Open Access Carrier Level Layered Modulation Method can Filter Out the Harmonics of Cascaded H - Bridge Topology

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1 Sed Orders for Repris o repris@behasiee.ae 6 The Ope Elerial & Eleroi Egieerig oral, 05, 9, 6- Ope Aess Carrier Level Layered Modlaio Mehod a Filer O he Harois of Casaded H - Bridge Topology Wag Hadog * ad Cai Xv Depare of Eleroi Iforaio ad Elerial Egieerig, Faly of Elerial Egieerig, Shaghai iaoog Uiversiy, Shaghai, Chia Absra: Aalysis of he reaso of asade H-bridge iverer opology sig arrier phase shif odlaio ehod ao opesae he haroi, sig arrier level layered odlaio ehod a solve he proble of asade H-bridge opology ha i ao opesae haroi probles. Experieal resls show ha he odlaio algorih a effeively rede he odlaio delay, iprove he orol badwidh, i a also ae he haroi opesaio apaiy irease fro 5 ies o. The sope of he appliaio of STATCOM is grealy ireased i he grid. Keywords: Casade H bridge, arrier level layered odlaio, arrier phase-shifig odlaio, haroi opesaio, PWM, STATCOM.. INTRODUCTION Casade H bridge is he aisrea opology srre of he high-volage power eleroi eqipe sh as sai syhroos opesaor STATCOM, large-sale eergy sorage, whih ses H bridge as a i. Sai syhroos opesaor STATCOM as show i Fig. a isse ay speified rre, iprove power qaliy, sppor he volage, sppress volage flier, orol power flow. H bridge asaded a wihsad high volage, eqipe wiho rasforer ad a be sraighly haged i he high volage power syse. A prese, odlaio ehods of asade H bridge are as follows: he ladder wave plse widh odlaio, lilevel volage spae veor odlaio, arrier phase shif odlaio []. The ladder wave plse widh odlaio refers o ha he odlaio sigal se plse widh odlaio ehod for sep wave, i filer o haroi by orollig he legh of he odio ie of he aieae of he sigle level, parilarly for low-order harois sppressio []. Mli-level volage spae veor odlaio is a odlaio ehod whih is developed o he basis of he wo-level volage spae veor odlaio [3]. For N-level volage spae veor odlaio, i he spae of roaig oordiae syse, he veor of ay ie are syheized by he adjae N ozero veor, hrogh he opiizaio of aig ie o he N ozero veor ad zero veor i a odlaio period. We a ge he op wavefor of PWM, is volage spae veor ber is N3, bease i is a bi relaioship bewee he ber of levels ad he ber of volage spae veor. Whe N is large, he *Address orrespodee o his ahor a he Depare of Eleroi Iforaio ad Elerial Egieerig, Faly of Elerial Egieerig, Shaghai iao Tog Uiversiy, P.O. Box: 000, Shaghai, Chia; Tel/Fax: ; E-ail: hadog.wag@sj.ed. ber of li-level volage spae veor will be oo h, asig he orol o be ore opliaed, so he sope of appliaio has bee grealy liied [-6]. Carrier phase shif odlaio: orol sigal for eah i is geeraed by he phase opariso of a sie odlaio wave ad wo opleeary riaglar arrier, The odlaed wave of he sae phase is sae, he differee of he arrier is /N. By orollig he phase shif of he arrier ell op volage plse shifed i phase fro eah oher, i a be speriposed o ge li-level wavefor [7, 8]. Carrier phase shif odlaio orol algorih is siple ad easy o iplee, ad i is also applied o oasios i whih N is large, so i is he oe ha is os widely sed as a asade H- bridge odlaio. Theoreially, STATCOM haroi opesaio apaiy, whih oly depeds o he swihig freqey. H- bridge IGBT high freqey swihig devie, he swihig freqey a be doe o dozes HZ. I is opleely possible o ra ad opesae for he 50 ies haroi whose freqey is wihi HZ, b i fa, he rre STATCOM a oly opesae haroi ear 3, 5 ies, as for haroi ore ha 5 ies, yo ao ahieve good opesaio effe, i is so far wih he heoreial opesaio apabiliy. This grealy liis he praial appliaio of STATCOM.. THE REASONS OF THE CASE THAT CURRENT STATCOM CANNOT COMPENSATE FOR THE HIGHER HARMONICS Assig ha he ber of asade H-bridge is, eah arrier of H-bridge is seqeially phase-shifed for 360 /, ad he age o he sisoidal odlaio wave a obai PWM wave, he phase shif odlaed arrier is as show i Fig.. Correspodig PWM wave is as show i Fig /5 05 Beha Ope

2 Carrier Level Layered Modlaio Mehod The Ope Elerial & Eleroi Egieerig oral, 05, Vole 9 7 Assig he ip of STATCOM DC-side is Ud, he odlaio sigal of sie wave is Ussiw φ, hereby he op volage haroi opoe of eah i is as follows.,3,5...,,6,...; os si... os si os si N N T M U N T M U T M U d N d d ϕ ϕ ϕ!! x x is a -order Bessel fio. The haroi volage i oal volage of Casade H- bridge s op a be obaied as follows.,3,5...,,6,...; si... ± T N NM U C d N N ϕ Fig.. H-bridge asade STATCOM. Fig.. Carrier phase odlaio i H-bridge asade oe yle. Fig. 3. Carrier phase PWM wave i H-bridge asade.

3 8 The Ope Elerial & Eleroi Egieerig oral, 05, Vole 9 Hadog ad Xv Fig.. Doble loop orol sed by STATCOM. Ths he op volage haroi aily disribed i he viiiy of N ies of he arrier freqey w, ad shows odd disribio. The haroi aplide ireases wih he irease of he odlaio deph M. The delay of PWM is half of arrier yle, assig ha he freqey of arrier is F, he delay of odlaio is /F, ha is o say he pre delay ie is τ 0 /F, he delay li is τ 0s G s e e τ0s I Chia, 0V STATCOM sally se H-bridge asade, assig ha he eqivale swihig freqey is.6hz, sig a arrier phase shif odlaio, he swihig freqey of eah level is.6.8hz τ The ie osa of his delay li is The ipa o biyli orol is as show i Fig.. Vref is he volage referee vale of BUS apaior i H Bridge, Iref is he referee vale of he haroi eeds o be opesaed or reaive rre. Corol algorih ses doble loop of volage orol loop ad rre loop. Gifs ad Gvfs is he orolled obje of rre loop ad volage loop. Gis ad Gvs is he orreio rig of he rre loop ad volage loop. Gs is a pre delay ased by he odlaio lis. Wheher by ay odlaio, pre delay ased odlaio are half yle of PWM arrier. So i praial appliaios of power elerois, he rre loop orol badwidh is geerally desiged o be abo oe eh of he PWM swihig freqey, odlaio delay a be igored. The orol loop a ahieve he ideal raig resls [9, 0]. Assig ha he eqivale swihig freqey is.6, rre loop badwidh is desiged o be.6 / 0 60Hz. The grid fdaeal freqey is 50HZ, ha is, i heory, he devie a ra ad opesae harois wihi 60/50 3 ies. B bease he H bridge asade is sig he odlaio of arrier phase shif odlaio, so he odlaio delay is o /.6, b o be τ 0 /.8. I oher words: PWM odlaio delay ie is h larger ha he eqivale PWM swihig ie [, ]. So as o ahieve sable ad arae raig rre referee give reqirees, he orol badwidh of rre loop a be desiged oly p o a axi of.8/080hz or so, isead of.6/060hz. Modlaio ses he ehod of arrier phase shif, STATCOM a oly opesae harois wihi 3,5 ies. STATCOM ha se of he arrier phase shif odlaio a ra ad opesae low-order harois effeively ha wihi five ies. I is aily sed o opesae reaive power ad isse reaive power o adjs he volage. 3. THE INNOVATION OF CARRIER LEVEL LAY- ERED MODULATION The odlaio effe of ie delay o asaded H bridges ao be igored, so his paper arries o he rasforaio o he PWM odlaio: For he arrier, X axis represes phase, Y axis represes he level. Sie ha he odlaio ehod of aig sharig of he phase i he X- axis will ase delay odlaio ha ao be igored, so we ry o ae hages i he Y-axis, aig sharig of he level [3, ]. Average aplide of he arrier is oe of he pois of he origial aplide. The arrier freqey is haged o be ies of he origial arrier, ha is, he eqivale swihig freqey. As is show i Fig. 5. The priiple of geeraig he PWM wave i every level of he H bridge is sill he sae. Whe he odlaio wave is higher ha he arrier level, he PWM ops a high level, whe he odlaio wave is lower ha he arrier level, he PWM ops a low level. The orrespodig levels of PWM wave are as i Fig. 6. Whe sig he ehod of arrier phase shif odlaio, he devie swihig freqey G ad he arrier freqey C are he sae, ad he eqivale swihig freqey D is f D N fg N fc. Whe sig he ehod of arrier level layered odlaio, he eqivale swihig freqey ad he arrier freqey are he sae, ha is D C, so ha he average swihig freqey of he devie is f G f / N C Therefore, orrespodig o he haroi aalysis forla, i he sae eqivale swihig freqey, he W is ore lager whe sig he ehod of arrier level layered odlaio.

4 Carrier Level Layered Modlaio Mehod The Ope Elerial & Eleroi Egieerig oral, 05, Vole 9 9 Fig. 5. Carrier level layered odlaio oe yle. Fig. 6. Carrier level layered odlaio PWM wave For he wo ids of odlaio ehods of Fig. 3 ad Fig. 6, sig he sae syhei ehod of PWM, he PWM wave oras har of he op of H bridge asaded are as show i Fig. 7. As a be see fro Fig. 7, he eqivale swihig freqey of he wo PWM is he sae. I order o failiae o see he differee bewee he, add a FIR filer i he ba of wo asaded PWM op, we a ge he op of wo sie waves. Copared wih he odlaed wave, i is as show i Fig. 8. I Fig. 8, he gree is he odlaio wave, he ble is level saed arrier odlaio, he red is arrier phase shif odlaio, Visibly, he op of arrier level asade odlaio ad he odlaio wave fis well, sbsaially wiho errors. While he op of arrier phase shif odlaio ad he odlaio wave has a obvios phase delay. The delay ie is half yle of he arrier wave, ad he wavefor disor. I heory, ay delays i odlaio are half of he arrier yle [5, 6]. The odlaio delay of arrier level layered odlaio is half of he arrier yle, b bease he arrier freqey of his odlaio is he eqivale swih freqey, is ies of he phase shif odlaio is he ber of asaded. Therefore, i he arrier level layered odlaio, he delay ie ased by odlaio delay is / of he laer. Assig ha he eqivale swihig freqey is.6, he he odlaio delay of level saed odlaio is /.6 / 3. Theoreially, applyig level layered odlaio a ra ad opesae haroi of he pper lii of 3. / 0 / 50! 86 ies. I fa, aig swihig loss, os, dead ad oher faors i realiy io ao, i he appliaio, we a ra ad opesae he haroi wihi ies. I he field of Casade H-bridge opology, has o see ay heory ad appliaios of arrier level saed odlaio ehods i his field.. EXPERIMENTAL VERIFICATION To verify he validiy of saed arrier level odlaio, we applied his odlaio ehod i a 0V level asaded H bridges STATCOM, he field devie is as show i Fig. 9.

5 0 The Ope Elerial & Eleroi Egieerig oral, 05, Vole 9 Hadog ad Xv a Op PWM of arrier level H-bridge layered odlaio. b Op PWM of arrier level asade H bridge asade odlaio. Fig. 7. The PWM op of wo ids of H-bridge asade odlaio. Fig. 8. The opariso of he op of wo odlaio ehods ad odlaed wave.

6 Carrier Level Layered Modlaio Mehod The Ope Elerial & Eleroi Egieerig oral, 05, Vole 9 Fig. 9. High volage STATCOM sie. a haroi rres before opesaio. b alos o haroi rre afer opesaio. Fig. 0. Three-phase volage ad rre wavefors before ad afer opesaig harois.

7 The Ope Elerial & Eleroi Egieerig oral, 05, Vole 9 Hadog ad Xv a The valid vales of rre harois before opesaio is 75A. b The valid vales of rre harois afer opesaio is A. Fig.. The disribio hisogra of rre haroi before ad afer opesaio. Power qaliy aalyzer reords he daa before ad afer he haroi opesaio, opesaio ierval before ad afer he load flaio wihi a ie a be igored [7, 8]. Fig. 0 is a opariso har of hree-phase volages ad rre before ad afer harois opesaio. Yo a see he rre wavefor opesaed sigifialy beae beer, ad he aplide was sigifialy reded. Fig. is a opariso of rre haroi disribio hisogra before ad afer opesaio. I a be see fro he figre ha afer opesaio, he haroi aplide of harois wihi ies has sigifia aeaio. Fig. is a opariso of he rre oal haroi disorio rae before ad afer opesaio. I a be see fro he figre ha afer opesaio, he rre disorio THDi is reded fro 9.9% o 3.3%. The haroi opesaio effes of 5, 7,,3,9 ies are obvios. Visibly, his odlaio effe is good i aal appliaio. Ad prior o he adopio of he arrier phase shif odlaio, haroi opesaio a oly be ahieved wihi five ies [9, 0].

8 Carrier Level Layered Modlaio Mehod The Ope Elerial & Eleroi Egieerig oral, 05, Vole 9 3 a b Fig.. The deeed vale of rre disorio THDi before ad afer opesaio. CONCLUSION This arile is preseed for he firs ie ad o apply he arrier level layered odlaio ehod i he H bridge asaded opology, i has he sae eqivale swihig freqey wih he arrier phase shif odlaio, b he odlaio delay shoreed o / is he ber of asaded, fdaeally solve he resriios o rre loop oroller badwidh proded by pre delay. The haroi opesaio will rage fro 5 p o ies. Fially, we verified he odlaio algorih proposed hrogh he experie, he experieal resls show he praialiy ad effeiveess of he algorih. CONFLICT OF INTEREST The ahors ofir ha his arile oe has o ofli of ieres.

9 The Ope Elerial & Eleroi Egieerig oral, 05, Vole 9 Hadog ad Xv ACKNOWLEDGEMENTS Delared oe. REFERENCES [] L. iali, Carrier Phase Shifed Casade H Bridge Mlilevel Coverers ad he Sdy of is Appliaio i Aive Power Filer, Zhejiag Uiversiy: Hagzho, 005. [] W. Yi, Researh o Novel Topology ad Corol Sraegy of Casaded Mlilevel Iverer, Norh Chia Eleri Power Uiversiy: Baodig, 005. [3] Y. Bo, Researh o H Bridge Effiiey Opiizaio ad he Proble of Capaior Volage Balae i Chai STATCOM, Xi'a Uiversiy of Tehology: Xi'a, 0. [] Z. Y, Asyeri Hybrid Mlilevel Iverer Modlaio Sraegy Eqilibri ad Power Corol, Harbi Uiversiy of Siee ad Tehology: Harbi, 00. [5] Y. Li, A. Q. Hag, W. Sog, S. Bhaaharya, ad G. Ta, Sall sigal odel based orol sraegy for balaig idividal DC apaior volages i asade lilevel iverer-based STAT- COM, IEEE Tras. Id. Elero., vol. 56, o. 6, pp , 009. [6]. I. Leo, R. Porillo, S. Vazqez,.. Padilla, L. G. Fraqelo, ad. M. Carraso, Siple ified approah o develop a iedoai odlaio sraegy for sigle-phase lilevel overers, IEEE Tras. Id. Elero., vol. 55, o. 9, pp , 008. [7] X. She, A. Q. Hag, ad G. Wag, 3-D spae odlaio wih volage balaig apabiliy for a asaded seve-level overer i a solid-sae rasforer, IEEE Tras. Power Elero., vol. 6, o., pp , 0. [8] H. Ia-Eii,. -L. Shae, S. Farhagi, ad. Rode, A odlar sraegy for orol ad volage balaig of asaded H-bridge reifiers, IEEE Tras. Power Elero., vol. 3, o. 5, pp. 8-, 008. [9] X. Shai, S. Qiag, ad Z. Yogqiag, Researh o opesaio for balaed rasforer isolaio ype hai D- STATCOM, I: Pro. CSEE, vol. 6, o. 9, pp. 37-, 006. [0] M. S. A. Dahidah, ad V. G. Agelidis, Seleive haroi eliiaio PWM orol for asaded lilevel volage sore overers: A geeralized forla, IEEE Tras. Power Elero., vol. 3, o., pp , 008. [] B. P. MGrah, ad D. G. Holes, Mliarrier PWM sraegies for lilevel iverers, IEEE Tras. Id. Elero., vol. 9, o., pp , 00. [] R. Naderi, ad A. Rahai, Phase-shifed arrier PWM ehiqe for geeral asaded iverers, IEEE Tras. Power Elero., vol. 3, o. 3, pp , 008. [3] G. Carrara, S. Gardella, ad M. Marhesoi, A ew lilevel PWM ehod ad heoreial aalysis, IEEE Tras. Power Elero., vol. 7, o. 3, pp , 99. [] B. Mwiyiwiwa, Z. Wolasi, ad Y. Che, Mliodlar lilevel overers wih ip/op lieariy, IEEE Tras. Id. Appl., vol. 33, o. 5, pp. -9, 997. [5] D. G. Holes, ad T. A. Lipo, Plse Widh Modlaio for Power Coverers: Priiples ad Praie. Wiley-IEEE Press: Aeria, 003. [6] A. Iqbal, ad S. Moiddi, Coprehesive relaioship bewee arrier-based PWM ad spae veor PWM i a five-phase VSI, IEEE Tras. Power Elero., vol., o. 0, pp , 009. [7] W. Fei, Sie-riagle verss spae-veor odlaio for hreelevel PWM volage-sore iverers, IEEE Tras. Id. Appl., vol. 38, o., pp , 00 [8] N. V. Nho, ad M.. Yo, Coprehesive sdy o spaeveor-pwm ad arrier-based-pwm orrelaio i lilevel iverers, IEEE Pro. Eler. Power Appl., vol. 53, o., pp. 9-58, 006 [9] D. G. Holes, The sigifiae of zero spae veor plaee for arrier-based PWM shees, IEEE Tras. Id, Appl., vol. 3, o. 5, pp. -9, 996. [0] S. Koro,. Rebolledo, ad. Rodrígez, Reded swihigfreqey-odlaio algorih for high-power lilevel iverers, IEEE Tras. Id. Appl., vol. 5, o. 5, pp , 007. Reeived: Oober 6, 0 Revised: Deeber 3, 0 Aeped: Deeber 3, 0 Hadog ad Xv; Liesee Beha Ope. This is a ope aess arile liesed der he ers of he Creaive Coos Aribio No-Coerial Liese hp://reaiveoos.org/lieses/by/.0/ whih peris resried, o-oerial se, disribio ad reprodio i ay edi, provided he wor is properly ied.