Control of A high-performance Z-Source Inverter for Fuel Cell/ Supercapacitor Hybrid Electric Vehicles

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1 Word Eectric Vehice Journa Vo. 4 - ISSN WEVA Page444 EVS5 Shenzhen, China, Nov. 5-9, 1 Contro of A high-performance Z-Source Inverter for Fue Ce/ Supercapacitor Hybrid Eectric Vehices Omar Eabban 1, Joeri Van Miero and Phiippe Lataire 1 R&D Department, Punch Powertrain, Schurhovenved 415, 38 Sint-Truiden, Begium, omar.eabban@punchpowertrain.com Vrije Universiteit Brusse, Peinaan, 15 Brusses, Begium Abstract This paper presents a supercapacitor () modue connected in parae with fue ce (FC) stack to suppy a high-performance Z-Source Inverter (HP-ZSI) feeding a three phase induction motor for hybrid eectric vehices appications. The supercapacitor is connected between the input diode and the bidirectiona switch of the highperformance ZSI topoogy. The indirect fied-oriented contro (IFOC) method is used to contro an induction motor speed during motoring and regenerative braking operations to produce the moduation index and a dua oop controer is used to contro the Z-network capacitor votage to produce the shoot-through duty ratio. MATLAB simuation resuts verified the vaidity of the proposed contro strategy during motoring and regenerative braking operations. Keywords: Z-source Inverter, fue ce, supercapacitor, indirect fied-oriented contro. 1. Introduction Fue ces (FC) have achieved goba attention as an aternative power source for hybrid eectric vehices. A fue ce vehice promises zero emission benefits of a battery-powered pure eectric vehice, with the driving range and convenience of a conventiona interna combustion engine vehice [1]. A stand aone FC system integrated into an automotive powertrain is not aways sufficient to satisfy the oad demands of a vehice. Athough FC systems exhibit good power capabiity during steady-state operation, the response of fue ces during transient and instantaneous peak power demands is reativey poor. Besides, if the FC system aone suppies a power demand, it woud increase the size and cost of the FC system. Moreover, avaiabe FC systems are not capabe of recovering the braking energy. Therefore, hybridizing FC system with an energy storage system (ESS) decreases system cost, improves performance and provides regenerative braking energy capturing, thus increases system efficiency and provides energy savings. The ESS is usuay a battery modue, a supercapacitor modue, or a combination of both. However, commerciay avaiabe battery systems present some drawbacks, such as ow cyce-ife, ong recharging time and ow power densities. Thus, supercapacitors () are being expored as repacements for the batteries in vehicuar appications [, 3]. For the purposes of improving the characteristic and efficiency of hybrid eectric vehices, different hybrid drive train topoogies with supercapacitor based energy storage have been anayzed and compared with concern about energy sources contro and management in [4]. It concuded that, the direct parae connection of the fue ce stack and supercapacitor bank to the DC bus, as shown in Fig. 1, resuts in the cheapest components soution and the owest fue consumption. The Z-Source Inverter (ZSI) is a singe-stage power converter that can perform both inversion and votage buck/boost without using two separate power conversion stages [5]. There are three different topoogies for three phase-two evevotage type ZSI, they are: the basic ZSI, the bidirectiona ZSI and the high performance ZSI. The high performance ZSI can operate at wide oad range with sma Z-network inductor, eiminate the possibiity of the dc ink votage drops, and simpify the Z- network inductor design and system contro. EVS5 Word Battery, Hybrid and Fue Ce Eectric Vehice Symposium 1

2 Word Eectric Vehice Journa Vo. 4 - ISSN WEVA Page445 So, the HP-ZSI topoogy appears to be the most suitabe topoogy for HEV appications [6, 7]. The ZSI can aso be appied to FCHEVs with sight modification to incude a battery; two configurations have been proposed for FCHEVs as shown in Fig. [8, 9]. The first configuration is using a battery connected in parae with one of the Z-network capacitors, this configuration has some disadvantages such as: a high votage battery must be used (the battery votage shoud equa to the Z- network capacitor votage) and the dc ink votage is twice the battery votage during regenerative braking when disconnect the fue ce. The second configuration is using a battery connected to the motor neutra point, this configuration aso has some disadvantages such as: some dc current fows through the traction motor, which increases the motor copper oss, therefore the motor needs to be oversized. In [1], a fue ce system with the basic singe phase ZSI topoogy and supercapacitors for votage sag compensation was proposed, the authors proposed six different positions to connect the supercapacitors and they concuded that, the best connection is to connect the supercapacitor between two diodes and overcharging switch, as shown in Fig. 3, however, this configuration doesn t aow bidirectiona power fow. Figure 3: ZSI with supercapacitor connected between two diodes and a switch [1] In this paper, the fue ce stack and the supercapacitor modue are direct connected in parae with the HP-ZSI, as shown in Fig. 4. The supercapacitor is connected between the input diode D and the bidirectiona switch S 7. The bidirectiona switch S 7 provides a path for the regenerative braking energy to be stored in the supercapacitor modue during the shoot-through state. The supercapacitor modue suppies the transient and instantaneous peak power demands and absorbs the deceeration and regenerative braking energy. Aso, a dua oop contro capacitor votage contro is used for controing the shoot-through d duty ratio and the indirect fied oriented contro (IFOC) strategy is used to contro the induction motor speed by controing the moduation index M. Figure 1: Configuration of FCHEV powertrain with supercapacitor as the energy-storage device Figure 4: A HP- ZSI with fue ce and Supercapacitor. System Modeing Figure : ZSI for FCHEV appication: (a) the battery connected in parae with one of the Z-network capacitors [8], (b) the battery connected to the neutra point of the traction motor [9].1 Modeing of a PEMFC A fue ce is an energy conversion device that converts the chemica energy of a reaction directy into eectricity with byproduct of water and heat. The fue ces are cassified according to the choice of eectroyte and fue into six major different types. The proton exchange membrane (PEM) fue ce which characterized by ow operating temperature, higher power density and quick start up for automotive vehices [11]. The FC mode used in this paper is reaized in Simuink/ MATLAB. Then, the mode is embedded into the SimPowerSystems of MATLAB as a controed votage source. Assuming constant temperature and oxygen concentration, the FC output votage may be expressed as: EVS5 Word Battery, Hybrid and Fue Ce Eectric Vehice Symposium

3 Word Eectric Vehice Journa Vo. 4 - ISSN WEVA Page446 V FC = E + η act + η ohmic (1) Where η = B n ( CI ) act int FC ηohmic = R I FC () RT ph PO E = N fcs E + og F O H O The FC system mode parameters used in this mode are in [1]. The FC system consists of a FC stack with N fcs ces in a series and N fcp in parae configuration, the vaues of N fcs and N fcp are in the appendix.. Modeing of Supercapacitor The natura structure of is appropriate to meet instantaneous peak power demands. The bank is used to provide the difference between the oad demand and the FC system output power. Without the bank, the FC system must suppy a power demand, thus increasing the size and cost of the FC system. Fig. 5 shows the cassica equivaent circuit of the unit. The mode consists of a capacitance C ce, an equivaent series resistance R Ssc representing the charging and discharging resistance and an equivaent parae resistance R Rsc representing the sef discharging osses. The output votage of the supercapacitor can be expressed as: V c e = i c e R s + v c 1 vc = i C ( t ) d t + v c C vc i C = i ce + RP (3) vc SOC = vce max SOC vc = V ce max 1 series to form a bank, and the tota capacitance determines the number of capacitors that must be connected in parae in the bank [13]. The BCAP3 P7 supercapacitor from Maxwe is seected in this paper due to its utra-ow [14]; the characteristics of with supercapacitor and the vaues of N s and N p are isted in the appendix..3 Modeing of ZSI To design a controer for the ZSI, we need a proper dynamic mode of the HP-ZSI for its switching operation. It is apparent that an accurate sma signa mode of ZSI is needed. The HP-ZSI has the same sma signa mode of the basic ZSI. The shootthrough duty ratio to capacitor votage G vd (s) and shoot-through duty ratio to inductor current G id (s) sma signa transfer functions of the HP-ZSI with inductive oad are given by Equations 4 and, where V in, R, L,V c, I and D are input votage, equivaent dc oad resistance, equivaent dc oad inductance, steady state vaues of inductor current, capacitor votage, oad current and shoot-through duty ratio at certain operating point respectivey, and L, C are the z-network capacitor and inductor. 3. System Contro Strategy In order to achieve high dynamic performance in an induction motor drive appication during motoring and regenerative braking operations, vector contro is often appied. The indirect fied oriented controed (IFOC) IM drive is widey used in high performance appications due to its simpicity and fast dynamic response. The indirect fied oriented contro based on PWM votage moduation with votage decouping compensation is used to insert the shoot-through state within the switching signas, as shown in Fig. 6. The parameters of the four PI controers are cacuated based on the desired damping and dynamics response specifications [15, 16]. Figure 5: supercapacitor equivaent circuit The bank mode used in this paper has been impemented in MATLAB and SimPowerSystem. The effective specific energy for a prescribed oad can be suppied by various supercapacitor bank configurations. The termina votage determines the number of capacitors that must be connected in Figure 6: Bock diagram of the IFOC of induction mot EVS5 Word Battery, Hybrid and Fue Ce Eectric Vehice Symposium 3

4 Word Eectric Vehice Journa Vo. 4 - ISSN WEVA Page447 G G vd id ( I ( s ) = ( V ( s ) = C L + I ) L L s V i n ) L C s + [ ( I L L C s L + I ) R L + ( 1 D 3 + [ R C ( V + R L C s C 3 L L C s V in + R L C s ) ( V + [ L ( 1 D ) + ( 1 D V C in ) ) ( I + [ L ( 1 D ) L + ( 1 D ) ( V + L ( D L ) + L ( D c 1 ) ] s + R ( D + I ) L ] s + ( 1 D V ) L ] s + ( 1 D ) ( V V i n ) ( V 1 ) V 1 ) ] s + R ( D C in 1 ) ) + ( 1 D c ) ( I L i n ) R (4) + I ) R (5) Figure 7: Cosed oop speed contro of three phase induction motor fed by a high-performance ZSI with fue ce stack and supercapacitor modue s Figure 7 shows the entire cosed oop system containing: the fue ce stack, the supercapacitor modue, the HP-ZSI, the Z-network capacitor votage controers and the IFOC speed controer, where the capacitor votage contro generates the shoot-through duty ratio d and the IFOC generates the moduation index M according to operating conditions. The dua oop controer (votage and current contro) is designed to contro the average vaue of the dc ink votage v i by controing the capacitor votage v c. Equations (4) and (5) gives the required transfer functions for designing the dua-oop contro for the HP-ZSI. Figure 8 shows the entire cosed oop system containing the outer votage oop controer, G cv (s), inner current oop controer, G ci (s), modified moduation transfer function, G M (s), [14], and the shoot-through duty ratio to capcitor votage G vd (s) and shoot-through duty ratio to inductor current G id (s).the oop gains for inner current oop T i (s) and outer votage oop T v (s) can be expressed as: T i ( s ) = G ci ( s ) G M ( s ) G id ( s ) G cv ( s ) G M ( s ) G vd ( s ) (6) T v ( s ) = 1 + T i ( s ) For outer votage and inner current oops, a two poes and one zero controer has been designed to compensate the ow-frequency oop gain and improving the phase margin, whose transfer function is given by: G ( 1 + ) ωz s ) = G c (7) s s( 1 + ) ω c ( p Figure 8: Dua oop capacitor votage contro bock diagram of a HP-ZSI 4. Simuation Resuts In order to verify the proposed contro strategy during motoring and regenerative braking a simuation mode is carried out using MATLAB/ Simuink software with a 15 kw induction motor. Fig. 9 show the motor response during motoring, regenerative braking operation modes: acceeration mode with rated oad torque during the time interva -. sec, steady state operation mode with rated oad torque and rated speed during the time interva.-.5 sec, overoaded transient mode with 1. the rated oad torque and rated speed during the time interva.5-.8 sec, deceeration transient mode from rated speed to haf the rated speed with rated oad torque during time interva.8-1 sec, ight oad transient mode with haf the rated oad torque and haf the rated speed during the time interva 1-1. sec, regenerative braking mode during the time interva sec and standsti mode during the EVS5 Word Battery, Hybrid and Fue Ce Eectric Vehice Symposium 4

5 Word Eectric Vehice Journa Vo. 4 - ISSN WEVA Page448 time interva sec. Fig. 1 shows the reference and actua the Z-network capacitor votage, where the capacitor votage is controed to be 653 V, the shoot-through duty ratio which is generated from capacitor votage contro, the moduating signas which is generated from the IFOC contro and the reference and actua Z- network inductor current. Fig. 11 shows the fue ce stack and the supercapacitor modue votages, currents and SOC of the supercapacitor modue during the above mentioned operations modes. Fig. 1 shows the fue ce stack, the supercapacitor modue and motor eectric powers during the above mentioned operations modes, the fue ce stack deivers the rated system power whie the supercapacitor modue deivers the transient and instantaneous peak power demands and absorbs the deceeration and regenerative braking energy. Figure 9: Motor response during motoring and regenerative braking operation modes Figure 1: High-performance ZSI response during motoring and regenerative braking operation modes EVS5 Word Battery, Hybrid and Fue Ce Eectric Vehice Symposium 5

6 Word Eectric Vehice Journa Vo. 4 - ISSN WEVA Page449 Figure 11: Fue ce and supercapacitor votage, current and supercapacitor state of charge during motoring and regenerative braking operation modes Figure 1: Motor deveoped power, fue ce output power and supercapacitor power 5. Concusions This paper has presented a FCHEV system suppied by a fue ce stack and a supercapacitor modue using the high-performance Z-source inverter. The fue ce and the supercapacitor are directy connected in parae. The supercapacitor modue deivers the transient and instantaneous peak power demands and absorbs the deceeration and regenerative braking energies whie the fue ce stack deivers the system mean power. MATLAB simuation resuts verified the vaidity of the proposed system configuration. EVS5 Word Battery, Hybrid and Fue Ce Eectric Vehice Symposium 6

7 Word Eectric Vehice Journa Vo. 4 - ISSN WEVA Page45 References [1] S. Pischinger, O. Lang, and H. Kemper, System Comparison of Hybrid and Fue Ce Systems to Interna Combustion Engines, in Proc.SAE Tech. Series, Oct.. [] Phatiphat Thounthong, Viboon Chunkag, Panarit Sethaku, Bernard Davat, and Meika Hinaje, Comparative Study of Fue-Ce Vehice Hybridization with Battery or Supercapacitor Storage Device, IEEE transactions on vehicuar technoogy, vo. 58, no. 8, October 9, pp [3] O. Erdinc, B. Vura, M. Uzunogu, Y. Ates, Modeing and anaysis of an FC/UC hybrid vehicuar power system using a waveet-fuzzy ogic based oad sharing and contro agorithm, Internationa journa of hydrogen energy, 9 vo. 34, no. 1, pp [4] Joeri Van Miero, Yonghua Cheng, Jean-Marc Timmermans, Peter Van den Bossche, Comparison of Fue Ce Hybrid Propusion Topoogies with Super-Capacitor, EPE-PEMC, 6, pp [5] F. Z. Peng, Z-source inverter, IEEE Transactions on Industry Appications, Vo. 39, no., pp [6] Omar Eabban, Joeri Van Miero and Phiippe Lataire, Comparison between Different PWM Contro Methods for Different Z-Source Inverter Topoogies, the 13th European Conference on Power Eectronics and Appications, EPE ' Sept. 9, Barceona-Spain. [7] Omar Eabban, Joeri Van Miero and Phiippe Lataire, Votage Mode and Current Mode Contro for a 3 kw High-Performance Z-Source Inverter, IEEE Eectrica Power & Energy Conference (EPEC), -3 Oct. 9, Montrea, Canada. [8] Fang Z. Peng, Miaosen Shen, Kent Hoand, Zsource Inverter Contro for Traction Drive of Fue Ce Battery Hybrid Vehices, IEEE Transactions on Power Eectronics, Vo. No.3 May/June, 7, pp [9] Miaosen Shen, Stefan Hodek, Fang Z. Peng, Contro of the Z-Source inverter for FCHEV with the battery connected to the motor neutra point, in Proc. of IEEE Power Eectronics Speciaist Conference, 7, pp [1] Kim Y-H, Moon H-W, Kim S-H, Cheong E-J,Won C-Y, A Fue Ce System with Z-Source Inverters and Utracapacitors, the 4th Internationa Power Eectronics and Motion Contro Conference; Aug. 4. p [11] A. Kirubakaran, Shaiendra Jain and R.K. Nema, A review on fue ce technoogies and power eectronic interface, Renewabe and Sustainabe Energy Reviews 13 (9) [1] M. Uzunogu, M.S. Aam, Dynamic modeing, design and simuation of a PEM fue ce/utracapacitor hybrid system for vehicuar appications, Energy Conversion and Management 48 (7) [13] Omar Hegazy and Joeri Van Miero, Partice Swarm Optimization for Optima Powertrain Component Sizing and Design of Fue Ce Hybrid Eectric Vehice, the 1th Internationa Conference on Optimization of Eectrica and Eectronic Equipment, OPTIM 1, May -, 1, Brasov, Romania. [14] DATASHEET_K_SERIES_11537.pdf [15] Chunting Mi, Fied-oriented Contro of Induction Motor Drives with Direct Rotor Current Estimation for Appication in Eectric and Hybrid Vehices, Journa of Asian Eectric Vehice, vo. 5, no., pp. 1-4, December 7. [16] Omar Eabban, Joeri Van Miero and Phiippe Lataire, A new Cosed Loop Speed Contro of Induction Motor Fed by A High Performance Z- Source Inverter, IEEE Eectrica Power and Energy Conference (EPEC 1) being hed during the period August 5-7, 1, Haifax, NS, Canada. Appendix: System Parameters Parameter Vaue PEM FC parameters Standard no oad votage, E.95 V No. of series FC in stack, N fcs 55 No. of parae stacks, N fcp 17 Supercapacitor (BCAP3 P7) parameters per ce Capacitance (-% / +1%), C 3 F DC equivaent series resistance, R Ssc.9 mω Leakage current, i Rpsc 5. ma No. of series, N S 55 No. of string parae, N scp 17 High performance ZSI parameters Inductance, L 5 µh Capacitance, C 5 µf Switching frequency, F S 1 khz Induction Motor Parameters Output power 15 kw RMS ine votage 4 V Input frequency 5 Hz No. of poes 4 Stator resistance, R s.5ω Rotor resistance, R r.147 Ω Stator inductance, L s.991 mh Rotor inductance, L r.991 mh Mutua inductance, L m mh Inertia, J.1 kg.m Fraction factor, F.9541 N.m.s Dr. Omar Eabban was born in Egypt in He received the B.Sc. from Hewan University, Egypt in 1998 and the M.Sc. degree from Cairo University, Egypt in 5, both in Eectric Power and Machines Engineering, and the Ph.D. degree in Eectrica Engineering from Vrije Universiteit Brusse, Begium in May 11 with the greatest distinction. In May 11, he joined the R and D department at Punch Powertrain, Sint- Truiden, Begium, where he and his team deveop a next generation, highy performing hybrid Powertrain. His research interests incude motor drives, artificia inteigent, power eectronics converters design, modeing EVS5 Word Battery, Hybrid and Fue Ce Eectric Vehice Symposium 7

8 Word Eectric Vehice Journa Vo. 4 - ISSN WEVA Page451 and contro, eectric and hybrid eectric vehices contro, DSP-based system contro and switched reuctance motor contro for automotive appications. He is a member at the IEEE, JPE and EPE journas. Prof. Joeri Van Miero obtained his Ph.D. in eectromechanica Engineering Sciences from the Vrije Universiteit Brusse in. He is now a fu-time professor at this university, where he eads the MOBI - Mobiity and automotive technoogy research group. Currenty his research is devoted to the deveopment of hybrid propusion (converters, supercaps, energymanagement, etc.) systems as we as to the environmenta comparison of vehices with different kind of drive trains and fues (LCA, WTW). He is the author of more than 1 scientific pubications. Prof. Van Miero chairs the EPE chapter Hybrid and eectric vehices ( is the secretary of the board of the Begian section of AVERE (ASBE) and is board member of AVERE. He is co-editor of the Journa of Asian Eectric Vehices. He is an active member of EARPA-the association of automotive R&D organizations. Furthermore he is member of Fanders Drive and of VSWB Femish Cooperative on hydrogen and Fues Ces. Prof. Van Miero is Chairman of the Internationa Program Committee of the Internationa Eectric, hybrid and fue ce symposium (EVS4). Prof. Phiippe Lataire received the degree of eectromechanica engineer in 1975 and the Ph.D. degree in 198, both from the Vrije Universiteit Brusse (VUB), Brusses, Begium. He is presenty fu time professor at the VUB. The prime factors of his research are in the fied of eectric drives, power eectronics and contro. EVS5 Word Battery, Hybrid and Fue Ce Eectric Vehice Symposium 8