Soft Switching Full Bridge DC-DC Converter for Electric Vehicle Application

Transcription

1 Internatinal Jurnal f Electrical Engineering. ISSN Vlume 6, Number (203), pp Internatinal Research Publicatin Huse Sft Switching Full Bridge DC-DC Cnverter fr Electric Vehicle Applicatin V. Delbin Jelaja and Dr. M. Rajaram 2 Abstract Sft switching full bridge dc-dc cnverter fr electric vehicle applicatin has been implemented. The high vltage and high pwer required fr electric vehicles can be btained using vltage dubler rectifier. The main bjective f this paper is t demnstrate experimentally that the cmbinatin f zebra battery, sft switching dc-dc cnverter and ultra capacitr bank can slve the prblems like pr specific pwer, high vltage spike acrss the rectifier dide and allwing excellent perfrmance in bth acceleratin and regenerative braking in an electric vehicle. The amunt f energy stred allws us t have 50kw f pwer in 5 secnds, which is enugh t accelerate the vehicle withut the help f the tractin battery. The vehicle uses a brushless dc mtr with nminal pwer f 40 kw and has a peak pwer f 55kw. Energy flw diagram fr this vehicle is als demnstrated. The peratin principle f the prpsed cnverter is analysed and verified with the help f simulatin results. Key wrds- Energy strage, regenerative braking, sft-switching, vltage dubler rectifier. I. Intrductin The dc-dc cnverters using in electric vehicles has sme f the draw backs such as pr specific pwer (in watts per kilgram), switching lses, pr energy strage capability and high vltage stress develped acrss the rectifier dides. The battery using in electric vehicle has the drawbacks such as fast and sudden battery discharge during the perid f acceleratin (r) fast charging during regenerative braking. This can be avided with the help f ultra capacitrs. On the ther hand, ultra capacitrs allw regenerative braking even when the batteries are fully charged. The ultra capacitr technlgy that allws t stre times mre energy than cnventinal electrlytic capacitrs [, 2]. In electric vehicles the key advantage f using ultra capacitr

2 20 V. Delbin Jelaja and Dr. M. Rajaram energy transfer methd is the high efficiency peratin ie. an inherent nature f many capacitr clamped r switch capacitr circuits. Sdium - Nickel chlride batteries (ZEBRA) are a very gd chice fr electric vehicles [3]. They are safe and lw cst and can endure mre than 000 cycles withut significant degradatin. Frm this the cmbinatin f ZEBRA battery and ultra capacitr bank prvide excellent perfrmance in bth acceleratin and regenerative braking in an electric vehicles. The pwer inverter using in electric vehicles use IGBTs switches. IGBTs can handle high vltage and high pwer with lwer cst cmpared with MOSFETs, s IGBTs have been replacing MOSFETs in several tens f kilwatts f pwer [4]. The cnventinal DC-DC cnverter using in electric vehicles has disadvantages such as circulating current flws thrugh the pwer transfrmer and switching devices during free wheeling interval, high vltage stress develped acrss the rectifier dide and due t the utput inductance the reactive pwer lss is high. Fr resetting the primary circulating current, several ptins have been prpsed (a) Inserting in the primary a dc blcking capacitr and either a Saturable inductr [5] (r) tw dides in series with the lagging leg. This slutin attracts increased cnductin lsses and reactive pwer lss (ie. Cre lss due t saturatin f transfrmer cre and it needs large blcking capacitr, s its use is restricted up t a few kw pwer level. Fig. shws the energy flw diagram f an electric vehicle, bidirectinal pwer management is an imprtant feature f dc t dc cnverter using in several autmtive applicatins such us hybride electric vehicles prpulsin system. Frm this accrding t Faraday s Law f Electr Magnetic Inductin an EMF gets induced in the generatr which is cnverted t DC with a help f rectifier, which is inverted using inverter fr tractin mtr. Then using sft switching full bridge DC t DC cnverter we can get smth ripple free variable DC utput. In hybrid electric vehicles a DC t DC cnverter is a integral part f the DC architecture. This DC t DC cnverter maintains a pwer balance between the input and any energy strage inside the vehicle and prvides cntinuus pwer t the electric mtr. This paper prpses the leakage inductance f the transfrmer tgether with ultra capacitr bank and vltage rectifier capacitr can reduce the vltage stress acrss the vltage dubler circuit and t give smth ripple free high vltage acrss the utput terminals. The cmbinatin f zebra battery and ultra capacitr bank t give excellent perfrmance in bth acceleratin and regenerative braking in an electric vehicles. Als in the prpsed design, the usage f inductance is less; s we can minimise the inductr lsses such as cre lss and cpper lsses. II Operatinal Principle The circuit diagrams and key wavefrms f the prpsed cnverter are shwn in figure. The peratinal principal f the prpsed cnverter are divided int five mdes. Due t the symmetry f peratin nly ne half cycle is depicted

3 Sft Switching Full Bridge DC-DC Cnverter fr Electric Vehicle Applicatin 2 here. With the help f equivalent circuits the peratinal principle is clearly explained. Fig. Energy flw diagram fr this vehicle Mde 0 After giving the supply the current starts t flws thrugh S and S 2 and the energy is transferred frm primary t the secndary side sme amunt f energy gets stred in the leakage inductance f the transfrmer, rectifier capacitr, ultra capacitr bank. Nw these devices are in charging mde and the primary current increases t high value due t the resnance between leakage inductance f the transfrmer and rectifier capacitr is given by V n n in i pri(t) = V t Sin t t r L n C c Z r, 2 Z n L 0, 3 C C=C +C 2, N n N i pri i 4 n i V n in ( t) V t Sin t t 5 Z V c - vltage acrss the capacitr r Mde When the vltage acrss the rectifier increases t high value high vltage stress develped acrss the rectifier dide. This can be minimized with the p s

4 22 V. Delbin Jelaja and Dr. M. Rajaram help f clamping dide and resnance cnditin (ie the resnance between leakage inductance f the transfrmer, rectifier capacitr and t sme extend ultra capacitr bank). Fig.2 Circuit diagram f the prpsed cnverter The clamped vltage is given by V DC (t) = 2V +V C -V in 6 The current flwing t the clamping dide is given by i DC (t) = t VC t 7 L Fig.3 Key wavefrms in ne switching cycle

5 Sft Switching Full Bridge DC-DC Cnverter fr Electric Vehicle Applicatin 23 Mde 2 With the help f clamping dide the vltage stress acrss the rectifier is sme what minised. Nw the clamping dide is cut ff, the vltage acrss the vltage dubler cell is equal t twice the secndary input, the current stress acrss the rectifier is minimized. During this perid the capacitrs are charging and the capacitr vltages are equal. I D Vin VCt Sin r t t n 8 Z Ts s V I t d I 9 C C C C 2 T V C 2 R The vltage acrss capacitr can be btained as V C t V T S 2 2CR 0 Mde 3 Nw switch S 3 turns ff, the intrinsic capacitrs f S 3 and S 2 are charged by the reflected lad current when the vltage acrss, S 3 increases t input vltage, the bdy dide f S 2 cnducts and S 3 attain ZCS and it turns ff, at the same time S 2 attains ZVS and it turns n large amunt f current reflected. The vltages increases very fast because large current reflected frm the lad. When the switch S 3 turns ff, the vltage acrss primary reduces t zer value, at that time current in primary starts decreasing. The decreasing slpe is btained as dip V dt n L c Mde 4 Nw the cnverter is in freewheeling stage. The current in primary decreases t zer and the primary circulatin lss is eliminated. Due t the symmetry f peratin the peratinal principle f ther half cycle are same. III Design Cnsideratins A. Sft Switching State-Plane Trajectry Fig. shws the sft switching state plane trajectry. This diagram clearly depicts the peratinal mdes f the prpsed cnverter. The dc-dc cnverters in electric vehicles use insulated Gae Biplar transistrs (IGBT s ) which are based n sft switching (ie. Switches are n under ZVS and OFF under ZCS). This is clearly indicated in the sft switching trajectry. Frm this diagram the peak value f the resnant current is I I L. The lad current increases during charging mdes and decreases during discharging mdes. The selectin f

6 24 V. Delbin Jelaja and Dr. M. Rajaram resnant capacitr is ne f the imprtant factr fr the prper peratin f the circuit, because the resnant capacitr reduces the turn ff lss and turnff dv/dt f the device. A large size capacitr can reduce the turn-ff lss and turn-ff circuits at the device. The rate f change f vltage acrss the resnant capacitr is given by dv C I L 2 dt C Fig.4 Equivalent circuits. (a) Mde 0 (b) Mde (c) Mde 2 (d) Mde 3 (e) Mde 4

7 Sft Switching Full Bridge DC-DC Cnverter fr Electric Vehicle Applicatin M2 I LK 40 I LK-I L Resnant Inductr Current (A) 20 0 M3 M4 I L Near zer vltage M M Resnant Capacitr Vltage Fig.5 Sft Switching State-Plane Trajectry Sft Switching Cntrl scheme I L * + - i e PI PWM Main Pulse T aux Timing I L Delay Fig.6 Sft switching cntrl scheme T d B. Selectin f Resnant Frequency Resnant frequency is the main factr t reduce the current stresses f rectifier dides and cnductin lsses. Which is decided by leakage inductance and rectifier capacitance. The resnance frequency shuld be lwer than switching frequency f r f s 3 f r 2 L C 4

8 26 V. Delbin Jelaja and Dr. M. Rajaram Leakage inductance is nt adjustable withut an additinal leakage inductance we can select the rectifier. Capacitance, using the equatin C C 2 n 2 8 L 2 Fs 2 f f s r 2 5 C. Selectin f Ultra Capacitr The ultra capacitr system installed in an electric vehicle uses a high specific pwer brushless dc mtr with a nminal pwer f 32kw and has a peak pwer f 53 kw. The ultra capacitr vltage is cntrlled thrugh the variables such as vehicle speed and the state-f-charge f the battery. Fig. shws the ultra capacitr charge curve. This curve is pltted accrding t the time needed by the cntrl t stre the right amunt f energy int the ultra capacitr bank. The amunt f energy stred in the ultra capacitr is accrding t the car speed and battery state-f-charge. Suppse if the battery is fully charge nly small amunt f energy stred in the ultra capacitr bank. Frm this diagram the ultra capacitr level f energy (r) charge is calculated thrugh electric vehicle speed (ie. car speed) and the battery state f charge (battery % DOD). The higher the speed, lwer the charge and the higher the battery state-f-charge, the lwer the charge t. The shape f the kinetic energy curve is estimated thrugh the f vehicle is prprtinal t square f speed and the time the cntrl takes t reach the desired ultra capacitr charge. The capacitance value is selected usually accrding t the vltage ripple level, which is usually less than % f utput vltage (V 0 ). Hence the capacitance can be determined as I0DmaxTs C 20 farad ultra capacitr bank V % Fig.7 Ultra capacitr charge curve

9 Sft Switching Full Bridge DC-DC Cnverter fr Electric Vehicle Applicatin 27 D. Design f Leakage Inductance A high turns rati result in higher leakage inductance that causes a severe vltage stress acrss the rectifier dides and increases pwer lss. When n 2 >n, current ripple f the leakage inductance will increase. Since a larger current ripple will result in larger cre lss in the leakage inductance, a high turns rati is nt desirable. In this study we chse n=2 L n 2D 2 max i V ripple f s 7 IV Simulatin Results Fig shws the simulated results f the prpsed cnverter. The requirements f high pwer in car is btained with the help f vltage dubler circuit. This is depicted in Fig. Due t the resnance between leakage inductance f the transfrmer and vltage dubler capacitrs, high vltage stress develped acrss the vltage dubler circuit. This is eliminated with the help f cnductin f clamping dide. With the help f clamping dide and ultra capacitr bank we can btain ripple free utput vltage. That is als depicted in fig. (a) (b)

10 28 V. Delbin Jelaja and Dr. M. Rajaram (c) (d) (e)

11 Sft Switching Full Bridge DC-DC Cnverter fr Electric Vehicle Applicatin 29 (f) (g) Fig.8 Experimental wavefrms f the prpsed cnverter (a-d) Gate Pulses (e) Transfrmer Primary Vltage(f) Transfrmer Secndary Vltage (g) utput vltage f the prpsed circuit (a)

12 30 V. Delbin Jelaja and Dr. M. Rajaram (b) Fig.9 Zer-Vltage Switching Wavefrms f leading leg Switches(a) turn-ff vltage (b) turn-ff current Efficiency (%) Output pwer (Watts) Cnventinal mdel Prpsed mdel Fig.9 Efficiency cmparisn with respect t cnventinal mdel V. CONCLUSION A hybrid energy strage unit cmprising zebra battery, sft switching full bridge DC-DC cnverter and ultra capacitr bank. Seems t be the prmising chice fr future electric drive vehicles. The purpse f the device is t allw higher acceleratins and deceleratins f the vehicle with minimum lss f energy and minimum degradatin f the battery pack. It is als having the advantage f nt using any inductr in the cnverter. This will increase the pwer density. Efficiency cmparisn is als pltted with cnventinal circuits. This will als depicts the imprvement f efficiency in the prpsed cnverter.

13 Sft Switching Full Bridge DC-DC Cnverter fr Electric Vehicle Applicatin 3 REFERENCES [] Eung-H Kim and Bng-Hwan, Kwn, Zer-vltage and zer-currentswitching full-bridge cnverter with secndary resurce, IEEE Trans. Ind. Electrn., vl.57, n.3, March 200. [2] J.G. Ch, J.A. Sabate, G.C. Hua and F.C Lee, A Primary-side-assisted zer-vltage and zer-current-switching full bridge PWM cnverter fr high pwer applicatin. IEEE Trans, Pwer Electin, vl.2 n.4, pp , July 996. [3] C.C. Chan and Y.S. Wna, Electric Vehicles Charge frward, IEEE Pwer Energy Mag., vl.2, n.6, pp.24-33, Nv/Dec [4] S.K. Han, T.S. Kim, GW. Mn and M.J. Yun, High efficiency active clamp frward cnverter fr sustaining pwer mdule f plasma display panel, IEEE Trans. Ind. Electrn, vl. 55, n.4, pp , Apr [5] K. Ruan and Y. Yam A nvel zer-vltage and zer current switching PWM full-bridge cnverter using tw dides in series with the lagging leg. IEEE Trans. Ind. Electrn. vl.48, n.4 pp , Aug [6] W. Jin Lee. Gun-W Mn, A New Phse-shifted Full-bridge cnverter with vltage Dubler Type Rec fr high efficiency PDP sustaining pwer mdule, IEEE Trans. Ind. Electrn. vl.55, n.6, June [7] Mrten and Michael A.E. Andersen, High-efficiency Islated Bst DC- DC Cnverter fr High-Pwer Lw-Vltage Fuel-Cell Applicatins, IEEE Transactins n Ind. Electrn. vl.57, n.2, February 200. [8] T.W. Ching, Sft-switching Cnverters fr Electric Vehicle Prpulsin, Jurnal f Asian Electric Vehicles, vl.5, n.2, Dec [9] A.F. Burke, Batteries and ultracapacitrs fr electric, hybrid and fuel cell-vehicles, Prc. IEEE, vl.95 n.4, pp , Apr [0] J.W. Dixn, M. Ortuzar, and E. Wiechmann, Regenerative braking fr an electric vehicle using ultracaacitrs and a buck-bst cnverter, in Prc. EVS8, Berlin, Germany, Oct. 200, p.48. [] J.W. Dixn and M. Ortizar, Ultracapacitrs + DC-DC cnverters in regenerative braking system, IEEE Aemsp. Electrn, Syst. Mag. vl.7, n.8, pp.6-2, Aug [2] Xinke Wu, Junming Zhang, Xin Ye and Zhaming Qian, Analysis and Derivatins fr a Family ZVS Cnverter Based n a New Active Clamp ZVS Cell, IEEE Trans. On Ind. Electrn. vl.55, n.2, Feb [3] H. Ta, A. Ktspulus, J.L. Durate and M.A.M. Hendrix, Transfrmer-cupled multiprt ZVS bidirectinal dc-dc cnverter with wide input range, IEEE Trans. Pwer Electrn, vl.23, n.2, pp.77-78, Mar [4] H.K. Yn, S.K. Han. J.S. Park, G.W. Mn and M.J. Yun, Zervltage switching tw-transfrmer full-bridge cnverter with lssless dide-clamp rectifier fr PDP sustain pwer mdule, IEEE Trans. Pwer Electrn, vl.2, n.5, pp , Sep.2006.

14 32 V. Delbin Jelaja and Dr. M. Rajaram [5] L.Shigu, Q. Weihng, W. Wenkai and I. Batarseh, Flybst pwer factr crrectin cell and a new family f single-stage AC/DC cnverters, IEEE Trans. Pwer Electrn. Vl.20, n., pp.25-34, Jan Authrs infrmatin V. Delbin Jelaja received his B.E degree in Electrical and Electrnics Engineering frm C.S.I Institute f Technlgy, Thvalai, Tamil Nadu India, in 2003 and thereafter, she did her M.E. degree in Pwer Electrnics and Drives frm Gvernment Engineering Cllege, Tirunelveli, Tamil Nadu, India in the year She is presently a research Schlar at Anna University Tirunelveli. Her area f interest is Electrical Engineering, Pwer Electrnics, which includes sft switching in electric vehicles and high pwer Applicatins. Dr. M. Rajaram, Vice Chancellr Anna University f Technlgy, Tirunelveli, Tamil Nadu, India. He cmpleted his B.E. Degree (Electrical and Electrnics Engineering) at Alagappa Chettiar Cllege f Engineering and Technlgy, Karaikudi in 98, M.E. Degree (Pwer Systems) at Gvernment Cllege f Technlgy, Cimbatre, in 988 and Ph.D (Cntrl Systems) at PSG Cllege f Technlgy, Cimbatre in 994. He has successfully supervised Ph.D and M.S (by Research) Schlars wh are awarded with the Dctral Degree and 0 candidates are pursuing Ph.D under his guideship at present. T his recrd he has published his Research findings in 75 Internatinal Jurnal/Natinal Jurnals, 6 Internatinal Cnferences and 53 Natinal Cnferences. He has als authred 6 Text Bks, which the Engineering students find infrmative and useful. He is a life member f ISTE and MIE and an AICTE Expert member and the Chairman in granting affiliatin t Engineering Clleges and Plytechnics.