International Journal of Scientific & Engineering Research Volume 9, Issue 3, March ISSN

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1 Interntionl Journl of Scientific & nineerin Reserch Volue 9, Issue 3, Mrch-8 9 ISSN A LOSD LOOP ONTROL OF BUK- BOOST A-A ONVRTR WITH RDUD THD MD. ALTHAFHUSSAIN, G.SURSHKUMARRDDY PG Student [P], Assistnt professor Dept. of, TKR collee of nineerin nd technoloy, Meerpet, Telnn Indi ABSTRAT:In this project we introduce converter with volte feedbc closed loop control schee with control on output volte plitude. A hih frequency opertion is crried for reduction of THD in the output volte wvefor. In the previous wor the output volte is vried by chnin the duty rtio nully here in the proposed ethod the duty rtio is chned utoticlly by closed loop syste with respect to v reference. The proposed converter utilies six unidirectionl current pssin nd bidirectionl volte blocin switches, executed by six reverse blocin insultedte bipolr trnsistors (IGBTs) or series MOSFT diode sets, two input nd output filters cpcitors, nd one inductor. It hs no over shoot issue of volte source not intinin constnt when ll switches re turned-on, nd in this nner, pulse width odultion ded-ties re not required brinin bout hih qulity wvefors, nd tes cre of the couttion issue without utiliin buly nd lossy R snubbers or devoted soft couttion techniques. The desin nd nlysis is crried out in MATLAB softwre with coplete results nd outputs with coprision of outputs with ll possible odes. KYWORDS: closed loop control, output volte, c-c converter, buc-boost, THD.. INTRODUTION Generlly, in industry, the c c power conversions re perfored by utiliin c thyristor power controllers, which utilie the phse nle or bsic cycle control on input c volte, to et the desired output c volte. The drwbcs of c thyristor controllers re low power fctor, lre totl hronic distortion in source current nd lower efficiency, hve restricted their utilition in c- c converters. For c c power conversions with vrible frequency nd volte, the utilition of indirect c c converters with dc-lin nd trix converters hve been proressed on the rounds tht they cn et better power fctor nd efficiency, nd littler filter requireents. In ny cse, for pplictions in which just volte control is required, the direct pulse width odultion (PWM) c c converters re ore fvored on the rounds tht they cn decrese the sie nd price of converter. These direct PWM c c converters in previous ppers re cquired fro their dc dc counterprts, where ll the unidirectionl switches re supplnted with bidirectionl. But every topoloy hs its own prticulr constrints; the buc-type c c converter cn just step down the input volte while boost type cn just step up the input volte. The buc boost nd u topoloy cn both step up nd step down the input volte; in ny cse, the phse nle is reversed. In ddition, the two topoloies hve disdvntes of hiher volte stress cross switches, nd there re discontinuous input nd output currents in the event of the buc boost converter. The u topoloy cn eliintes the currents discontinuity t the price of extr pssive coponents, expndin the sie nd price of converter nd reducin the efficiency. The c c converters in view of the ipednce source ornie liewise clled (q)zs c c converters in previous ppers, it cn both step up nd step down the input volte. However the step-down opertion lwys brins bout reversin of phse nle. In ddition, they utilie ore pssive coponents nd hve hiher current flowin throuh ctive switches id shoot-throuh, which e their utilition less ttrctive. In buc-type ultilevel c c converters in view of the ide of flyin cpcitors re proposed, which cn decrese the volte stress of switches nd reduce the qulity of output volte. In ny cse, they require RL booster to be ssocited in prllel to lod, eepin in ind the end ol to decrese the volte iblnce issue of lyin cpcitors. 8

2 Interntionl Journl of Scientific & nineerin Reserch Volue 9, Issue 3, Mrch-8 ISSN The proposed converter is invulnerble fro shoot-throuh of potentil difference source (or cpcitors) notwithstndin when ll switches re turned on t the se tie, which uprdes its dependbility nd it needn't bother with PWM dedtie which brins bout superb output volte. Despite the fct tht it utilies six unidirectionl current directin bidirectionl volte blocin switches, just two of the re exchned t hih frequency in ech hlf-cycle id ny worin ode, brinin bout littler switchin losses. In the proposed converter, no current flows throuh body diodes of switches, nd ccordinly, it cn utilie power MOSFTs lonside quic recupertion diodes in rrneent, which diinishes switchin losses nd poor turn round recupertion issue of MOSFTs body diodes is dditionlly doded. The non-invertin buc boost ethods of proposed converter re pproprite for pplictions with both step-up nd step-down request while the invertin buc boost ode cn liewise be used in DVR ppliction to reunerte both potentil difference ss nd swells. Fiure. Bsic PWM c-c converter.() Buc type. (b) Boost -type. (c) Invertin buc boost type Becuse of these conspicuous disdvntes, the dc dc counterprt of this invertin buc boost c c converter is frequently replced with non-invertin buc boost converter (two switch. LITRATUR SURVY buc boost converter) which is cquired by cscdin siple buc topoloy with boost topoloy. The non-invertin buc boost c c converter in Fi. (), (b), nd (c) deonstrte the trditionl Fi..() cn be otten by replcin ll non invertin buc nd boost converters nd unidirectionl switches in its dc dc counterprts in invertin buc boost converter, individully. The with bidirectionl switches. The tin sinls desin buc topoloy in Fi. () hs volte in of D for buc nd boost odes re iven in Fi. (b) nd (where D is duty rtio, nd D ), nd lon these.(c), individully. This converter hs volte in lines, it hs just step-down opertion. The boost topoloy in Fi. (b )hs in of/( D), with just volte step-up opertion. The buc boost converter in Fi. (c) hs volte in of D/( D), with both step-up nd step-down opertions, but output volte is inverted. Also, it hs hiher switch volte stresses, hiher inductor current nd current ripple, nd discontinuous input nd output currents. of D in buc ode nd /( D)in boost ode. This non-invertin buc boost converter hs benefits in tht it covers wide rne of input volte, it hs non-invertin output volte, lower volte stress on switches, nd lower inductor current nd current ripple. In ny cse, it hs followin drwbcs; it utilies eiht switches, needs PWM ded- - ties nd devoted sfe couttion ethodoloy to te cre of couttion issue, nd cn't utilie MOSFTs s the current flows throuh body diodes of switches. In ddition, it cn et just non-invertin buc boost volte nd lcs invertin buc boost opertion, which is dditionlly wnted in its ppliction s DVR, to copnste both volte ss nd swells. 8

3 Interntionl Journl of Scientific & nineerin Reserch Volue 9, Issue 3, Mrch-8 ISSN Fi. 3 deonstrtes the circuit confiurtion of the c c converter uses of six unidirectionl current flowin bidirectionl potentil difference blocin switches S S6, one inductor L, nd two input nd output filter cpcitors in nd o. The six unidirectionl current switches cn be cnowleded by series cobintion of power MOSFTs with externl quic recovery diodes, re in Fi. 3 In this fiure, body diodes of MOSFTs re not ppered s they never conduct, nd lon these lines, their poor reverse recovery issue is nelected. For hih power pplictions, it cn either utilie six reverse blocin IGBTs (RB-IGBTs) or six IGBTs (without body diode) with outside quic recovery diodes in rrneent. The proposed converter cn wor s conventionl non-invertin buc nd boost converters with volte in of D nd /( D), individully, nd furtherore s invertin buc boost converter with volte in of D/( D). By utiliin just six switches, it cn consolidte the usefulness of eiht switches non-invertin buc boost converter ppered in Fi. (), nd four switches invertin buc boost converter ppered in Fi. (c). In this wy, it cn be utilied s noninvertin buc boost converter to replce the trditionl invertin buc boost converter in Fiure. Non-invertin buc-boost c-c different c c chne pplictions. For its converter () ircuit topoloy.(b) Gtin sinl ppliction s DVR, the non-invertin buc boost for buc ode opertion. (c) Gtin sinls for ode cn be utilied to copenste volte ss boost ode opertion. (which hppens ll the ore reulrly), nd invertin buc boost ode for volte swells (which hppens less frequently). 3. A BUK-BOOST A-A ONVRTR The bove fiure cn be operte in three odes they re buc, boost nd buc-boost ode. Non-invertin Buc Mode Opertion. Fiure 3. ircuit topoloy of the buc-boost c-c converter. The PWM switchin sequence of the A- A converter durin non-invertin buc ode opertion nd ey wvefors re ppered in Fi For positive hlf of input c volte (vin > ), switches S,S3,S6 re lwys turn on nd S4,S5 re lwys turn off, while switch S is switched t hih frequency. Fi.4.deonstrtes the coprble circuits of the A-A converter for vin>. The circuit ppered in Fi. 4() is throuhout DT intervl in which switch S is turned on nd the input enery is stored in inductor L. Despite the fct tht the switch S is dditionlly turned on, in ny cse its outside series diode becoes reverse bised due to inverse input volte vin cross it. Alon these lines, no current flows throuh switchs throuout this intervl, s ppered in Fi. 4. 8

4 Interntionl Journl of Scientific & nineerin Reserch Volue 9, Issue 3, Mrch-8 ISSN second djust condition on inductor L fro () nd (), the picup in this buc ode is iven by Fiure 4. Non-invertin buc opertion when v in >. quivlent circuit () durin DT nd (b) durin ( D)T. Durin ( D)T intervl s in Fi. 3.3.(b), switch S is turned off while Sconducts in this intervl s its series diode becoe forwrd bised Fiure 6. Key opertionl wvefors durin noninvertin buc ode opertion. becuse of free-wheelin ction of inductor L current. nery stored in inductor is dischred to lod in this intervl. Non-invertin Boost Mode Opertion. The opertion of boost ode is se s buc ode but only the pulses for switch s5 nd s re interchned nd s nd s6 re interchned. Invertin Buc Boost Mode Opertion. The opertion of bu-boost ode is se s boost ode but only the pulses for switch s6 nd s4 re interchned nd s5 nd s3 re interchned. ontrol strtey Fiure 5. Non-invertin buc opertion when v in <. quivlent circuit () durin DT nd (b) durin ( D)T. For vin <, switches S,S4,S5 re dependbly turn on while switches S3,S6 re dependbly turn off, nd Sbecoeshih frequency switch. The opertion for vin < is se s clrified for vin >, with only difference is tht now the switchs perfors se s S (for vin > ), nd the other wy round. The coprble circuits id this netive hlf-cycle re ppered in Fi. 5() nd 5(b). By pplyin volt The output volte of the converter hs to be intined constntly s se s the desired vlue. The PI controller is eployed to ttin the bucboost c output volte which is chieved by vryin the duty rtio of the converter circuit. The feedbc loop of the converter is desined to control the duty rtio nd control the output volte. 8

5 Switch s Switch s Interntionl Journl of Scientific & nineerin Reserch Volue 9, Issue 3, Mrch-8 3 ISSN Siultion results Siultion of closed loop control of buc converter Output results of closed loop control of buc converter Switchin wvefors In this syste by pplyin the closed loop control schee to previous converter for control on output volte plitude. In this syste the hih frequency opertion is crried out for reduction of THD in output volte. Discrete, Ts = e-6 s. powerui Goto6 <IGBT v olte> D5 L S5 [S] Fro Fro [S] S Fro3 Fro S S3 D D3 in o RL [rs] PI Discrete Fro RMS vlue Volte ontroller Genertor4 Fiure 8. Switchin wvefors of closed loop [S] D.9 Gin Product Add Goto5 Fro control of buc converter. Unit Dely Vref rs Fro4 Fro Vo S4 Genertor6 Multieter Goto7 The bove fi shows the switchin <IGBT v olte> D4 Fro9 S6 opertions of boost converter in invertin ode. In D6 this ode switch s3,s6 on for positive hlf cycle nd off for netive hlf cycle. switch s4,s5 off for Fiure 7. MATLAB siultion of closed loop positive hlf cycle nd on for netive hlf cycle for control of buc converter. fundentl frequency.s is pulse rtin for positive hlf cycle with switchin frequency off 5KHZ nd The bove fiure shows the MATLAB copletely on for netive off cycle. The switch s is desin of proposed buc odule. In our previous copletely on for positive hlf cycle nd pulstin odule we cn step down the input volte by for netive hlf cycle with frequency of 5KHZ. chnin the duty rtio. In our previous odule the output volte is not stble.but in our odule by Input, output volte pplyin closed loop PI controller to previous odule we cn et the stble output volte. In this odule the feedbc loop control s the RMS bloc it does not enerte the finite vlue for one cycle or two cycles nd it enertes t lest one or two cycles. So we hve to provide initil duty rtio between nd. We hve set tie of.5 sec t which the syste chne fro open loop to closed loop.in this odule we hve ive v reference volte nd error detector in odule enerte error between v output volte nd v reference nd it ives to PI controller then the PI controller reduced the error nd ives to PWM. Here the chnes the duty rtio. In the bove odule we cn ive v reference s V rs / 6 HZ nd fter siultion we cn et 9V rs / 6 HZ in c converters the output is not precies nd it is instntneously. In this odule we cn step down the input volte..5 initil Duty rtio Step >= Switch d D c PWM Genertor Genertor Genertor Product Unit Dely Genertor3 NOT Loicl Opertor Goto Goto Goto Goto3 Add [S] Goto4 Multieter Fro5 Fro6 [S] Fro7 [S] Fro8 Multieter Vo Vo RMS (discrete) Scope [rs] Goto8 8.4 Vo rs volte(v) switch s switch s switch s switch s Fiure 9. Volte coprisionof closed loop control of buc converter. The bove fiure shows the volte coprision of input nd output. In odule the output is chned fter.5 sec becuse we re Vo 8

6 Discrete, Ts = e-6 s. powerui Goto6 <IGBT v olte> Goto7 <IGBT v olte> [S] Fro Fro [S] Fro3 Fro4 Fro9 Fro [rs] Fro.5 initil Duty rtio Step PI Volte ontroller >= Switch Genertor Genertor Product D Unit Dely d c PWM Genertor Genertor3 Genertor4 Product Unit Dely Genertor6 [S] Goto Goto NOT [S] Loicl Goto Opertor Goto3 Add Add Goto4 Goto5 Fro Fro Fro5 Fro6 [S] Fro7 [S] Fro8 Vo Vo Scope Vo [rs] Goto8 Interntionl Journl of Scientific & nineerin Reserch Volue 9, Issue 3, Mrch-8 4 ISSN ivin initil tie of.5 sec. But in our odule the output volte decresed. In this converter we cn perfor step down opertion. Siultion of closed loop control of boost converter Autotic chnin of Duty rtio in buc ode.8 D5 S5 D3.6 duty rtio.4. S3 D -. S in o RL Multieter Multieter Duty rtio L S D.9 Gin RMS (discrete) Discrete RMS vlue 8.4 Vo rs Fiure. Duty rtio chnes of closed loop control of buc converter D6 S6 S4 D4 Vref rs Multieter The bove fiure shows the chnin of duty rtio in our odule. In the previous odule by chnin the duty rtio to et the desired output volte.but in this odule by ivin v reference we et the output volte. In this odule the duty rtio is utoticlly chned due to closed loop control. In the feedbc loop control of RMS bloc does not enerte the finite vlue for cycle it provides finite vlue for or cycles. So we hve to provide initil duty rtio vlue of.5. Previously the duty rtio is intined t.73 by chnin it nully where s here it is intined constnt i.e.73 by usin closed loop circuit. Fiure. MATLAB siultion of closed loop control of boost converter. The bove fiure shows the MATLAB desin of proposed boost odule. In our previous odule we cn step up the input volte by chnin the duty rtio. In our previous odule the output volte is not stble. But in our odule by pplyin closed loop PI controller to previous odule we cn et the stble output volte.. In the bove odule we cn ive v reference s V rs / 6 HZ nd fter siultion we cn et THD of closed loop control of buc converter 9V rs / 6 HZ in c converters the output is not precies nd it is instntneously. In this odule we cn step up the input volte. Selected sinl: 6 cycles. FFT window (in red): 5 cycles M (% of Fundentl) Tie (s) Fundentl (6H) = 3., THD=.67% Frequency (H) Output results of closed loop control of buc converter The below fi shows the switchin opertions of boost converter in invertin ode. In this ode switch s,s3 on for positive hlf cycle nd off for netive hlf cycle. switch s,s4 off for positive hlf cycle nd on for netive hlf cycle for fundentl frequency. Fiure. THD of closed loop control of buc converter. In the previous we et the THD of.95%. But in this odule by pplyin hih frequency to et reduced the THD.Then fter we et THD of.67%. 8

7 Interntionl Journl of Scientific & nineerin Reserch Volue 9, Issue 3, Mrch-8 5 ISSN Switchin wvefors switch s switch s switch s switch s output volte incresed. In this converter we cn perfor step up opertion. Autotic chnin of Duty rtio in boost ode.9.8 Duty rtio.7.6 Switch s5 Duty rtio Fiure 3. Switchin wvefors of closed loop control of boost converter. Previously the duty rtio is intined t.37 by chnin it nully where s here it is The bove fi shows the switchin opertions of intined constnt i.e.39 by usin closed loop boost converter in invertin ode. In this ode circuit. switch s,s3 on for positive hlf cycle nd off for netive hlf cycle. switch s,s4 off for positive hlf THD of closed loop control of boost converter cycle nd on for netive hlf cycle for fundentl frequency. Selected sinl: 6 cycles. FFT window (in red): 5 cycles S5 is pulse rtin for positive hlf cycle with Tie (s) switchin frequency off 5KHZ nd copletely on Fundentl (6H) = 76., THD= 3.9% for netive off cycle. The switch s6 is copletely on 6 for positive hlf cycle nd pulstin for netive hlf 5 4 cycle with frequency of 5KHZ. 3 Input, output volte Switch s6 Fiure 5. Duty rtio chnes of closed loop control of boost converter The bove fiure shows the chnin of duty rtio in our odule. In the previous odule by chnin the duty rtio to et the desired output volte. M (% of Fundentl) Frequency (H) Vo Fiure 6. THD of closed loop control of boost converter. In this odule by pplyin hih frequency to et reduced the THD.Then fter we et THD of 3.9% Fiure 4. volte coprision of closed loop control of boost converter. The bove fiure shows the volte coprision of input nd output. In odule the output is chned fter.5 sec becuse we re ivin initil tie of.5 sec. But in our odule the Siultion of closed loop control of buc-boost c-c converter In this syste by pplyin the closed loop control schee to previous converter for control on output volte plitude. In this syste the hih frequency opertion is crried out for reduction of THD in output volte. 8

8 Discrete, Ts = e-6 s. powerui Goto6 <IGBT v olte> D5 Goto7 <IGBT v olte> D6 L S5 Fro [S] Fro [S] S Fro3 Fro4 Fro9 S6 D S4 Fro D4 S S3 D D3 in o RL [rs] Fro 3 Vref rs.5 initil Duty rtio Step PI Volte ontroller Gin -K- >= Switch Genertor Genertor Product D Unit Dely d c PWM Genertor Genertor3 Genertor4 Product Unit Dely Genertor6 [S] Goto Goto NOT [S] Loicl Goto Opertor Goto3 Add Add Multieter3 Goto4 Multieter Vo Multieter Vo Switch s Switch s Goto5 V M_V_I I P_Q Power Fro Fro Multieter Fro5 Fro6 [S] Fro7 [S] Fro8 Scope Vo e- Po [rs] Goto Vo rs Interntionl Journl of Scientific & nineerin Reserch Volue 9, Issue 3, Mrch-8 6 ISSN Discrete Active & Rective RMS (discrete) Discrete RMS vlue The bove fiure shows the volte coprision of input nd output. In the bove fiure the output volte is phse shifted to 8 derees. In odule the output is chned fter.5 sec becuse we re ivin initil tie of.5 sec. In our previous odule the output volte is 8 derees phse shifted. But in our odule the output volte is incresed nd decresed with 8 derees phse shift. In this converter we cn perfor both step up nd step down. Fiure 7. MATLAB siultion of closed loop control of buc-boost c-c converter. The bove fiure shows the MATLAB desin of proposed odule. In our previous odule we cn step up nd step down the input volte by chnin the duty rtio. But in our previous odule the output volte is not stble.in our odule by pplyin closed loop PI controller to previous odule we cn et the stble output volte. Input, output volte nd inductor current volte(v) urrent il 3 Inductor current Output volte Input volte Output results of closed loop control of buc-boost converter fiure. Input volte, output volte nd inductor current wvefors of closed loop Switchin wvefors control of buc-boost converter. switch s The bove fiure shows the input nd output switch s volte nd inductor current of our odule. In fter sec the inductor current will be incresed switch s becuse we cn ive initil tie of.5sec. switch s Autotic chnin of duty rtio Fiure 8. Switchin wvefors of closed loop control of buc-boost converter. Input, output volte Output volte Input volte Fiure. Duty rtio chnes of closed loop control of buc-boost converter in boost ode Fiure 9. Volte coprision of closed loop control of buc-boost converter. 8

9 Interntionl Journl of Scientific & nineerin Reserch Volue 9, Issue 3, Mrch-8 7 ISSN THD of closed loop control of buc-boost converter M (% of Fundentl) - Selected sinl: cycles. FFT window (in red): cycles Tie (s) Fundentl (6H) = 48.6, THD=.87% 73 8, My 9. [3] L. hen, nd F. Z.Pen, Siple topoloies of PWM c-c converters, I Power lectron. Lett., vol., no., pp. 3, Mr. 3. [4] S.-. Won, B.-H. Kwon, B.-D. Min, nd J.-H. Ki, A PWM buc-boost c chopper solvin the couttion proble, I Ind.lectron. Lett., vol. 45, no. 5, pp , Oct [5] F. Z. Pen, Z. M. Qin, nd X. P. Fn, Sinlephse Z-source PWM c-c converters, I Power lectron. Lett., vol. 3, no. 4, pp. 4, Dec. 5. [6] X. RUAN nd Y. Zhn, A-A converter with controllble phse nd plitude, I Trns. Power lectron., vol. 9, no., pp , Nov Frequency (H) [7]. A. PTRY, T. B. SOIRO, I. BARBI, nd J..D.S. FAGUNDS, Direct c-c converters usin coercil power odules pplied to volte restorers, I Trns. Ind. lectron., vol. 58, no., pp , Jn.. fiure. THD of closed loop control of bucboost converter. Andersen, A switched-cpcitor three-phse c- [8] T. B. LAZZARIN, I. BARBI, nd R. L. c converter, I Trns. Ind. lectron., vol. 6, no., , Feb. 5. In the previous we et the THD of 3.87%. But [9] M. K. Nuyen, Y.. LIM, nd Y. G. JUNG, in this odule by pplyin hih frequency to et Sinle-phse c c converter bsed on qusi-zsource topoloy, I Trns. Power lectron., reduced the THD.Then fter we et THD of.87%. vol. 5, no. 8, pp., Au.. 5 ONLUSION [] D.TANG AND L.LI, scded three-level c/c direct converter, ITrns. Ind. rlier projects or wors hve done with open loop lectron., vol. 59, no., pp. 7 34, Jn.. control syste, so there is no feedbc fro the output side nd hence there is no control of output volte. So here hve to control the output volte hs to intin hih in which depends upon the duty rtio. In our project the duty rtio vried by nully. So tht extension introducin PI controller s feedbc loop syste, the duty rtio of MOSFT is controlled dyniclly, this controls the output volte of the circuit topoloy with ny chne in input or lod. In the previous project the THD will be hih but in our project by pplyin hih frequency to et reduced the THD. RFRNS [] Hfi furqnhed, honnyon ch,shrflihn novel buc-boost c-c converter with both invertin nd noninvertin opertions nd without couttion proble, I Trns. Power lectron., vol. 3, no. 6, jun. 6. [] S. Schul, A. Lindenn, nd. cleble, Bidirectionl switch co-uttion for trix converter supplyin series resonnt lod, ITrns. Power lectron., vol. 4, no. 5, pp. 8