Switch-Off Behaviour of 6.5 kv IGBT Modules in Two-Level Voltage Source Inverter

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1 > > Scienific Journal of iga echnical niversiy Power and lecrical ngineering Volume 7 Swich-Off Behaviour of 6.5 kv IGB Modules in wo-evel Volage Source Inverer Andrei Blinov, allinn niversiy of echnology, anel Jalakas, allinn niversiy of echnology, Dmiri Vinnikov, allinn niversiy of echnology, Kuno Janson, allinn niversiy of echnology Absrac. his paper presens an analysis of he swich-off process of 6.5 kv/ A IGB modules in a wo-level half-bridge volage source inverer. During experimens, i was saed ha real swiching process is far from ideal swich-off since parasiic inducance and capaciance in he circui cause volage spikes and high frequency illaions during ransiion processes. Operaion saes of he inverer are described and analyzed. xperimenal and simulaion resuls are compared, he main ransiens are analyzed and mahemaically expressed and possible problems and soluions are discussed. Keywords: pulse widh modulaed power converers, insulaed gae bipolar ransisor, freewheeling sae, illaions I. ODCION ecen advancemens in power elecronic echnologies have made furher opimizaion possibiliies in high-volage highpower converers available. he inroducion of 6.5 kv IGBs has enabled simple and reliable wo-level half-bridge volagesource inverer (VSI) opologies o be implemened for he rolling sock auxiliary power unis. Invesigaions have shown ha an experimenal converer based on very simple halfbridge opology wih wo Infineon A/6.5 kv IGBs (FZ65KF) is capable of providing required performance wihin he whole range of rolling sock supply volage of. 4. kv and a wide power range 7 kw []. Such inverers (Fig., able I) are very simple in conrol and proecion, have reduced componen coun and provide good reliabiliy. Converers wih described opology and swiching elemens are perfecly suiable for use in isolaed DC/DC rolling sock converers as fron-end converers of auxiliary power supplies. Main problems of his opology are high power losses in semiconducors due o hard swiching and consequenly, limied swiching frequency because of hermal issues. his imposes increased requiremens on passive componens of he converer. hese downsides are relaed o he common peculiariy of half-bridge opologies volage spikes afer ransisor urn-off (Fig. ). he volage spikes are followed by illaions, obviously caused by presence parasiic capaciive and inducive circui elemens. his paper describes he reasons of hese processes in high volage ( kv) high power ( kw) half-bridge inverers wih modified sine wave oupu operaion as well as heir effec on he overall performance of he converer. II. OPAION OF H WO-V HAF-BIDG V wo equal capaciors C and C are conneced in series across he DC inpu volage source, providing a consan poenial of he one-half a heir juncion. wo-level halfbridge inverer has wo operaing saes: acive saes (A, A) and a freewheeling sae (FW). During acive saes, he wo ransisors (op swich) and B (boom swich) are swiched alernaely, providing posiive and negaive squarewave impulses wih he ampliude of / on he isolaion ransformer X primary winding (able II). ven a shor-ime simulaneous opening of he wo ransisors will resul in C C Iso laion ran sformer X ecifier & Filer ou 35 VDC B 6.5 kv IGB Module D 6.5 kv IGB Module Fig.. wo-level half-bridge 6.5 kv IGB based converer. AB I MA PAAMS OF H HAF-BIDG CONV Parameer Symbol Value Maximum inpu volage, V (max) 4 Minimum inpu volage, V (min) Nominal inpu volage, V (nom) 3 Oupu power, W P ou 5 Nominal oupu volage, V ou 35 Swiching frequency, Hz f SW urn-off S pike Ch : A, 5 ms Ch : Vol, 5 ms B urn- off Os cill aions Fig.. IGB collecor-emier volage (op) and curren (boom) waveforms during he es of he prooype ( 3 V; f SW khz, D.3, 46 % load).

2 Scienific Journal of iga echnical niversiy Power and lecrical ngineering Volume 7 AB II SWICHG SAS OF A WO-V V Inverer sae ransisor sae Oupu B Volage A ON OFF - / FW OFF OFF A OFF ON + / AB III PAASIIC AND OW-SIGNA CAPACIANCS OF H IGB Capaciances C G C C C GC C IS C G + C GC C S C GC C OS C GC + C C on(min) Gae-emier capaciance Designaion Collecor-emier capaciance Gae-collecor capaciance (Miller capaciance) Inpu capaciance everse ransfer capaciance Oupu capaciance on(max) and urn-off. Generally, a urn-off resisor mus have a higher value han a urn-on one. AB IV DAASH VAS OF FON FZ65KF MODS Parameer Symbol Value DC collecor curren, A I C Collecor-emier blocking volage, V I CS 65 Maximum juncion emperaure, ºC j max 5 Inpu capaciance, nf C IS 8 urn-on delay ime, µs d(on).75 ise ime, µs r.4 urn-off delay ime, µs d(off) 6 urn-off fall ime, µs f.5 Diode peak reverse-recovery curren, A I rm 7 ypical urn-on gae resisance, Ω G,on 3 ypical urn-off gae resisance, Ω G,off 75 Collecor A.5 A.5 CGC B B Gae CC X X G A FW A FW A FW A FW CG Fig. 3. Swiching waveform of a wo-level half-bridge DC/DC converer: maximal inpu volage and minimal inpu volage. shor-circui, herefore he maximum on-sae ime on of he ransisor conrol pulse should no exceed 8% of he half period (Fig. 3). his implemens a freewheeling sae when boh ransisors are off. During his sae, he oupu volage is zero []. III GNAIZD QIVAN CICIS OF A WO-V HAF-BIDG CONV In a real inverer, every deail has sray inducance, resisance and capaciance. hese parasiic componens have an influence on he performance and if no considered, could lead o dangerous overvolages, MI problems and damage of he inverer. Swich-off process is mos influenced by he sray inducance of he isolaion ransformer and parasiic inducance of he wiring as well as he juncion capaciances of HV IGB modules. A. Srucure of he IGB module he swiching behaviour (urn-on and urn-off) of an IGB module is generally deermined by is srucural, inernal capaciances (charges) and he inernal and ouer (gae drive) resisances (Fig. 4, able III). he gae resisor G is limiing he magniude of he gae curren I G, which dicaes wha he ime is needed o charge/discharge IGB inpu capaciance C IS during urn-on mier Fig. 4. quivalen inrinsic capaciances of he IGB. In high frequency inverers, overvolage caused by he energy sored in he sray inducance of a ransformer could cause a high volage spike on he IGB. However, his process does no occur in he invesigaed inverer since he nominal swiching frequency f SW is only khz and freewheeling diode sars o conduc before noiceable overvolage spike occurs. I is eviden ha he increased gae resisance slows he IGB swiching process, limiing overvolage, on he oher hand, increasing swiching losses. eference values of Infineon FZ65KF modules are presened in able IV [3][4]. IGB parasiic capaciance values are dependen on he ransisor module ype and no presened in he daashee of FZ65KF, complicaing furher calculaions. B. quivalen parameers of he converer Based on he parameers, mos influenial o he acive and freewheeling saes, he simplified equivalen circuis for he considered half-bridge converer were elaboraed. he value of he equivalen load resisance can be obained from [5]: Prms, () P r

3 > > > Scienific Journal of iga echnical niversiy Power and lecrical ngineering Volume 7 where Prms is he ransformer primary rms volage and P r is he power of he isolaion ransformer (neglecing losses). IV ANAYSIS OF FWHG SA OF H WO-V HAF-BIDG CONV wo-level half-bridge inverers have wo basic operaing saes: acive sae and freewheeling sae. During he acive G 3 ½ C C h : 5 V, us C h : V, us Fig. 5. Isolaion ransformer primary (op) and secondary volage (boom) waveforms during he es of he prooype ( 3 V; f SW khz, D.3, 46 % load). I r () B A D Fig. 6. Acive sae of he ransisor in he wo-level half-bridge converer. he ransformer primary rms volage is proporional o he converer inpu volage: Prms D, () As Fig. 5 reveals, he parasiic illaions occur only on ransformer primary winding, hence only primary winding parameers are considered. Freewheeling sae model includes a hird-order illaory circui. he oal parasiic inducance of he equivalen circui is described by: n I C C C i, (3) i where n is he inducance of he inverer circui elemens including bus, wiring and conac parasiic inducance, as well as he equivalen sray inducance of he ransformer primary. he magniude of he circui impedance is: Z ( f /( f C ) r _ p + π r _ p ) π (4) where f is he frequency of parasiic illaions, is he equivalen acive resisance of inverer busbar, wiring and ransformer primary winding. Parasiic capaciive componen C r-p is generally represened by effecive disribued capaciances of he primary winding. Fig. 7. Generalized represenaion of he urn-off process of IGB. G is he gae-emier volage of ransisor (conrol signal), C is he collecoremier volage, I r is he curren impulse hrough, evens -3 are marked. sae eiher or B is urned on. During he acive sae he curren I C flows hrough he op or boom ransisor, inpu capaciors C and C and he primary and secondary windings of he isolaion ransformer. he acive sae of he ransisor is presened in Fig. 6. he freewheeling sae akes place when boh swiches are off. A he end of he acive sae, a negaive gae conrol volage is applied o he ransisor, closing i and saring he freewheeling sae (Fig. 7) [6]. he following evens can be disinguished:. ransisor inernal capaciances begin o discharge and he collecor-emier volage C () of he IGB begins o rise. As he curren I C hrough he ransisor decreases, he energy sored in he sray inducance of he power circui develops a negaive volage poenial a poin A calculaed by: Sray dic, (5) d where is he sray inducance of he power circui, di C /d is he rae-of-fall of he ransformer primary curren, Fig. 8(). his volage poenial is added o he collecoremier volage afer ransisor urn-off: +. (6) Cpeak. Afer he volage poenial a poin A becomes lower han he ground poenial of, he curren I r begins o flow hrough he freewheeling diode (Fig. 8). he maximal reverse curren I r(peak) hrough he diode a he insan of urnoff is equal o he collecor curren I C(max) before urn-off. he curren hen decays exponenially when I r () according o [7]: Pr IC( max) Ir ( peak ) (7) D Sray 3

4 Scienific Journal of iga echnical niversiy Power and lecrical ngineering Volume 7 I ( ) I r I r( peak ) r( peak ) e + e e. he curren follows his equaion unil i equals zero. (8) ω ω δ f, () π π where undamped resonance frequency ω / C, aenuaion δ HF /( ), HF is equivalen highfrequency resisance and C is generally represened by he sum of equal paralleled IGB parasiic capaciances C and C B. C CB A D C Z r_p I rr C Fig. 8. everse curren of he diode afer ransisor swich-off. AB V VAS OF SIMAION PAAMS Parameer Symbol Value Inpu volage, V 4 Inverer inpu capaciances, µf C, C 3 IGB parasiic capaciances, pf C, C B 45 quivalen impedance a 3 khz, Ω Z r_p 8.8 Swich duy cycle D..4 Swiching frequency, khz f SW C D C According o he measuremens, he illaion frequency is 3 khz (Fig.7). Oscillaion is described by he illaory circui qualiy facor Q: A Zr_p I π f Q P s HF C ln( n π / ( n+), () ) CB C where n and n+ are ampliude values of volage illaions separaed by he ime inerval of. he equivalen sray inducance can be obained by Fig. 9. C circui causing he illaions afer IGB swich-off. he curren hen remains a zero unil he nex diode conducion. he duraion Ir of decaying reverse curren is described by equaion: HF ln( n / n+ ) ) f. () quivalen module capaciances can be obained from he illaion frequency equaion I r ln I r peak + ln. (9) ( ) C C. (3) B ( ω + δ ) 3. Afer depleion of he energy sored in sray inducance, he reverse curren hrough sops. he oupu capaciances of IGB modules C and C B ogeher wih he sray inducance and equivalen impedance of circui Z r-p form an illaing C circui (Fig. 9). C B and C begin o charge and discharge. Volage and curren in his C circui illaes unil being damped by and he volage poenial of poin A becomes equal o /. V ABOAION OF H SIMAION MOD Deerminaion of he parasiic elemens causing illaions requires a simulaion model o be elaboraed. he illaion frequency of he damped circui f is [8] he volage illaions across ransisor afer reverse curren impulse follow he equaion [9]: ω δ cos ω arcan e ω ω and illaing curren is described by: I δ. (4) ω sin ω e δ VI SIMAION SS. (5) According o he generalized equivalen circui, a simulaion model is creaed using PSIM sofware. he simulaion model elaboraed has he same configuraion as he 4

5 > > > > > Scienific Journal of iga echnical niversiy Power and lecrical ngineering Volume 7 es prooype in Fig. and includes he values presened in able V. Obained simulaion resuls were compared wih laboraory measuremens of he converer prooype (Fig. ). Furher, inverer performance was simulaed under differen operaion 5 condiions (Figs. -). he presence of he illaions showed no significan impac on he performance in he simulaions as well as during he laboraory ess. he curren ampliude during illaions remained relaively low; hence, he energy of he illaions is relaively low as well. Volage (V) -5 Curren (A) ime (us) Ch : A, 5 us Ch : Vol, 5 us Fig.. Simulaed and experimenal ransformer primary volage (op) and curren (boom) ( in3v; f khz; D.3; 48.4 Ohm) ime (us) Ch : 5 V, 5 us Fig.. Simulaed and experimenal IGB collecor-emier volage ( 3 V; f SW khz, D.3; 48.4 Ohm) Volage (V) 5 Volage (V) ime (us) ime (us) Fig.. Simulaed IGB collecor-emier volage: in3v; f khz; D.3; 88 Ohm(% load) ; 8.8 Ohm (% load). VII. CONCSIONS During he laboraory es of he prooype, as well as in he compuer simulaions, he frequency of illaions was found independen of he inpu volage or he swiching frequency of ransisors and remained a approximaely 3 khz. he ampliude value of illaions is proporional o he inpu volage. he value of he reverse curren impulse depends on he converer oupu power, i.e. he more energy is sored in he parasiic inducance, he more reverse curren is required o deplee i. On he conrary, under ligh load operaion, he duraion of reverse impulse is decreased. he simplified simulaion model showed similar resuls compared o he values obained during he laboraory es of he converer prooype. Alhough no enirely precise, he simulaion model gives an adequae esimaion of he processes ha occurred during he laboraory ess. 5

Scienific Journal of iga echnical niversiy Power and lecrical ngineering Volume 7 High sray inducance of he isolaion ransformer resuls in higher losses as well as volage and curren illaions afer

Due o he required high isolaion volage of he isolaion ransformer, he high sray inducance is hard o avoid, moreover he capaciance of HV IGB modules canno be avoided.

On he oher hand, he losses are increased, hus he nominal swiching frequency is limied a khz.

Due o high-volage supply, implemenaion of snubber circuis is complicaed and is unlikely o significanly improve he performance of he converer. ACKNOWDGMN Auhors hank sonian Science Foundaion (Gran No.

, Developmen of 5-kW Isolaed DC/DC Converer wih High-Volage IGBs, Compaibiliy in Power lecronics, 7. CP '7, pp. -6, May 9, 7 - June, 7, Poland. [] Xiaoming i, B.

[Accessed Feb 8, ] [4] Hermwille, M; IGB Driver Calculaion, Semikrone applicaion noe AN 74; pp -3, 3..7. [5] Vinnikov, D; Jalakas,.;.; Galkin, I.

6 Scienific Journal of iga echnical niversiy Power and lecrical ngineering Volume 7 High sray inducance of he isolaion ransformer resuls in higher losses as well as volage and curren illaions afer swich-off. Alhough he frequency of hose illaions is no high enough o generae srong radiaed MI, i can cause some problems wih conduced MI in he conac line. Due o he required high isolaion volage of he isolaion ransformer, he high sray inducance is hard o avoid, moreover he capaciance of HV IGB modules canno be avoided. In he case of he considered high-volage inverer, hese parasiic effecs are no dangerous o HV IGB modules, neiher are hey dangerous o oher circui elemens since hey do no creae noiceable overvolage. On he oher hand, he losses are increased, hus he nominal swiching frequency is limied a khz. Generally, he ways o reduce he impac of parasiic effecs are dissipaive snubber circuis and low induciviy busbar sysem. Due o high-volage supply, implemenaion of snubber circuis is complicaed and is unlikely o significanly improve he performance of he converer. ACKNOWDGMN Auhors hank sonian Science Foundaion (Gran No. 745 esearch of Dynamic Performance of High- Volage IGBs ) for financial suppor of his sudy. FNCS [] Jalakas,.; Vinnikov, D.; augis, J., Developmen of 5-kW Isolaed DC/DC Converer wih High-Volage IGBs, Compaibiliy in Power lecronics, 7. CP '7, pp. -6, May 9, 7 - June, 7, Poland. [] Xiaoming i, B.. Design of a hree-evel Inverer for an lecric Vehicle, Maser of engineering hesis pp. 7-5; niversiy of Canerbury, Chrischurch, New Zealand [3] Infineon homepage: daashee informaion. [Accessed Feb 8, ] [4] Hermwille, M; IGB Driver Calculaion, Semikrone applicaion noe AN 74; pp -3, [5] Vinnikov, D; Jalakas,.;.; Galkin, I. Middle-Frequency Isolaion ransformer Design Issues for he High-Volage DC/DC Converer. I. allinn niversiy of echnology/deparmen of lecrical Drives and Power lecronics, allinn, sonia; iga echnical niversiy/insiue of Indusrial lecronics and lecrical ngineering, iga, avia, 8. [6] Schüze, ; Design Aspecs for Inverers wih IGB High Power Modules, upec GmbH & Co KG, Warsein, Germany. [7] sing DC oupus wih inducive loads, Measuremen echnology imied, applicaion noe, ngland. [Accessed Jan 7, ] [8] Hagerman. J; Calculaing Opimum Snubbers, Gagerman echnology July 4, 995. [9] Kalanarov, P., Neumann,., lekroehnika eoreeilised Alused eine osa: Vahelduvvooluahelae eooria pp. 69-7, allinn 967. [] Vinnikov, D; gorov, M; Srzelecki, ; valuaive Analysis of - and 3-level DC/DC Converers for High-Volage High-Power Applicaions, pp. -6; allinn niversiy of echnology (allinn, sonia), Gdynia Mariime niversiy (Gdynia, Poland). Andrei Blinov received he B.Sc. and M.Sc. echn. degrees in elecrical drives and power elecronics from allinn niversiy of echnology, allinn, sonia, in 5 and 8, respecively.. From year 8 is he pursues docoral sudies in allinn niversiy of echnology. Andrei Blinov is a Ph.D. suden of he Deparmen of lecrical Drives and Power lecronics, allinn niversiy of echnology. esearch ineress of Andrei Blinov include simulaion and research of swichmode power converers, semiconcducor hea dissipaion and differen cooling sysems. anel Jalakas received he M.Sc degree in elecrical drives and power elecronics from allinn niversiy of echnology, allinn, sonia, in 6. From year 6 is he pursues docoral sudies in allinn niversiy of echnology. anel Jalakas is a researcher in he Deparmen of lecrical Drives and Power lecronics, allinn niversiy of echnology. esearch ineress of anel Jalakas include simulaion and modeling of power sysems and swichmode power converers. Dmiri Vinnikov received he Dipl.ng, M.Sc. and Dr.Sc.echn. degrees in elecrical engineering from allinn niversiy of echnology, allinn, sonia, in 999, and 5, respecively. He is presenly a Senior esearcher in he Deparmen of lecrical Drives and Power lecronics, allinn niversiy of echnology. He has auhored more han published papers on power converers design and developmen and is he holder of several iliy Models in his applicaion field. His research ineress include swichmode power converers, modeling and simulaion of power sysems, applied design of power converers and conrol sysems and applicaion and developmen of energy sorage sysems. Prof. Kuno Janson was born in 94 in Haapsalu, sonia. He received Dipl. ng. grade in elecrical engineering from he allinn niversiy of echnology (), sonia, in 987, Ph.D. degree in 99 from Gorki (now Nizhni- Novgorod) Sae echnical niversiy, ussia, and D.Sc. degree in from. Presenly he is a Professor and Head of Chair of lecrical Machines a Deparmen of lecrical Machines and Fundamenal of lecrical ngineering a. His areas of ineres include reacive power compensaion and elecric power qualiy, in paricular, reacive power parameric compensaion and load self-adjusing converers for power supply of elecrical arcs. 6

Power losses in pulsed voltage source inverters/rectifiers with sinusoidal currents

Power losses in pulsed voltage source inverters/rectifiers with sinusoidal currents ree-wheeling diode Turn-off power dissipaion: off/d = f s * E off/d (v d, i LL, T j/d ) orward power dissipaion: fw/t = 1 T T 1 v () i () d Neglecing he load curren ripple will resul in: fw/d = i Lavg