Design And Implementtion Of Luo Converter For Electric Vehicle Applictions A.Mnikndn #1, N.Vdivel #2 ME (Power Electronics nd Drives) Deprtment of Electricl nd Electronics Engineering Sri Shkthi Institute Of Engineering nd Technology, Coimbtore, Indi Abstrct This pper proposes the stble nd ripple free output voltge from the design of developed Dc-Dc converter topology. Dc voltge provided by bttery contins high voltge ripples nd it is not constnt enough voltge, thus it is not pplicble for most devices like electric-vehicle controller, dc-chrgers, etc. Dc- Dc converters re employed to ttenute the ripples regrdless of chnge in the lod voltge. In the existing method, the clssicl buck converter for electric vehicle pplictions does not meet the lod requirement contining more ripples on the output voltge nd prsitic effects. To overcome this problem the dvnced developed Dc-Dc luo-converter technology ws introduced. luo converter is the developed converter derived from the buck-boost converter. In this proposed model the dditionl filter elements in the luo-converter eliminte the output ripples nd effectively enhnce the output voltge level. A computer simultion using MATLAB/SIMULINK confirms the predicted results. Keywords dc-dc converter, electric vehicle, low pss filter, luo converter I. INTRODUCTION The dc-dc conversion technology is mjor subject re in the field of power electronics nd drives, nd hs been under development for pst six decdes. Dc-dc converters re widely used in industril pplictions nd computer hrdwre circuits. Dc-dc conversion techniques re developed very quickly. This compres to the c-dc power supply mrket, which will hve certin growth of only bout 7.5% during the sme period. In ddition to its higher growth rte, the dcdc converter mrket is undergoing evlute chnges s result of two mjor trends in the electronics industry like low voltge nd high power density. From this investigtion it cn be seen tht the production of dc-dc converters in the world mrket is much higher thn tht of c-dc converters. In 1920s the dc-dc conversion is process is strted. A simple voltge conversion, the simplest dc-dc converter is voltge divider (such s rheostt, potentil meter, nd so on) [1], but it only trnsfers output voltge lower thn input voltge with poor efficiency. The multiple-qudrnt chopper is the second step in dc-dc conversion more time hs been spent for to find equipment to convert the dc energy source of one form voltge to nother DC ctutor with nother voltge form, s does trnsformer employed in AC-AC conversion. Some initil types of DC-DC converters were used in industril pplictions before the Second World Wr. Reserch of Dc- Dc converter ws blocked during the wr, but pplictions of DC-DC converters were recognized. After the wr, communiction technology developed very quickly nd required low voltge DC power supplies for the communiction. This resulted in the rpid development of DC-DC conversion techniques. Initil stge prototypes cn be derived from choppers. The emerging DC-DC converters cn be offered s method to generte multiple output voltge levels from single source dc supply voltge to feed the different sub-circuits in the device [2]. This method of generting multiple output voltge levels from single bttery source cn reduce the re of the device substntilly. On the other hnd dc supply voltge provided by bttery or rectifier contins high voltge ripples (hrmonics) nd it is not constnt enough, thus it is not pplicble for most devices. DC-DC regultors re employed to ttenute the ripples regrdless of chnge in the lod current or input voltge [3]. Buck converter is type of switching-mode power supply which is used for stepping-down dc voltge level. Switch controller circuit nd power circuit re two min prts of buck converter circuit. One of the most criticl issues for the environment tody is pollution generted by hydro-crbon gses, which is one of the min sources of power for trnsporttion. Hybrid electric vehicles (HEV) nd full electric vehicles (EV) re rpidly dvncing s lterntive power trins for green trnsporttion. The electric vehicle ppliction not only involves the trction prts, but it is lso generting the new pplictions for conversion of electric power from lod to source. One of the key blocks inside hybrid electric vehicles is the DC DC converter for uxiliry power supply of electric lods. This converter hs to be possible of hndling the electric energy trnsfer from the 12V DC bus nd the high voltge DC bus (used for electric trction pplictions).the DC-DC converter enbles the energy trnsfer between the high voltge side nd low voltge side giving tremendous dvntges in terms of low cost, flexible, relible nd efficient, incresed due to the possible constrints of esy to mke synchronous rectifiction nd implementtion. The fetures include resonnt clmping circuit implementtion in the boost mode nd soft-switching ISSN: 2231-5381 http://www.ijettjournl.org Pge 4437
opertion, due to phse shift opertion, in the buck mode, without need dditionl devices, nd provide high efficiency nd esy to control. Power electronic converters nd new semiconductor devices re key components to meet the trgets of extended milege rnge nd reduced pollution. The rpidly efficient DC-DC converters must be used to provide pproprite voltge levels nd the power mngement between different energy level sources nd storge elements. The proposed developed DC-DC converter is Luo converter it overcomes the prsitic problems present in the clssicl dcdc converter [11]. Fig 1 shows the circuit digrm for developed dc-dc luo converter. The hrmonics Levels present in the luo converter less compred to the clssicl buck converter. II. CIRCUIT OPERATION OF LUO CONVERTER The circuit digrm of the Buck - output Luo converter is shown in Fig. 1. In the circuit, S is the power switch nd D is the freewheeling diode. The energy storge pssive elements re inductors A. Modes of opertion Mode 1: when the switch is ON, the inductor L1 is chrged by the supply voltge E. At the sme time, the inductor L2 bsorbs the energy from source nd the cpcitor C1. The lod is supplied by the cpcitor C2. The equivlent circuit of Luo converter in mode 1 opertion is shown in (). Mode 2: switch is in OFF stte, nd hence, the current is drwn from the source becomes zero, s shown in (b). Current il1 flows through the freewheeling diode to chrge the cpcitor C1. Current il2 flows through C2 R circuit nd the freewheeling diode D to keep itself continuous. () Fig. 1. Circuit digrm of Luo converter. L1, L2 nd cpcitors C1, C2, R is the lod resistnce. To nlyse the opertion of the Luo converter, the circuit cn be divided into two modes. When the switch is ON, the inductor L1 is chrged by the supply voltge E. At the sme time, the inductor L2 bsorbs the energy from source nd the cpcitor C1. The lod is supplied by the cpcitor C2. The equivlent circuit of Luo converter in mode 1 opertion is shown in (). During switch is in OFF stte, nd hence, the current is drwn from the source becomes zero, s shown in (b). Current il1 flows through the freewheeling diode to chrge the cpcitor C1. Current il2 flows through C2 R circuit nd the freewheeling diode D to keep itself continuous. If dding dditionl filter components like inductor nd cpcitor to reduce the hrmonic levels of the output voltge (b) In discontinuous conduction mode, output should be in the form of discontinuous. In this mode diode is not present nd inductor dischrge through V0 nd L2. The output stge of the Luo buck converter is comprised of n inductor nd cpcitor. The output stges stores nd delivers energy to the lod, nd smooths out the switch node voltge to produce constnt output voltge. Inductor selection directly influences the mount of current ripple seen on the inductor current, s well s the current cpbility of the buck converter itself. Inductors vry from mnufcturer to mnufcturer in both mteril nd vlue, nd typiclly hve tolernce of 20%. Inductors hve n inherent DC resistnce (known s the DCR) tht impcts the performnce of the output stge. Minimizing the DCR improves the overll performnce of the converter. For tht ppliction it requires high lod current, it is recommended to select n inductor with low DCR. The DCR is smller for lower inductor vlues, but there is trde off between inductnce nd ripple current; the lower the inductnce, the higher the ripple current through the inductor. ISSN: 2231-5381 http://www.ijettjournl.org Pge 4438
A minimum inductnce must be met in order to meet the ripple current requirements of the specific ppliction circuit. The output cpcitnce directly ffects the output voltge of the converter nd the response time of the output feedbck loop, lso the mount of output voltge overshoot tht occurs during chnges in lod current. A ripple voltge exists on the DC output s the current through the inductor nd cpcitor increses nd decreses. Incresing the vlue of output cpcitnce vlue reduces the mount of voltge ripple present in the circuit. However, there is trde-off between cpcitnce nd the output response. Incresing the cpcitnce reduces the output voltge ripple nd output voltge overshoot, but increses the response time it tkes output voltge feedbck loop to respond to chnges in lod. Therefore, minimum cpcitnce must be considered, in order to reduce the ripple voltge nd voltge overshoot requirements of the converter, while mintining feedbck loop tht cn respond quickly enough to lod chnges. Cpcitors lso hve prsitic series resistnce, known s the equivlent series resistnce (ESR). The stedy stte cpcitor vlue is 0A shown in fig (c). Duty cycle, Ton T Output voltge eqution, Vo Vin 1 (2) Averge Voltge cross the cpcitor C1 is, Vc1 Vin 1 Pek to pek inductor current is, TVin IL1 L1 eqution (4) inductor L1 vlue, TVin L1 IL1 Pek to pek inductor current L2 is, TVin IL2 L2 (3) (4) (5) (6) eqution (6) inductor L2 vlue, TVin L2 IL2 (7) The chrge on series cpcitor (C1) increses during off period by IL2 (=Io) nd decreses during on period by IL1 The chnge in chrge on C1 must be zero Pek to pek ripple voltge cross the cpcitor C1, The ESR impcts the output voltge ripple nd the overll efficiency of the converter. Becuse of this, designers re moving to low ESR designs. Surfce mount cermic cpcitors re becoming prevlent in systems tht require high performnce in smll form fctor. The choice of multiple cpcitors connected in prllel llows designers to chieve the necessry cpcitnce for the system while gretly reducing the equivlent ESR. (c) 1 VC1 TI1 C1 eqution (8) C1 vlue, 1 C1 TI1 VC1 IV. SIMULATION RESULTS (8) (9) III. ANALYSIS OF LUO CONVERTER The inductor current IL2, 1 IL2 IL1 (1) In electric vehicle pplictions, different kinds of electric lods re used. The pplicbility of the concept on different electric lods used in electric vehicle pplictions is tested with simultion models tht would provide the most relistic predictions. SIMULINK model for Luo converter is shown in (d). ISSN: 2231-5381 http://www.ijettjournl.org Pge 4439
TABLE I DESIGN PARAMETERS AND SIMULATION CONDITIONS Input voltge Output voltge Cpcitor C1,C2 Inductor L1,L2 Switching frequency Lod current 60V 12V 0.1mF 0.27mH 50KHz 10A (d) A.Pwm model The duty cycle cn be generted by compring the reference dc signl Vr with swtooth crrier signl Vcr. This is shown in fig(e),modultion index is the rtio of crrier signl to reference signl the duty cycle cn be vried from 0 to 1.To obtin the squre wve pulses compre these signls by comprtor to generte the difference (Vc-Vcr).Any vrition in Vcr vries linerly with the duty cycle. (e) The pulse width modultion output nd switching output wveforms of Luo converter is shown in fig (f) nd fig(g) (g) IV. CONCLUSIONS (f) In the current study, the proposed developed luo converter hs been shown to be cpble of providing topology tht reduces the output ripple nd prsitic effects. Using this method stble nd ripple free output is obtined. Simultion results verified the design nd clcultions. This developed dc-dc converters re suitble nd convenient to be pplied into electric vehicle pplictions with low ripples. The dvnced dc-dc converter enhncement technique such s luo converter is used. The min objective is to rech the high efficiency, low THD, high power density nd simple structures. ISSN: 2231-5381 http://www.ijettjournl.org Pge 4440
APPENDIX The Component vlues re Inductor L1-0.27mH, L2-0.27mH, Cpcitor C1-0.1mF, Cpcitor C2-0.1mF, Switching frequency 50 MHz, Mx Lod current 12 A. ACKNOWLEDGEMENT The uthor would like to cknowledge the contribution of Ampere Vehicles Pvt Ltd for mking the dvnced dc-dc converter. REFERENCES [1] Mrin K. Kzimierczuk, Pulse-width Modulted DC-DC Power Converters, Edition, Wiley. [2] Ned Mohn, Tore M. Undelnd, Willim P. Robbins, Power Electronics: Converters, Applictions, nd Design, 3rd Edition, Wiley. [3] Jerrold Foutz, Switching-Mode Power Supply Design Tutoril Introduction, SMPS Technology, http://www.smpstech.com/tutoril/t01int.htm, ccessed: Mr 2012. [4] Abrhm I. Pressmn, Switching Power Supply Design, Second Edition, McGrw-Hill, Publiction Dte: Nov 1997. [5] Chester Simpson, Liner nd Switching Voltge Regultor Fundmentls, Ntionl Semiconductor, http://www.ntionl.com/ssets/en/ppnotes/f4.pdf, ccessed: Mr 2012. [6] Mxim Integrted Products, Inc., DC-DC Converter Tutoril, Appliction Note 2031, Nov 29, 2001. [7] Ry Ridley, CURRENT MODE or VOLTAGE MODE?, Switching Power Mgzine, Oct2000, http://encon.fke.utm.my/nikd/ltest/octcurrentmode.pdf, ccessed: Mr 2012. [8] Mdhurvsl Vijyrghvn G., Extreme temperture switch mode power supply bsed on vee-squre control using silicon crbide, silicon on spphire, hybrid technology, Doctorl Thesis, Oklhom Stte University, 2009. [9] L. K. Wong, T. K. Mn, How to best implement synchronous buck converter, Ntionl Semiconductor, Apr 2008, http://www.eetimes.com/design/power-mngement-design/4012225/tip-ofthe-week-how-to-best-implement--synchronous-buck-converter, ccessed: Mr 2012. [10].Fng Lin nd Hong Ye [2004], Positive Output Multiple-Lift Push- Pull Switched-Cpcitor Luo-Converter, [11] He.Ye nd Luo F.L.[2005], Anlysis of Luo converter with Voltge Lift Circuit, IEEE Precedes Electricl on Power Applictions,Volume:52,No.5,Pge1239-1252 [12] Luo.F.L nd Ye.h [1999], Positive output cscde Boost converters, IEEE Precedes Electricl on Power Applictions,Volume: 151,No.5,Pge:590-606. [13] Fng Lin Luo nd Hong ye [2007], mthe mticl modeling for Dc- Dc converter IEEE trnsctions on power electronics, vol. 22, no. 1 ISSN: 2231-5381 http://www.ijettjournl.org Pge 4441