Designing of Higher Order DC-DC Converter

Transcription

1 Deigning of Higher Orer DC-DC Converter DURGESH SARANKAR, ASHISH KUMAR SHINGHAL, Department of Electrical Engineering, Sagar intitute of cience, Technology an Engg. Bhopal, Inia Abtract -- A two-input DC-DC converter uitable to raw more power from two ifferent c ource feeing a common c-loa i preente in thi paper. Thi multiwitch converter belong to higher-orer family an perform bucking an booting action. The alient feature of the propoe converter i that both the ource either iniviually or imultaneouly upply power to the owntream loa at reuce ripple current. Thi feature i particularly attractive for c gri application. A igital voltage-moe controller i eigne for owntream c-bu regulation while the current controller regulate the power from the weak input power ource. I. INTRODUCTION Switch-moe power converter application in the c power itribution i increaing in the recent year. Particularly in the area of automotive ytem the main focu i on hybri vehicle. A the power converion ytem i becoming miniaturize, increaing the power enity i one of the challenging iue for the power upply eigner. One of the main orientation in power electronic in the lat ecae ha been the evelopment of witching-moe converter with higher power enity an low electromagnetic interference. Light weight, mall ize an high power enity are alo ome of the key eign parameter []- []. Several ifferent type of witch-moe c-c converter, belong to buck, boot an buck-boot topologie, have been evelope an reporte in the literature to meet variety of application. Major concern in the recent c itribution ytem, uch a in automotive an telecom power upply ytem, i to meet the increae power eman an reucing the loa on the primary energy ource, i.e. built-in battery. Thi i poible by aing aitional power ource in parallel to the exiting battery ource. The aitional power ource can be: (i) renewable energy ource uch a photovoltaic (PV) or win, (ii) fuel cell torage power. Power ource upplementing other reource are normally categorize a hybri power ource an the correponing cheme i calle hybri itribute generation ytem. Integration of renewable energy ource to form a itribute generation ytem i a viable option for the hybri vehicle, automotive inutrie an even in remote tan-alone power upply ytem. In orer to efficiently an economically utilize renewable energy reource it i neceary to tap the energy a an when it i available an then tore for ubequent utilization. Nowaay, electric ouble layer capacitor are coming up in the energy torage ytem in aition to the conventional battery ytem. However, in all thee cae the power converion efficiency an it control i major challenge for the power upply eigner. The efficiency improvement with higher power enity, from the teay-tate point of view, of the itribute energy generation i one of the conieration for the eigner. The other contraint while eigning uch ytem i to evolve imple an reliable power control trategy. To are ome of the above iue, multi-input converter, with ifferent topology combination, are evolving. Although everal power converion topology configuration can eaily be evelope, but an integrate converter with bucking, buck-boot feature i eire in mot of thee cheme. To thi affect, there i not enough literature covering the evelopment of converter an control cheme for uch application. Furthermore, literature covering eign apect of igital controller for uch kin of converter i alo limite. In orer to brige thi gap, a new two-input c-c converter i propoe in thi paper an then igital controller have been eigne to enure c-bu voltage regulation together with power itribution control of the input c power ource. IRE 77 ICONIC RESEARCH AND ENGINEERING JOURNALS 6

2 () imple control trategy, with or without overlap of uty ratio ignal, a there are only two witching evice nee to be controlle. Fig.. Two-input c-c converter circuit iagram. Several compenator eign approache have been reporte in the literature for Op-Amp or IC bae analogue controller. However, in the cae of igital controller eign, two main approache are wiely ue, that i: (i) igital reeign metho (DRM), (ii) irect igital eign metho (DDDM). In the firt cae, the compenator i eigne in the conventional way by uing -omain tranfer function together with linear ytem theory an the reulting compenator i tranforme into the igital omain uing appropriate z-tranformation. On the other han, in DDDM, the compenator eign i carrie out in the z-omain itelf an hence there i no nee for -to- z-omain tranformation. In view of thee feature here DDDM i ue for the robut igital controller eign. II. MODELING OF TWO-INPUT DC-DC CONVERTER The propoe two-input c-c converter, hown in Fig., ha two witching evice, ix energy torage element an hence it form a ixth-orer ytem. In the power converion proce it perform bucking operation for one c ource, buck-boot converion for the econ ource. It ha the following alient feature (a) both the c ource are upplying continuou current an hence their ripple current i low, (b) leer filtering requirement on the input ie, (c) automatic loa tranfer on to the firt c ource if the econ c ource capacity, weak ource with limite power upplying capacity, i le than the loa eman, an The circuit can operate either in continuou or icontinuou inuctor current moe. But, the propoe converter i mainly for higher loa power requirement, where one c ource unable to meet the complete loa eman an hence the inuctor current are almot all the time are continuou. In view of thi the converter i analyze here for continuou current moe of operation. Here the circuit operation alo epen on the type of controlling ignal ue for witching evice S an S, an the two witching evice, (S an S ), can be ynchronize either with trailing-ege or leaing ege operation. Each of thee cheme ha their own avantage an limitation an etaile icuion on the uitability an application requirement will be icue in the final paper. Furthermore, epening on the loa eman an available power with each c ource three ifferent cae will arie, which are: (i), (ii), (iii). In the firt two cae the circuit unergoe three ifferent tructural change, while in the lat cae only two ifferent operating moe in one witching cycle. In thi paper the cae i analyze for the trailing-ege ynchronize witching ignal. Loa voltage i controlle by the both the witch uty ratio ignal an alo epen on both input c ource. The analyi of the remaining two ifferent cae i quite imilar to one preente in thi paper. For cae the witching equence in one witching cycle i: (i) moe-: S an S both ON, (ii) moe-: S -ON an S -OFF, (iii) moe-: Dioe- ON. In each moe of operation the power tage ynamic can eaily be ecribe by a et of tate equation given by: x A x B u v K C x K k () T c c c Where x i i i v v v, T uv V, g g an k=,, for moe-, moe- an, repectively. Detail of variou matrice will be IRE 77 ICONIC RESEARCH AND ENGINEERING JOURNALS 7

3 given in the final paper. The mall-ignal icretetime moel [] can be written a: ˆ xˆ n xˆ n n () The output tate-pace equation can be written a follow: yˆ n C xˆ n. () i In c-c converter two ifferent pule-withmoulation cheme are wiely ue, which are: trailing-ege an leaing ege-moulation. In thi paper, trailing-ege OFF-time ampling with a ampling frequency f (=/T ), a hown in Fig., i implemente an it etaile mathematical analyi i icue in the following paragraph. From Fig. over interval-: n- <t< n- T T t T, the ytem tate equation can eaily be written a x A x (4) Auming the ource voltage i almot contant uring each moe of operation of the witching cycle, the icrete-time moel with tate x[(n-)t ] at the beginning [5] an uty ratio can eaily be efine by A tt n- x T t T e x n T (5) Along imilar line, the icrete-time moel for the remaining time interval are etablihe a Iinterval-: n- <t< n- T t T T t, n- x T t T T A T e e e x n T K T e ˆ (7) A T T A t T AT Interval 4: n- T t T T <t< nt A T T t T A t T AT A T x nt e e e e x n T A T ˆ K T e e K T e ˆ (8) A T T t T A T T t T The mall-ignal icrete-time moel in tanar form for the converter uner icuion can be written a: ˆ ˆ xˆ nt ˆ x n T n T n T (9) Comparing eqn. (8) & (9), it i eay to obtain e AT, A T T t T K Te, A T T t T AT K Te e, K A A x B B U, K A A x B B U. Taking the z-tranform of eqn. (4), x z zi z z () A T n- A t T Taking the z-tranform of equation (8) reult in x T t e e x n T t T y( z) Ei x( z) () (6) Interval-: n- T t <t< n-t t T T Combining eqn. (9) an () reult in y( z) E zi z E zi z. () i i IRE 77 ICONIC RESEARCH AND ENGINEERING JOURNALS 8

4 i Fig. 4. Boe plot of voltage an current loopgain (LGV: Voltage loop, LGI: Current loop). T T T T i PWM PWM A elay greater than T, t =(kt +t ) can be taken into account by replacing ˆ n with ˆ n k, t with t, an the correponing icrete-time moel i: t M M M M4 (n-)t T nt Sampling Intant Fig.. PWM gating ignal an Off-Time ampling proce. (n+)t ˆ x nt x n T n k T ˆ n k T () Taking the z-tranform of eqn. () reult in v _ref i g _ ref T ( ) cv z T ( ) cc z ˆ ( z) Converter mall-ignal moel ˆ ( z ) G ( z) G ( z) G ( z) G ( z) vˆ ( z) iˆ ( z) g k k x z z zi z z zi z (4) The above equation ecribe the mall-ignal ynamic of the propoe converter, with the converter tate variable epening on the two control variable, an. In orer to eign uitable control trategie bae on an, it i eential to know the egree of interaction between the control loop. Detail of control loop interaction uing relative gain array theory an loop eign apect will be icue in the final paper. III. DIGITAL CONTROLLER DESIGN Fig.. Block iagram of the cloe-loop converter ytem. Magnitue (B) Phae (eg) Boe Diagram Gic(z) Converter Loopgain Loopgain Gi(z) Compenator Gi(z) Compenator Gic(z) Converter -7 Frequency (Hz) 4 5 Several ifferent type of control trategie are reporte in literature, an they are broaly claifie into: (i) ingle-loop voltage-moe, (ii) ingle-loop current-moe, (iii) two-loop current moe control, an (iv) multi-loop cheme. Although the ingle-loop trategie are imple to implement, but their ynamic repone time are lightly higher ie. Although twoloop current-moe cheme are popular in the power upply application, but their compenator eign preent complexity. In thi paper two ecouple control cheme are propoe, of which one for c-bu voltage regulation an the other for loa iviion on econ c ource. Thi tructure i capable of maintaining the loa voltage regulation while feeing available power from the weak c ource. The control cheme can be interchangeable from one to other epening on the ource power upply capacity. IRE 77 ICONIC RESEARCH AND ENGINEERING JOURNALS 9

5 However, ue of current-control loop for heavier ource limit the loa upplying capacity an hence it i not recommene. In view of thi ifficulty it i alway recommene to ue current-control loop for the weaker ource an connecte to the circuit portion that give buck-boot feature. DC-bu voltage regulation loop houl be cloe together with the heavier ource. Detaile mathematical treatment will be preente in the final paper to upport above icuion. For ecouple igital controller eign two ifferent loopgain have been efine here, one for current-control loop while the econ one for the c-bu voltage regulation loop. The general block iagram for loop eign i hown in Fig. where G c(z): Compenator, F m: PWM generator tranfer function, K i the loa voltage ening gain, an loopgain T L(z)=KF mg c(z)g p(z). Here, G p(z) can be either control to- inuctor current tranfer function in cae of current controller eign, or control tooutput voltage tranfer function for the voltage regulator eign. In any cae the igital compenator i eigne uing iotool of the MATLAB in the frequency omain. Pole-zero placement technique i ue an then final eign i arrive. Fine tuning of the compenator i performe to enure relative tability margin, i.e. gain margin> 6 B, 5 <phae margin<75 an reaonable croover frequency, which normally epen on the orer of the converter uner conieration. ource with it power upplying capacity le than the loa eman. For a loa eman 96 W, the loa itribution pattern on the two input c ource i hown in Fig. 5. In thi imulation it ha been kept current limit of A on the c ource- an it maximum power elivering capacity i 4 W. In the loa eman of 96 W cource- upplie 7 W, while ource- upplie 4 W. When the c ource- upplying it full rate power then any aitional loa coming on to the converter i going reflect on c ource-. To illutrate thi feature the loa reitance i change from 6 to 4 Ω an the correponing reult are hown in Fig. 6. It i clear from the imulation reult that loa voltage i almot contant an the aitional loa eman i tranferre on the c ource-. The loa iviion control trategy effectivene i alo verifie when the ource voltage are varying between minimum an maximum value. To emulate thi apect, c ource-voltage kept at it rate value, while the c ource- voltage i graually varie between 6 an 46 V an the correponing reult are plotte in Fig. 6..5( z.9)( z.95) Gvc( z) ( z)( z.854) (5).6( z.8)( z.88) Gic( z) ( z)( z.998) (6) IV. SIMULATION RESULTS To extract the alient feature of the propoe converter an to verify the loa itribution together with c-bu regulation capability a 48 V, 76 Watt two-input c-c converter ytem wa coniere in thi tuie an it parameter are lite in Table I. PSIM i ue for imulation purpoe. In thee tuie DC ource- coniere a heavier ource having ufficient power upplying capacity, more than loa eman, while DC ource- coniere a weaker Fig. 5. Steay-tate waveform howing loa iviion on the two input c ource. IRE 77 ICONIC RESEARCH AND ENGINEERING JOURNALS

6 V I(R) Vg Time () Fig. 6.Dynamic repone of loa voltage againt graual variation of ource voltage (V : 6 46 V). V. CONCLUSION Conference (APEC), 6, CD-ROM proceing. [4] R. D. Milebrook, Cuk. S, A general unifie approach to moelling witching converter power tage, IEEE Power electronic pecialit conference, 976, pp. -4. [5] D. Makimovic an R. Zane, Small-Signal Dicrete Time Moeling of Digitally Controlle PWM Converter, IEEE Tran. on Power Electronic, vol., no. 6, pp , Jun. 7. [6] Krihna Mohan. B, Robut Digital Voltage Moe Controller for Fifth-Orer Boot Converter, IEEE Tran. Inutrial Electron., vol. 58, no., pp. 6-77, Jan.. [7] M. Veerachary, Two-loop controlle buck- SEPIC converter for input ource power management, IEEE Tran. On Inutrial Electronic, Vol. 59(), pp ,. [8] MATLAB uer manual,. [9] PSIM, uer manual, 4. A new two-input DC-DC converter uitable for rawing power from two ifferent c ource an feeing to common c bu wa propoe in thi paper. Moe of operation have been analyze an then ecouple control-loop were eigne to itribute the loa eman on both the input ource. Voltagemoe control trategy wa ue to enure c bu voltage regulation, while current-control loop wa implemente to retrict the loa iviion on the econ ource. Simulation reult were in agreement with the theoretical preiction. REFERENCES [] Hirofumi Matuo, Wenzhong Lin, Fujio Kurokawa, Teturo Shigemizu, Nobuya Watanabe, Characteritic of the Multiple- Input DC DC Converter, IEEE Tran. on In. Electron, vol. 5, no., pp.65-6, Jun. 4. [] Jian Liu, Zhiming Chen, Zhong Du, A new eign of power upplie for pocket computer ytem, IEEE Tran. on In. Electronic, 998, Vol. 45(), pp [] K. P. Yalamanchili, M. Ferowi, Keith Corzine, New Double input c-c converter for automotive application", IEEE Applie Power Electronic IRE 77 ICONIC RESEARCH AND ENGINEERING JOURNALS