A Novel Quasi-Resonant Snubber-Assisted ZCS-PWM DC-DC Converter with High Frequency Link

Transcription

1 124 Journal of Power Electroncs, Vol. 7, No. 2, Aprl 27 JPE 725 A Novel QuasResonant SnubberAsssted ZCSPWM DCDC nverter wth Hgh Frequency Lnk Khary Fathy * and SoonKurl Kwon * Department of Electrcal Engneerng, Kyungnam Unversty, Masan, Korea ABSTRACT In ths paper, a novel type of auxlary swtched capactor asssted edge resonant soft swtchng PWM resonant DCDC converter wth two smple auxlary commutaton lossless nductor snubbers s presented. The operaton prncple of ths converter s desbed usng the swtchng mode equvalent cuts. Ths newly developed mult resonant DCDC converter can regulate ts DC output AC power under a prncple of constant frequency edgeresonant soft swtchng commutaton by an asymmetrcal PWM duty cycle control scheme. The hgh frequency power regulaton and actual power characterstcs of the proposed soft swtchng PWM resonant DCDC converter are evaluated and dscussed. The operatng performances of the newly proposed soft swtchng nverter are represented based on smulaton results from an applcatons pont of vew. Keywords: DCDC converter, seres capactor compensated transformer leakage nductance, auxlary lossless snubbng nductor, swtched capactor, zero current soft swtchng, and auxlary edge resonant snubber 1. Introducton Advanced developments n a varety of soft swtchng PWM DCDC power converter cuts wth or wthout a hgh frequency transformer lnk for the purpose of mprovng ther actual effcency, mnmzng power densty n volumetrc sze and weght, and achevng hgher performances as hgh qualty waveforms wth qucker responses have actvely been ntroduced. In addton, the current rngng and voltage surge caused by parastc cut component and hgh d/dt and dv/dt dynamc stresses n the power semconductor swtches are Manuspt receved December 4, 26; revsed Feb. 9, 27 rrespondng Author: soonkurl@kyungnam.ac.kr Tel: , Fax: , Kyungnam Unv. * Dept. of Electrcal Eng., Kyungnam Unv. more sgnfcant n accordance wth hgh frequency swtchng pulse modulaton. Some cut topologes wth soft swtchng pulse modulaton controlled voltage source full brdge nverter type DCDC converters wth a hgh frequency transformer have been developed so far and evaluated for telecommuncaton DC feedng power plants, automotve power supples and new energyrelated power condtoners. In ths paper, a novel cut topology of a voltage source softswtchng mult resonant ZCS DCDC converter wth constant frequency PWM control strategy usng actve auxlary quasresonant lossless nductor snubbers and swtched capactor snubbers s newly proposed. Addtonal outstandng practcal features are also presented. The operatng prncple of the proposed edge resonant snubber asssted DCDC converter topology ncorporatng ZCSPWM control scheme s llustrated and

2 A Novel QuasResonant SnubberAsssted ZCSPWM DCDC nverter wth 125 evaluated on the bass of operaton mode waveforms and equvalent cuts of each mode accordng to smulaton results. The effectveness of ths hgh frequency ZCS DCDC nverter usng IGBTs s substantally proved. The voltage source type ZCS DCDC converter and ts modfcatons match the practcal operatng requrements mentoned prevously. The proposed ZCS PWM scheme s able to regulate ts output DC power under a constant frequency asymmetrcal PWM control strategy and under softswtchng operaton condtons. 2. Proposed ZCS PWM DCDC nverter wth Actve Edge Resonant Snubber 2.1 Crcut nfguraton Fg. 1 shows the newly developed multresonant ZCSSEPP PWM DCDC converter cut usng the latest trench gate IGBTs and operatng wth a constant frequency PWM control strategy. Ths voltagefed ZCS PWM modfed half brdge DCDC converter cut conssts of the followng: two man swtches of reverse conductng IGBTs (SW1/D1) and (SW2/D2), a sngle auxlary swtch (SW3/D3) n seres wth auxlary edgeresonant swtched capactor as an actve snubber n parallel wth and LS1, two ZCSasssted lossless nductor snubbers LS1, LS1 connected n seres wth the man swtches and, power factor compensated seres load resonant capactor, hgh frequency centretapped transformer and DC flter. The output flter s connected n parallel wth the DC load that used to smooth out the DC output voltage. The proposed ZCSPWM DCDC converter s confgured by a few cut components and power semconductor devces as three actve control swtches are used. Fg. 1(b) ndcates a modfed halfbrdge ZCSPWM DCDC converter wth hgh frequency lnk. Fg. 1(c) Sngle ended pushpull ZCS PWM DCDC power converter wth a voltage doubler rectfer. 2.2 Gate Pulse Tmng Sequences The hgh frequency AC rectfed output power of the proposed DCDC converter cut, can be contnuously regulated by a constant frequency asymmetrcal PWM (duty cycle) control scheme under a condton of zero current soft swtchng commutaton. The gate voltage pulse tmng PWM sequences for the actve swtches Q 1, Q 2, and the auxlary swtch Q 3 are represented schematcally n Fg. 2. The man actve swtch Q 1 s frstly swtched on durng the perod of tme T on1 and before the man swtch Q 1 s turned off by a tme of T o. On the other hand, the auxlary swtch Q 3 s turned on for a perod T on3, nsertng an overlappng tme of T o between the swtches Q 1 and Q 3. In other words, the operaton of the auxlary swtch Q 3 s synchronzed to the man swtch Q 1. It s turned on just before the nstant that the man swtch Q 1 s due to be turned off. Then, the man swtch Q 2 s turned on after turnng off the auxlary swtch Q 3 wth a dead tme of T d1. The man swtch Q 1 s agan swtched on after a dead tme T d2 as another perod starts, as depcted n Fg. 2. /2 /2 D1 D1 D2 D2 D1 D2 D3 D3 Lr Lr Lm (a) D3 (b) Lm (c) Fg. 1 (a) Sngle ended pushpull ZCS PWM DCDC power converter wth hgh frequency lnk (b) Halfbrdge ZCSPWM DCDC converter wth hgh frequency lnk (c) Sngle ended pushpull ZCS PWM DCDC power converter wth voltage doubler rectfer C1 C2

3 126 Journal of Power Electroncs, Vol. 7, No. 2, Aprl 27 V Gsw1 3. Prncple of Soft Swtchng nverter V Gsw2 V Gsw3 Ton1 T on To T on3 T d1 T on2 T Fg. 2 Proposed PWM gate pulse tmng sequences for man and auxlary swtches 2.3 Duty factor as ntrol Varables By adjustng the constant frequency asymmetrcal PWM control varable, the duty cycle, whch s defned as the sum of the conducton tme T on1 of the man actve swtch Q 1 and conducton tme T on3 of the auxlary swtch Q 3 to the total swtchng perod operatng tme T of the hgh frequency swtchng mode, of the proposed hgh frequency ZCSPWM nverter can regulate ts hgh frequency output power contnuously under a condton of zero current soft swtchng. The conducton tme T on1 of the man actve swtch Q 1 can be controlled whle keepng the conducton tme T on3 of the auxlary swtch Q 3, the overlappng tme T o and the dead tme T d1 constants. As a control varable, the duty cycle D s defned as D = T / on T (1) T on = Ton 1 Ton3 To (2) The proposed ZCS PWM DCDC converter wth two lossless nductor snubbers for ZCS assstance and a sngle swtched capactor can not only be controlled by the constant frequency asymmetrcal PWM technque for hgh power settngs, but can also be controlled by a constant hgh frequency pulse densty modulaton (PDM) technque at low power settngs under ZCS condton. In addton, by usng a dual mode hybrd control of the asymmetrcal PWM and PDM at a constant hgh frequency, soft swtchng operatng range can be effectvely expanded from hgh power to low power settngs. T d2 At the begnnng of each swtchng cycle, the hgh sde man swtch SW1 of Q 1 turns on, the resonant nductor Lr ensures ZCS by lmtng the rate of the current rse. After ths tme, the prmary sde energy s suppled to the load R n the secondary sde cut through the hgh frequency transformer HFT. After the swtch current SW1 through SW 1 of Q 1 naturally commutates to the antparallel dode D 1 of Q 1 by quasresonance due to ZCSasssted hgh sde nductor snubber L S1, n seres wth the swtch Q 1, together wth the auxlary seres leakage nductance prmary sde of the HFT tuned capactor C s, the auxlary swtch SW 3 of Q 3 s turned on and the man swtch SW 1 of Q 1 s turned off. As a result, a ZCS commutaton at a turnoff swtchng mode transton can be acheved by a tmng process n whch the man swtch SW1 of s arbtrarly turned off. In ths mode, snce an auxlary resonant current SW3 flows through the swtch SW 3 of Q 3 and neases slowly, a ZCS commutaton at a turnon swtchng mode transton can be acheved for SW 3 of Q 3. After SW3 s commutated to the antparallel dode D3 of by the resonance formed by and Lr., leakage nductance of the transformer cutry and seres compensated capactor, a ZCS commutaton at a turnoff swtchng mode transton can be performed by turnng off SW3 of. Whle the auxlary swtch SW 3 of Q 3 s conductng, the voltage v aoss the low sde man swtch SW 2 of Q 2 deeases towards zero. The low sde man swtch SW 2 of Q 2 s turned on as soon as the dode D 2 of Q 2 attans a reverse basng state and begns to conduct naturally. Whle the dode D 2 contnues conductng, the current flowng through D 2 of Q 2 s naturally commutated to SW 2 of Q 2. Therefore, a complete ZVS and ZCS (ZVZCS) hybrd commutaton transton can be actually acheved for SW 2 of Q 2. On the other hand, after the current SW2 through the low sde man swtch SW 2 of Q 2 s naturally commutated to D 2 of Q 2 wth the ad of a low sde ZCSasssted nductor snubber L S2, and seres tuned capactor C s, ZCS commutaton at a turnoff swtchng mode transton can be performed by turnng off the swtch SW 2 of Q 2. Whle the dode D 2 of Q 2 s conductng, the D 2 s commutated by turnng on the swtch SW 1 of Q 1 when a second swtchng

4 A Novel QuasResonant SnubberAsssted ZCSPWM DCDC nverter wth 127 cycle starts. In ths mode, a ZCS turnon swtchng commutaton can be realzed wth the ad of a ZCSasssted nductor snubber L S1. The proposed edge resonant snubber type ZCS PWM DCDC converter offers a complete ZCS for all the man and auxlary swtches and acheves ZVZCS hybrd commutaton at turnon swtchng mode transton for the swtch SW 2 of Q Operaton Modes of nverter The swtchng operaton mode equvalent cuts of the proposed zero current soft swtchng DCDC converter n steady state durng one swtchng cycle are shown n Fg. 3. The current and voltage operatng waveforms of each element and the relevant operatng modes n steady state durng one swtchng perod are llustrated n Fg. 4. For a duty cycle D =.36. Ths mult resonant hgh frequency soft swtchng DCDC converter cut ncludes eleven operatng swtchng modes as shown n Fg. 3. The operaton prncple of the proposed zero current soft swtchng DCDC converter cut wll be explaned n the followng by usng the correspondng swtchng mode equvalent cuts, whch are dvded nto twelve operatonal modes. Mode 1 (t o t 1 ): A gatng sgnal s appled to the man swtch Q 1, whle the quasresonant snubber capactor starts to dscharge through the snubber nductor and dode D 3 of Q 3 and the man swtch s turned on. Then, the swtch current I neases softly wth a quas resonance due to L r1 and C r1, so the ZCS turnon commutaton of S1 s accomplshed. At the same tme, the prmary current starts to nease supply to the load and as a result dode conducts. The lossless snubber capactor C r1 s charged reversely, and consequently the capactor voltage reverses ts polarty untl the end of ths mode. The current of the man swtch durng mode 1 and the turnon transton of, whch corresponds wth the dscharged current of C r1, are expressed as; C r Q 1 = V sn ω o t L s1 where p s the prmary cut current and represents the ntal voltage of pror to the turn on of S1 and the resonant frequency ω o = 1/ Ls 1 p (3) V Mode 2 (t 1 t 2 ): The hgh frequency transformer prmary current I p starts to rse at t 1, and the quas resonance n the edge resonant snubber cell s termnated at t 1 when t matches wth I. At the same tme dode D3 commutates, the power s suppled now to the load through Q 1, C s, HFT and dode D 5. Mode 3 (t 2 t 3 ): As soon as the gatng sgnal s appled (see Fg. 2) to the auxlary swtch S3 of the s turned on at t 2 and current flows through D1. A quasresonance due to L r1 and C r1 occurs whch forces a negatve current through the reverse conductng dode of the man swtch (D1 of ) and I commutates whle D 1 conductng. At ths tme, the gate drve sgnal of the man swtch can be removed whle the swtch s under zero current condtons achevng Zero Voltage and Zero Current Swtchng (ZVZCS). Thus, turnoff commutaton can be acheved for S 1. As long as ths dode conducts, the correspondng IGBT can be turned on wth essentally zero voltage aoss t, thus performng a lossless swtchng. At mode 3, the turn of the current of the man swtch Q 1, s expressed by; = C L r s1 V sn ω t o where V s the ntal voltage of pror to the turn off of S1 and p s the prmary cut current. nsequently, the current waveform of auxlary swtch Q 3 s defned by; C r Q 3 = V sn ω ot L s1 The overlap tme T o of the gatng pulse perod between the swtch and auxlary swtch, can be determned by; T o p p (4) (5) π C r (6) 2 The duty cycle as a control varable ndcated by (1), (2) depends upon the value of T o. Mode 4 (t 3 t 4 ): Now the gatng pulse s removed from Q 1 and the dode D 1 commutates. Current suppled to the load through the auxlary swtch Q 3 and dode D 6 n the secondary cut starts conductng whle current n D 5 deeases.

5 128 Journal of Power Electroncs, Vol. 7, No. 2, Aprl 27 Mode 1 Mode 7 Mode 2 Mode 8 Mode 3 Mode 9 Mode 4 Mode 1 Mode 5 Mode 11 Mode 12 Mode 6 Fg. 3 Operatng mode transtons and equvalent cuts n steady state durng one swtchng cycle

6 A Novel QuasResonant SnubberAsssted ZCSPWM DCDC nverter wth 129 Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 Mode 6 Mode 7 Mode 8 Mode 9 Mode 1 Mode 11 Mode 12 V SW1 SW2 V SW3 V V V G1 SW1 V SW2 p V G3 Sw3 V G2 1 V/dv 5 A/dv 1 V/dv 2 A/dv 1 V/dv 1 A/dv 1 V/dv 1 A/dv 2 V/dv 2 A/dv reaches t maxmum value. Mode 8 (t 7 t 8 ): The swtch SW 2 of Q 2 turns on at ZVZCS commutaton. At t 7, the capactor starts dschargng. Mode 9 (t 8 t 9 ): SW2 of Q 2 s stll conductng and n the secondary cut commutates at t 8. Mode 1 (t 9 t 1 ): The capactor voltage wll be zero and starts to nease n the mnus drecton so that dode wll conduct. Mode 11 (t 1 t 11 ): SW2 s turned off wth ZVZCS at t 1 and D2 starts conductng. As a result, the current through the prmary cut changes ts drecton chargng the capactor. Mode 12 (t 11 t 12 ): commutates wth no power transfer from the prmary to secondary cut and energy stored n the output flter capactor C o wll supply the load. D2 stll conducts and current culatng exsts n the prmary cut. Thereafter, the aforementoned operatng processes are perodcally repeated n sequence durng each swtchng cycle. 5 A/dv 5. Smulaton Analyss and Dscussons to t 1 t 2 t 3 t4 t 5 t6 t7 t8 t9 t1 t11 t12 Tme 5 µs/dv Fg. 4 Voltage and current operatng waveforms durng one swtchng cycle for a duty cycle D=.36 Mode 5 (t 4 t 5 ): Before swtch Q 3 turns off, the dode D 2 of the man swtch Q 2 starts to conduct to compensate for the dfference between I and I p (I ), the stored energy n the prmary cut neases charge of capactor C s. Mode 6 (t 5 t 6 ): The gatng pulse sgnal s removed from auxlary swtch Q 3 and ts reverse conductng dode D 3 conducts so that SW3 turns off at zero voltage zero current swtchng ZVZCS commutaton. Mode 7 (t 6 t 7 ): At t 6, reverse conductng dode D 3 commutates. Although the gatng pulse s appled to Q 2 the dode D 2 contnues conductng and the stored energy n the hgh frequency transformer leakage nductor and compensatng capactor s suppled to the load. The capactor current I reaches zero value at t 7, whle V 5 A/dv 5 A/dv The prospectve expermental setup assembly s mplemented by usng trench gate reverse conductng IGBTs wth low saturaton voltage to valdate the steady state performance evaluatons of the proposed zero current soft swtchng hgh frequency lnk DCDC converter cut. The desgn specfcatons and cut parameters used n the smulaton are ndcated n Table 1. The cut parameters of ths hgh frequency ZCSPWM DCDC converter are determned by consderng the operatng condton of zero current soft swtchng commutaton and the requred output power ranges. Although the proposed hgh frequency swtchng DCDC converter operatng under a prncple of asymmetrcal PWM control or duty cycle control can acheve a complete soft swtchng commutaton operaton n low and medum output power settngs, t becomes a partally hard swtchng commutaton operaton n certan hgh power settngs and ts actual effcency for ths reason mght be substantally reduced. The soft swtchng range s from D= to 43% for all swtches. However, ths hgh frequency DCDC converter can stll operate under a consderably wde soft swtchng operatons, because the

7 13 Journal of Power Electroncs, Vol. 7, No. 2, Aprl 27 man swtch and auxlary swtch are turned on and off at soft swtchng condtons n the whole power range. In the case of duty cycles D more than.43, swtch turns on at ZCS, but turns off durng hard swtchng. In the case of low and medum output power settngs, a requrement of the duty cycle PWM control scheme, a soft swtchng operaton s employed. In addton, the zero current soft swtchng operatng range of the proposed DCDC converter can be actually extended by the use of new control scheme based on hgh frequency pulse densty modulaton (PDM) control strategy under low power settngs or by the use of a dual mode mplementaton of the PWM control. The output voltage regulaton characterstcs versus the duty cycle s shown n Fg. 5 Table 1 Desgn specfcatons and cut constants Item Symbol Value DC Source Voltage V s 22 V Swtchng Frequency f sw 5 khz ZCSasssted Inductor L s1, L s2.2 µh Snubber Capactor C r.2 µf Seres tuned capactor C s 2 µf Output flter nductance 5 µh Output flter capactance 5 µf HF transformer turns Rato N 1 :N 2 :N 3 1:2:2 HFT magnetzng nductance L m 5mH HFT prmary leakage nductance L 1 1 µh HFT secondary leakage nductance L 2 1 µh Output Voltage [V] Zero Current Soft Swtchng.2.4 Duty cycle HardSwtchng Fg. 5 Output power regulaton vs. duty cycle.6 6. nclusons In ths paper, a new topology for an actve auxlary quasresonant snubberasssted voltage source type.8 1 ZCSPWM DCDC power converter usng IGBTs was proposed. It s composed of an actve auxlary swtched snubber capactor and two lossless snubber nductors. The hgh frequency operaton prncple, swtchng mode transtons and the operatng characterstcs of ths converter were llustrated and evaluated on the bass of smulaton analyss. The practcal effectveness of the newlyproposed voltage source type mult resonant ZCSPWM DCDC converter wth hgh frequency transformer lnk has been proved on the bass of smulaton results. A wde soft swtchng commutaton operaton range was obtaned as compared wth prevously developed voltage source type ZVSPWM DCDC converters wth hgh frequency transformer lnks. It was found that the hgh frequency power regulaton strategy of ths proposed converter could be effcently suppled from full power to relatvely small power settngs. By applyng a dual mode pulse modulaton control strategy wth an asymmetrcal PWM, the output power of ths soft swtchng pulse modulated mult resonant DCDC converter could be regulated under a condton of expanded stable soft swtchng operaton ranges as compared wth prevously developed ZVSPWM hgh frequency DCDC converters. Ths dual mode ZCS PWM DCDC converter could actually acheve hgher effcency, hgher performance and wder soft swtchng operatng ranges for fuel cell power condtoners. In the future, the new prototype topology of ths ZCSPWM DCDC converter wth hgh frequency lnk should be evaluated for use n PEM fuel cell stack power condtoners. Ths ZCSPWM DCDC power converter usng 1 khz IGBTs or 15 khz IGBTs should be ntroduced and dscussed further wth the ad of a hgh frequency planar transformer. Acknowledgment Ths work s supported by the Kyungnam Unversty Research Fund, 27. References [1] HangSeok Cho; Bo Hyung Cho; Novel zero currentswtchng (ZCS) PWM swtch cell mnmzng addtonal

8 A Novel QuasResonant SnubberAsssted ZCSPWM DCDC nverter wth 131 conducton loss, IEEE Transactons on Industral Electroncs, Vol. 49, No. 1, pp: , Feb. 22 [2] H. Tanmatsu, H. Sadakata, T. Iwa, H.Omor, Y.Mura, E.Hrak, H.W.Lee, and M. Nakaoka, QuasResonant Inductve SnubbersAsssted Seres ad Resonant Tank Soft Swtchng PWM SEPP HghFrequency Mult Resonant Inverter wth Auxlary Swtched Capactor, Proceedng of Internatonal nference on Power Electroncs ICPE, pp II299, Busan, Korea, October, 24 [3] K. Yamamoto, Ej Hrak, T. Tanaka, Mutsuo Nakaoka, T. Mshma, Bdrectonal DCDC nverter wth Fullbrdge / Pushpull cut for Automoble Electrc Power Systems, IEEE PESC, Vol. 1 PP28284, June 26. [4] F.T Wakabayash,.; M.J Bonato,; C.A Canesn,.; Novel hghpowerfactor ZCSPWM preregulators, IEEE Transactons on Industral Electroncs, Vol. 48, No. 2, pp Aprl 21. [5] Khary Fathy, S. K. Kwon, K. Y. Suh, H. W. Lee, E. Hrak and M. Nakaoka, A Novel Swtched Capactor ssless Inductors QuasResonant Snubber Asssted ZCS PWM Hgh Frequency Seres ad Resonant Inverter, The Proceedngs of IEEUK PEMD nference, Aprl 26. was a Vstng Professor n VPEC at Vrgna Polytechnc Insttute and State Unversty, USA from 1997 to Hs research nterests nclude soft swtchng DCDC power converter topologes, hgh frequency nverter applcatons, renewal energy related power condtoners and control schemes. He s a member of KIEE, KIPE,and IEEE. Khary Fathy Abd ElSayed receved hs B.S. degree n Electrcal Power and Machnes n 1997 from Assut Unversty, Assut, Egypt. He s now workng towards hs Masters degree at Graduate School of Electrcal Engneerng, Kyungnam Unversty, Masan, Korea. Hs research nterests nclude soft swtchng DCDC power converter topologes, hgh frequency nverter applcatons, renewal energy related power condtoners and control schemes. He receved the 21 Best Student Paper Award at the 57 소 annual conference of the Internatonal Applances Techncal nference IATC26 held at owne Plaza, Chcago, USA, March He s a student member of KIEE, KIPE and IEEE. SoonKurl Kwon receved hs B.E. degree n Electrcal Engneerng from YoungNam Unversty, Daegu, Korea, and receved hs M.S. degree n Electrcal Engneerng from Busan Natonal Unversty, Busan, Korea, He receved hs Ph.D. (DrEng) degree n Electrcal Engneerng from YoungNam Unversty, Daegu, Korea. He joned the Electrcal Engneerng Department of Kyungnam Unversty, Masan, Korea n 1983 as a Professor. He