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

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1 Interntionl Journl of Scientific & Engineering Reserch Volue 9, Issue 3, Mrch ISSN A Novel Closed Loop Topology for Coupled Inductor Bsed DC-DC Converter Srinivs Singiriond, Meber of IEEE, Grgi Desi, Meber of IEEE, Abstrct In the closed loop topology for coupled inductor bsed DC-DC converter we hve tendency to introduce voltge ultiplier converter with coupled inductnce for high gin output chrging the bttery of feedbc loop for DC chine drive for vrible input voltge. The dul switches structure is helpful to scle bc the voltge stress nd current stress of the switch. Additionlly, 2 ultiplier cpcitors re chrged throughout the switch-on period nd switch-off period, which will increse the voltge conversion gin. Menwhile, the energy stored within the inductnce is recycled with the clped cpcitors. Thus, 2 in power switches with low on-resistnce nd low current stress re vilble. This project illustrtes the opertion principle of the designed DC-DC converter, the output voltge of the high step-up converter is intined constnt by utotic vrition of the duty rtio with feedbc s PI Controller. The constnt output voltge for vrying input DC voltge is represented grphiclly using MATLAB siultion for vrious industril pplictions. Index Ters Dul switches, high step-up converter, switched cpcitor, three-winding coupled inductor, closed loop, duty rtio, PI controller. INTRODUCTION OWADAYS, due to the energy usge nd pplictions. Hence, bsed on the entioned Ntosphere pollution, the renewble considertions, odifying conventionl dul energy is widely used. The renewble energy switches converter which is n open loop syste sources lie fuel cells nd other PV cells generte to closed loop converter is suitble ethod. low voltge output. Thus, high the step-up dc/dc converters re widely used for renewble energy systes []-[7]. In recent yers severl novel high step-up converters re developed. The syste cn convert the voltges fro PV cells source into the high voltge vi high step-up boost converter nd then the renewble energy is trnsitted to the lod nd utility through the inverter. Hence, the high step-up converter is essentil. In order to chieve the high step-up gin, the conventionl step-up converters, such s the boost converter nd flybc converter cn be used to fulfil the high step-up requireent. In the recent yers, the ny high step-up converters hve been developed. Despite the dvnces, the current nd voltge stress of the power switch in high step-up single switch converters re lrger, lrge conduction losses which cnnot be voided nd the duty rtio vrition is nully vried. However the voltge converter gin is liited in high step-up The closed loop syste is used to control the output voltge to constnt vlue for vrible input voltges using PI controller. The voltge conversion rtio reins high, thus ing the converter ore suitble for step up dc-dc power conversion. The converter is siulted using MATLAB. Output levels re obtined s per the designed vlues for both converter (Open loop nd closed loop) opertions. Siultion results convey the operbility of the dul switch converter with coupled inductor nd voltge ultiplier cell in closed loop syste. In the closed loop syste with PI controller the output voltge is s the desired voltge nd the duty rtio of the switches vry utoticlly s the input voltge chnges intining the output voltge constnt (i.e., 200V or 360V). The dc-dc converters with high step-up voltge gin re widely used for ny pplictions lie lsers, fuel cells energy 208

2 Interntionl Journl of Scientific & Engineering Reserch Volue 9, Issue 3, Mrch ISSN conversion systes, solr cell energy conversion syste, X-ry systes nd high intensitydischrge lp bllsts for utoobile hedlps. Theoreticlly, dc-dc boost converter chieves high voltge gin with extreely high duty rtio. However, in prctice, the step-up voltge gin is liited due to the effect of power switches, rectifier diodes, nd the series resistnce of inductors nd cpcitors. The clssicl boost converter with nonisolted dc-dc opertion cn provide high stepup voltge gin long with the penlty of high voltge nd current stresses, high duty cycle opertion nd dynic response. When operting with high current nd voltge levels, the efficiency cn be reduced by the diode reverse recovery current. Aong the few non-isolted dc-dc converters chieve high sttic gin, s the qudrtic boost converter, but dditionl filter cpcitors nd inductors should be used nd the switch voltge is high. A new lterntive for the ipleenttion of high stepup structures is proposed in the step-up converter with the use of the voltge ultiplier cells integrted with clssicl non-isolted dc dc converters. The uses of the voltge ultiplier in the clssicl dc dc converters dd new opertion chrcteristics, becoing the resultnt structure well suited to ipleent high-sttic gin step-up converters [9]. The novel non-isolted dc-dc to converter with high voltge gin bsed on threestte switching cell nd voltge ultiplier cells, this topology hs the dvntges of input current is continuous with low ripple, input inductor is designed for twice the switching frequency, with consequent volue nd weight reduction; the voltge stress cross the switches is lower thn hlf of the output voltge, nd nturlly clped by one output filter cpcitor. As disdvntge, sll snubber is necessry for ech switch nd one dditionl winding per cell is required for the utotrnsforer. Lter, in [7] the high step-up dc-dc converter for the pplictions of AC Photovoltic odule design includes floting switch to isolte the PV pnel when the c odule is off to interrupt the energy conversion fro PV pnel to the c odule. Here, the operting odes include two odes of opertion continuous conduction ode (CCM) nd discontinuous conduction ode (DCM) where in the coupled inductor bsed dc-dc converter there is only CCM which es the studies of the switching wvefors flexible. The turns rtio of the coupled inductor nd duty rtio re not extreely vried which results in high output voltge conversion, the energy of the lege coupled inductor is recycled to the lod efficiently. In the conversion of energy nd sfety perspective it hs been designed to operte only when the c odule is on nd this high step-up converter is isolted when it is off. Then, n [3] interleved high step-up converter with built-in voltge ultiplier cell trnsforers for the ppliction of sustinble energy for the voltge gin conversion ws ipleented with turns rtio of 4:4 for the optiiztion of switch duty rtio. Here, the builtin trnsforer voltge ultiplier cells helps to void extree duty rtio in the interleved boost converter, hence the power level is lso incresed. But here due to the trnsforer turns rtio the losses re ore hence the circuit configurtion lso gets coplicted. 2 CONTROL STRATEGY In dul switch DC-DC converter with chrge pup nd three-winding coupled inductor [], high voltge gin nd efficiency is obtined which is siilr circuit s the coupled inductor bsed converter nd the opertion is perfored on open-loop nd there is no control over the output voltge. The PI controller is eployed to chieve the constnt DC output voltge by controlling the pulse width with the vrible DC supply. Here, the converter consists of two ctive switches, five diodes nd five cpcitors. The two switches shre se opertion signl nd one control circuit is needed. The vrible input voltge is given s the source with the help of PV pnel, constnt output voltge is se s the reference vlue nd the error is fed bc to the PI Controller generting duty rtio which is vried utoticlly. The equivlent circuit odel of the threewinding coupled electricl device includes the gnetizing inductnce luen, the lege inductnce L, nd perfect electricl device with priry N turns nd 2 secondry windings N2 nd N3. The converter device consists of 2 ctive switches, 5 diodes, nd 5 cpcitors. The switches S nd S2 shre siilr opertion 208

3 Interntionl Journl of Scientific & Engineering Reserch Volue 9, Issue 3, Mrch ISSN signl nd one feedbc loop is required. The dischrge electricl device energy of the coupled electricl device is recycled to the cpcitors C nd C2, nd therefore the voltge spies on the switches re significntly reduced. This es low conducting resistnce Rds(on) of the switches out there. Thus, the efficiency is upgrded nd therefore the high conversion gin will be chieved. The objective of the novel closed loop topology for coupled inductor bsed DC-DC converter is to perfor opertion of the converter with PI controller which copres the reference vlue nd the error is fed to it genertion dynic duty rtio. This duty rtio is utoticlly vried wherein in previous studied it is vried nully in open loop syste. The opertion of the converter with PI Controller is studied in continuous conduction ode (CCM) nd the odes of opertion re nlyzed in detil. The eight operting odes re described s follows. To lter the circuit nlysis of the converter, the subsequent ssuptions re de, the voltges cross the cpcitors C3 nd C4 will be djusted by the turns rtio of the coupled inductor. is N : N2 : N3 =:: N. The priry winding with N turns, two secondry windings with N2 nd N3 turns of the idel trnsforer re, respectively, represented by L, L2 nd L3 (L : L2 : L3 =:: N2). 2. Opertion of Voltge Multiplier Converter The operting principles for the continuous conduction ode (CCM) re nlyzed in detil herein. The eight operting odes re described s follows. CCM Opertion Mode I [t0, t]: During the trnsition intervl, the switches S nd S2 begin to conduct. Diodes D, D2, D3, nd Do re reverse bised. Diode D4 is forwrd bised. The current flow is s shown in Fig.2. The outpouring inductnce L nd gnetizing inductnce L re chrged by the input supply Vin. The inductnce L2 is dditionlly chrged by the input supply. The L2 inductnce current il will increse linerly. Becuse of the lege inductnce, the inductnce current il3 nd diode current id4 decrese slowly. Therefore, the voltge of diode D3 is clped by input supply Vin, clped voltges VC nd VC4; the voltge of diode Do is clped by voltges VC3, VC4, nd VC2. The Fig. Circuit Configurtion voltge steps re generlly fored. The output Co provides the energy to lod R nd the current id4 becoes zero (i.e., sort = il), this opertive ode ends. ) The Cpcitors C, C2, C3, C4, nd Co squre esure gint enough; so, VC, VC2, VC3, VC4, nd Vo squre esure thought to be constnt vlues; 2) The bility devices squre esure idel, however the prsitic cpcitors of the switches squre esure considered; Fig.2 Mode II [t, t2]: During the trnsition intervl, the switches re still turned on. Diode D3 is forwrd bised. Diodes D, D2, D4, nd Do re reverse bised. The current flow pth is shown in Fig. 3. 3) The coupling coefficient of the coupled inductor is equl to L/ (LL), the turns rtio 208

4 Interntionl Journl of Scientific & Engineering Reserch Volue 9, Issue 3, Mrch ISSN Fig.3 Fig.5 The gnetizing inductnce L nd inductnce L2 re chrged in prllel by the input supply Vin. The energy fro the input supply Vin trnsfer to the inductnce L3 to C4 with the input supply Vin, clped voltges VC, VC3 long. The output cpcitor Co provides the energy to lod R. once the switches squre esure turned off t t = t2, this intervl is finished. Mode III [t2, t3]: In this trnsition intervl, the switches re turned off. Diodes D, D2, D4, nd Do re reverse bised. Fig.4 shows the current-flow pth. The energies of the lege inductnce L nd gnetizing inductnce L re relesed to the prsitic cpcitors of the switches, respectively. The blocing cpcitor C4 is still chrged. The output cpcitor Co provides the energy to lod R. When the diodes D nd D2 re forwrd bised t t = t3, this operting ode ends. The energies of the lege inductnce L nd gnetizing inductnce L re relesed to the clped cpcitor C nd energy of the inductor L2 is trnsferred to the clped cpcitor C2. The blocing cpcitor C4 eeps chrging. In ddition, due to the lege inductnce, nd the diode current id3 eeps flowing though diode D; therefore, the voltge cross the diode D4 is clped by the blocing voltge VC4. The output cpcitor Co provides the energy to lod R. When the currents id3, ic3, nd il3 decrese to zero t t = t4, this operting ode ends. Mode V [t4, t5]: In this trnsition intervl, the switches re turned off. Diodes D, D2, nd Do re forwrd bised. Diodes D3 nd D4 re reverse bised. The current-flow pth is shown in Fig.6. Fig.6 Fig.4 Mode IV [t3, t4]: In this trnsition intervl, the switches re turned off. Diodes D, D2, nd D3 re forwrd bised. Diode Do is reverse bised. Fig. 5 shows the current-flow pth. The energies of the lege inductnce L nd the gnetizing inductnce L re relesed to the clped cpcitor C nd the energy of inductor L2 is trnsferred to the clped cpcitor C2. The diode current ido increses lost t constnt slope. The input source Vin, three-winding coupled inductor, nd the blocing voltge VC4 re connected in series to chrge the output cpcitor Co nd provide 208

5 Interntionl Journl of Scientific & Engineering Reserch Volue 9, Issue 3, Mrch ISSN energy to the lod R. When the diode current ido is equl to diode current id2 (i.e., cpcitor current decreses to zero) t t = t5, this operting ode is finished. Mode VI [t5, t6]: In this trnsition intervl, the diodes D, D2 nd Do re forwrd bised during the switches turned off nd the D3 nd D4 re in reverse bis. The flow of current is shown in Fig.7. It is lost se s Mode V but the cpcitor C2 is dischrged. This operting ode ends t t=t6, D4 is forwrd bised t this tie of intervl. cpcitor C3 while the diodes currents id nd id2 re equl to zero t=t7 in this ode. Mode VIII [t7, t8]: In this trnsition intervl, the switches re turned off. Diodes D3 nd Do re forwrd bised. Diodes D, D2, nd D4 re reverse bised. The current-flow pth is shown in Fig.9 Fig.7 Mode VII [t6, t7]: In this trnsition intervl, Diodes D, D2, D3 nd D0 re in forwrd bis only D4 is in reverse bis during the switch off ode. The flow of current is shown in Fig.8. Fig.9 The lege inductnce L, the gnetizing inductnce L, the input source Vin, the inductor L3, the blocing voltge VC4, nd the clped cpcitor voltge VC2 re connected in series to provide energy to the output cpcitor Co nd the lod R. Menwhile, cpcitor C3 eeps chrging. The voltges cross the diodes D nd D2 re clped by the windings of the coupled inductor nd the clped cpcitors C nd C2. Therefore, the voltge steps of diodes D nd D2 re fored, nd the voltge drops of the switches re obtined. The output diode current ido drops linerly. When the output diode Do is reverse bised t t = t8, this operting ode ends. When the switches re turned on, the new switching period begins. 2.2 Theoreticl Anlysis of Voltge Multiplier Converter Voltge Gin Expression Fig. 8 The lege nd gnetizing inductnce releses the energies to clped cpcitor C. The prllel connection of the inductor L2 nd cpcitor C2 dischrges the energies to the lod nd output cpcitor Co. Siultneously, the input Vin, L, L2 nd the blocing voltge VC4 provides the energy to the output cpcitor Co nd lod R. The ido drops lost constnt slope. In ddition, the energy of the inductor L2 is trnsferred to the When the proposed converter opertes in the switching-on stte, the following equtions cn be found in Fig. 3 V L = V in () V L = ( )V in (2) At odes V VII, the energies of the lege inductors re relesed to the cpcitors C nd 208

6 Interntionl Journl of Scientific & Engineering Reserch Volue 9, Issue 3, Mrch ISSN C2. According to the duty cycle of the relesed energy cn be pproxitely obtined D o = 2( D) (N ) (3) By using the volt second blnce principle on the lege inductnce L nd gnetizing inductor L, the voltges of L nd L re found s V L = DV in ( D) (4) V L = D( )(N )V in ( 2( D)) (5) V N3 = NDV in ( D) (6) The voltges of cpcitors C, C2, C3, nd C4 cn be expressed s V C3 = NDV in ( D) (7) During the tie intervl [t2, t8], the onstte currents of the diodes D0, D nd D2 cn be expressed s I D0(t2,t 8 ) = I 0 D (5) I D(t2, t 7 ) = I D2(t2,t 7 ) = I 0 D C (6) Then, bsed on the cpcitor chrge blnce, during the tie intervl [t0, t2], the verge current of cpcitor C cn be written s I C[t0,t 2 ] = I 0 D (7) Hence, the currents of secondry side N3 of the coupled inductor cn be obtined s I N3[t0,t 2 ] = I 0 D (8) I N3[t2,t 8 ] = I 0 ( D) (9) V C = V C2 = V L V L = (VinD(( ) N( ))) 2( D) (8) V C4 = V in V C V C3 V N3 (9) Accordingly, collecting the ters, the voltge gin cn be expressed s Duty Rtio During the tie intervl [t2,t8], while using KCL t points of the priry side N of the coupled inductor, diode D nd cpcitor C4, the current of the lege inductor cn be expressed s I = (N 3)I L[t 0 (2( D) (20) 2,t8] G = V o V in = V cv c2 V c3 V c4 V in V in. (0) G = V o = 2N D(N) V in D D Voltge Stress nd Current Stress Expression () According to the bove nlysis, the voltge stresses on the power devices re given s follows: V S = V S2 = V D = V D2 = V in D = V O 2N(N)D V D4 = NV in = NV D O 2 N (N )D (3) V D3 = V D0 = (N)V in = D (N )V 0 (2 (N )D) (4) (2) In order to show how different duty cycle nd prsitic preters influence the efficiency, soe preters re ssued in the following three cses. Cse I: RL =0.02 Ω, N =2, RDS =0.075 Ω, RD =0.05 Ω, R = 200 Ω, VD =0.8V, Vin =20V. Cse II: RL =0.04 Ω, N =2, RDS =0.075 Ω, RD =0.05 Ω, R = 200 Ω,VD =0.8V, Vin =20V. Cse III: RL =0.06 ΩN =2, RDS =0.075 Ω, RD =0.05 Ω, R = 200 Ω,VD =0.8V, Vin =20V. 3 SIMULATION RESULTS 3. Open Loop Syste The below converter is n open loop syste with dul switches, three-winding 208

7 s Interntionl Journl of Scientific & Engineering Reserch Volue 9, Issue 3, Mrch ISSN coupled inductor nd voltge ultiplier cells by chieving high output gin to liited vlue. Tble I Coprison with Different Duty Rtio Discrete e-07 s. powergui C <Diode current> [id] <Diode voltge> [VD <Diode current> <Diode voltge> D4 D3 D C4 C3 [id3] [VD3 <Diode current> <Diode voltge> Pulse Genertor [id4] [VD4 [S] Goto [S2] Goto [S] Fro2 il [VD2] - Fro5 Gin [id2] Fro6 ic2 [VD3] - Fro7 Gin2 [id3] Fro8 [VD4] - Fro9 Gin3 S.No Input Voltge Duty Rtio Output Voltge Vin [S] Fro ::2 g D S S2 [S2] Fro g D S S <MOSFET current> <MOSFET voltge> <MOSFET current> Do [is] [VS] [is2] <Diode current> [ido] <Diode voltge> [VDo [VD] - Fro3 Gin [id] Fro4 Co R ic il2 il3 Scope [id4] Fro0 ic3 [VDo] - Fro Gin4 [ido] Fro2 [VS] Fro3 Scope <Diode current> <Diode voltge> D2 <MOSFET voltge> [id2] [VD2 [VS2] [VS2] Fro4 [is] Fro Multieter2 [is2] Fro Multieter Product Eleentsof Po C2 Fig.0 MATLAB siultion of voltge ultiplier converter with coupled inductor without controller (Open Loop Syste) Principle of Opertion Multieter Scope Vo 6.7 [S] Fro7 [S2] Fro8 Scope3 The input voltge is ept constnt t 20V, the output voltge vries s the duty rtio is vried nully. As the xiu duty rtio will be less thn, the xiu vlue to the output voltge would be pproxitely 530V. 3.2 Closed Loop Syste with PI Controller Here, the converter consists of two Here coprison of error nd chnge in ctive switches, five diodes nd five cpcitors. error signls re to be de nd gives the The two switches shre se opertion signl controlled output is esured by scope. nd one control circuit is needed. The input Discrete, [VD2] - Ts = e-07 s. voltge is intined t 20V nd the duty rtio is Fro5 powergui d c [S] Gin PI C [id2] Vo Goto Discrete PWM Genertor PI Controller Fro6 [S2] vried giving constnt output voltge s 200V. D4 D3 200 Goto D Vref ic2 [VD3] - C4 Duty Rtio Fro7 Gin2 C3 [id3] Fro8 Experientl Results [VD4] - ::2 Fro9 Gin3 Do Goto2 [id4] [Vin] Vin Fro0 The following wvefors shows the [S] g [S2] ic3 [VDo] - Fro D S Fro Co R Fro Discrete S2 Gin4 output voltge t 200V with 20V s input Tier [ido] Fro2 C6 C5 [VS] intining the duty rtio t 0.5 Fro3 g D S S D2 2 Multieter Product of Eleents Po 99.7 [VS2] Fro4 [is] Fro5 [is2] Fro6 Scope2 C2 [Vin] Fro2 Coprison 99.8 Multieter Vo Fig.2 MATLAB siultion of voltge ultiplier converter with coupled inductor with PI controller Fig. Coprison of input nd output voltge of 200V Output Voltge coprison with Different Duty Rtio In the below Tble I, the vlue of output voltge chnges s the duty rtio is vried, here, the duty rtio is vried nully giving different output voltges with constnt input voltge of 20V. Principle of Opertion of PI controller Here the input voltges re given s 0V, 5V, 20V, 25V, 30V, 40V nd Reference voltge is given s 200V, these two inputs re given to the PI Controller. Coprison of the ctul output voltge nd reference voltge is crried out by using Error controller. It copres the error nd chnge in error vlue nd gives the controlling output voltge. Siultion Experientl Results 208

8 Interntionl Journl of Scientific & Engineering Reserch Volue 9, Issue 3, Mrch ISSN The following wvefors shows the coprison between the input nd output voltge with reference voltge. Here, we discuss different cses of the vrition in duty rtio for different reference vlue. 360v intining the output voltge t 366.6V, in this the duty vries utoticlly. In the below tble, the desired vlue of the output voltge is chieved s the duty rtio is vried, here, the duty rtio is utoticlly vried giving different output voltges with vrible input voltges. Vrible input voltge TABLE II For Reference Voltge = 200V Output Voltge(Volts) Output Power(Wtts) [ ] The bove tble shows the vlues of vrible input voltges t reference voltge of 200v intining the output voltge t 99V, in this the duty vries utoticlly. Fig.3 Wvefors of the Constnt Output Voltge with vrying Duty Rtio Vrible input voltge TABLE III For Reference Voltge = 360v Output Voltge(Volts) Output Power(Wtts) [ ] The bove tble shows the vlues of vrible input voltges t reference voltge of Fig.4 Wvefors of the Constnt Output Voltge with vrying Duty Rtio The bove figures (Fig.3 & Fig.4) nd shows the utotic vrition of duty rtio giving constnt output voltge. 4 COMPARISON WITH PREVIOUS CONVERTERS Tble IV shows the perfornce nd coprison for the proposed converter nd cscde boost converter. The nuber of diodes nd cpcitors re ore thn tht in the cscde boost converter. However, the voltge stress of the ctive switch in cscde boost converter is equl to the output voltge, wherein, the voltge stress of the switch in proposed converter is very less thn the output voltge. This es the low on-resistnce MOSFET vilble hence iproving the efficiency. With the help of the controller, s the duty rtio increses, the voltge gin in the converter is fr ore thn tht in cscde boost converter. TABLE IV Coprison ong different Converters Topology Cscde Boost Converter Proposed Converter No. of Active 2 Switches No. of 3 5 Diodes No. of

9 Interntionl Journl of Scientific & Engineering Reserch Volue 9, Issue 3, Mrch ISSN Cpcitors Voltge Gin /(-D)² =0.04 (2ND(N))/ (-D) = Voltge stress of ctive switches Vo = 200v Vo/(2N(N) D)= 44.45v The proposed circuit intins the output voltge constntly with the vrible input voltge by eploying the PI controller which controls the output voltge by controlling the width of the triggering pulses or switching signls. The output response with the vrible input voltge is represented in the Fig.5. Initilly, during the trnsient tie the output voltge increses up to xiu vlue nd with the control ction of the PI controller the desired output voltge is ttined round 0.06 to 0.07secs. The Fig.4 represents coprison of input nd output voltge with the reference voltge s 200V. The desired output voltge cn be vried nd is obtinble with the PI control strtegy with the proposed circuit. The control ction of PI controller is represented in Fig.3 in the for of gte pulses. Fro the siultion result, it cn be observed tht the gte pulses re being vried with PI control to chieve desired output voltge. photovoltic syste, IEEE Trns.Power Electron., vol. 28, no. 6, pp , Jun J. T. Bilsiewicz, Renewble energy systes with photovoltic power genertors: Opertion nd odeling, IEEE Trns. Ind. Electron., vol. 55, no. 7, pp , Jul Y. Xiong, X. Cheng, Z. J. Shen, C. Mi, H. Wu, nd V. K. Grg, Prognos-tic nd wrning syste for powerelectronic odules in electric, hybrid electric, nd fuel-cell vehicles, IEEE Trns. Ind. Electron., vol. 55, no. 6, pp , Jun K. Jin, X. Run, M. Yn, nd M. Xu, A hybrid fuel cell syste, IEEETrns. Ind. Electron., vol. 56, no. 4, pp , Apr W. Li nd X. He, Review of non-isolted high-step-up DC/DC converters in photovoltic grid-connected pplictions, IEEE Trns. Ind. Electron., vol. 58, no. 4, pp , Apr Z. Song, C. Xi, nd T. Liu, Predictive current control of three-phse grid-connected converters with constnt switching frequency for wind energy systes, IEEE Trns. Ind. Electron., vol. 60, no. 6, pp , Jun S. M. Chen, T. J. Ling, L. S. Yng, nd J. F. Chen, A sfety enhnced, high step-up DC DC converter for AC photovoltic odule ppliction, IEEE Trns. Power Electron., vol. 27, no. 4, pp , Apr Y. Zho, W. H. Li, nd X. N. He, Single-phse iproved ctive clp coupled-inductor-bsed converter with extended voltge doubler cell, IEEE Trns. Power Electron., vol. 27, no. 6, pp , Jun CONCLUSION The Siultion experientl results hve been presented for coupled inductor bsed DC-DC converter. The ipleenttion of high step-up voltge conversion with utotic vrition of duty rtio, voltge clping feture nd by turns rtio of the coupled inductor. The output voltge is copred with the reference vlue nd the error is fed to PI Controller generting dynic duty rtio. So, s copred with cscded boost converters, here the duty rtio is utoticlly vried giving constnt output voltge for ny given constnt vlue of the input voltges. The output voltge is s the user-defined vlue which is intined constnt. REFERENCES.K.-C. Tseng, C.-C. Hung, nd W.-Y. Shih, A high stepup converter with voltge ultiplier odule for 9.M. Prudente, L. L. Pfitscher, G. Eendoerfer, E. F. Roneli, nd R. Gules, Voltge ultiplier cells pplied to non-isolted DC DC converters, IEEE Trns. Power Electron., vol. 23, no. 2, pp , Mr A. Aji, H. Ardi, nd A. Frhor, A novel high step-up DC/DC con-verter bsed on integrting coupled inductor nd switched-cpcitor tech-niques for renewble energy pplictions, IEEE Trns. Power Electron., vol. 30, no. 8, pp , Aug Y. Tng, D. J. Fu, J. R. Kn, nd T. Wng, Dul switches DC/DC converter with three-winding-coupled inductor nd chrge pup, IEEETrns. Power Electron., vol. 3, no., pp , Jn G. V. Torrico-Bscope, R. P. Torrico-Bscope, D. S. Oliveir Jr., S.V. Arujo, F. L. M. Antunes, nd C. G. C. Brnco, A high step-up converter bsed on three-stte switching cell, in Proc. IEEE Int. Syp. Ind. Electron., 2006, pp W. Li, W. Li, X. Xing, Y. Hu, nd X. He, High step-up interleved converter with built-in trnsforer voltge ultiplier cells for sustinble energy pplictions, IEEE 208

10 Interntionl Journl of Scientific & Engineering Reserch Volue 9, Issue 3, Mrch ISSN Trns. Power Electron., vol. 29, no. 6, pp , Jun