Modeling nd Control o Fuel Cell Bsed Z-source Converter or Distributed Genertion Systems Jin-Woo Jung, Ph. D. Student Advisor: Pro. Ali Keyhni October, 4 IAB 4 Mechtronic Systems Lbortory Deprtment o Electricl nd Computer Engineering he Ohio Stte University
Publictions Journl Ppers [] J. W. Jung, H. Lee, nd A. Keyhni, Modeling, Anlysis, nd Control o Fuel Cell Bsed Distributed Genertion Systems, Prt I: Stndlone AC Power Supply, IEEE rnsctions on Energy Conversion. Will be submitted in November, 4 [] J. W. Jung nd A. Keyhni, Modeling, Anlysis, nd Control o Fuel Cell Bsed Distributed Genertion Systems, Prt II: Grid-Interconnection, IEEE rnsctions on Energy Conversion. Will be submitted in November, 4 [3] J. W. Jung, M. Di, nd A. Keyhni, Modeling nd Control o Fuel Cell Bsed Z-Source Converter or Distributed Genertion Systems, IEEE rnsctions on Energy Conversion. Will be submitted in October, 4 [4 ] J. W. Jung nd A. Keyhni, Modeling nd Control o Z-Source Converter or Fuel Cell Systems, IEEE rnsctions on Energy Conversion. Submitted in April, 4 nd being reviewed [5] M. N. Mrwli, J. W. Jung, nd A. Keyhni, Control o Distributed Genertion Systems, Prt II: Lod Shring Control, IEEE rnsctions on Power Electronics, vol. 7, no. 6, pp., Nov. 4. In Print
Publictions Conerence Ppers [] Jin-Woo Jung, Min Di, nd Ali Keyhni, Modeling nd Control o Fuel Cell Bsed Z-Source Converter, IEEE Applied Power Electronics Conerence APEC 5 in Austin, exs, USA, Mrch 6-, 5. Accepted nd will be presented [] Min Di, Mohmmd N. Mrwli, Jin-Woo Jung, nd Ali Keyhni, "A PWM rectiier control technique or three phse double-conversion UPS under unblnced lod, IEEE Applied Power Electronics Conerence APEC 5 in Austin, exs, USA, Mrch 6-, 5. Accepted nd will be presented [3] Min Di, Mohmmd N. Mrwli, Jin-Woo Jung, nd Ali Keyhni, Power Flow Control o Single Distributed Genertion Unit with Nonliner Locl Lod, IEEE Power Systems Conerence & Exposition PSCE 4, New Yor, USA, October -3, 4. [4] J. W. Jung, M. Di, nd A. Keyhni, Optiml Control o hree-phse PWM Inverter or UPS Systems, IEEE Power Electronics Specilist Conerence PESC 4, pp. 54-59, Achen Germny, June -4, 4.
Publictions 3 Conerence Ppers [5] Jin-Woo Jung nd Ali Keyhni, Design o Z-source Converter or Fuel Cells, Electric Supply Industry in rnsition, pp. 7/6 7/67, AI hilnd, 4-6 Jn. 4. [6] Min Di, Ali Keyhni, Jin-Woo Jung, nd A.B. Proc, "A Low Cost Fuel Cell Drive System or Electricl ehicles," Proceedings o the 3 Globl Powertrin Congress Conerence nd Exposition, vol. 6, pp. -6, USA, Sept. 3. [7] A. Keyhni, M. Di, nd J. W. Jung, Prllel Opertion o Power Converters or Applictions to Distributed Energy Systems, nd IASED he Interntionl Assocition o Science nd echnology or Development Interntionl Conerence on Power nd Energy Systems, Greece, June 5-8,.
ORGANIZAION I. Introduction II. Circuit Anlysis/System Modeling/PWM Implementtion A. Circuit Anlysis B. System Modeling C. Spce ector PWM Implementtion III. Control System Design A. Discrete-time Sliding Mode Current Controller B. Discrete-time Optiml oltge Controller C. Discrete-time PI DC-lin oltge Controller I. Simultion Results I. Conclusion
I. INRODUCION Why re uel cell systems incresingly used in industry? Emerging power genertion technologies Wind turbines nd photovoltic cells renewble technologies Full-grown technologies No emission Climte constrints: wind nd sunshine Eiciency: wind turbines 4%, photovoltic cells 5 5% Fuel cells Regrdless o climte conditions Hydrogen nd oxygen Products: electricity, het, nd wter Nerly ero emission Eiciency: electricity up to 6%, co-genertion up to 85%
I. INRODUCION Operting Principle o Fuel Cell Systems Opertion o the uel cells Air Reormer Nturl gs Propne Methnol Gsoline Hydrogen Oxygen Stcs Chemicl energy to Electricl energy DC power Power Converter AC power Fig. Fuel cell genertion system.
I. INRODUCION Fetures o Fuel Cell Systems ypes o uel cells Phosphoric Acid PAFC, Solid Oxide SOFC, Molten Crbonte MCFC, Proton-Exchnge-Membrne PEMFC, Alline, Zinc-Air ZA uel cells, etc. Applictions o uel cells Residentil domestic utility, rnsporttion Fuel cell vehicle, Portble power lptop, cell phone, Sttionry buildings, hospitls, etc, Distributed power or remote loction, etc. Chrcteristics o uel cells Environmentl-riendly nerly ero emission Modulr electric genertion High eiciency co-genertion Slow dynmic response during initil strt-up nd lod chnge Boosted or most pplictions due to low DC output voltge rying output voltge ccording to the lod current
I. INRODUCION Overview o Fuel Cell Systems Fuel Cells or sttionry or distributed power pplictions ypes PAFC SOFC MCFC PEMFC Sie W W MW 5W MW 3 5W Fuel Nturl gs, lndill gs, digester gs, propne Nturl gs, hydrogen, lndill gs, uel oil Nturl gs, hydrogen, lndill, propne Nturl gs, hydrogen, propne, diesel Operting emperture 4 F,8 F, F F Instlled Cost $/W 3, 3,5,3, 8, 4, Cooling Medium Boiling Wter Excess Air Excess Air Wter Environmentl riendly Nerly ero emission Yes Yes Yes Yes Commercil Avilbility Yes R&D R&D R&D
I. INRODUCION Overview o Fuel Cell Systems Fuel Cells or sttionry or distributed power pplictions ypes PAFC SOFC MCFC PEMFC Cogenertion Yes hot wter Yes hot wter, LP or HP stem Yes hot wter, LP or HP stem Yes 8 C wter Eiciency Electricity 36 4% 45 6% 45 55% 3 4% Eiciency Cogenertion Up to 85% Up to 85% Up to 85% Up to 85% Commercil Sttus Some commercilly vilble Liely commercilition 4 Liely commercilition 4 Liely commercilition 3/4 Applictions Sttionry power 998, Rilrod Propulsion 999 Sttionry power nd Rilrod Propulsion 998-5 Sttionry power -5 Sttionry power 997-, Bus/Rilrod/Autom otive Propulsion -
I. INRODUCION Wht is the reserch ocus? Reserch Focus Control o Power Electronic Interce System i.e., Control o Power Converter Inexpensive, relible, smll-sied, nd light-weighted Min ctors: sie o L-C ilter, number o power devices nd sensors Good perormnce: Nerly ero stedy-stte voltge RMS error Low otl Hrmonic Distortion HD Fst/no-overshoot current response Good voltge regultion Power genertion pplictions three-phse AC 8 L-L /6 H
I. INRODUCION Conventionl opology Conventionl: DC-DC boost converter nd DC/AC inverter DSP controller: two controllers DC/DC nd DC/AC power converters Power devices: DC to DC boost converter: our power switches nd our diodes DC to AC inverter: six power switches Sensors: DC input, DC output, nd AC output DC to DC boost converter DC to AC inverter S S3 S S3 S5 Fuel Cell in S4 S S4 S6 S 3-phse lod Fig. Conventionl system conigurtion.
I. INRODUCION Conventionl opology Control Bloc Digrm Fig. 3 Control bloc digrm o conventionl system.
I. INRODUCION Conventionl Z-source opology Conventionl Z-source converter: Impednce source L-C nd DC/AC inverter Boosted by shoot-though ero vectors both switches turned-on Open-loop control under only liner/hevy lod Dynmic lod pplictions lie motor Fuel cell modeled by DC voltge source bttery Fig. 4 Conventionl Z-source converter.
I. INRODUCION Proposed Z-source opology Proposed Z-source converter: Sttic lod pplictions with ixed pe voltge/requency i.e., three-phse AC 8 nd 6 H Dynmic response o uel cell considered System modeling/modiied SPWM implementtion/closed-loop control system design Good perormnce under both liner lod nd nonliner lod Wide rnge o lod, i.e., light lod to ull lod Fig. 5 Proposed Z-source converter.
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion Equivlent Circuit o the Fuel Cell Slow Dynmics o Reormer nd Stcs oltge-current chrcteristic o cell
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion Equivlent Circuit o the Fuel Cell Selected Equivlent Circuit Model o the Fuel Cell Dynmic modeling o reormer nd stcs: R-C circuit oltge-current chrcteristic o cell: Region o Ohmic Polrition Fig. 6 Equivlent circuit o the uel cell.
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion Z-source converter conigurtion Z-source converter: uel cell, diode, L-C impednce, DC/AC inverter, DSP controller, L/C ilter, nd lod Diode: to prevent reverse current tht cn dmge the uel cell Fig. 7 otl system conigurtion with Z-source converter.
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion Z-source converter conigurtion Fig. 8 otl system digrm o uel cell bsed Z-source converter.
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion A. Circuit Anlysis wo Opertion Modes: Mode Fig. 9 : Shoot-through switching mode: both switches in leg re simultneously turned-on Mode Fig. 9 b : Non-shoot-through switching mode: bsic spce vectors,,, 3, 4, 5, 6, 7 In the shoot-through switching mode. b In the non-shoot-through switching mode. Fig. 9 Equivlent circuit o two opertion modes.
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion A. Circuit Anlysis Assumption: L L, C C C C nd v L v L. Cse : one o shoot-through ero vectors Fig. 9 v L C, v C, nd v i. Cse : one o non-shoot-through switching vectors Fig. 9 b loop : v L in C nd loop : v i C - v L C - in, where, in is the output voltge o the uel cell. Averge voltge o the inductors L vl v L dt C + b in C C where, + b, : switching period, : totl durtion o shoot-through ero vectors over b b in in nd b : totl durtion o non-shoot-through switching vectors over.
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion A. Circuit Anlysis 3 Averge DC-lin voltge: C in b b in C b i i i dt v v + Pe DC-lin voltge: in in b in C DC p K _.5, < b K Pe phse voltge o inverter output where, K is clled boost ctor, in DC p p K M M Control Fctors: M nd K where, M denotes the modultion index, M b b + +
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion B. System Modeling Simpliied system circuit model S S3 S5 L-C Output ilter Lod + dc A B C S4 S6 S iab ibc + + L i ia i ib i ic LAB LBC C R L i LA i LB i LC N Fig. Simpliied system circuit model o Z-source converter. Note tht uel cell, diode D, nd impednce components L, nd C, re replced with DC-lin source dc. ht is, dc is equl to C or C.
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion B. System Modeling Current/voltge equtions rom the L-C ilter KL nd KCL d dt d dt d dt LAB LBC di dt di dt di dt LCA iab ibc ica 3C 3C 3C i i i iab ibc ica L L L 3C 3C 3C LAB LBC LCA i i LA i i LB i i LC + L + L + L iab ibc ica LB LC LA d dt L 3C I i 3C dii L + dt L L I i i L where, where, stte vribles: L [ LAB LBC LCA ] nd I i [i iab i ibc i ica ] [i ia -i ib i ib -i ic i ic -i ia ], control input u: i [ iab ibc ica ], disturbnce d: I L [i LA i LB i LC ]. i
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion B. System Modeling 3 Coordinte rnsormtion: three vribles two vribles b q K dq s bc where, dq [ d q ], bc [ b c ], nd denotes either voltge or current vrible. c d K s 3 / / 3 / / 3 / Fig. Reltionship between bc reerence rme nd sttionry dq reerence rme.
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion B. System Modeling 4 Stte equtions in the sttionry dq reerence rme idq Ldq idq Ldq idq idq Ldq L L dt d C C dt d I I I 3 3 + 3 3 3 ] [,,, row column s i s idq K K where, Continuous-time stte spce eqution o the given plnt model t t t t Ed Bu AX X + + &,, 4 4 3 I L I C A, 4 3 idq C E 4 I L B where, Lq Ld Ldq i i ] [I d [ ] iq id idq u 4 idq Ldq I X,,
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion C. Spce ector PWM Implementtion Conventionl Spce ector PWM: / 3, 4 / 3, / 3, / / 3 3 q xis 3 3 4 5 7 5 6 re α 6 / 3, / 3 / 3, / 3, / 6 ctive vectors:,, 3, 4, 5, 6 ero vectors:, 7 3 d xis + + dt dt + re + re + cos α re sin α 3 where, α 6 sin α sin π / 3 sin π / 3 α sin π / 3 + dc + where, 3 dc cos π / 3 sin / 3 π re 3 dc Fig. Bsic spce vectors nd switching ptterns.
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion C. Spce ector PWM Implementtion Modiied Spce ector PWM Implementtion Sector ~6 b Sector 6 ~ shoot-through ero vectors /3 Fig. 3 Modiied SPWM implementtion.
II. Circuit Anlysis/System Modeling /Spce ector PWM Implementtion C. Spce ector PWM Implementtion 3 Switching time clcultion t ech sector Note tht when the shoot-through durtion is equl to ero, the switching time o ech power switch or the Z-source converter is exctly the sme s tht or the conventionl one.
III. Control System Design Entire Control-loop Structure Fig. 4 otl control system bloc digrm. where, hree controllers. Discrete-time Optiml oltge Controller. Discrete-time Sliding Mode Current Controller DSMC 3. Discrete-time PI DC-lin oltge Controller One observer. Asymptotic Observer or estimtion o lod currents
III. Control System Design A. Discrete-time Sliding Mode Current Controller Bloc digrm o Current Controller Fig. 5 Discrete-time current controller using DSMC.
III. Control System Design A. Discrete-time Sliding Mode Current Controller Asymptotic observer design or estimtion o lod currents Stte eqution or symptotic observer dˆ Iˆ dt Ldq Ldq 3C L ˆ Ldq I idq 3C Ldq idq L ˆ Ldq Ldq Continuous-time stte-spce representtion or symptotic observer & Xˆ t A dˆ t Iˆ Ldq Xˆ t t + A L b ˆ L Xˆ X Ldq X b t A Ldq X t where, X ˆ [ ˆ Ldq ], X b [ I idq ], X [ Ldq ], L constnt observer gin. A 3L C idq, A b I 3C,
III. Control System Design A. Discrete-time Sliding Mode Current Controller 3 Discrete-time stte-spce model or symptotic observer + + ˆ ˆ ˆ ˆ ˆ L Ldq b b X X I d X A X A X A X d e τ τ A A A b b d e τ τ A A A, where, A e A, Bloc digrm o symptotic observer Fig. 6 Bloc digrm o symptotic observer.
III. Control System Design A. Discrete-time Sliding Mode Current Controller 4 Continuous-time stte spce eqution + + ˆ t t t t t t t t t idq y re y e C X y Ed Bu AX X &, 4 4 3 I L I C A, 4 I L B, 4 3 idq C E 4 idq Ldq I X, where, C [ ] iq id idq u,, [ ] iq id idq I I I y, Lq Ld Ldq i i ˆ ˆ ] [ˆ ˆ I d Discrete-time stte spce eqution + + + ˆ idq y re y e C X y d E u B X A X d e τ τ E E A, d e τ τ B B A where, A e A,
III. Control System Design A. Discrete-time Sliding Mode Current Controller 5 Sliding-mode mniold s y y _ re CX y _ re Equivlent control lw s + y + y + C A X + C B u + C E dˆ y u Control limit eq _ re _ re + C B I idq C A X C E dˆ u u eq u u eq u eq or or u u eq eq u > u where, u 3 dc
III. Control System Design B. Discrete-time Optiml oltge Controller Bloc digrm o oltge Controller Robust Servomechnism Controller RSC Servo compenstor: internl model principle Stbiliing compenstor: optiml control Fig. 7 Discrete-time optiml voltge controller using RSC.
III. Control System Design B. Discrete-time Optiml oltge Controller Discrete-time stte spce plnt model X + A X + B u + E dˆ Augmented system model including DSMC X + Ad X + Bdu + E y d Cd X d dˆ where, A A B C B C A, B C B, E E B C B C E d B d d, [ ] C d I, u I cmd, idq, y d Ld [ ] Ldq Lq
III. Control System Design B. Discrete-time Optiml oltge Controller 3 Continuous-time servo-compenstor Sinusoidl rcing/disturbnce model Ldq Ldq vdq vdq c c e e B η A η +, & 4 4 I I i ci ω A 4 I B ci 3 4 4 4 4 4 4 4 4 4 4 c c c c A A A 3 c c c B c B B B,,,, where, A A c is the given trcing/disturbnce poles, ω i i,, 3, ω ω, ω 5 ω, ω 3 7 ω. ω π [rd/sec], 6 H. Discrete-time servo-compenstor vdq c c e B η A η + + c c c d e τ τ B B A where, c e A c A,
III. Control System Design B. Discrete-time Optiml oltge Controller 4 Augmented system combining both the plnt nd the servo-compenstor X ˆ + AX ˆ ˆ + Bu ˆ ˆ ˆ ˆ + Ed + Eyd_re where, ˆ X X ˆ A d, A ˆ B d, η B ˆ E B ccd A c, d E, E ˆ, B c u, ˆ d I, y Ldq I cmd, idq Ldq d _ re Liner qudrtic perormnce index J ε ˆ X QXˆ + εu u where, Q is symmetricl positive-deinite mtrix nd ε> is smll number Control input ˆ X u KX η [ K K ] K X K η
III. Control System Design C. Discrete-time PI DC-lin oltge Controller Discrete PI DC-lin voltge controller eqution + + + C e e K e e K i p C e Bloc digrm o DC-lin oltge Controller Fig. 8 Discrete-time PI controller to regulte the DC-lin verge voltge.
III. Control System Design C. Discrete-time PI DC-lin oltge Controller Durtion cl /3 o shoot-through ero vectors Desired cpcitor voltge: C C 34 C b b in in C in C in 34 in 68 in cl 3 _ mx _ min.384,.5, where, where, in in 3 3
I. Simultion Results System Prmeters or Simultions ble II. System Prmeters or Simultions Fuel Cell Output oltge ime Constnt o Reormer nd Stcs Desired Averge DC-lin oltge Output Rted Power Impednce Components Inverter Output Filters AC Output oltge Switching/Smpling Period in 3 3 R r.5 Ω, C r 4.8 mf, R s. Ω, C s 4. mf C 34 P out A L L µh, C C µf L µh, C µf L, RMS 8 L-L, 6 H /5.4 H 85. µsec where, Hevy lod W: the output voltge o uel cell is 3 Light lod.5 W: tht o uel cell is 3 Liner lod: resistor nd n inductor Nonliner lod: n three-phse inductor mh, three-phse diode bridge, DC-lin cpcitor 8 µf, nd resistor 7 Ω Lod chnge: 5 W 5 to W 3, vice vers
I. Simultion Results A. Liner Lod R in, C [] LAB, LBC, LCA i LA, i LB, i LC 4 -.5.55.6.65.7.75.8.85.9.95. 4-4.5.55.6.65.7.75.8.85.9.95. 5-5.5.55.6.65.7.75.8.85.9.95. ime [sec] 3/W Hevy lod in C in, C [] LAB, LBC, LCA 4 -.5.55.6.65.7.75.8.85.9.95. 4-4.5.55.6.65.7.75.8.85.9.95. i LA, i LB, i LC -.5.55.6.65.7.75.8.85.9.95. ime [sec] b 3/.5W Light lod in C Fig. 9 Simultion wveorms under liner lod. : Fuel cell output voltge in nd cpcitor voltge C, : line to line voltges LAB, LBC, LCA, 3: lod phse currents i LA, i LB, i LC.
I. Simultion Results B. Nonliner Lod Rectiier lod in, C [] 4 in C LAB, LBC, LCA i LA, i LB, i LC [A] -.5.55.6.65.7.75.8.85.9.95. 4-4.5.55.6.65.7.75.8.85.9.95. 5-5.5.55.6.65.7.75.8.85.9.95. ime [sec] Fig. Simultion wveorms under nonliner lod 3/7Ω. : Fuel cell output voltge in nd cpcitor voltge C, : line to line voltges LAB, LBC, LCA, 3: lod phse currents i LA, i LB, i LC.
I. Simultion Results C. Lod Chnge P [W] in, C [] LAB, LBC, LCA i LA, i LB, i LC 5 5.5.55.6.65.7.75.8.85.9.95. 4 in C.5.55.6.65.7.75.8.85.9.95. 4 - -4.5.55.6.65.7.75.8.85.9.95. 5-5.5.55.6.65.7.75.8.85.9.95. ime [sec] Lod increse P [W] in, C [] LAB, LBC, LCA i LA, i LB, i LC 5 5.5.55.6.65.7.75.8.85.9.95. 4 in C.5.55.6.65.7.75.8.85.9.95. 4 - -4.5.55.6.65.7.75.8.85.9.95. 5-5.5.55.6.65.7.75.8.85.9.95. ime [sec] b Lod decrese Fig. Simultion wveorms under lod chnge t 7msec. : Fuel cell output voltge in nd cpcitor voltge C, : line to line voltges LAB, LBC, LCA, 3: lod phse currents i LA, i LB, i LC.
I. Simultion Results d. Six gting signls nd estimted lod current S PWM Signls or Six Power Switches 5 Lod current i LA nd estimted lod current i LA i LA i LA S4.67.68.68.69.69.7.7.7.67.68.68.69.69.7.7.7 i LA nd i LA [A] S3.67.68.68.69.69.7.7.7-5.5.55.6.65.7.75.8.85.9.95. S6 5 S5.67.68.68.69.69.7.7.7.67.68.68.69.69.7.7.7 i LA nd i LA [A] i LA i LA S.67.68.68.69.69.7.7.7 ime [sec ] -5.5.55.6.65.7.75.8.85.9.95. Gting signls or six power switches. b Estimted lod currents under hevy lod. Fig. Six gting signls nd estimted lod current. S nd S4: phse A, S3 nd S6: phse B, S5 nd S: phse C, Upper switches: S, S3, nd S5, Lower switches: S4, S6, nd S.
I. Conclusions L-C Impednce components insted o DC to DC boost converter Inexpensive, relible, smll-sied, nd light-weighted Slow dynmic response o uel cell Discrete-time stte-spce system model Modiied PWM echnique using Shoot-through ero vectors Feedbc controller design under both liner nd nonliner lod Good perormnce: Nerly ero stedy-stte voltge RMS error Low otl Hrmonic Distortion HD Fst/no-overshoot current response Good voltge regultion