DC-DC CONVERTOR STRUCTURE RE FOR ENERGY MANAGEMENT ON (HYBRID) ELECTRIC VEHICLE

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1 THE WELDING TECHNOLOGY INFLUENCE ON THE DOUBLE T GIRDER BEAMS BUCKLING (Paper Title) DC-DC CONVERTOR STRUCTURE RE FOR ENERGY MANAGEMENT ON (HYBRID) ELECTRIC VEHICLE Assist. Eng. Daniel-Adrian STICEA, PhD 1, Prof. Eng. Gheorghe LIVINŢ PhD 1, Assoc. Prof. Eng. Mihai ALBU, PhD 1. 1 Technical University of Iasi, Electrical Engineering, Energetics and Applied Informatics Faculty REZUMAT. Lucrarea prezinta o structura de convertor C.C.- C.C. multinivel bidirectional pentru gestionarea energiei pe vehiculele electrice hibride. Structura este alcatuita din mai multe brate de punte si inductori cuplati magnetic. Convertorul a fost proiectat si realizat practic pentru a interfata sistemul de stocare al energiei, reprezentat prin baterii, la reteaua de C.C. a unui stand de vehicul electric hybrid. Cuvinte cheie: convertor C.C.-C.C., Vehicule Electrice Hibride, managementul energiei. ABSTRACT. This paper presents a DC-DC convertor structure multilevel bidirectional for energy management on hybrid electric vehicles. The structure consists of several half bridge and magnetic coupled inductor. The convertor was designed for interface to the energy storage system, represented by batteries, with DC net of a hybrid electric vehicle stand. Keywords: DC-DC Convertor, Hybrid Electric Vehicle, energy management. 1. INTRODUCTION Electrical energy storage systems used in electric and hybrid vehicles may consist of supercapacitors, batteries and fuel cells [1]-[5], [8], [9]. In order to compensate the deficiencies of these sources of energy storage have been designed hybrid energy storage systems, such as those presented in [1]-[3], [10]. These systems combine the advantages of each source of making a more efficient storage systems. For efficient energy management, each storage system is connected to DC bus through a convertor, as in Fig. 1. These convertors often must be bidirectional to allow both charging and discharging the accompanying source. parallel. The series connection is presented in [14]. By connecting in parallel of the bidirectional switching cells is obtained a general structure of the convertor as shown in Fig. 2., where n represents the number of the half bridge. Fig. 1. Hybrid energy storage system for Electric Vehicle. A bidirectional convertor is based on the half bridge structure integrated in different configurations [2], [3], [5], [11]. The half bridge structure is known as bidirectional switching cell (2 Level Bidirectional 2L- B) [12]. These cells can be connected in series or in Fig. 2. Bidirectional DC-DC Convertor made with 2L-B cells. The power electronic system of the fig. 2. is a multilevel convertor, at which the benefits of conversion increase with the number of half bridge is used. The main advantage of this convertor is the fact that it can operate both as Buck and Boost mode using the same structure. Overall system operation, in Buck or Boost mode, is given by the direction movement of the global power convertor. Other advantage of the convertor consist in continuous mode even at low currents. This is done through a proper command of the half bridge. Also, for a convertor that uses n parallel 2L-B switching cells, the command corresponding to each bridge arm must be shifted with T S /n where T S is Buletinul AGIR nr. 4/2012 octombrie-decembrie 1 207

2 CONFERINŢA NATIONAL NAŢIONALĂ CONFERENCE DE ACŢIONĂRI OF ELECTRICAL ELECTRICE, DRIVES ediţia XVI, CNAE SUCEAVA the switching period of the transistors. These gaps allow obtaining an n+1 voltage levels on the DC bus [7]. Advantages of bidirectional convertor using 2L-B cells with magnetically coupled inductors are: Current through the output capacitor has a frequency of n*f S (f S / frequency switching) and a ripple of amplitude equal to 1/n of the corresponding current convertor with one arm The absorbed current to the inlet is triangular and 1/n 2 amplitude and ripple frequency is also n*fc, The losses through the inductors are reduced because their corresponding current will be 1/n. A disadvantage in achieving DC-DC convertors is given by the large size of inductance, mainly for the high power (tens of kilowatts). To reduce the size, the coupled inductance [6], [7], [13] or forced cooling can be used, as are presented in [5]. When using for boost convertor with 2L-B cells is used magnetic coupling for two inductors, according [6] obtain a low current ripple for each phase (half bridge). The current ripple decreases, in the same time with the increase of the coupling factor between the two inductors. For this variant, can occur, the discontinuous current mode that brings many disadvantages. If Coupled-Inductance (CI) is used, as in [7] and [13] is not possible to appear the discontinous current mode due to an appropriate control and in the same time, the converot can functioning in two modes Buck and Boost. Nevertheless, the current ripple per phase increase if a magnetic coupled inductor is used. However, the main advantage brought by a magnetically coupled inductor in this case is given by the reduction in expense growth inductor current gauge on the arm of the bridge (on phase). 2. DC-DC CONVERTOR WITH FOUR HALF BRIDGE AND MAGNETIC COUPLED INDUCTOR DC-DC Convertor modeling. Modeling of DC DC convertor with four half bridge was performed using the Psim 9.0 program. Energy storage source was modeled by a large capacitor (5.8 F) in series with a resistance, as in Fig. 3. The structure of this convertor consists of two convertors connected in parallel. Each convertor is made of two arms of the bridge and a magnetically coupled inductor. To simulate both buck and boost regime, to the DC bus of convertor is connected a resistive load or a constant current source (ISTEP1). In this way it was tested how the convertor response to a shock load. Fig. 3. The DC-DC convertor modeling made with four half bridge and magnetically coupled inductors. Simulation. In Fig. 4 is show the simulation data of DC-DC convertor for buck and boost operating conditions, including a variety of situations. Fig. 4. Response converter to the step signal to operate in the buck and boost modes. Further, the figure below, to highlight the behavior of the convertor in all four cases seen in Fig. 4, we presented detailed waveforms of voltage and current to the load stage DC / bus, for the overall operation under boost and buck mode operation. Fig. 5. Waveforms of current and voltage for the case when the duty cycle is >50% (Boost operation)

3 THE WELDING TECHNOLOGY INFLUENCE ON THEMANAGEMENT DOUBLE T GIRDER BEAMS BUCKLING Title) DC-DC CONVERTOR STRUCTURE FOR ENERGY ON (HYBRID) ELECTRIC (Paper VEHICLE Fig. 6. Waveforms of current and voltage for the case when the duty cycle is equal with 50%. Fig. 9. The DC-DC bidirectional convertor with two half bridge (phase) and magnetically coupled inductors. Fig. 7. Waveforms of current and voltage for the case when the duty cycle is >50% (Boost operation). The convertor was designed to interface the energy storage system represented by 24 Pb batteries, with (approx. 300 Vdc) to the DC bus of vehicle (approx. 600 Vdc) at which is connected the inverter that supply the vehicle propulsion induction motor. Converter rated current is 60 A (30 A on each arm). Due to increased computing power necessary for the converter control, a numerical system was designed around an FPGA system and a dspic30f4011 microcontroller. The numerical system with microcontroller performs communication of convertor with other system through CAN (Control Area Network) Network. The communication between dspic and FPGA is achieved by SPI (Serial Peripheral Interface). An overview of DC-DC actually made is presented in Fig. 10. Fig. 8. Waveforms of current and voltage for the case when the duty cycle is <50% (Buck operation) 3. DC-DC CONVERTOR WITH TWO HALF BRIDGE AND MAGNETICALLY COUPLED INDUCTORS DC-DC Convertor designed. The topology of the DC-DC convertor with two arms and inductor magnetically coupled is presented in Fig. 9. This convertor connects the battery pack to the DC bus (of the hybrid electric vehicle bench). Fig. 10. Overview of DC-DC convertor made practical. Buletinul AGIR nr. 4/2012 octombrie-decembrie 3 209

4 CONFERINŢA NATIONAL NAŢIONALĂ CONFERENCE DE ACŢIONĂRI OF ELECTRICAL ELECTRICE, DRIVES ediţia XVI, CNAE SUCEAVA Experimental results. In Fig. 11 are presented the waveforms of currents through the two arms of the converter (CH1 and CH2) and the waveforms of the common mode current (CH1+CH2) and differential mode (CH1-CH2), for operation of the converter under boost regime. The experimental data presented in this figure were tobtained by connecting 4 batteries of 12 V to the input of the DC-DC converter and an open loop operation of the convertor. Load connected to the DC-Link is only resistive. Duty cycle of PWM signal for control the two arms of a bridge to the situation presented in Fig. 5 is about 25%. This case corresponds to the highest common mode ripple current (i 1 +i 2, where i 1, i 2 are the currents through the two arms of the bridge). Fig. 12. The common mode current and differential mode current for boost regime to a duty cycle < 50% of PWM signal. Fig. 11. The current waveforms for the boost regime of convertor. In Fig. 12 and 13 can be seen the waveforms of common mode current (CH1) and differential mode current (CH2) for values of the duty cycle of the PWM signal near to 50%. Also, it can be see the necessity to implement a control loop differential mode current (i 1 - i 2 ) to eliminate the imbalances that may appear between the two arms of the convertor. These imbalances are given by the DC component of the waveform corresponding to a differential current. Fig. 13. The common mode current and differential mode current for boost regime to a duty cycle > 50% of PWM signal. 4. CONCLUSIONS The DC-DC convertors made with half bridge structure, connected in parallel, increase the conversion performance at the expense of computing power necessary to control the convertor. The absorbed current ripple from the energy storage system is reduced. Reducing gauge inducers used in DC-DC convertors can be achieved by using magnetically coupled inductances. The disadvantage in this case gave rise ripple current is given by the arm (phase) and thus the transistor, which currently is not problem. Designing a convertor to work in around 50% of the Pulse Width Modulation (PWM) signal provides the advantage of the current ripple drawn from the energy storage system approximately zero

5 THE DC-DC WELDING CONVERTOR TECHNOLOGY STRUCTURE INFLUENCE FOR ENERGY ON THE MANAGEMENT DOUBLE T GIRDER ON (HYBRID) BEAMS BUCKLING ELECTRIC (Paper VEHICLE Title) BIBLIOGRAPHY [1] M.B. Camara, H. Gualous, F. Gustin, A. Berthon, Control strategy of Hybrid sources for Transport applications using supercapacitors and batteries, Power Electronics and Motion Control Conference, Volume 1, pp. 1 5, ( 2006). [2] M. B. Camara, H. Gualous, F. Gustin, A. Berthon, B. Dakyo, DC/DC Converter Design for Supercapacitor and Battery Power Management in Hybrid Vehicle Applications Polynomial Control Strategy, IEEE Transactions on Industrial Electronics, Volume 57, No. 2, pp , (2010). [3] J. Caou and A. Emadi, A New Battery/Ultra-Capacitor Hybrid Energy Storage System for Electric, Hybrid and Plug-in Hybrid Electric Vehicles, Vehicle Power and Propulsion Conference, pp , (2009). [4] Kyoungmin Son, Sejin Noh, Kyoungmin Kwon, Jaeho Choi, Eun-Kyu Lee, Line Voltage Regulation of Urban Transit Systems Using Supercapacitors, Power Electronics and Motion Control Conference, (2009). [5] D. P. Urciuoli and C. W. Tipton, Development of a 90 kw Bi- Directional DC-DC Converter for Power Dense Applications, Applied Power Electronics Conference and Exposition, (2006). [6] J. Gallagher, Designing Coupled Inductors, Field Application Engineer, Power Division, Pulse, San Diego, Power Electronics Technology, January [7] A. Fratta, G. Griffero, S Nieddu, G. M. Pellegrino, F. Villata, Inductive Three-Level V.- Supplied Conversion Cell by New Hybrid Coupling Reactor Family, Industry Applications Conference, Volume 4, pp , (2002). [8] G. Calderon-Lopez, A. J. Forsyth and D. R. Nuttall, Design and Performance Evaluation of a 1O-kW Interleaved Boost Converter for a Fuel Cell Electric Vehicle, Power Electronics and Motion Control Conference, Volume 2, pp. 1 5, ( 2006). [9] Sharanya Jaganathan, Wenzhong Gao, Battery Charging Power Electronics Converter and Control for Plug-in Hybrid Electric Vehicle, Vehicle Power and Propulsion Conference, pp , (2009). [10] Xiaofei Liu, Qianfan Zhang, Chunbo Zhu, Design of Battery and Ultracapacitor Multiple Energy Storage in Hybrid Electric Vehicle, Vehicle Power and Propulsion Conference, pp , (2009). [11] Jian-ming HU, Yuan-rui CHEN, Zi-juan YANG, Study and Simulation of One Bi-directional DC/DC Converter in Hybrid Electric Vehicle, Power Electronics Systems and Applications, pp. 1 4, (2009). [12] Dan Floricau, Elena Floricau, and Guillaume Gateau, New Multilevel Converters With Coupled Inductors: Properties and Control, IEEE Transactions on Industrial Electronics, Volume 58, No. 12, pp , (2011). [13] A. Fratta, P. Casasso, G. Griffero, P. Guglielmi, S. Nieddu, G.M. Pellegrino, New design concepts and realisation of hybrid DC/DC coupling reactors for light EVs, Industrial Electronics Society, IECON '03, Volume 3, pp , (2003) [14] Petar J. Grbovic, Philippe Delarue, Philippe Le Moigne and Patrick Bartholomeus, A bi-directional three-level dc-dc converter for the ultra-capacitor applications, IEEE Trans. Industrial Electronics, Vol 57. No.10, pp , (Oct. 2010). About the authors Assist. Eng. Daniel-Adrian STICEA, PhD danisticea@yahoo.com Graduate of the Electrical Engineering Faculty of Tehchnical University Gheorghe Asachi from Iaşi in Prof. Eng. Gheorghe LIVINŢ, PhD. glivint@tuiasi.ro He is graduated at the Gheorghe Asachi Technical University of Iasi, Electrotechnical Faculty, and electromechanical specialization in After graduation he worked directly in higher education as assistant, and then as lecturer, associated professor. Since 1996 working as professor at the disciplines: The systems theory, the identification and modeling of systems. Also since 2004 he is supervisor of doctoral theses in electrical engineering. He is author of over 150 articles and 15 patents. His research topics are control of electrical drives and industrial processes, hybrid electrical vehicles. Assoc. Prof. Eng. Mihai ALBU, PhD. albu@tuiasi.ro Buletinul AGIR nr. 4/2012 octombrie-decembrie 5 211