Fully Soft-switched Bidirectional Resonant DC-DC Converter with A New CLLC Tank

Transcription

1 Fully Sof-swiched Bidirecional esonan DC-DC Converer wih A New CLLC Tank Wei Chen Siran Wang Xiaoyuan Hong Zhengyu Lu (Senior member IEEE) Shaoshi Ye College of Elecrical Engineering Dela Elecronics (Shanghai) Co. LTD. Zhejiang Universiy No. 8 inxia oad Pudong Hangzhou Zhejiang China Shanghai 9 China Absrac-A bidirecional dc-dc converer wih a new CLLC ype resonan ank which feaures in ZS for he inpu invering por swiches and ZCS for he oupu recifier por swiches regardless of he direcion of he power flow is proposed. If he OSFETs are implemened as all of he main swiches he proposed converer has a minimized swiching loss. The deail operaion principles as well as he design consideraions are presened. A prooype which inerfacing he /8 DC buses for he UPS sysem wih a power raing of A whose highes conversion efficiencies for he bidirecional mode boh exceed 96% was developed o verify he validiy and applicabiliy of his proposed converer. Keywords-Bidirecional dc-dc converer ZS ZCS Topology combinaion I. INTODUCTION Nowadays pleny of sof swiching Bidirecional Dc-dc Converers (BDC) wih focus on eliminaing he swiching loss reducing he elecromagneic inerference (EI) and achieving an aainable high frequency operaional abiliy and hereby power densiy wihou sacrificing he efficiency have been praised and exensively repored in he open lieraure []-[7]. As implemened wih he power OSFETs he zero-volage-swiching (ZS) echnique is desirable when he OSFETs are employed as he inpu por invering device since he urn-on loss due o he energy discharging of he oupu capaciance is large enough. However if he OSFETs used as he oupu por recifier wih S he zero-curren-swiching (ZCS) echnique is very suiable o miigae he reverse-recovery problem exhibiing in he inrinsic diode of he OSFET. Consequenly a perfec sof swiching BDC should have he feaures as ZS for he inpu por invering swiches and ZCS for he oupu por recifier swiches in eiher power flow direcion o subsanially eliminae he swiching loss as low as possible. [] inroduces a BDC operaing in he phase-shifed manner which can realize ZS for he volage-fed side swiches. However he swiches on he curren-fed side remain operaing under hard swiching condiions. In []-[] several BDCs are presened where he ZS aribue is enabled for he swiches operae in he inpu invering sage according o he power flow direcion. However on he corresponding oupu por he recifier swiches snap off and high volage surge is observed where he reverse-recovery loss remains unsolved and he CDi snubber is required []. To alleviae he reverse-recovery issue several ZCS BDCs are presened []-[7]. In hese ZCS BDCs boh of he inpu and oupu por S S C S Original Type- LLC Addiional esonan Tank esonan Cap. v Cs i Ls v Cs C S C S i Lm odified Type- LLC esonan Tank Figure. The proposed BDC and is opology decomposiion swiches realize ZCS regardless of he direcion of he power flow which have a significan reducion of he reverse-recovery power loss for recifier sage. Unforunaely he urn-on loss for he invering swiches of he inpu por is considerable and unsolved. This paper presens a novel bidirecional resonan dc-dc converer which possesses he aforemenioned sof swiching advanages as ZS for he invering swiches and ZCS for he recifier swiches for boh of he power flow direcions. Thus since he urn-on loss and reverse-recovery loss for he applied OSFET are boh eliminaed he proposed converer is oally snubberless. Following he inroducion he converer operaions and design consideraions are described respecively. The experimenal resuls are presened from a A prooype o confirm validiy and applicabiliy of he proposed converer. II. TOPOLOGY DEIATION AND OPEATION PINCIPLES The circui configuraion of he proposed converer is presened in Fig. which can be recognized as a combinaorial resonan ank merging he Type- and Type- LLC resonan converer presened in [8] [9] ogeher. Wih he ZS+ZCS feaure for he wo resonan sub-anks he proposed CLLC resonan ank achieves he desired sof swiching feaure of ZS+ZCS. Boh of he direcions of he power flow are modulaed under he variable Frequency odulaion (F) above resonance. The driving signals for he invering sage swiches and he main principle waveforms are shown in Fig.. In eiher mode here are 8 operaion sages during a swiching period. The equivalen circuis in he former operaion The Novel CLLC esonan Tank C S C S Original Type- LLC Addiional esonan Tank esonan Cap. v Cs i Cs i Ls v Cs C S i Lm odified Type- LLC esonan Tank Projec suppored by Naional Naural Science Foundaion of China (6776) //$. IEEE 8

2 v gs S S S v gs S67 S8 S67 v ds v ds67 v ds v ds8 i Ls&i Lm ils ilm i Cs&i Lm ics ilm v Cs v Cs Cs v Cs v Cs Cs i ds is6&is7 is&is8 is6&is7 i ds is&is is&is is&is v ds8 v ds (a) Operaion principles of converer wih he odified Type- LLC ank (b) Operaion principles of converer wih he odified Type- LLC ank Figure. Operaion principles of he proposed CLLC resonan ank S S C S C S C S C S S S Sage [ ] S Sage [ ] S C S C S C S C S Sage [ ] Sage [ ] T- ode Figure. Equivalen circuis for each sage under he boh direcions of he power flow sages in a half swiching cycle for T- mode are given by Fig.. Oher sages in each mode are symmerical o hose of he previous half cycle. The deailed operaing processes of he T- ode are presened here in he following ex: Sage [ ]: A he ime of and are conducing. The resonan curren i Cs will increase in a sine-wave shape. On he secondary side he recified curren i S and i S are proporional o he difference beween i Cs and i Lm. Sage [ ]: i Cs equals o he increasing magneic curren i Lm a ime. S & urn off under ZCS condiions. The volage on he resonan capacior C S also resonaes o is peak wih he absolue value of Cs and will keep unchanged unless excies again in he nex resonance. Sage [ ]: A ime and are urned off. i Cs begins o charge he parasiic capaciors of & and discharge hose of & symmerically. This sage ends up wih v ds67 reaching inpu volage and v ds8 decreasing o zero. Sage [ ]: Afer he fully discharge of and he resonan curren of i Cs immediaely flows hrough he body diodes of and and feeds back o he inpu source. A ime S and urn on under ZS condiions he firs-half swiching period ends and he converer eners he nex half. From he operaion principles i can be comprehended ha during he T- ode he addiional resonan capacior C S appears and disappears wih he load a he same ime. As a consequence he inserion of he C S o he original Type- resonan ank will only slighly modify he resonan frequency when all of he four resonan elemens are involved bu no influence he fundamenal of he original resonan ank. III. DESIGN CONSIDEATIONS A. Behavioral Difference for he T- and T- Tanks The characerisics of he T- and T- modes can be invesigaed rapidly by he frequency-domain mehodology of Fundamenal ode Approximaion (FA) []. The C S CS T- ode T- ode Figure. Equivalen circuis for Forward and everse odes C S S C S 9

3 = Plane ω (a) DC gain curve for Forward ode Figure. Three-dimensional DC gain conour over swiching frequency = Plane ω (b) DC gain curve for everse ode g= g= g=. g= g= g= g=. g=. (a) Forward ode (b) everse ode Figure. 6 Parameer sweep agains g under wo modes equivalen circuis for he T- and T- resonan anks are where: a shown by Fig. respecively where is he equivalen load = + h h ω resisance. The equaions of he DC gain for boh of he T- and T- modes can be expressed as follows: Q ( + h) Q b = Q ω +. ( + ZCs)// ω g h ω g h ω T = () ZCs + ZLs + ( + ZCs)// + ZCs and: T = = a ( + ZLs + ZCs)// j b () a T = () + b ( + ZLs + ZCs) // + ZCs + ZLs + ZCs where: a = L h ω S CS Define Q = CS Q = Q ω T _ = ( + h g) g Q b = Q C ω +. S ω h ω h ω ω ω S ω h = ω T _ = ω = S ωt _ ( // Lm ) C S ωt _ + h According o () and () he normalized DC gain over swiching frequency can be ploed in Fig.. From Fig. i can be observed he frequency of L h = m C S ω is he swiching frequency hen resonance for boh wo modes have no been he.. ω g = where S CS () and () can be simplified as: T = a j b a + b = ().. ω ωt _ or ωt _ any more since he exra capacior for each mode acually paricipaes in he resonance and subsanially changes he resonance frequency. Neverheless he new resonance frequency is no mean exac o be he frequency

4 of. This is because he resonan inducor ( CS // CS ) sill needs some porion of energy o excie during he sages ha ransfer energy o load. The precise symbolic soluions for he resonance frequency of he wo modes can be solved by le he image par of () and () o be zero. However for he complexiy he expressions are omied here. B. Design Procedure for he CLLC esonan Tank Due o he difficulies when i comes o solve all of he elemens a he same ime i becomes more convenien o design a basic Type- or Type- resonan ank firs hen cope wih he las remaining resonan capacior lasly. I is more suiable o sar wih he design of a Type- LLC resonan ank firsly han wih he Type- resonan ank. The design procedure can be oulined by he following 7 seps: ). Choose a proper value for resonance frequency ω (or f T- ). T _ ft = π CS ). Parameer of h should be specified as large as possible e.g. h= o accommodae a wide inpu range adapabiliy. ). The inducance of can be deermined by he opimal design mehodology provided by []: Lm dead fs COSS () = 8 (6) where dead is he dead ime beween he wo swiches in he same bridge leg f S is he swiching frequency and C OSS is he equivalen oupu capaciance of he invering swiches. According o () and (6) and C S can be deermined. If he aainable maximum DC gain under his se of parameers can no fulfill he requiremen of he inpu range go back o Sep o rese a new h. ). Sweep parameer of g under he heavies load of Q. Fig. 6 shows a se of ypical DC gain curves for he boh wo modes. The appropriaely choosing of parameer g highly depends on how similar he curves of DC gain of he wo modes are. A fine g should make he wo DC gain curves as he same as possible. 6). Having he parameer g been known he second C resonan capacior C S can be calculaed by g = S which CS has been menioned above. Check wheher he DC gain can mee he variaion of load and line change. If no go back o Sep 6 o re-choose a more proper g. 7). Deermine he DC gain of T- mode a he resonance frequency assuming T_ hen he urn raio n (T- mode) of he ransformer can be obained direcly by: n = in T _ O (7) Wih n was presened he design procedure for he proposed CLLC resonan ank complees. C. Topology Exension Two Type- LLC resonan anks can also be combined and creae a new resonan ank wih he ZS+ZCS feaure. However he magneic inegraion echnique should be adoped shown as Fig. 7. The leakage inducance beween he primary and secondary windings funcions as he resonan inducor for he corresponding power flow direcions. C S Inegraed C S Inegraed C S Forward ode everse ode Figure. 7 The combinaorial ZS+ZCS bidirecional resonan ank wih wo inegraed Type- LLC resonan anks I. EXPEIENTAL ESULTS A A prooype verifies is operaion principle of he proposed converer. The specificaion and main parameers are specified as follows: Forward ode: in : - dc; O : 8 dc; I O : - A. everse ode: in : -8 dc; O : dc; I O : -. A. The componens of he power sage shown in Fig. are lised as follows: High olage Fed Side Swiches S ~ : SK9; Low olage Fed Side Swiches ~ : IPP7N8N; : n=:; : 8 uh; : 76 uh; C S : nf/6; C S : 7nF (g.9) Operaion waveforms for he Forward ode of full load under and inpu are shown in Fig. 8. Fig. 8 (a)-(b) show he ZS feaure of S. Fig. 8 (c)-(d) show he waveforms obained from he T- resonan ank. Fig. 8 (e)-(f) show he ZCS feaure for he recifier swiches. The operaion waveforms for he everse ode are also given by Fig. 8 (g)-(l). A simple way o appreciae hese waveforms for he T- resonan ank is jus considering he power flows hrough he T- resonan ank backward. Fig. 9 shows he conversion efficiency for boh Forward ode and everse ode under all condiions. The highes efficiencies for he wo modes are boh exceeding 96% under high line inpu. Fig. shows he swiching frequency versus load under differen volage inpu.. CONCLUSIONS The new bidirecional dc-dc converer proposed in his paper which has a combinaorial CLLC resonan ank possesses he opimal sof-swiching feaures as ZS for he invering sage swiches and ZCS for he recifier swiches regardless of he direcion of he power flows. Thus he swiching loss of he proposed converer has been minimized if he OSFETs are implemened as he main swiches. The experimenal resuls verify he heoreical analysis and he meris of he proposed converer. Therefore he proposed converer provides designers wih an alernaive choice for wide inpu range high efficiency and high power densiy bidirecional dc-dc conversion applicaions in indusry. C S

5 v gs:[/div] v gs:[/div] v gs6:[/div] v ds6:[/div] v gs6:[/div] v ds6:[/div] v ds:[/div] v ds:[/div] i ds:[a/div] Time: [us/div] (a) v gs v ds and i ds of i ds:[a/div] Time: [us/div] (b) v gs v ds and i ds of i ds6:[6a/div] Time: [us/div] (g) v gs v ds and i ds i ds6:[6a/div] Time: [us/div] (h) v gs v ds and i ds v Cs: [/div] Time: [us/div] v Cs:[/div] v Cs: [/div] Time: [us/div] v Cs:[/div] v Cs:[/div] v Cs: [/div] v Cs:[/div] v Cs:[/div] i Ls: [A/div] (c) v Cs v Cs and i i Ls: [A/div] (d) v Cs v Cs and i i Cs:[A/div] Time: [us/div] (i) v Cs v Cs and i i Cs:[A/div] Time: [us/div] (j) v Cs v Cs and i v ds6:[/div] v ds6:[/div] i ds:[a/div] v ds:[/div] i ds: [A/div] v ds:[/div] v Trs:[/div] v Trs: [/div] v Trs :[/div] Time: [us/div] v Trs :[/div] Time: [us/div] i ds6:[a/div] Time: [us/div] i ds6:[a/div] Time: [us/div] (e) v Trs v ds6 and i (f) v Trs v ds6 and i Forward ode (k) v Trs v ds and i (l) v Trs v ds and i everse ode Efficiency (%) Forward ode everse ode Figure. 9 easured efficiency a differen loads EFEENCE [] L. Zhu A Novel Sof-Commuaing Isolaed Boos Full-Bridge ZS-PW DC DC Converer for Bidirecional High Power Applicaions IEEE Trans.on Power Elecron. vol. issue pp. -9 arch 6. [] E. Hiraki K. Yamamoo and T. ishima An Isolaed Bidirecional DC-DC Sof Swiching Converer for Super Capacior Based Energy Sorage Sysems in Proc. IEEE PESC 7 pp June 7. [] a G. Qu W. Yu G. e al A Zero-olage-Swiching Bidirecional DC DC Converer Wih Sae Analysis and Sof-Swiching-Oriened Design Consideraion Indusrial Elecronics IEEE Transacions on vol. 6 Issue 6 pp. 7-8 June 9. [] H. F. Xiao and S. J. Xie A ZS Bidirecional DC DC Converer Wih Phase-Shif Plus PW Conrol Scheme IEEE Trans. Power Elecron. vol. issue pp. 8-8 ar. 8. [] Y. S. Lee and G. T. Cheng Quasi-esonan Zero-Curren-Swiching Bidirecional Converer for Baery Equalizaion Applicaions IEEE Trans. Power Elecron. vol. issue pp. - Sep. 6. [6] H. S. -H. Chung W. L. Cheung and K. S. Tang A ZCS bidirecional Efficiency (%) Figure. 8 Experimenal Waveforms Swiching Frequency (khz) Forward ode Swiching Frequency (khz) Figure. Swiching frequency versus load flyback DC/DC converer IEEE Trans. Power Elecron. vol. 9 issue 6 pp. 6- Nov.. [7] Y. S. Lee Y. S. Lin S. H. Hsiao and Y. P. Ko uliple Oupu Zero-Curren Swiching Bi-direcional Converer in IEEE Proc. IECON 7 pp. 8-6 Nov. 7. [8] Severns.P. Topologies for hree-elemen resonan converers. Power Elecronics IEEE Transacions on vol. 7 Issue pp Jan. 99. [9] Wei Chen Zhengyu Lu Invesigaion on opology for Type- LLC resonan Dc-Dc converer in IEEE PESC 8 pp June 8. [] Foser.P. Sewell H.I. Bingham C.. e al ehodologies for he design of LCC volage-oupu resonan converers Elecric Power Applicaions IEE Proceedings- vol. Issue pp July 6. [] Bing Lu Wenduo Liu Yan Liang e al Opimal design mehodology for LLC resonan converer in IEEE APEC 6 pp arch everse ode