Low Voltage Energy Harvesting by an Efficient AC-DC Step-Up Converter

Transcription

1 ISR Journal of Eletral and Eletron Engneerng (ISR-JEEE) e-issn: ,-ISSN: , olume 7, Iue 3 (Se. - t. 03), PP 3-47 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter K. Madhur, r.a Srujana Student n EEE eartment Profeor & H for EEE eartment Sr enkatehwara Engneerng College, Suryaet Atrat: In th aer, a dret a-to-d ower onverter rooed for effent energy harvetng from the low voltage nertal mro generator. The onventonal ower onverter ue dode rdge retfer and ondton the mro generator outut n two tage. Hene, they are neffent and may not e a feale oton for very low voltage mro generator. Moreover, they are not onduve for otmum energy harvetng. The rooed onverter avod the ue of rdge retfer, and dretly onvert the a nut to the requred d outut. Th onverter ue a oot onverter and a uk-oot onverter to roe the otve and negatve half yle of the a nut voltage, reetvely. Furthermore, ung th onverter, maxmum energy harvetng an e mlemented effetvely. Analy of the onverter arred out. Baed on the analy, two heme are rooed to ontrol the onverter. egn gudelne are reented for eletng the onverter omonent and ontrol arameter. A elf-tartng rut rooed for ndeendent oeraton of the onverter. Smulaton reult are reented to valdate the rooed onverter toology and ontrol heme. Key word: AC C onveron, oot onverter, energy harvetng, low ower, low voltage, ower onverter ontrol. I. Introduton The reent develoment of omat and effent em ondutor tehnologe ha enaled the develoment of low-ower wrele deve. Tyal alaton for uh deve are wrele enor node for trutural montorng, data tranfer, omedal mlant et. Battere have een tradtonally ued a the energy oure for uh low-ower wrele alaton. However, they are nherently lmted y aaty and ze onderaton. Therefore, they need to e reharged and relaed erodally. For low-ower requrement of a few mll watt, harvetng energy from the envronment ha eome feale oton. raton aed energy harvetng a oular way of extratng eletral energy from the envronment. In artular, eletromagnet mro generator work on the rnle of faraday law of eletromagnetm. They utlze ament vraton to enale movement of a ermanent magnet whh ndue an eletromotve fore n a tatonary ol. The amount of harveted energy an e ontrolled y hangng the load retane onneted to the ol. Unlke other oular vraton-aed generator lke ezo-eletr mro generator, eletromagnet generator have to e efally degned for a artular envronment. Many tye of mro generator, ued n the elf-owered deve, are reorted n the lterature for harvetng dfferent form of ament energe [] [6]. The ower level of the nertal -mro-generator normally very low rangng from few mrowatt to ten of mll watt. Baed on the energy onveron rnle, the nertal mro-generator an e lafed manly nto three tye: eletromagnet, ezoeletr, and eletrotat [5], [6], among them, the eletromagnet mro-generator have the hghet energy denty [5], [7] - [0]. The eletromagnet generator are tyally rng-ma damer- aed reonane ytem a hown n Fg. n whh the mall amltude ament mehanal vraton are amlfed nto larger amltude tranlatonal movement and the mehanal energy of the moton onverted to eletral energy y eletromagnet oulng. Fg. Shemat dagram of an nertal mro generator 3 Page

2 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter An eletromagnet ower generator ont of a oer ol, a ermanent magnet (alo atng a a ma), and a rng, the ermanent magnet attahed to the ol through the rng. Th generator work when there a vraton nut, the ol ut through the magnet flux formed y the ermanent magnet due to the relatve dlaement etween the ermanent magnet and the ol. A nuodal eletromotve fore (EMF) n the ol an e generated and thu tranfer mehanal energy nto eletral energy. Sne the outut ower of the ower generator very low, rangng from few mro-watt to ten of mll-watt, an energy harvetng nterfae rut wth hgh ower tranfer effeny need to reharge and tore the eletral ower nto the energy torage element. In the eletromagnet mro-generator, due to ratal ze lmtaton, the outut voltage level of the generator very low (few hundred of mll volt), wherea the eletron load requre muh hgher d voltage (3.3 ) [9].The onventonal ower onverter, reorted for energy harvetng [3] - [5], motly Cont of two tage, a dode rdge retfer and a tandard uk or oot d-to-d onverter. However, there are major dadvantage n ung the two-tage ower onverter to ondton the outut of the eletromagnet mrogenerator. For very low-voltage eletromagnet mro-generator, retfaton not feale y the ue of onventonal dode. Fg.onventonal two-tage ower onveron. To addre the rolem of the two-tage ower onverter a new dret a-to-d ower onverter a hown n Fg.3, wthout onventonal dode rdge retfer. Fg.3 dret a-to-d ower onveron A dual olarty oot onverter toology for uh a-d onveron wa rooed a hown n Fg.4. Fg. 4 dual olarty oot onverter Th onverter ue two ndutor and the outut d u lt nto two ere onneted aator. The fundamental rnle ehnd the rooed toology the ue of two oot onverter eah oeratng n one half yle of the a voltage. Eah aator harged only n the reetve half yle. However, they dharge to the load ontnuouly aung large voltage dro. Extremely large aator are needed to make the voltage rle aetale. Th make the onverter reone very low; the ontrol of the onverter alo requre nut lne olarty enng addng further omlexty. Sne the outut d u lt nto two ere onneted aator and eah of thee aator harged only for one half yle of the mro generator outut voltage. A the tme erod of the reonaneaed mro generator outut voltage are normally n the order of mlleond, very large voltage dro wll our n the aator durng the half yle when they are not harged y the onverter. Extremely large aator wll e requred to aheve aetale voltage rle at the outut d u. Th not ratal due to the ze lmtaton of the mro generator. To addre the rolem of the onventonal two tage onverter, dret a-to-d onverter rooed (). The rooed onverter hown n fg.5.the rooed onverter ont of a oot onverter n arallel wth a uk-oot onverter. The outut d u realzed y ung a ngle aator. The outut aator harged y the oot onverter n the otve half yle and y the uk-oot onverter n the negatve half yle. Therefore, t reolve the rolem reent n a dual-olarty oot onverter. 33 Page

3 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter Fg.5 rooed dret a-to-d onverter The rooed dret a-to-d onverter utlze the negatve outut to nut voltage gan of a ukoot onverter to te-u the negatve half nut voltage of the mro generator to a otve hgh-d outut voltage. The H-rdge onverter toology for dret a-to-d oot onveron(), tandard 4-wth H-rdge onverter or the -wth, a hown n Fg.6(a), and (). Fg.6 H-rdge a-d oot onverter (a) 4-wth, () -wth To aheve the oot oeraton, the lower wthe (S and S ) thee two onverter hould e ale to ondut n oth the dreton. The dretonal onduton aalty of the two MSFET (S and S ) an e ued to aheve the oot oeraton. urng the otve half yle of the nut voltage, S ket on for the entre half yle and the gate ule to S ontrolled to aheve the oot oeraton. Lkewe, n the negatve half yle, S ket on for the entre half yle and S ontrolled. To aheve the oot oeraton, thee two toologe ue ngle ndutor omared to the two ndutor ued n the rooed onverter. However, there are everal dadvantage n thee Two H- Brdge onverter. In H-rdge onverter, there are two deve n the onduton ath durng harge or dharge of the oot ndutor. But n the rooed onverter, only a ngle deve ondut durng the harge or dharge of the ndutor. In H-rdge onverter, the MSFET, ued for the oot oeraton (S and S ), are oerated for the entre yle of the nut a voltage. But n the rooed onverter, any MSFET oerated only for a half yle of the nut a voltage. Therefore, the deve onduton loe n the rooed onverter are redued y more than a fator of two. The nut voltage olarty ha to e ened to ontrol S and S, ut n the H-rdge toologe, the nut voltage oure floatng wth reet to the outut voltage ground. Therefore, the mlementaton of the ontrol rut dffult. In the energy harvetng alaton, a the ower level very low, thee loe are gnfant omared to the total outut ower. A, the MSFET are degned for forward onduton, n the revere onduton mode they offer hgher on-tate retane. Th further nreae the onduton loe n the H- rdge toology. It an e mentoned that although the rooed onverter ue two ndutor ( L and L ), they do not oerate n the ame half yle. Therefore, ther total loe are almot equal to the loe of the ngle ndutor ued n the H-rdge onverter. The ret of the aer organzed n the followng manner: etaled analy of the onverter and the rooed ontrol heme to ontrol the onverter are exlaned n II. egn gudelne are exlaned n III. Prooed elf-tarng rut and the onverter ontrol rut mlementaton are exlaned n I &. Smulaton are reented n I. Fnally the onluon reented. 34 Page

4 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter II. ret A-To- Converter The rooed dret a-to-d onverter, a hown n Fg 5, ont of a uk-oot and a oot onverter. The d u of the rooed onverter realzed y ung only one aator. The outut aator C of th onverter harged y the oot onverter (omrng ndutor L, wth S, and dode, ) and a uk oot onverter (ndutor L, wth S, and dode ) durng the otve half yle and negatve half yle of the nuodal a nut voltage (v), reetvely. N-hannel MSFET are utlzed to realze the wthe S and S. It an e noted that the MSFET are ujeted to revere voltage y the a outut of the mro-generator. To lok the revere onduton, the forward voltage dro of the ody dode of the MSFET hoen to e hgher than the eak of the nut a voltage. Two hottky dode ( and ) wth low forward voltage dro are ued n the oot and the uk-oot onverter rut for low loe n the dode. It an e noted that the dode an e relaed y MSFET to further mrove the effeny of the onverter. Sne the nut urrent of a uk-oot onverter dontnuou. Hene, n th tudy, oth the oot and uk-oot onverter are oerated n dontnuou mode (CM) to ontrol the outut urrent of mrogenerator. It an e noted that under ontant duty yle CM oeraton, the nut urrent roortonal to the nut voltage at every wthng yle; therefore, the overall nut urrent wll e n-hae wth mro-generator outut voltage. A onverter oeratng wth a ontant duty yle ha only fundamental and wthng harmon frequeny omonent (muh hgher than the fundamental) thu, offer a retve load to the mro-generator. By hangng the equvalent load retane offered to the mro-generator, the damng fore n a mrogenerator an e et to an otmal value to aheve maxmum energy harvetng. The rooed onverter oerate manly n four mode durng one yle of the nut a voltage. The oeratng mode are dued. The ath of the ndutor urrent, L and L, n thee mode, are deted n thn lne. Mode and Mode are for otve nut voltage, when only the oot onverter oerate. Mode 3 and Mode 4 are for negatve nut voltage, when only uk-oot onverter oerate. Mode oeraton: Th mode tart when the gate drve voltage, g, hgh, and hene, the oot-wth S, turned on. The urrent n the oot-ndutor, L, tart to uld from zero. urng th mode, gate drve voltage, g, low, o S, n off ondton and the dode, and are alo off. The urrent dreton durng th mode a hown n Fg.7. Fg.7 rut of the onverter durng mode Mode oeraton: Th mode tart at the end of Mode when g eome low and S turn off. urng th mode, L forward ae and t tored energy harge the outut aator, C.S and reman off n th mode. It an e noted that durng Mode and Mode, the nut ale revere voltage aro S ut the hgher forward voltage of the MSFET ody dode hold ak any urrent onduton though t, the urrent dreton durng th mode a hown n Fg.8. Fg.8 rut of the onverter durng mode Mode 3 oeraton: In th mode the gate drve voltage, g, eome hgh and S turn on. The urrent n the ndutor L uld n the negatve dreton a hown n Fg Page

5 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter Fg.9 Crut of the onverter durng mode 3 Mode 4 oeraton: The MSFET S turned off n th mode and the ndutor L forward ae the dode. The energy tored n L harge the outut aator C, the urrent dreton durng th mode a hown n Fg.0. Fg.0 Crut of the onverter durng mode 4 It hould e noted that other than th mode there wll e CM oeraton of oth the onverter; n whh all the wthe and dode wll e n off onduton. It an e noted that the outut aator harged n the ame dreton n eah half-yle. To aheve maxmum energy harvetng y offerng otmal damng to the mro-generator, the nut urrent hould e ontrolled. Hene, n th tudy, the oot and the uk-oot onverter are ontrolled wth fxed duty yle to aheve an nut urrent roortonal to the nut voltage. A. CNERTER ANALYSIS Conder the nut urrent waveform of the onverter for the analy a hown n Fg. (a). Conder any (a) th k wthng yle of the oot onverter a hown n Fg. (), () Fg. oot onverter (a) Inut urrent and () gate drve gnal and nut voltage durng a wthng yle. Where T the tme erod of the wthng yle, the duty yle of the oot onverter, d the oot ndutor urrent fall tme (or the dode onduton tme), the duty yle of the f T 36 Page

6 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter uk oot onverter, v the nut voltage of the generator wth amltude, and o the onverter outut voltage. Aumng the wthng tme erod ( T ) of the onverter muh maller than the tme erod of the T ), durng the oot onverter oeraton, the nut urrent and the oot ndutor urrent ( nut a yle ( ) are equal. When the oot wth S turned on, the urrent n the oot ndutor L tart to uld from zero and reahe a eak value. The eak value of the ndutor urrent ( k ) n the oot onverter k = m T = v k v T k L kt n( ) () T () Where m = After the oot onverter wth S turned FF, the urrent n the ndutor tart to fall untl the wth S turned N agan n the next wthng yle from Fg.(). th The loe ( m ) of th urrent deded y the voltage aro the ndutor, n a k wthng yle, the voltage aro the ndutor durng the ndutor urrent fall tme Therefore the ndutor urrent fall tme d k f T = m k L v k (3) v k L o and v. Where m = voltage aro the ndutor durng the ndutor fall tme t / L urng the oot onverter wth S FF, the ndutor urrent fall, and the energy tored n the ndutor L tranferred to the load. In the oot onverter, the energy to the outut more than energy tored n the ndutor hene, for the equal duty yle, nut voltage, ndutor value ( Energy tranferred durng wth ( S ) turn on, E I = v T ) (4) t on k k ( Energy tranferred to the load durng wth ( S ) turn off, E I t v ) ( d T ) (5) off ( k k f k L ), L th urng the k wthng yle, the total energy ( E k ) tranferred from the nut of the oot onverter an e ETon EToff Ek vk kt vk kd f T vk k( d f ) T (6) The averaged ower uled y the generator n the oot wthng yle E vk k( d f ) k Pk (7) T The numer of wthng yle durng the tme erod of one nut a yle defned a.ne the oot onverter oerated for the half tme erod of tha nut a yle (T /). The average nut ower ( P ) of the oot onverter over th half yle tme erod / N / N v P P k = N K N k ( k k d f ) (8) L N T / T 37 Page

7 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter The average ower uled ( P ) an e T P k = t n L T k n t (9) T The average nut ower of the oot onverter P an e alulated y ntegratng the term n the ummaton over the half yle ( T / ) erod of the nut a voltage. P T T I dt n t T / 0 T L n t T P = Where T S 4L d 0 n (0) It an e noted that n (0), β ontant for fxed value of and o. Alo, t noted that for large wthng frequeny of the onverter, the average ower ndeendent of the mro generator outut voltage. In teady tate, the average nut ower of the onverter equal to the um of the average outut ower and the varou onverter loe. Hene, y defnng the onverter effeny a for a load retane R, the nut ower and the outut ower an e alaned a T 4L R From aove, the duty yle of the oot onvereter ( ) an e otaned a L () RT Further, onder the oeraton of the uk oot onverter; n th ae the nut ower uled only durng the N erod of the wth S (ee Fg. 5). urng the FF erod of the wth S, the nut urrent zero [ee Fg. (a)]. th Conder any k wthng yle of the uk-oot onverter a hown n Fg Page

8 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter Fg. uk-oot onverter Inut urrent, gate drve gnal and nut voltage durng a wthng yle. Where T the tme erod of the wthng yle, the duty yle of the uk oot onverter, the nut voltage of the generator wth amltude, and o the onverter outut voltage. The man alaton of a te-down/te-u or uk-oot onverter n regulated d ower ule, where a negatve-olarty outut may e dered wth reet to the ommon termnal of the nut voltage, and the outut voltage an e ether hgher or lower than the nut voltage. When the uk-oot wth S turned N, the nut rovde energy to the ndutor.e. urrent flow through the ndutor L, tart to uld from zero and reahe a eak value. The eak value of the ndutor urrent ( k ) n the uk-oot onverter k v m T = k L T () When the uk-oot wth S turned FF, the energy tored n the ndutor tranferred to the outut. No energy.e. urrent uled y the nut durng th nterval nothng ut nut urrent zero. th Hene for any k wthng yle, the average ower uled y the uk-oot onverter P k P k = v k k (3) The average ower an e exreed n ntegraton form over a half yle T erod of the nut a voltage a P TI T = t dt T n L T 0 T P = (4) 4L By defnng the onverter effeny a for a load retane R, the nut ower and the outut ower an e alaned a n equaton (5) T (5) 4L R From the aove, the duty yle of the uk oot onverter ( ) an e otaned a L RT (6) 39 Page

9 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter B.CNERTER CNTRL SCHEME Ung equaton () and (6), the duty yle of the oot onverter and duty yle of the ukoot onverter L L an e related a (7) Baed on the equaton (7), two dfferent ontrol heme are rooed, for the oot and uk ootaed onverter to delver equal average nut ower. In heme, the value of the ndutor are ket to e equal (L = L) and the onverter are ontrolled wth dfferent duty yle uh that t atfe the ondton: (8) C L L In heme, oth the oot and the uk oot onverter are ontrolled wth ame duty yle ( ), wherea the ndutor value are hoen to atfy the ondton: (9) The varale β from equaton (0) lotted a a funton of the te-u rato (o /) a hown n Fg.3. Fg.3 lot for o/ veru β For large value of voltage te-u rato (o/), the value of β aroahe to. Hene, for hgher voltage te-u rato alaton, the oot and the uk oot onverter an e degned wth ndutor of equal value and they an e ontrolled wth the ame duty rato to uefully delver the requred average ower to the outut. For o/, the value of β aroahe to nfnty. Therefore, from Equaton (0), the nut ower for the oot onverter may eem to aroah nfnty a well. But n th ae, the duty yle of the oot onverter aroahe to zero for o/. Therefore, no ower tranferred from the nut to the outut and the equaton reman vald even when o / =. It an e mentoned that there ould e two ole energy harvetng enaro. ne, n whh the onverter ontrolled to harvet maxmum ower avalale from the vratng ody and the mro generator ytem and tore t n an energy torage omonent (lke attery) at the outut. In th ae, the outut voltage manly deded y haratert of the energy torage omonent. In the eond enaro, the onverter ontrolled to harvet the amount of ower demanded y the load whle mantanng the dered outut voltage. In th aer, the eond enaro ondered to ontrol the onverter. III. egn Gudelne For Seleton f Converter The degn te for th onverter are to elet the MSFET, ndutor, and the wthng frequeny of the onverter. In a ratal energy-harvetng enaro, the ontroller and the MSFET drver rut of the onverter are requred to e elf tartng and they hould e owered y the energy harvetng ytem to ower the ontroller and the drver at the egnnng, when the onverter tart u. For a gven mro generator and a load, the nut and outut voltage are efed. Therefore, n th ae, the voltage ratng of the MSFET are deded y the outut voltage of the onverter. The urrent ratng of the MSFET ha to e deded y the degner. It an e noted that the MSFET arre maxmum urrent at the eak of the nut voltage from Fg. (a). The maxmum urrent Imax of the onverter an e gven a P I max (0) Lf 40 Page

10 Here Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter f the wthng frequeny of the onverter, L I the ndutane value for oth oot and uk-oot ).From equaton (4) and (0), the onverter, and I the duty yle of the onverter ( maxmum urrent an e exreed a a funton of average nut ower Pn a n equaton (). 4Pn I max () The relatonh etween the maxmum nut urrent and the duty yle for dfferent Inut ower a hown n Fg.4. Fg.4 uty yle veru maxmum nut urrent Ung the ( I max) hart, the MSFET urrent ratng and onverter duty yle an e eleted. Wth thee eleted value of the duty yle ( ) and the MSFET maxmum urrent, the ndutor value and the P wthng frequeny an e otaned from equaton I max Lf The relatonh etween the value of the ndutor (L) and the duty yle over a range of wthng frequeny a hown n Fg.5. Fg. 5 duty yle veru ndutane Ung thee hart and the equaton, the ntal value of the key omonent of the onverter an e deded. It an e noted that the value of the maxmum urrent ( max ) hange roortonally wth the nut ower (Pn) of the onverter. Therefore, the ze of the MSFET an e aled a er the ower requrement of the load. Th alale for even low-ower alaton, demandng le than mw of ower. The duty yle and the frequeny of the onverter an e arorately eleted to hooe the dered value of the ndutor. I. Auxllary Self-Startng Crut The rooed elf-tartng auxlary rut utlze a attery and hottky dode for th uroe a hown n Fg.6. I 4 Page

11 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter Fg. 6 Prooed auxlary elf-tartng rut ung a attery For the ueful oeraton of th elf-tartng rut, the attery nomnal voltage hould e le than the target outut voltage mnu the forward voltage dro of a dode, and t hould e aove the mnmum voltage requrement of the ontroller and drver rut () f Here we are onderng, the target outut voltage = 3.3 and forward voltage dro of the dode f = 0.. A attery wth nomnal voltage = 3 eleted for the elf-tartng. At the egnnng of the onverter oeraton, when the outut voltage not avalale, the ontroller and the drver rut wll e owered y the attery through the Sotty dode aator to the referene voltage. f. Th wll allow the onverter to harge the outut When the outut voltage ha reahed the value 3.3, the dode would e reverng aed; therefore, the attery wll not e owerng the ontroller and the drver. At th tme, they wll e owered from the onverter outut through the dode a. urng th ondton, the attery wll reman under floatng ondton. It an e noted that only a very mall amount of energy taken from the attery for the tartu of the energy harvetng ytem. Furthermore, the ued energy of the attery an e relenhed y rehargng t from the outut of onverter through the dode. Therefore, the entre amount of energy ued for the onverter oeraton, nludng the energy ued durng t tartng, harveted from the amene. Therefore, wth roer degn and eleton of the omonent, th auxlary rut an e ued to oerate the energy harvetng ytem vrtually for ndefnte erod of tme.. Control Crut f The Converter The rut dagram for the mlementaton of the rooed energy-harvetng onverter and t ontrol heme a hown n Fg.7. Fg. 7 rut dagram of the energy-harvetng onverter 4 Page

12 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter The reonane-aed eletromagnet mro generator modeled a an a voltage oure. A gnal generator followed y a hgh-urrent uffer ued to realze the mro generator outut voltage from Fg.7. Th uffer an e realzed y ung a ower oeratonal amlfer n voltage follower mode. The ened outut voltage of the onverter roeed y a low-a flter. The roeed gnal omared wth the referene voltage ref. The error gnal ued y the PI ontroller to etmate the ontrol voltage that omared wth a aw-tooth waveform n the ule wdth modulator (PWM). The ule gnal rodued y the PWM fed to the two uffer that an e enaled y external gnal. The omarator n the olarty detetor unt enale the arorate uffer to rodue the gate ule (g and g ) that ontrol the MSFET of the oot and uk oot onverter durng arorate half yle It an e ummarzed that the elf-retane and elf-ndutane of the eletromagnet mro generator are very mall, therefore, the elf-medane of the mro generator are not nluded for the analy of the rooed onverter oeraton. However, t an e nororated n the analy, for the redton of the erformane of the entre energy harvetng ytem. I. Smulaton Reult A reonane-aed eletromagnet mro-generator, rodung 400 m eak nuodal outut voltage, wth 00-Hz frequeny ondered n th tudy for verfaton of the rooed onverter toology. The referene outut voltage ( ) ondered to e 3.3. The energy-harvetng onverter degned for ref ulyng ower to a 00-Ω load retane, hene, ulyng aout 55 mw of outut ower. The MSFET eleted to realze the wthe S and S.the forward voltage of the eleted MSFET ody dode aout 0.8, whh hgher than the eak nut voltage. Th revent any revere onduton n the MSFETS. The nomnal duty yle of the onverter taken to e 0.7.The ndutor degned to have a tandard value of 4.7 H to realze L and L. Baed on thee value the wthng frequeny P f = 0.4(0.7) =50 khz *0 LI max & The dode are hoen to e hottky tye wth low forward voltage 0.3. The outut aator value 68µF.arou value for rut omonent of the degned onverter are reented n Tale I. Tale 6. Crut omonent of the onverter To verfy the rooed ontrol heme, at frt mulaton arred out for the ontrol heme, ung L L 4.7H and duty rato of the two onverter are not equal. In the mulaton duty yle etmated y a PI ontroller from Fg.7. The uk-oot onverter duty yle alulated from the etmated duty yle. L L ( L L 4.7H ) = 43 Page

13 d 0 n = = d n = = Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter =.056 = = The nut urrent of the oot onverter and the nut urrent of the uk-oot onverter for load retane R=00Ω a hown n Fg 8 and 9. Fg 8 wave form for nut urrent of the oot onverter Fg. 9 wave form for nut urrent of the uk-oot onverter It an e een that the oot onverter oerated durng the otve half yle, whle the uk-oot onverter oerated durng negatve half-yle of the mro generator outut voltage. The onverter outut voltage and the duty yle, etmated y the ontroller are a hown n Fg 0 (a), (). Fg.0 (a) equal duty yle of the oot and uk-oot onverter 44 Page

14 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter L ) Fg.0 () unequal duty yle of the oot and uk oot onverter wth ( The referene outut voltage ondered a3.3 and the outut voltage rle aout 0. 4, whh 4.4% of the nomnal outut voltage. uty yle alulated from the oluton a hown n Fg. L Fg. outut voltage rle wth referene voltage In th tudy, the outut voltage to nut voltage eak te-u rato For hgh te-u rato, the duty yle of the onverter wth ame ndutor value wll e almot equal. Hene, to aheve mle ontrol truture, le omonent ount and for all other ratal advantage, oth the oot onverter and the uk-oot onverter an e ontrolled wth ame duty yle for uh hgh te-u alaton. From fgure 0, t an e een that wth the equal duty rato ontrol, the onverter an uefully rodue the dered outut voltage. To verfy the oeraton of the onverter under dfferent load ondton, the load retane nreaed R L 400 to The nut voltage, nut urrent, and the etmated duty yle y the ontroller are a hown n Fg. Fg. Inut urrent, a nut voltage, and duty yle For th load ondton, the duty yle value aout Th mathe wth alulated duty P yle from I max Lf I max Lf (4.7 )50 = = 0.5 P 0.4 The outut voltage under th ondton a hown n Fg Page

15 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter Fg 3 outut voltage The mulaton are arred out wth the elf-tartng rut from Fg.6 rooed for the onverter. The attery of the elf-tartng rut modeled a a ontant voltage oure of 3.0. durng tart-u erod of the onverter, the ower onumed y the ontrol rut from the attery and the onverter a hown n Fg 4. Fg.4. onverter, attery ower and voltage durng elf tart-u. urve (), (), (), and (v) how the ower uled y the attery, ower draw from the onverter outut, attery voltage, and onverter outut voltage, reetvely The mulaton are arred out for heme.e., wth equal ndutor value for hgh te-u rato, the duty yle of the onverter wth ame ndutor value wll e almot equal. Hene, to aheve mle ontrol truture, le omonent ount and for all other ratal advantage, oth the oot and uk-oot onverter an e ontrolled wth ame duty yle for uh hgh te-u alaton. The mulaton are arred out wth the elf-tartng rut rooed for the onverter. It an e found that the tart-u tme taken y the onverter aout 4.6 m. th le than the half yle erod of the nut a voltage (00 Hz). II. Conluon The reented dret a-to-d low voltage energy-harvetng onverter avod the onventonal rdge retfaton and aheve hgher effeny. The rooed onverter ont of a oot onverter n arallel wth a uk oot onverter. The negatve gan of the uk oot onverter utlzed to oot the voltage of the negatve half yle of the mro generator to otve a voltage. etaled analy of the onverter for dret at d ower onveron arred out and the relaton etween varou onverter rut arameter and ontrol arameter are otaned. Baed on the analy, a mlfed ontrol heme rooed for hgh-voltage te-u alaton. egn gudelne are reented for eletng value of the key omonent and ontrol arameter of the onverter. A elf-tartu rut, ung a attery only durng the egnnng of the onverter oeraton, rooed for the energy-harvetng onverter oeraton and the mlementaton of the elf-tartu rut and the ontrol rut of the onverter reented n detal. Baed on the analy and the degn gudelne, a rototye of the onverter develoed. The rooed ontrol heme wth the elf-tartu rut mlemented and the onverter uefully oerated to dretly te-u the low a voltage to a hgh d voltage. Referene [] J. A. Parado and T. Starner, Energy avengng for mole and wrele eletron, IEEE Pervave Comut., vol. 4, no.,. 8 7, Jan./Mar [] S. Mennger, J.. Mur-Mranda, R. Amrtharajah, A. P. Chandrakaan, and J. H. Lang, raton-to-eletr energy onveron, IEEE Tran. ery Large Sale Integr. Syt., vol. 9, no., , Fe. 00. [3] M. El-Ham, P. Glynne-Jone, N. M. Whte, M. Hll, S. Beey, E. Jame, A.. Brown, and J. N. Ro, egn and faraton of a new vratonaed eletromehanal ower generator, Sen. Atuator A: Phy., vol. 9, , 00. [4] T. M. Thul, S. war, R.. Lorenz, and L. Para, Energy harvetng and effent ower generaton from human atvte, n Pro. Center Power Eletron. Syt. (CPES) Semn., Ar. 007, [5] N. G. Stehen, n energy harvetng from ament vraton, J. Sound raton, vol. 93, , Page

16 Low oltage Energy Harvetng y an Effent AC-C Ste-U Converter [6] J. R. Amrtharajah and A. P. Chandrakaan, Self-owered gnal roeng ung vraton-aed ower generaton, IEEE J. Sold-State Crut, vol. 33, no. 5, , May 998. [7] B. H. Stark, P.. Mtheon, M. Peng, T. C. Green, E. Yeatman, and A. S. Holme, Converter rut degn, emondutor deve eleton and analy of arat for mroower eletrotat generator, IEEE Tran. Power Eletron., vol., no.,. 7 37, Jan [8] C. B. Wllam and R. B. Yate, Analy of a mro-eletr generator for mroytem, n Pro. Int. Conf. Sold-State Sen. Atuator, 995, [9] P..Mtheon, T. C. Green, E.M.Yeatman, and A. S. Holme, Arhteture for vraton-drven mroower generator, J. Mroeletromeh. Syt., vol. 3, no. 3, , Jun [0] S. Xu, K.. T. Ngo, T. Nhda, G. B. Chung, and A. Sharma, Low frequeny uled reonant onverter for energy harvetng, IEEE Tran. Power Eletron., vol., no., , Jan [] S. war, R. ayal, and L. Para, A novel dret AC/C onverter for effent low voltage energy harvetng, n Pro. IEEE Ind. Eletron. So. Annu. Conf., Nov. 008, [] J. C. Salmon, Crut toologe for ngle-hae voltage-douler oot retfer, IEEE Tran. Power Eletron., vol. 8, no. 4,. 5 59, t. 993 BIGRAPHY K Madhur:Pot graduate tudent n the deartment of Eletral and Eletron Engneerng (P.E) at Sr enkatehwara Engneerng College, Suryaet, nalgonda, andraradeh, Inda. r.a.srujana: B. Teh(Eletral), M.Teh (P.E), Ph. (HC). Preently She workng a Profeor & H.. for eartment of Eletral and Eletron Engneerng at Sr venkatewara engneerng ollege, Suryaet. 47 Page