A COMPARATIVE STUDY OF SINGLE-SWITCH, THREE-PHASE, HIGH-POWER-FACTOR RECTIFIERS

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1 A OMPAATIVE STUDY OF SINGLESWITH, THEEPHASE, HIGHPOWEFATO ETIFIES Yungaek Jang and Milan M. Jovanović DELTA Power Elecronics Lab., Inc. 87 Pra Drive, Suie 4 Blacksburg, VA 46 Absrac Three reephase, singleswich, highpowerfacor recifier implemenaions were evaluaed on a comparaive basis. Specifically, e disconinuousconducionmode boos recifier w 5 harmonicrap filer, e disconinuousconducionmode boos recifier w harmonicinjecion circui, and e muliresonan, zerocurrenswiching buck recifier were compared wi respec o eir efficiencies, compliance wi e IE555 specificaions, volumes, weighs, and coss. The comparisons were done for e reephase, lineoline inpu volage of 38 V rms ± % and for 6 kw oupupower range. I. Inroducion Lowharmonic, highpowerfacor (HPF) recificaion in reephase power sysems can be implemened w large number of opologies and conrol sraegies []. Based on e number of conrollable swiches, HPF recifiers can be classified as muli or singleswich recifiers. Generally, e recificaion performance of e muliswich recifiers is superior o a of e singleswich recifiers since e mulipleswich recifiers can achieve higher power facors and lower harmonic disorions of e line currens. Specifically, sixswich recifiers have been exensively used in a variey of HPF applicaions []. While e use of muliswich recifiers is quie jusified in highpower, highperformance applicaions, e increased number of swiches and e complexiy of eir conrol make muliswich recifiers oo expensive in lower power, cossensiive applicaions. For example, oday s HPF elecommunicaion recifiers, which only need o reduce e oal harmonic disorion (THD) of e line curren o below 5%, are exclusively implemened eier wi passive L filers or acive, singleswich recifiers. So far, several reephase, HPF recifiers employing a single swich have been inroduced [][4]. Since ese recifiers have a single acive swich and perform HPF recificaion naurally wiou a need for a complex conrol circuiry, ey are very suiable for e lowcos, lowpower, reephase acdc applicaions. In is paper, ree singleswich HPF recifiers were sudied and evaluaed on a comparaive basis. The comparisons were done wi respec o eir efficiencies, compliance wi e IE555 specificaions, volumes, weighs, and coss. The recifiers were designed for e reephase, lineoline inpu volage of 38 V rms ± % and for 6 kw oupupower range. The ree opologies compared in is paper are: e singleswich, reephase, disconinuousconducionmode (DM) boos recifier w 5 harmonicrap filer; e singleswich, reephase, DM boos recifier w harmonicinjecion circui; and e singleswich, reephase, muliresonan, zerocurrenswiching (ZS) buck recifier. II. SingleSwich, ThreePhase, DM Boos ecifier The circui diagram of e power sage of e singleswich, reephase, PWM, DM boos recifier is shown in Fig.. Since e boos recifier in Fig. is operaed in DM w consan frequency and consan duy cycle, all reephase inpu currens,, i b, and i c, are zero a e end of a swiching period, immediaely before boos swich S is urned on. Afer swich S is urned on,, i b, and i c increase linearly o e peak values, which are proporional o e lineoneural volages as shown in Fig.. Therefore, during e swichon period, each line curren forms a riangular pulse wi e peak value proporional o e associaed lineoneural volage. As a resul, during e swichon period, e average line currens are proporional o e lineoneural volages. When e swich is urned off, e inpu currens sar decreasing because oupu volage V O is higher an e peak of e inpu volage. In DM, e inpu currens reach zero before e end of e swiching period. Since e rae of e inpucurren decrease is proporional o e difference beween oupu volage V O and lineoneural volage, e average line currens during e off period of e swich are no proporional o e line volages, i.e., even if e line volages are perfecly balanced and sinusoidal, e line currens are disored. Figure shows e normalized harmonic conen of e recifier inpu curren as a funcion of e volageconversion raio M, which is defined as Vo M = () 3Vm where V O is e recifier oupu volage and V m is e peak lineoneural volage. As can be seen from Fig., e

2 V a V b V c EMI filer i b i c i c inpu inducor L i b swich on T S swich off Fig. Singleswich, reephase DM boos recifier: circui diagram; inpu curren waveforms during swiching cycle. recifier inpucurren specrum, which conains only odd harmonics, is dominaed by e 5 order harmonic, i.e., e lowes order harmonic. For example, a M =., e 5 order harmonic is 8 imes larger an e 7 order harmonic, which is e nex larges. Also, i should be noed a e value of e normalized 5 order harmonic monoonically decreases as e value of M increases. In fac, i decreases from slighly over 3% of e fundamenal componen a M =. o approximaely 7% a M =. Generally, e maximum inpu power a which e reephase, consanfrequency, DM boos recifier can mee e IE555 specificaions is limied by e 5 order harmonic of e inpu curren. As an illusraion, Fig. 3 shows e 5, Fig... Ik I E3 E4 k = k = 5 E M S k = 7 k = 3 D k = 7 Vo Normalized inpucurren harmonics of e singleswich, reephase, consanfrequency, consanduycycle, DM boos recifier. are normalized wi respec o e fundamenal componen. Harmonic curren (rms, A) Fig. 3 5 kw 5 kw M =.4 V = 38 V IE limi 5 kw ,, and 3 harmonics of e DM boos recifier wi M =.4 and inpu power levels from 5 kw o kw along wi e corresponding IE555 limis. As can be seen from Fig. 3, for M =.4 e recifier can mee e IE555 requiremens only for power levels up o 5 kw because of e 5 harmonic limiaion. The higherorder harmonics, i.e., 7,, 3, ec., are well below e IE555 limis, even for power levels over kw. To mee e IE555 specificaions a power levels above 5 kw, e reephase, consanfrequency, consanduycycle DM boos recifier needs o be designed w higher M. However, i should be noed a for a given power line volage, larger M requires a boos swich w higher volage raing, which has a derimenal effec on e conversion efficiency and cos. Nevereless, e IE555 limis can be me w relaively low value of M if eier a passive 5 order harmonicrap filer is used, or e duycycle of e swich is modulaed by a harmonicinjecion signal o aenuae e 5 order harmonic. III. DM Boos ecifier wi 5 Order Harmonic Trap To reduce e magniude of e 5 harmonic in e inpu curren, e 5 order harmonicrap filer, which consiss of inducances L T and L T and capaciance T, needs o be added a e inpu of e power sage, as shown in Fig. 4. If e resonan frequency of e series resonan ank L T T is seleced a e frequency of e 5 harmonic of e line, e 5 harmonic of e recifier curren will be mainly flowing rough e L T T branches of e filer and no rough e source. The harmonicrap inducance L T can also be uilized as a par of e differenialmode inpu filer formed by e addiion of filer capacior T. Figure 5 shows e harmonicrap filer and is magniude frequency response. This filer has a passband beween dc and in (LL, rms) V O = 75 dc V P O = 5 kw kw omparison beween e inpucurren harmonic conen of e singleswich, reephase, consanfrequency, consanduycycle, DM boos recifier and harmoniccurren limis of e IE555 for M =.4, V O = 75 V, V in(ll) = 38 V rms, P in = 5 kw kw.

3 3phase 38V rms Va 5orderharmonic rap and differenialmode inpu filer boos L T T inducor D D D3 D7 75V dc L T Z I HS I HF Z eq Vb Vc L T T L S D4 D5 D6 6kW DM boos recifier Vo ac inpu Z L Z F Parallel esonance Pa L T T Series esonance Pa I H Z eq Fig. 4 Singleswich, reephase DM boos recifier wi 5 harmonic rap. cuoff frequency f c and provides a seep rae of aenuaion from f c o noch frequency f. The characerisics of e filer in Fig. 5 are compleely described by e following design equaions [5]: fc m = f, L T = ml k, L T = mk, f c = L k k T m = m L k,, and f = L T T The raio m represens e slope of e magniude characerisic from f c o f. If e value of m is uniy, en L T becomes zero, and L T and T are equal o L k and k respecively. Therefore, is circui becomes a simple L lowpass filer where L k and k are e filer elemens which define e cuoff frequency f c. As m in e filer in Fig. 5 decreases, e filer aenuaion rae increases. The filer has e flaes impedance over e greaes par of e passband when m is designed as approximaely.6. However, e value of m should be seleced so a i resuls in a good compromise beween e aenuaion performance and volume and cos. One problem in using a harmonic rap in a harmonic generaing power sysem (e.g., DM boos recifier) is e possibiliy o excie harmonic resonances [6]. Bo series and parallel resonances may occur in a power sysem due o e exisence of e filer and power line reacive componens. To furer explain ese resonances, Fig. 6 shows e equivalen harmonic circui for a power sysem a consiss of e recifier bridge and e harmonic rap. In Fig. 6, e DM boos recifier is modeled as a harmonic curren source. The i L T i. Fig. 6 f c ~ f OP f ~ f OS Harmonic resonances of harmonicrap filer: equivalen circui of DM boos recifier wi harmonicrap circui. magniude vs. frequency plo of oupu impedance of e filer. impedances Z F and Z, and Z L are e filer impedances and e line impedance, respecively. The harmonic curren flowing rough e rap filer is Z ZL ZS IHF = IH = IH, () Z ZL ZF ZS ZF while e harmonic curren flowing rough e source is ZF ZF IHS = IH = IS, (3) Z ZL ZF ZS ZF where Z S =Z Z L. Since a series resonan frequency f OS =f, Z F << Z S, mos of e harmonic curren flows rough e harmonic rap impedance Z F. However, a parallel resonan frequency f OP, Z F = Z S, and a high circulaing curren flows in e loop consising of e rap filer and e ac source. Therefore, o avoid is problem, e cuoff frequency of e rap filer should always be below e 5 harmonic line frequency, including possible frequency variaions. For 6 Hz line frequency, e 5 harmonic rap filer should have a noch frequency f of 3 Hz. To ensure a e cuoff frequency of e filer is safely below 3 Hz, cuoff frequency f c should be seleced o be f %, or approximaely 75 Hz. Wi is selecion of e filer, e parameers and e componens values of e filer are m =.36, L k = 5.9 mh, k = 55 uf, L T =. mh, L T = 4. mh, and T = uf. f Fig. 5 L i T i db T D f c f Frequency Harmonicrap circui and is frequency response. IV. DM Boos ecifier wi HarmonicInjecion ircui The harmonicinjecion approach does no increase e volage sress of e boos swich and requires only a few addiional componens for is implemenaion [7] []. In e echnique presened in [], a volage signal which is

4 3phase 38V rms Va Differenialmode inpu filer s Ls s3 L s4 s5 boos inducor 6kW DM boos recifier D D D3 D7 75V dc V an Vb Vc Fig. 7 B s S a c V d b c a Harmonic generaor V an V bn cn V V V V ab bc ca V d V inj s4 d OP d b h proporional o e invered ac componen of e recified, reephase, lineoline inpu volage is injeced ino e oupuvolage feedback loop o vary e duy cycle of e recifier wiin a line cycle in order o reduce e 5 order harmonic and improve e THD of e recifier inpu currens. The simples implemenaion of e harmonic injecion circui and is key waveforms are shown in Fig. 7 []. In e implemenaion in Fig. 7, e reephase line volage is firs recified by reephase bridge recifier B, and en aenuaed by e resisive volage divider a b. The scaleddown line volage developed across b, V d, is en invered by difference amplifier OP before i is processed rough e highpass filer b h o remove e dc componen of V d and generae injecion signal V inj. Finally, V inj is injeced in e conrol circui a e noninvering inpu of e PWM comparaor rough summing resisor. When signal V inj, shown in Fig. 7, is injeced a e PWM modulaor, i modifies e duy cycle so a e 5 order harmonic of e inpu curren is reduced and e THD is improved. In fac, since e variaion of duy cycle d() is L V inj gae driver V AMP S D4 D5 D6 phaseoneural volages lineoline volages recified line volage V = ac componen of V d inj d c Van Z V ONT 4 OP Z V EF onroller V inj(pp) Vo Singleswich, reephase DM boos recifier wi harmonic injecion circui: circui diagram; key volage waveforms. 3 6 direcly proporional o signal V inj, e modulaion of e duy raio during a line cycle can be described as DMOD () = D[ d() ], (4) where D MOD is e modulaed duy cycle, D is e duy cycle in e absence of e modulaion, and d() is e duy cycle modulaion. Since d() is proporional o e invered ac componen of e recified reephase lineoline inpu volage, e variaion of duy cycle d() during half of e fundamenal line period can be ploed along wi e lineoneural inpu volage, as shown in Fig. 8. The periodic funcion d() in Fig. 8 can be expressed in erms of e Fourier series represenaion as n m 6 d () = cos( 6nω). (5) 6 n = d() 3 ( ) ( n) ω Fig. 8 Duycycle variaions during half of fundamenal line period. From Eq. (5), i can be seen a e generaed injecion signal conains no only e 6 order harmonic bu also higherorder harmonics such as, 8, ec. As shown in [], ese higherorder harmonics help o improve e THD more an if only e 6 order harmonic is injeced. A any given volageconversion raio M, e opimal modulaion index m which produces e minimum THD can be deermined. To maximize e inpu power of e recifier a which e IE555 specificaions are me, modulaion index m should be deermined so a e raio of e 7 order harmonic and e 5 order harmonic is equal o corresponding IE555 limis []. V. SingleSwich, ThreePhase, Muliesonan, ZS Buck ecifier Figure 9 shows e reephase, muliresonan, ZS buck recifier and e volage waveform across inpuside resonan capacior r. Since inpufiler inducors L a, L b, L c, and oupufiler inducor L f are relaively large, ey have small swichingfrequency curren ripples. In a seady sae, e average volages of r r3 during a swiching period are equal o e associaed inpu volages. Because e peak volages of r r3 are proporional o e inpu currens, and swiching frequency f S is much higher an line frequency f L, e inpucurren waveforms follow e inpuvolage waveforms. As a resul, e circui possesses a high power facor and a low harmonic conen in e inpu curren. =3 5 =6

5 3phase 38V rms L a Va Vb Vc L b L c V r r r r3 Vr D D D 3 D 4 D 5 D 6 V an = V r,average 4Vdc In e circui shown in Fig. 9, e amoun of inpucurren disorion depends on e shape of e volage waveform across r, shown in Fig. 9(c). During e firs period, when S passive clamp circui L c c D c c D c V r r L r d D d L f f V r A B (c) Fig. 9 Muliresonan, ZS buck recifier: circui diagram, volage waveform of r and inpu curren waveform, and (c) enlarged V r waveform during one swiching period. Vo swich S is off, V r is increasing linearly w slope proporional o inpu curren. During e second period when swich S is on, resonan capacior r resonaes wi inducor L r, unil V r reaches zero volage. Finally, V r remains a zero for e ird period, during which swich S is sill on. Since V r is proporional o inpu curren only during e off ime of swich S, e inpucurren waveform becomes more proporional o e inpuvolage waveform if e firs period is longer an e sum of e second and e ird periods. Because in e muliresonan scheme in Fig. 9 e duraions of e second and ird periods are significanly reduced, e circui performs e recificaion w low THD. VI. Evaluaion esuls To compare e performance of e ree recifier opologies, e ree circuis were buil for e reephase, lineoline inpu volage of 38 V rms ± % and for 6 kw oupupower range. The powersage and inpufiler componens used in e ree experimenal prooypes are given in Table. The oupu volage of e DM boos recifiers wi e 5 order harmonic rap and e harmonic injecion was 75 V, whereas e oupu volage of e ZS buck recifier ecifiers Swich S Inpu Bridge Diode D in Oupu Diode D DM boos recifier wi 5 harmonic rap filer APT6 ( V, 33 A) BYT3PIV ( V, 3 A) DSEI6A ( V, 6 A) Table omponens of recifiers DM boos recifier wi harmonicinjecion circui Power Sage omponens APT6 ( V, 33 A) BYT3PIV ( V, 3 A) DSEI6A ( V, 6 A) Muliresonan, ZS buck recifier IXSH35N4A (4 V, 35 A) in Parallel DSEI3A ( V, 3 A) in series DSEI3A ( V, 3 A) in series Boos Inducor L = 3 4 uh L = 3 4 uh None Inpu Filer omponens Inducors L T = 3. mh, L T = 3 4 mh L S = 3 4 uh, L S4 = 3 6 uh L a L c =.9 mh apaciors T = 3 uf T = 3 uf S = 3.7 uf, S = 3 47 nf S3 = uf, S4 = 3. uf S5 = uf Oupu Filer omponens Inducors None None L f =.8 mh apaciors = 33 uf = 33 uf f = 47 uf esonan omponens Inducors None None L r = 43 uh apaciors None None r r3 = 33 nf, d = 8 nf None

6 ecifiers DM boos recifier wi 5 harmonic rap filer DM boos recifier wi harmonic injecion Muliresonan, ZS buck recifier Table omparisons of volumes, weighs, and coss of recifiers Inducive omponens apaciive omponens onrol ircui Power Sage Overall Volume Overall Weigh os 3 cm 3 cm 3 cm 3 cm 3 8 cm 3.5 kg Medium cm 3 cm 3 cm 3 cm 3 5 cm 3 5 kg Low 7 cm 3 cm 3 cm 3 3 cm 3 6 cm kg High was 4 V. The oupu volages of e boos prooype circuis were conrolled w consanfrequency PWM conrol a 45 khz. Due o e wide inpuvolage and load ranges, e closedloop conrol of e buck prooype recifier was implemened by a combinaion of a variable and consanfrequency conrol. The circui is conrolled by e frequency conrol for e oupu power in e range from 6 kw o 6 W. In is power range, e swiching frequency of e recifier varies from 9 khz a full power o khz a % load. When e oupu power falls below 6 W a e nominal inpu volage, e consan frequency PWM conrol akes over []. Since w consanfrequency PWM conrol, e swich operaes wi hard swiching, e passive clamp circui is used o limi e maximum volage of e swich. Because in e consanfrequency PWM conrol mode e oupu power is low, e clamping circui operaes wi negligible losses. Table summarizes e overall volumes and weighs of e ree prooypes. In addiion, Table also shows e volumes of inducive and capaciive componens separaely, as well as e volumes of e conrol circuis and power sages. Similarly, Figs. o show e comparisons beween e measured inpucurren harmonic conen of e experimenal recifiers and e IE555 harmoniccurren limis a differen inpu volages. Finally, Fig. 3 presens e measured efficiencies of e experimenal prooypes. As can be seen from e presened experimenal daa, e 5 harmonic rap reduces e 5 order harmonic in e inpu curren so a e recifier produces THD from 6% o %, and achieves 95.8% o 97.6% efficiency a e full load and oupu volage V O = 75 V dc. The THD and all harmonic currens mee e IE555 requiremens over e enire inpuvolage and oupupower ranges. However, as shown in Table, e size and, especially, e weigh of e circui wi e 5 harmonic rap is significanly greaer an e size and weigh of e oer opologies. The approximae overall volume and weigh are 8 cm 3 and.5 kg, respecively. The DM boosrecifier wi e harmonicinjecion circui has THD from 7.5% o.9% and efficiency from 96.4% o 98% a e full load and for V O = 75 V dc. The approximae overall volume and weigh are 5 cm 3 and 5 kg, respecively. Finally, e muliresonan ZS buck recifier can achieve e THD less an 5% over e inpuvolage and oupupower ranges. Efficiency of e recifier is abou 95% a e full load and for V O = 4 V. The approximae overall volume and weigh are 6 cm 3 and 6.4 kg, respecively. Alough e muliresonan, buckype recifier exhibis e lowes THD, e sresses on e semiconducor devices, ogeer wi eir conducion losses, resul in is limied efficiency and higher cos Fig Fig. 456 V rms 34 rms V V = 75 V P = 6 kw 456 V rms 34 rms V 5 7 IE limi omparison of inpucurren harmonic conen of experimenal 6kW DM boos recifier wi 5 harmonic rap and IE555 harmoniccurren limis a differen inpu volages. V = 75 V P = 6 kw 456 V rms 34 rms V 5 7 IE limi omparison of inpucurren harmonic conen of experimenal 6kW DM boos recifier wi harmonic injecion circui and IE555 harmoniccurren limis a differen inpu volages.

7 Fig V rms 34 rms V 456 V rms 34 rms V V = 4 V P = 6 kw 456 V rms 34 rms V 5 7 IE limi omparison of inpucurren harmonic conen of experimenal 6kW muliresonan, ZS buck recifier and IE555 harmoniccurren limis a differen inpu volages. EFFIIENY [%] DM Boos ecifier wi Harmonic Injecion DM Boos ecifier wi 5Harmonic Trap 94 Muliresonan 93 ZS Buck ecifier Po = 6 kw INPUT VOLTAGE [Vac] Fig. 3 Measured efficiency of experimenal prooypes. VII. Summary The performance comparisons of e reephase, DM boos recifiers wi e 5 harmonic rap filer and e harmonicinjecion conrol, and e muliresonan, zerocurrenswiching buck recifier show a e DM boos recifier wi harmonicinjecion conrol can be implemened o mee e IE555 specificaion wi e smalles size and weigh, as well as e highes efficiency. However, if oalharmonic disorion below 5% is required, e singleswich, muliresonan, ZS buck recifier appears o be e only viable approach. eferences [] F.. Lee, D. Boroyevich, Power Facor orrecion ircuis Topologies and onrol, IEEE Applied Power Elecronics onference (APE) Professional Educaion Seminars Workbook, Seminar 4, 993. [] A.. Prasad, P.D. Ziogas, S. Manias, "An Acive Power Facor orrecion Technique for ThreePhase Diode ecifiers," IEEE Power Elecronics Specialiss onf. (PES) ecord, 989, pp [3] E.H. Ismail,.W. Erickson, "A Single Transisor Three Phase esonan Swich for High Qualiy ecificaion," IEEE Power Elecronics Specialiss onf. (PES) ecord, 99, pp [4] Y. Jang,.W. Erickson, "New SingleSwich Three Phase High Power Facor ecifiers Using Muli esonan Zero urren Swiching," IEEE Applied Power Elecronics onference (APE) Proc., 994, pp [5] J.W. lark, A Power ondiioners, Academic Press, San Diego, 99. [6] E. H. Ismail, ThreePhase High Qualiy ecificaion, Ph. D. Thesis, Universiy of olorado, Boulder, 993. [7] J. W. Kolar, H. Erl, F.. Zach, "Space VecorBased Analyical Analysis of e Inpu urren Disorion of A ThreePhase DisconinuousMode Boos ecifier Sysem," IEEE Power Elecronics Specialiss onf. (PES) ecord, 993, pp [8] Q. Huang, F.. Lee, "Harmonic educion in A Single Swich, ThreePhase Boos ecifier wi High Order Harmonic Injeced PWM," IEEE Power Elecronics Specialiss onf. (PES) ecord, 996, pp [9] J. Sun, N. Frohleke, H. Grosollen, "Harmonic educion Techniques for SingleSwich ThreePhase Boos ecifiers," IEEE IAS Annual Meeing ecord, 996, pp [] Y. Jang, M.M. Jovanovi}, "A Novel, obus, Harmonic Injecion Meod for SingleSwich, ThreePhase, DisconinuousonducionMode Boos ecifiers," IEEE Power Elecronics Specialiss onf. (PES) ecord, 997, pp [] Y. Jang, M.M. Jovanovi}, "Design onsideraions and Performance Evaluaion of A 6kW, SingleSwich, ThreePhase, HighPowerFacor, Muliesonan, Zero urrenswiching Buck ecifier, IEEE In l Telecommunicaions Energy onf. Proc., 997, pp