Design of Sinusoidal Current Charger with Optimal Frequency Tracker for Li-ion Battery

Transcription

1 Design of Sinusoidal Curren Charger wih Opimal Frequency Tracker for Li-ion Baery Liang-ui Chen*, Shing-Lih Wu*, Chung-Ping Chou,** and Tsair-ong Chen* * Naional Changhua Universiy of Educaion, Deparmen of Elecrical Engineering, Changhua Ciy, Taiwan OC ** Naional Taiwan Police College, Deparmen Disaser Managemen,Taipei Ciy, Taiwan OC Absrac In his paper, a sinusoidal curren charger (Sin-CC) wih opimal frequency racker is proposed for Li-ion baery. The proposed opimal frequency racker is mainly consruced by he phase-lock-loop so ha he feaures of deecing, racking and locking in he opimal charging frequency can be achieved. The experimenal resuls show ha he charging speed charging efficiency and increasing surface emperaure of he proposed Sin-CC are improved abou 5%, 5.5% and 51.5%compared wih ha of he convenional consan curren charge sysem. Index Terms Opimal charging frequency, Li-ion baery, Tracker, Phase- locked -loop, I. INTODUCTION As renewable energy, elecrical ransporaion sysem and porable apparauses have developed rapidly in hese years. The baery charging echnique becomes more and more imporan. Nowadays, many baery charging echniques, such as he consan rickle curren (CTC) charge, he consan curren (CC) charge, and he consan curren and consan volage (CC-CV) charge are proposed. Among hem, he CC-CV is used mos widely, bu is performance is sill no able o mee he users needs [1], [2]. Consequenly, he fuzzy conrol, neural nework, geneic algorihms, an algorihms, and grey predicion are applied o obain beer baery charging performance [3]-[6]. Unforunaely, he inelligen baery charger has wo disadvanages, is complicaed circui and is expensive cos. Hence, he phase-locked-loop echnique is adoped o achieve he purpose of high performance and low cos [7]-[9]. ecenly, advanced baery charging sysems have used he pulse curren/volage paern o obain an evener disribuion of ions in he baery elecrolye o advance he charging performance [9]-[14]. In his ype of pulse charging sysem, he charging frequency affecs he baery charging performance. Tradiionally, he experience mehod and he rial-and-error mehod are adoped o deermine he suiable charging frequency. However, he way we can decide he suiable charging frequency is no explored. In order o find he opimal pulse frequency, differen frequency pulses wih he same ampliude are sequenially applied o he baery, and he average currens are measured a he same ime. Then, he opimal frequency wih he maximum average charging curren can be found [15]. In addiion, he opimal duy cycle for charging Li-ion baery is also presened [16]. ecenly, analyzing 1 he relaionship beween he AC impedance of a baery and is charging performance has been explored [17]. The opimal charging frequency o obain maximum energy ransfer efficiency (i.e., bes elecrochemical reacion) can be obained by analyzing he AC impedance of a Li-ion baery. The opimal charging frequency is he minimum AC impedance frequency f Z min [17]. In addiion, he minimum AC impedance frequency fz min is almos same as he resonan frequency f r. Therefore, a sinusoidal curren charger(sin-cc)wih opimal frequency racker is proposed in his paper. In he proposed sysem, a phase locked loop ( PLL ) is used o auo-racking and auo-locking he frequency f r o implemen he opimal frequency racking funcion. The experimenal resuls show ha he charging speed charging efficiency and increasing emperaure of he proposed Sin-CC are improved abou 5%, 5.4% and 51.5% compared wih ha of he convenional consan curren charge sysem. II. AC IMPEDANCE ANALYSIS The AC impedance echniques have been widely used in he las decades for exploring elecrochemical sysems. Fig. 1(a) shows he AC impedance model for a Li-ion baery ha consiss of an anode inducance L a, a cahode inducance L c, an anode capaciance C al, a cahode capaciance C cl, wo Warburg impedances Zaw and Z cw, an anode-elecrolye reacion resisance al, a cahode-elecrolye reacion resisance cl, and an ohmic resisance o [18]. The ohmic resisance o is aribued o he elecrode geomery, he elecrolye resisance, he separaor, and he connecions. The elecrode-elecrolye reacion resisances al and cl are represenaions for charge ransfer impedances in elecrode-elecrolye inerfaces. Warburg impedances Z aw and Z cw are due o ion diffusion in elecrolye C al and C cl. The capaciances Cal and C cl represen he capaciances on boh elecrode-elecrolye inerfaces. The inducances L d and L c are aribuable o he elecrodes geomery and he connecions. The baery impedance Z AC can be described as he sum of he ohmic resisance o and he impedances Za and Z c shown as

2 Z = Z + + Z (1) AC c o a Z Then a baery model can be consruced by an AC impedance Z AC and an ideal baery as shown in Fig. 1(b). In elecrical circui view, i is possible o find a frequency fz min o minimize he baery impedance Z AC o reduce he energy loss in baery impedance Z AC. I means ha he energy loss in elecrical energy ransfer o chemical energy is minimized. In he proposed Sin-CC, he frequency of he charge frequency is varied o keep he baery impedance Z AC a a minimum o effecively keep he elecrochemical reacion in he bes sae. When a Li-ion baery is charged by he minimum AC impedance frequency f Z min, he charging ime, charging efficiency, and increased emperaure are grealy improved. This indicaes ha he opimal charging frequency of a Li-ion baery is is minimum AC impedance frequency f Z min. Zc Ccl Cal Za? 0 Hz fr Hz Fig.2 A ypical Li-ion baery AC impedance Bode plos Lc cl Zcw o (a) Z AC (b) al Zaw La Ideal Baery Ideal Baery Fig.1 (a) Li-ion baery AC impedance model, (b) simplified Li-ion baery equivalen circui model Fig. 2 shows a ypical baery AC impedance Bode plo. From Fig. 2, we can clearly see ha he baery lowes impedance is almos locaed a he resonan frequency f r ( i.e., phase angle is 0 ). Therefore, PLL can be used o deec he resonan frequency o indirecly know he opimal frequency for charging Li-ion baery. III. SYSTEM DESCIPTION Fig.3 shows he Sin-CC block diagram. The sysem has he funcions of auomaically deecing and racking he opimal baery charging frequency. The proposed Sin-CC consiss of a frequency-conrolled sinusoidal curren source (FC-SCS), a high-pass filer, and he a PLL. The operaion principle of he proposed Sin-CC is described as follows. Firs, he baery volage V b is sen o he high pass filer (HPF)Ⅰo filer he DC componen volage V b, dc o obain he AC componen volage as shown Fig. 4(a).A he same ime, he charge curren I C() is also sen o he HPFⅡ o obain is AC componen as shown in Fig. 4(b). Then, he AC componens of baery charging volage and he baery charging curren are sen o he phase comparaor. Afer ha, he phase error pe beween he wo inpu phases is produced and sen o he VCO. Finally, he VCO frequency f o is changed according o he phase error p e. Thus, he frequency of he frequency-conrolled sinusoidal curren source o uned o ensure he baery charge volage and curren in phase and hen baery is charged a he opimal frequency. As shown in Fig. 4(c), he charging frequency of he proposed Sin-CC is no he opimal frequency and a phase error p e exis. According o he phase error θ e he PLL adjuss he baery charging frequency so ha he baery volage and curren in phase as shown in Fig. 4(d). Therefore, So he Li-ion baery is charged a he opimal frequency during charging sae. Frequency-Conrolled Sinusoidal Curren Source vb HPFⅠ HPF Ⅱ v b,ac IC() fv Phase Comparor f i f VCO o pe 2 Fig. 3 Sysem block diagram of he proposed Sin-CC

3 V b = + V b,dc V b,dc he VCO oupu square wave signal is convered ino sinusoidal volage V S() by he waveform conver shown as VS () = Vm + Vm sin 2πf o (1) (a) were V m is peak volage, and f o is charge frequency. Second, he sinusoidal volage V S() is convered ino he sinusoidal charge curren IC() hrough he volage/curren converer o charge he baery shown as (b) VS() V V sin 2 f I m + m π o C() = = (2) Vb,ac I C () I C () (c) (d) were is curren limied resisor. Then, he HPF and he zero-crossing deecor are used o conver sinusoidal singles of baery volage and curren o square single. And hese wo signals are sen o he phase comparaor and produce a phase errorθ e. Vcc Frequency-Conrolled Sinusoidal Curren Source Waveform converer Vs() + OP - A I C () MOSFET Baery Q + v b,ac v b,ac + V b,dc High pass filer _ fo Zero-crossing deecor Volage conrolled oscillaor C fi Zero-crossing deecor f v Phase comparaor Phase Locked Loop, MC4046 Fig. 4 A waveforms of he Sin-CC IV. DESIGN EXAMPLE In order o verify he feasibiliy and superioriy of he proposed Sin-CC, a pracical design example for SANYO mAh Li-ion baery, labeled as baery A, is designed and implemened. Fig. 5 shows he circui diagram for his prooype. This prooype conains a FC-SCS, a high-pass filer, wo zero-crossing deecors, and a PLL. The FC-SCS is made up of a volage/curren converer and a waveform converer. The volage/curren converer of he circui is made up of an OPA, a MOSFET, and a resisor. The volage/curren converer s main purpose is o conver he volage ino curren. The waveform converer is used o conver he square charging single ino he sinusoidal charging curren. The high-pass filer circui is consiued of resisors and capaciors. I is o filer he DC componen volage V o obain he b, dc AC componen volage. The zero-crossing deecor including he Schmi circui is o conver he sinusoidal volage and curren signals ino square wave signals. MC4046 PLL IC is used o rack he opimal charging frequency o keep he baery in bes elecrochemical reacion. The circui operaion is described as follows: Firs, 3 Fig. 5 Circui diagram of he proposed Sin-CC According o he phase errorθ e, VCO can change he oupu frequency o adjus he FC-SCS baery charging frequency. So when he PLL is in-locked, he circui operaes a he resonan frequency f r. This means ha he proposed Sin-CC can charging he Li-ion baery wih resonan frequency f r o improve he charging performance. When he baery AC impedance changes, he Sin-CC also changes he charging frequency. So he PLL is coninuously used o rack he baery's volage and curren phase and make i a he same phase which will be able o make he circui always operae on he resonan frequency unil Li-ion baery is fully charged up. V. EXPEIMENTAL ESULTS As shown in Fig. 6, i is he waveform of he baery volage V b which conains he DC componen volage Vb,ac 2.8V and AC componen volage V b, ac. As shown in Fig. 7, he frequency charging is no a he opimal charging frequency. The phase error θ e occur beween

4 he baery volage b, ac I C (). As shown in Fig. 8, he frequency charging is a he opimal charging frequency. The phase error θe is zero beween he baery volage Vb, ac and he charging curren I C(). baery charging speed of he proposed Sin-CC is faser abou 8% han ha of he CC. Also from Fig.10, we can see ha he surface emperaure of he baeries charged by he proposed Sin-CC and he ypical CC are 25 and 30, respecively. This indicaes ha increasing surface emperaure of baery are 4.6 and 9.5. Obviously, he increasing surface emperaure of baery charged by he proposed Sin-CC is reduced abou 51.5% han ha charged by CC. This means ha hermal deeriaion can be grealy improved, and hen he life of a Li-ion baery can be exended by using he proposed Sin-CC [22]. Fig. 6 The baery volage V b and charging curren I C() waveforms (CH2:2V/div CH4:1A/div) Fig. 9 The charging ime of he Sinusoidal curren charger wih consan curren (CC) charging Fig. 7 The waveforms of he small signal volage Vb, ac of he no opimal frequency recharging baery and charging curren I C() (CH2:200mV/div CH4:1A/div) Fig. 8 The waveform of he small signal volage V b, ac and he baery charge curren I C() (CH2:2V/div CH4:1A/div) In order o verify he charging performance of he proposed Sin-CC, a ypical CC baery charger is also conduced o be compared. Figures 9 and 10, and TableⅠ show he experimenal resuls. Fig.9 shows he charging ime curve of he proposed Sin-CC and he ypical CC. From Fig.9, we can see ha he charging imes of he proposed Sin-CC and he ypical CC are 162 minues and 176 minues, respecively. Obviously, he Fig. 10 Sinusoidal curren charger wih consan curren (CC) charging of he baery surface emperaure Table Ⅰ shows he experimenal daa of capaciy, discharge capaciy, and efficiency under boh he proposed Sin-CC and he ypical CC mehods. According o Table Ⅰ, we can see ha he charge capaciy of he proposed Sin-CC and ypical CC are respecively 1.35Ah and 1.46Ah. The charge capaciy of he proposed Sin-CC is comparaively smaller. As o he baery discharge, we use 2A consan curren baery discharge in his experimen. The discharge capaciy of he proposed Sin-CC and he ypical CC are same as 1.33Ah. We can calculae he baery charging efficiency according o he baery charging efficiencies of he proposed Sin-CC and ypical CC are 98.5% and 91.1%, respecively. Compared wih he ypical CC, he baery charging efficiency is improved abou 7.5%. To sum up, using he proposed Sin-CC wih he opimal charging frequency o charge a Li-ion baery, he charging ime, he charge efficiency and increasing surface emperaure are obviously baer han ha of he ypical CC. 4

5 Table I Experimenal resuls of Tes Baery A Sin-CC CC Charging Capaciy(Ah) Discharging Capaciy(Ah) Baery Charging Efficiency (%) Fig13. AC impedance plo of es baery C Fig11. AC impedance plo of es baery A Figure 11 is he AC impedance Bode plos of he es baery. We can easy see ha he resonan frequency f r of he esed baery A is 1KHz and is AC impedance value is abou 0.329Ω. In order o reconfirm he amazing charging perform, wo single cell SANYO mAh Li-ion baeries, labeled Baery B and Baery C, are also adaped o be verified. Figs. 12 and 13 show he AC impedance plos of Baeries B and C. We can see ha he resonan frequency f r of he Baeries B and C are 750Hz and 707Hz, respecively. Is AC impedance values are abou 0.15Ω and 0.21Ω, respecively. The experimenal resuls for Baeries B and C, are lised in Tables and III. I is clear ha he charging speed and he charging efficiency of a Li-ion baery charged by he resonan frequency fr are much beer han hose of a Li-ion baery charged by CC. From Tables II, we can see ha he charging imes of he proposed Sin-CC and he ypical CC are 162 minues and 170 minues, respecively. Obviously, he baery charging speed of he proposed Sin-CC is faser abou 5% han ha of he CC. We can calculae he baery charging efficiency according o he baery charging efficiencies of he proposed Sin-CC and ypical CC are 98.5% and 93.6%, respecively. From Tables III, we can see ha he charging imes of he proposed Sin-CC and he ypical CC are 163 minues and 172 minues, respecively. Obviously, he baery charging speed of he proposed Sin-CC is faser abou 5% han ha of he CC. We can calculae he baery charging efficiency according o he baery charging efficiencies of he proposed Sin-CC and ypical CC are 95.5% and 90.3%, respecively. I is ineresing ha differen Li-ion baery has differen resonan frequency f r. However, he bes charging performance of a Li-ion baery always occurs a resonan frequency f r. This means ha he opimal charging frequency of a Li-ion baery is is resonan frequency f r, and he proposed Sin-CC can auo rack i. Table II Experimenal resuls of Tes Baery B Sin-CC CC Charging Capaciy(Ah) Charging Time (min) Discharging Capaciy(Ah) Baery Charging Efficiency (%) Fig12. AC impedance plo of es baery B 5

6 Table III Experimenal resuls of Tes Baery C Sin-CC Charging Capaciy(Ah) CC Charging Time(min) Discharging Capaciy(Ah) Baery Charging Efficiency (%) VI. CONCLUSION In his paper, a sinusoidal curren charger(sin-cc)wih opimal frequency racker is successfully proposed for Li-ion baery. The proposed opimal frequency racker is mainly consruced by he phase-lock-loop so ha he feaures of deecing, racking and locking in he opimal charging frequency can be achieved. In order o verify he performance of he proposed Sin-CC are improved abou 5%,5.4% and 51.5% compared wih ha of a ypical consan curren charge sysem. eferences funcion, IEEE Trans. Ind. Elecron., vol. 55, no. 8, pp , Aug [15] L.. Chen, A design of opimal pulse charge sysem by variable frequency echnique IEEE Trans. Ind. Elecron., vol. 54, no.1, pp , Feb [16] L.. Chen, Design of Duy-Variedn Pulse Charger for Improving Li-ion Baery-Charging esponse," IEEE Trans. Ind. Elecron., vol. 56., no. 2., pp , Feb [17] L.. Chen, S. L. Wu, T.. Chen, W.. Yang, C. S. Wang and P. C. Chen, Deecing of opimal Li-ion baery charging frequency by using AC impedance echnique Proc. 4h IEEE Inernaional Conference on Indusrial Elecronics and Applicaions (ICIEA)., May [18] J. Zhang, j. Yu, C.Cha, and H. Yang, The effecs of pulse charging on inner pressure and cycling characerisics of sealed Ni/MH baeries, J.power Sources., vol. 136,no. 1, pp , Sep [19]. Shalini, N.Munichandraiah and A.K. Shukla, AC Impedance and sae-of-charge analysis of a lihium-ion rechargeable baery, J Solid Sae Elecrochem., pp , Feb [20]. M. Sponiz, AC impedance simulaion for lihium-ion cells, in Proc. 35 h In. Power Sources Symp., pp , Jun. 1992, [21] D. Qu, The ac impedance sudies for porous MnO 2 cahode by means of modified ransmission line model, J. Power Sources, vol. 102, pp , Dec [22] Anna M. Andersson, Krisina Edsro m, and John O. Thomas, Characerisaion of he ambien and elevaed emperaure performance of a graphie elecrode Journal of Power Sources., vol.81, no. 82, pp Jan [1]. C. Cope and Y. Podrazhansky, The ar of baery charging, Proc. 14h Baery Conf. on Applicaions and advance., Long Beach, CA., Jan. 1999, pp [2] J. J. Chen, F. C. Yang, C. C. Lai, Y. S. Hwang, and.g. Lee, "A high-efficiency mulimode Li-ion baery charge wih variable curren soure and conrolling previous-sage supply volage," IEEE Trans. Ind. Elecron., vol. 56, no. 7, pp , July [3] Z. Ullah, B. Burford, and S. Dillip, Fas inelligen baery charging: neural-fuzzy approach, IEEE Aerospace and Elecron. Sys.Magazine., vol. 11, iss. 6, pp , June [4] G. C. Hsieh, L.. Chen and K. S. Huang, Fuzzy-conrolled Li-ion baery charge sysem wih acive sae-of-charge conroller, IEEE Trans. Ind. Elecron., vol. 48, no. 3, pp , June [5] Y. H. Liu, J. H. Teng, and Y. C. Lin, "Search for an opimal rapid charging paern for lihium-ion baeries using an colony sysem algorihm," IEEE Trans. Ind. Elecron., vol. 52, no. 5, pp , Dec [6] L.. Chen,. C. Hsu and C. S. Liu, A design of a grey-prediced Li-ion baery charge sysem, IEEE Trans. Ind. Elecron., vol. 55, no. 10, pp , Oc [7] L.. Chen, PLL-based baery charge circui opology, IEEE Trans. Ind. Elecron., vol. 51, pp , Dec [8] L.. Chen, C. S. Liu, and J. J. Chen, Improving phase-locked baery charge speed by using resisence-compensaed echnique," IEEE Trans. Ind. Elecron., vol. 56., no. 4., pp , June [9] L.. Chen, J. J. Chen, N. Y. Chiu and J. Y. Han, Curren-pumped baery charger," IEEE Trans. Ind. Elecron., vol. 55., no. 6., pp , June [10] P. H. Cheng and C. L. Chen, High efficiency and nondissipaive fas charging sraegy, IEE Proc.-Elecr. Power Appl., Vol. 150, No. 5, pp , Sep [11] J. Díaz, J. A. M. amos, A. M. Pernía, F. Nuno, and F. F. Linera, Inelligen and universal fas charger for Ni-Cd and Ni-MH baeries in porable applicaions, IEEE Trans. Ind. Elecron., vol. 51, iss. pp , Aug [12] Z. Jiang and. A. Dougal, Synergeic conrol of power converers for pulse curren charging of advanced baeries from a fuel cell power source, IEEE Trans. Power Elecron., vol. 19, no. 4, pp , July [13] H. J. Chiu, L. W. Lin, P. L. Pan, and M. H. Tseng, A novel rapid charger for Lead-Acid baeries wih energy recovery, IEEE Trans. Power Elecron., vol. 21,no. 3, pp , May [14] L.. Chen, N. Y. Chu and C. S. Wang, Design of a reflex-based bidirecional converer wih he energy recovery 6