range beween full load and ligh load. In his power range he swiching frequency varies from 75 khz a full load o 20 khz a ligh load. When he swiching frequency falls o 20 khz, he consan frequency PWM conrol akes over o regulae he oupu volage wihou furher decreasing he swiching frequency. When he consan-frequency PWM conrol is acive, he swich operaes wih hard swiching. To minimize swiching loss during he PWM operaion, he swich curren should be minimized. This can be achieved by selecing inpu inducors L A -L C o form a 20-kHz resonan ank circui wih inpu resonan capaciors C 1 -C 3. A he momen when swiches and are urned off, he currens of inpu inducors L A -L C begin o charge inpu resonan capaciors C 1 - C 3 in resonan fashion. Because he resonan frequency and he swiching frequency are nearly he same, he sored energy in inpu resonan capaciors C 1 -C 3 was already decreased o near zero by he resonan currens of inpu inducors L A -L C a he momen when swiches and are urned on again. As a resul, because here is no energy in inpu resonan capaciors C 1 -C 3 o resonae wih resonan inducor L R, he swich curren decreases dramaically a 20- khz operaion, hence swiching losses are minimized even when operaing wih hard-swiching PWM operaion. The value of inpu inducors L A -L C is seleced o be approximaely 300 µh o form a 20-kHz resonan ank circui wih inpu resonan capaciors C 1 -C 3. Since during operaing condiions when he consanfrequency PWM conrol or line and load ransiens are acive and he swiches operae wih hard swiching, he passive clamp circui, shown in Fig. 1, is used o preven any volage overshoo. In fac, if he swich is urned off while a cerain amoun of curren is flowing hrough i, he swich curren is divered hrough diodes D C1 -D C3 and clamping capacior C C. Because he oupu power is low in he consan-frequency PWM conrol mode, he clamping circui operaes wih negligible losses. III. EXPERIMENTAL RESULTS The performance of he proposed isolaed, 3-phase, HPF, resonan, wo-swich forward recifier opology was verified on a 3-kW experimenal prooype operaing a 20 khz o 75- khz swiching frequency and providing 400-V dc oupu volage. A. Componen Selecion To reduce he conducion loss and emperaure of he swiches, wo IGBTs were conneced in parallel for and (Fairchild, FGL60N100, ES = 1000 V, I C90 = 60 A). Because he swiches are punch-hrough (PT) ype IGBTs ha have a negaive hermal feedback characerisic, he parallel operaion of he IGBT provides much beer hermal performance han ha of he single IGBT operaion. A high volage diode from Fairchild (FFAF10U170S, V RRM = 1700 V, I FAVM = 10 A) was employed as secondary side forward diode D F. Because he maximum volage sress across inpu bridge diodes D 1 -D 6 and oupu diode D D is approximaely 700 V, high volage diodes from Fairchild (FFAF10U170S, V RRM = 1000 V, I FAVM = 30 A) were employed. High volage polypropylene capaciors wih values of 100 nf (CDE, 940C20P1K, 2kV, 8.3 A RMS ) and 10 nf (CDE, 940C30S1K, 3kV, 2 A RMS ) were used in parallel for inpuside resonan capaciors C 1 -C 3. Two polypropylene capaciors wih values of 47 nf (CDE, 940C20S47K, 2kV, 5.2 A RMS ) and 10 nf were conneced in parallel and used for oupu-side resonan capacior C D. The oal values of he inpu- and oupu-side resonan capaciors were 110 nf and 57 nf, respecively. 813
V GATE-S2 [20 V/div] V IN =200 V L-L THD=5.7% PF=99.8% 1 2 3 (a) (a) V S1 [500 V/div] [500 V/div] V IN =220 V L-L THD=4.7% PF=99.8% (b) (b) [20 A/div] V DF [1 kv/div] V IN =242 V L-L THD=3.8% PF=99.8% (c) Fig. 7. Measured hree-phase curren waveforms of experimenal prooype a P O =3 kw and (a) V IN =200 V L-L, (b) V IN =220 V L-L, (c) V IN =242 V L-L,. Time base: 2 ms/div. D [1 kv/div] i PRI (c) The desired inducance of inpu filer inducors L A, L B, and L C was 300 µh for each phase. Two high-flux oroidal cores (Arnold, HF488075-2) were used in parallel o reduce he flux densiy and number of urns of he winding. A magne wire (45 urns, AWG# 13) was used as he inducor winding. The inducance of resonan inducor L R was 80 µh o obain he desired resonan frequency of 76 khz. A se of ferrie EE cores (ETD44/21-3F3, air gap=6 mm) was used. Liz wire (435 srands, AWG# 40, 45 urns) was used o reduce he proximiy effec of he winding. The inducance of oupu filer inducor L F was 900 µh. A se of ferrie EE cores (E65/32/27-3C94, air gap=40 mils) was used. A solid magne wire (50 urns, AWG# 12) was used because he proximiy effec in he oupu filer inducor was negligible. V B [500 V/div] V PRI [1 kv/div] (d) Fig. 8. Measured waveforms of experimenal prooype a V IN =220 V L- L, V O =400 V DC, and P O =3 kw. Time base: 5 µs/div. Finally, wo ses of EE cores (E80/38/20-3C94, air gap=1 mil) were used in parallel o consruc isolaion ransformer TR. Two Liz wires (435 srands, AWG# 40, 22 urns) conneced in parallel were used as he primary winding and a 814
Fig. 9. 1 2 3 1 2 3 Liz wire (435 srands, AWG# 40, 44 urns) was used as he secondary winding of he ransformer. B. Measured Resuls Figures 7(a) 7(c) show he measured waveforms of he inpu line curren delivering 3 kw a prooype recifier s hree inpu volages: V IN = 200 V, 220 V, and 242 V. Resuls demonsrae oal-harmonic-disorion (THD) of less han 6% a full oupu power and less han 5% THD a 50% oupu power. The recifier efficiency is approximaely 91% a 50% load and approximaely 90% a full load and nominal line. Figures 8(a)-8(d) show he measured waveforms of key componens. All he measured waveforms in Fig. 8 have he same ime scale and aligned o he equal rigger momen. Figure 8(a) shows he measured gae-o-source volage of swich which is idenical o he gae-o-source volage of swich and he measured volage waveforms of inpu resonan capaciors C 1 -C 3. Figure 8(b) shows he measured curren waveform of swich and he drain-o-source volage waveforms of swiches and. As shown in Fig. 8(b), he measured volage sresses of he swiches are well below he employed IGBT s nominal volage raing (1 kv). Figure 8(c) shows he measured curren waveform of resonan inducor L R, volage waveforms across forward diode D F and oupu resonan capacior C D. Figure 8(d) shows he curren and volage waveforms of primary winding of ransformer TR and volage waveform of V B. As shown in (a) (b) Measured waveforms of experimenal prooype delivering (a) P O =3 kw a f S =67 khz and (b) P O =200W a f S =23 khz and V IN =220 V L-L. Time base: 10 µs/div. Fig. 8(c), he volage across forward diode D F is well clamped o 1 kv, which is also well below he device raing of 1.7 kv. Finally, Fig. 9 shows he measured curren waveforms of swich and he volage waveforms of inpu resonan capaciors C 1 -C 3 a full load wih swiching frequency of 67 khz and ligh load wih swiching frequency of 20 khz. The swich curren decreases dramaically a 20-kHz operaion. IV. SUMMARY A hree-phase sof-swiched recifier ha provides galvanic isolaion and auomaically achieves HPF by employing a DVM resonan inpu circui and a wo-swich forward converer has been inroduced. The performance of he proposed opology was verified on a 3-kW prooype operaing from a hree-phase inpu volage of 220 V L-L ± 10%. The experimenal resuls show ha he inpu-currenshaping using he proposed recifier can be performed wih less han 6% THD over boh he enire line range and full load o less han 10% load range. The measured efficiency a full load and nominal line is approximaely 90%. REFERENCES [1] A. R. Prasad, P. D. Ziogas and S. Manias, "An acive power facor correcion echnique for hree-phase diode recifiers," IEEE Power Elecronics Specialiss Conf. (PESC) Record, pp. 58 66, 1989. [2] H. Mao, D. Boroyevich, A. Ravindra, and F. C. Lee, "Analysis and Design of High Frequency Three-phase Boos Recifiers," IEEE Applied Power Elecronics Conf. (APEC) Record, pp. 538 544, 1996. [3] E. H. Ismail and R. W. Erickson, "A single ransisor hree-phase resonan swich for high qualiy recificaion," IEEE Power Elecronics Specialiss Conf. (PESC) Record, pp. 1341 1351, 1992. [4] L. Simonei, J. Sebasian, and J. Uceda, "Single-Swich Three-Phase Power Facor Under Variable Swiching Frequency and Disconinuous Inpu Curren," IEEE Power Elecronics Specialiss Conf. (PESC) Record, pp. 657-662, 1993. [5] J. W. Kolar, H. Erl, and F. C. Zach, "Space Vecor-Based Analyical Analysis of he Inpu Curren Disorion of A Three-Phase Disconinuous-Mode Boos Recifier Sysem," IEEE Power Elecronics Specialiss Conf. (PESC) Record, pp. 696-703, 1993. [6] Q. Huang and F. C. Lee, "Harmonic Reducion in A Single-Swich, Three-Phase Boos Recifier wih High Order Harmonic Injeced PWM," IEEE Power Elecronics Specialiss Conf. (PESC) Record, pp. 1266-1271, 1996. [7] J. Sun, N. Frohleke, and H. Grosollen, "Harmonic Reducion Techniques for Single-Swich Three-Phase Boos Recifiers," Conference Record of he 1996 IEEE Indusry Applicaions Sociey Annual Meeing, pp. 1225-1232, 1996. [8] Y. Jang and M. M. Jovanović, A New Inpu-Volage Feedforward Harmonic-Injecion Technique wih Nonlinear Gain Conrol for Single- Swich, Three-Phase DCM Boos Recifier, IEEE Transacions on Power Elecronics, Vol. 15, no. 2, pp. 268-277, March 2000. [9] Y. Jang and R. W. Erickson, "New single-swich hree-phase high power facor recifiers using muli-resonan zero curren swiching," IEEE Applied Power Elecronics Conf. (APEC) Record, pp. 711 717, 1994. [10] Y. Jang, M. M. Jovanović, Design Consideraions and Performance Evaluaion of a 6-kW, Single-Swich, Three-Phase, High-Power- Facor, Muli-Resonan, Zero-Curren-Swiching Buck Recifier, Inernaional Telecommunicaions Energy Conf. (INTELEC) Record, pp. 715-722, 1997. 815