th TERATOAL SYMPOSUM on POWER ELECTROCS - Ee 00 X Međunarodn smpozjum Energetska elektronka Ee 00 OV SAD, YUGOSLAVA, OCT. OV., 00 A ovel 0kW -U Three-Phase Unty Power Factor Rectfer Module Johann Mnböck m-pec Power Electroncs Consultant Purgstall 5 A-75 Walkensten AUSTRA mnboeck@t-onlne.at Johann W. Kolar Swss Federal nsttute of Technology (ETH) Zurch Power Electronc Systems Laboratory ETH-Zentrum/ETL/H CH-809 Zurch/SWTZERLAD Phone: +--6-8 kolar@lem.ee.ethz.ch Abstract: n ths paper the current stress on the power components a drect three-phase boost-type unty power factor rectfer s analyzed n order to provde a bass for a system desgn under restrcton of the heght to -U. The conducton losses of the power semconductors are calculated usng analytcal approxmatons of the average and rms values of the component currents; the swtchng losses are taken from prevous expermental nvestgatons. Based on ths data an overvew of the estmated power losses s gven for the rectfer system for 0.5kW/800VDC output and 0V/00V/80V/50V (rms, lne-to-lne) mans voltage and the correspondng effcency fgures are calculated. Fnally, topcs of the contnuaton of the research are dentfed as, e.g., the realzaton of a prototype n order to verfy the theoretcal results expermentally also for unbalanced mans voltage condtons and wth non-deal components such as nonlnear nput nductors employng ron powder cores.. TRODUCTO Modern hgh-power telecom power supply modules are typcally desgned for a rated output power of P O,max 8V. 00A 0kW and show a two-stage topology, where a three-phase hgh power factor rectfer does supply an output-sde DC/DC converter. can be thought to be derved from the VEA Rectfer topology by replacng the four-quadrant swtch per phase by two ndvdual swtches and seres connected dodes. Ths does result n ncreased gate drve effort and reduced swtch utlzaton but, as a more detaled analyss shows, the effcency and the power factor of the system depcted n Fg. s very close to the hgh performance of the VEA Rectfer. The space vectors of the nput phase voltages u U [] of the three-level rectfer are shown n Fg.. The system shows for a gven nput voltage a requred output voltage level of U O. Û (Û denotes the peak value of the nput phase voltage) whch corresponds to the modulaton lmt M max / (cf. ()). However, one does not have to employ a space vector modulaton technque for the nput current control. An average current mode control n combnaton wth a trangular-shaped carrer sgnal and a mans voltage pre-control or, accordng to [], a multpler-free approach (cf. Fg.) does allow to acheve comparable performance. The rectfer, although utlzng sx swtches, does employ only three gatng sgnals,.e. s + s s, (R, S, T). Fg.: Basc structure of the power crcut of the three-phase sx-swtch three-level boost-type unty power factor rectfer as proposed n []. The rectfer system shown n Fg. can be consdered as a frst step n the development of the well known VEA Rectfer []. The sx-swtch topology Fg.: Rectfer nput voltage space vectors avalable for nput current control (cf. Fg. n []).
Fg.: Block dagram of the output voltage and multplerfree nput current control (cf. Fg..6(c) n []). Accordng to Fg. the rectfer shows a nearly constant peak to peak value of the rpple of the nput phase currents durng a mans fundamental perod due to the hgh number of swtchng states and/or nput voltage space vectors avalable for current control. u, Fg.: Tme behavor of a mans phase voltage R, of the equvalent rectfer nput phase voltage u U, R (cf. Fg. n [5]) and of the rpple component, R of the mans phase current, R (smulaton results). n the followng n secton the average and rms current stresses on the power components of the rectfer system are calculated n analytcal form. Secton shows the dmensonng of the rectfer system for an nput lneto-lne voltage range of U, j 0...50Vrms and an output power level of P O 0.5kW as requred for supplyng a 0kW output DC/DC converter module wth an estmated effcency of η DC/DC 95%. Fnally, a photo of a laboratory model s shown n secton and topcs to be nvestgated n the contnuaton of the research are compled.. STRESSES O THE COMPOETS n the followng the average and the rms values of the current stresses on the power semconductor components are calculated as requred for the calculaton of the conducton losses. Smple analytcal approxmatons are derved whch can be used beyond the scope of ths paper for the dmensonng of the power components of the rectfer. We assume: a purely snusodal phase current shape; ohmc fundamental mans behavor; no (neglectable) mans frequency voltage drop across the boost nductors requred for the snusodal shapng of the nput current; constant swtchng frequency; lnear behavor of the boost nductors (nductance not dependent on the nput current level. For characterzng the modulaton we defne a modulaton ndex ÛU Uˆ M () U U O O whch accordng to Fg. shows a maxmum value of M max. () For a frst estmaton of the core losses of an nput nductor an ron powder core and a modulaton ndex M are assumed. Accordng to [5] we then have for the normalzed rms value of the rpple current, rms,, 0.075. () rms n For a pulse frequency of f P /T P 50kHz, an nductance value of L 5µH, and an output voltage of U O 800V ths results n U ot 8L p 8.88A and/or n an rms value of current rpple of 0.075 8.88 667mA. (5), rms For L 5µH ths results n an rms value of the rpple of the flux lnkage of Ψ () L 50µVs (6) rms, j, rms whch s requred for a core loss calculaton accordng to [0]. The nput nductor s realzed n helcal wound technology ([], Schott corporaton [], type number: 99). The related flux densty B rms for a number of turns of 8 and an E-Type core (A.8cm ) results as Ψ rms Brms.7mT 7Gauss. (7) A As a more detaled analyss shows, for the conventonal rectfer the nductor rpple current harmoncs do occur domnantly at the pulse frequency f f P and at twce the pulse frequency f f P n about equal shares [5]. t s nterestng that for assumng a lnear dependency on the frequency and a quadratc dependency of the core losses on the flux densty ths does reduce the core losses due to the fact, that for the loss calculaton one has to take the squares of half of the total value B B B/,.e.: P ~ f B + f B f P B (8) wth f Fe f P 50kHz, V Fe 7.5cm and (7) the ron power loss of one nput choke results n approxmately
P Fe ~ 9.07 0 50mW 0 f.6 Fe[Hz] B. rms[gauss] V Fe[cm ] whch can easly be tolerated even f the core s not arranged n a forced ar-cooled envronment.. Current Stresses on the Power Components The rpple of the nductor current s not consdered for the analytcal calculaton of the average and rms current stresses [6] of the power components. (9) Mans Dodes For the average and the rms current stress on the mans dodes D we have ˆ D (0), avg π D, rms ˆ. () Free-wheelng Dodes The average and the rms current stress on the freewheelng dodes D F s M D ˆ F, avg () M ˆ. () D F, rms π Power Transstors The average and the rms current stress on the power transstors S + and S _ s M S avg ( ) ˆ () π M ˆ. (5) 6π S rms Output Capactor The rms current stress on the output capactor s calculated usng 0 M 9M 8π C Î out, rms 6. (6) The results of the analytcal calculatons are compled n Fg.5.. Thrd Harmonc njecton A zero sequence voltage component,.e. a thrd harmonc at the pulse-wdth modulator nput of each phase s employed n order to extend the modulaton range M (0...), as gven for purely snusodal modulaton, to M M (0... / ). Fg.5: Crcut structure of a brdge leg of the rectfer and current stresses on the power components accordng to (0) (6). Advantageously, ths furthermore results n a reducton of the rpple of the nput nductor current and n a reducton of the ampltude of the thrd harmonc of the center pont current. The optmum rato of the ampltude of the thrd harmonc component to the ampltude of the pulse-wdth modulator nput generatng the rectfer nput voltage fundamental dffers accordng to the optmzaton to be performed; e.g. for maxmum modulaton range we have a rato of M /M / 6, for a mnmzaton of the nput current rpple rms value M / M / and for the elmnaton of the thrd harmonc of the center pont current M / M 7 / 7. The current stress values of the rectfer have been calculated based on purely snusodal modulaton. As a more detaled analyss shows these current values, however, do hold wth suffcent accuracy also n case a thrd harmonc s njected for extendng the modulaton range.. DMESOG, EFFCECY For the dmensonng of the rectfer system the followng specfcatons are defned: lne-to-lne nput voltage range U, j 0...50Vrms output voltage U O 800V output power of the DC/DC converter suppled by the rectfer stage P O,DC/DC 0kW, whch results n an nput power of the rectfer of P 0.85kW assumng an effcency the DC/DC converter of η DC/DC 95% and a rectfer effcency of η R 97%. pulse frequency f P 50kHz. The stresses on the power components and the resultng power losses are lsted n Tab.. The characterstc fgures compled n Tab. are based on the analytcal expressons derved n secton and on expermental swtchng loss data accordng to [7] and [8]. The effcency s for an nput lne-to-lne voltage of, e.g. U, j 80V n the range of η 97.7% for hard swtchng. n case a soft turn-on technque [9] would be employed (whch would not cause an ncrease of the transent turn-off overvoltage, [9]) the effcency could be mproved to η S 98.%.
nput power P 0850 0850 0850 0850 W nput voltage U,l-l 0 00 80 50 V nput current,rms 9.58 5.66.05.8 A Output voltage U O 800 800 800 800 V Modulaton ndex M 0.65 0.8 0.98.08 Swtch current S,rms 9. 6..79.9 A R DS,on 0.Ω @5 C S,avg.9.5.5 0.80 A Conducton loss P S,C 0..5.7 0.68 W Turn-on (k on 8.5µJ/A) P S,on.56 0.05 8.7 7.58 W Turn-off (k off 8.µJ/A) P S,off.6.89..8 W 6x Swtch total losses P S 58.5 0.7 75.0 6.7 W Free-wheelng dode current DF,rms 0. 9. 8. 8.0 A U DF00.95V, r DFmΩ DF,avg.5.5.5.5 A 6x Free-wheelng dode losses P DF. 8.0 6.0 5.0 W Mans dode current D,rms.8.07 9. 8.6 A U D0 0.85V, r D 0mΩ D,avg 8.8 7.05 5.87 5. A 6x Mans dode losses P D 56.. 5.. W Total power semconductor losses 56.0 86.0 6.0 9.0 W nput choke (R L 9.5mΩ, P FE W, worst case) P L 8. 0. 6.0. W Output capactor current CO,rms.7 9.6 6.8.9 A x Output capactor 0µF/50V (R ESR0.Ω) P CO 6. 9..6. W Auxlary power P aux 0 0 0 0 W (housekeepng, fans) Snubbers, PCB, var. dstrbuted losses P add 50 50 50 50 W Total power losses P 80.5 95.6 6.6 5.6 W Effcency η 96.5 97. 97.7 97.9 % Effcency wth turn-on snubber (k on 0µJ/A) η s 97. 97.8 98. 98. % Tab.: Losses of a 0.85kW/50kHz three-phase rectfer accordng to Fg.. The mprovement of the overall effcency n case a turn-on snubber would be employed would be n the range of 0. 0.7%. n Table the semconductor components employed for the calculaton of the effcency are compled. Part S D F D Type nfneon SPW760C nt. Rect. HFA5PB60 ST TY00 (Thyrstor) Tab.: Lst of power semconductor components whch have been selected as bass for the calculaton of the effcency of the rectfer (cf. Tab.). Devces D n Fg. realzed by thyrstors whch are employed besdes rectfcaton for the brdgng of the output capactor precharge resstors after start-up n order to avod mechancal contacts,.e. a relay.. COCLUSOS As ths paper shows the proposed three-phase sxswtch three-level rectfer system s an nterestng alternatve to the well known VEA Rectfer topology. Accordngly, ths rectfer concept as well as the VEA Rectfer wll be further nvestgated at the ETH Zurch n collaboraton wth m-pec where the man topcs wll be: practcal realzaton of a rectfer system fttng nto an enclosure of -U heght (cf. Fg.6), expermental nvestgaton of the power factor, the total harmonc dstorton of the phase currents, the system effcency and of the losses of the power components for dfferent nput voltage condtons, determnaton of the power densty, nvestgaton of the nfluence of a mans voltage unbalance, of a non-lnearty of the boost nductor magnetc cores and of the system behavor n dscontnuous nductor current mode as occurrng at lght load condton. Fg.6: Photo of the prototype of the 0kW -U rectfer system. n front: nput choke n helcal wound technology [], rght: x 80mm hgh arflow fans, n the mddle on top: control board realzed n surface mount technology, n the back: output capactors 6 x 0µF/50V, n the left background: auxlary power supply. Dmensons (wthout housekeepng, wth fans): 0mm x 60mm x 88mm (-U). 5. REFERECES [] Zhao, Y., L, Y., and Lpo, T.A.: Force Commutated Three-Level Boost Type Rectfer. Record of the 8th EEE ndustry Applcatons Socety Annual Meetng, Toronto, Canada, Oct. -8, Vol., pp. 77-777 (99). [] Kolar, J. W., and Zach, F. C.: A ovel Three-Phase Utlty nterface Mnmzng Lne Current Harmoncs of Hgh-Power Telecommuncatons Rectfer Modules. Proceedngs of the 6 th EEE nternatonal Telecommuncatons Energy Conference, Vancouver, Canada, Oct. 0-ov., pp. 67-7 (99). [] Kolar, J.W., Drofenk, U., Mnböck, J., and Ertl, H.: A ew Concept for Mnmzng Hgh-Frequency Common- Mode EM of Three-Phase PWM Rectfer Systems Keepng Hgh Utlzaton of the Output Voltage. Proceedngs of the 5th EEE Appled Power Electroncs Conference, ew Orleans, Feb. 6-0, 000. [] Mnböck, J., Stögerer, F., and Kolar, J.W.: A ovel Concept for Mans Voltage Proportonal nput Current Shapng of a VEA Rectfer Elmnatng Controller Multplers. Part : Basc Theoretcal Consderatons and Expermental Verfcaton. Proceedngs of the 6th EEE Appled Power Electroncs Conference, Anahem, March - 8, 00. [5] Kolar, J. W., Stögerer, F., and shda, Y.: Evaluaton of a Delta-Connecton of Three Sngle-Phase Unty Power Factor Rectfer Systems ( -Rectfer) n Comparson to a Drect Three-Phase Rectfer Realzaton. Part Modulaton Schemes and nput Current Rpple. Proceedngs of the 7 th European Power Qualty Conference, uremberg, Germany, June 9-, pp. 0-08 (00). [6] Kolar, J.W., Ertl, H., and Zach, F. C.: Desgn and Expermental nvestgaton of a Three-Phase Hgh Power Densty Hgh Effcency Unty Power Factor PWM (VEA) Rectfer Employng a ovel Power Semconductor Module. Proceedngs of the th EEE Appled Power Electroncs Conference, San Jose, USA, March -7, Vol., pp. 5-5 (996). [7] Mnböck, J., Stögerer, F., Kolar, J.W.: Expermental Analyss of the Applcaton of Latest SC Dode and CoolMOS Power Transstor Technology n a 0kW Three- Phase PWM (VEA) Rectfer. Proceedngs of the rd
nternatonal Power Electroncs Conference, uremberg, Germany, June 9-, pp. -5 (00). [8] Mnböck, J., Stögerer, F., and Kolar, J.W.: Comparatve Theoretcal and Expermental Evaluaton of Brdge Leg Topologes of a Three-Phase Three-Level Unty Power Factor Rectfer. Proceedngs of the EEE Power Electroncs Specalsts Conference, Vancouver, Canada, June 7-, Vol., pp. 6-66 (00). [9] Mantov, G., and Wallace, K.: Dode Recovery Current Suppresson Crcut. Proceedngs of the nd nternatonal Telecommuncatons Energy Conference, Phoenx (AZ), USA, Sept. 0-, pp. 5-9 (000). [0]Mcrometals: ron Powder Cores, Power Converson & Lne Flter Applcatons. Catalog /ssue H, 995. []Shonts, D.: mproved PFC Boost Choke usng a Quas- Planar Wndng Confguraton. Proceedng of the th EEE Appled Power Electroncs Conference, Dallas, Texas, USA, March -8, (999). []Schott Corporaton: HWT Output nductors 9 Seres. Product Catalog 998 or www.schottcorp.com. 5