Simulation of Fully-Directional Universal DC- DC Converter for Electric Vehicle Applications

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1 Simulation of Fully-Directional Universal DC- DC Converter for Electric Vehicle Applications Saikrupa C Iyer* R. M. Sahdhashivapurhipurun Sandhya Sriraman Tulsi S Ramanujam R. Ramaprabha Department of Electrical and Electronics Engineering, SSN College of Engineering, Kalavakkam , Tamilnadu, India ABSTRACT This paper proposes a converter that interfaces the energy storage of the vehicle with its motor drive and external charger. In the converter, the circuitry of both Buck and Boost modes are interfaced. This converter applies to Electric Vehicles, Hybrid Electric Vehicles, and Plug-In Hybrid Electric Vehicles. Keywords Universal converter; Electric Vehicle;Battery; MatLab. I. INTRODUCTION The gap between the supply and demand of fossil fuels continues to grow today. This has helped in the development of the electric and hybrid vehicular industries. In a hybrid electric vehicle, a bidirectional dc-dc converter is placed between the battery and the high voltage dc bus. In acceleration or cruising mode, the converter should deliver power from the battery to the dc link [1]. In regenerative or braking mode, the converter delivers power from the dc link to the battery. In an electric vehicle, along with the above operation, the bidirectional dc-dc converter also interfaces the battery with the ac-dc converter during charging/discharging from/to the grid. Hence, the bidirectional dc-dc converter should interface the battery with charging converter as well [2]-[7]. Fig. 1 shows the power electronic interface in an electric vehicle. In this assembly, the bidirectional dc/dc converter should convert the output voltage of the ac/dc converter into a voltage that can recharge the batteries, and vice versa while injecting back to the grid [8]-[18]. The above is known as grid connected mode. In driving mode, the dc/dc converter regulates the dc link (grid) voltage. Fig. 1. Block diagram of the bidirectional dc-dc converter interface in electric vehicle In the condition that Vdc > Vbatt, the battery voltage is stepped up during acceleration and dc link voltage is stepped down during braking [10]. In the condition that Vdc < Vbatt, the battery voltage is stepped down during acceleration and dc link voltage is stepped up during regenerative braking. Considering the need for bi directional flow of power, the proposed dc-dc converter, can meet the needs of the auto industry. It has stepping up and stepping down functionalities that operate in all four quadrants. In this paper, a fully directional universal dc-dc converter is analyzed for electric vehicle applications. The analysis has been carried out using MatLab-Simulink and results are presented.

2 II. DESCRIPTION OF THE UNIVERSAL DC-DC CONVERTER Fig. 2 shows the circuit of a universal dc-dc converter. It consists of 5 MOSFETs, T1-T5 and 5 power diodes, D1-D5. Fig. 2. Circuit schematic of the universal dc-dc converter These power devices are properly combined to select buck and boost modes of operation. Vdc represents the motor drive nominal input voltage during the driving mode or the rectified ac voltage at the output of the grid interface during plug-in mode. The nominal voltage of the vehicle s energy storage system (ESS) is represented by Vbatt [12]. The different modes of operation of the converter are Vdc to Vbatt (buck and boost Operations) and Vbatt to Vdc (buck and boost Operations). In all of the modes, one switch is operated in PWM mode, and the other switches are either ON or OFF. The reasons for which the universal converter is preferred over a conventional converter are; it allows bidirectional power flow and the output is non-inverted with respect to the input, excluding the need for an inverting transformer, thus reducing the overall size and cost [15]. However, the controls of this converter and conventional converter are the same [17]. III. MODES OF OPERATION OF THE UNIVERSAL DC-DC CONVERTER In this section, the different modes of operation of the universal converter are explained with pulse generation. In the bidirectional power flow there are two modes in each direction of power flow. This is explained with the help of the flowchart shown in Fig. 3. Fig. 3. Flowchart showing the modes of operation The modes of operation in each direction are explained below: Mode 1: Vdc < Vbatt, Boost mode T1 and T4 are switched ON, T2 and T3 are switched OFF and T5 is in PWM switching mode. During this mode, Vdc and Vbatt sequentially become the input and output voltages, also inductor current is a state variable in this operation and can be controlled, so the charging power delivered can be controlled.

3 Mode 2: Vdc < Vbatt, Buck mode T2 is switched ON, T1, T4 and T5 are switched OFF and T3 is in PWM switching mode. During this mode, Vbatt and Vdc sequentially become the input and output voltages, while delivering power from the battery to the dc link the inductor is at the output and the current is a state variable. Therefore the DC link voltage and the current delivered to the dc link can be controlled. Mode 3: Vdc > Vbatt, Buck mode T4 is switched ON, T2, T3 and T5 are switched OFF and T1 is in PWM switching mode. During this mode, Vdc and Vbatt sequentially become the input and output voltages, the dc link voltage can be regulated by controlling the current delivered to the battery during driving mode. In Plug-In mode the current delivered can also be controlled. Mode 4: Vdc > Vbatt, Boost mode T1 and T4 are switched OFF, T3 and T2 are switched ON and T5 is in PWM switching mode. During this mode, Vbatt and Vdc sequentially become the input and output voltages; the current drawn to the battery is controllable thereby regulating the dc link voltage. IV. PULSE GENERATION USING MATLAB M FILE Based on the logic explained in the previous section, gating pulses for the switches have been generated using M-file coding [19]. The generated pulse pattern is shown in Fig. 4. Fig. 4. Logic used for generating pulses using MatLab- M-file V. SIMULATION OF THE BIDIRECTIONAL CONVERTER The schematic shown in Fig. 2 has been implemented using MatLab and shown in Fig.5. Fig. 5. MatLab Schematic of Fig. 2 The parameters used for simulation is listed in Table 1.

The pulses for the switches T1 to T5 are generated as explained in Section IV and the pulses for different

4 TABLE I Simulation Parameters for Universal Converter Paramet Values DC link ers voltage, Vdc 24 V / 42 Battery voltage, Vbatt V 42 V / 24 Switching frequency, fs V 20 khz Capacitance, Cdc, 2200 µ F Cbatt Inductance 3 mh, L The pulses for the switches T1 to T5 are generated as explained in Section IV and the pulses for different modes are shown vide Fig. 6 to Fig. 9. Fig. 6. Pulses for switches in Mode 1 Fig. 7. Pulses for switches in Mode 2

5 Fig. 8. Pulses for switches in Mode 3 Fig. 9. Pulses for switches in Mode 4 The simulation results are presented vide Fig. 10 to Fig. 13.

6 Fig. 10. Waveforms for Mode 1 Fig. 11. Waveforms for Mode 2

7 Fig. 12. Waveforms for Mode 3 Fig. 13. Waveforms for Mode 4 The load is kept the same for all the modes. In Fig.10, power is fed from dc link to battery by boost action. In mode 2 (Fig. 11), battery is delivering power to dc link by buck operation. The operation of mode 3 and mode 4 are vice-versa

8 of mode 2 and mode 1 respectively, that is battery and dc link are changed with voltage levels. In mode 1 and mode 3, load current is negative. In all the modes the universal dc-dc converter performs the satisfactory with respect to regulator operation. VI. CONCLUSION In this paper, the simulation of universal dc-dc converter has been done using MatLab software. The proper firing pulses have been generated and the working of the converter has been explained in different modes. The simulation of universal dc-dc converter has proved its capabilities of being used in a wide range of application areas. The topology uses less number of switches compared to that of dc-dc converters required for conventional electric vehicles. Bidirectional power flow capability has been verified through simulation. This work can be extended to interface renewable energy sources for hybrid vehicle applications. ACKNOWLEDGMENT The authors wish to thank the management of SSN College of Engineering, Chennai for providing all the computational facilities to carry out this work. REFERENCES [1] A. Emadi, Y. L. Lee, and R. Rajashekara, Power electronics and motor drives in electric, hybrid electric, and plug-in hybrid electric vehicles, IEEE Trans. Ind. Electron., vol. 55, no. 6, pp , Jun [2] Omar C. Onar, Jonathan Kobayashi, Alireza Khaligh, Fully directional universal power electronic interface for EV, HEV, and PHEV Applications, IEEE transactions on Power Electronics, Vol. 28, No. 12, December [3] R. Ghorbani, E. Bibeau, and S. Filizadeh, On conversion of electric vehicles to plug-in, IEEE Trans. Veh. Technol., vol. 59, no. 4, pp , May [4] C. Erb,O. C.Onar, anda.khaligh, Bi-directional charging topologies for plug-in hybrid electric vehicles, in Proc. 25th Annu. IEEE Appl. Power Electron. Conf. Expo., Palm Springs, CA, Feb. 2010, pp [5] Y.-J. Lee, A. Khaligh, and A. Emadi, Advanced integrated bidirectional AC/DC and DC/DC converter for plug-in hybrid electric vehicles, IEEE Trans. Veh. Technol., vol. 58, no. 5, pp , Oct [6] F. H. Khan, L. M. Tolbert, and W. E. Webb, Bi-directional power management and fault tolerant feature in a 5-kW multilevel dc-dc converter with modular architecture, IET Power Electron., vol. 2, no. 5, pp , [7] G. Zorpette, The smart hybrid, IEEE Spectrum, vol. 41, no. 1, pp , Jan Energy Independence and Security Act of 2007 (CLEAN Energy Act of 2007), One Hundred Tenth Congress of the United States of America, At the First Session, Washington DC Jan [8] Z. Amjadi and S. S. Williamson, Power-electronics-based solutions for plug-in hybrid electric vehicle energy storage and management systems, IEEE Trans. Ind. Electron., vol. 57, no. 2, pp , Feb [9] S. Han and D. Divan, Bi-directional DC/DC converters for plug-in hybrid electric vehicle (PHEV) applications, in Proc. 23rd Annu. IEEE Appl. Power Electron. Conf. Expo., Austin, TX, Feb. 2008, pp [10] D. C. Erb,O. C.Onar, anda.khaligh, Bi-directional charging topologies for plug-in hybrid electric vehicles, in Proc. 25th Annu. IEEE Appl. Power Electron. Conf. Expo., Palm Springs, CA, Feb. 2010, pp [11] S. S. Raghavan, O. C. Onar, and A. Khaligh, Power electronic interfaces for future plug-in transportation systems, IEEE Power Electron. Soc. Newslett., vol. 24, no. 3, pp , Third Quarter [12] Y.-J. Lee, A. Khaligh, and A. Emadi, Advanced integrated bidirectional AC/DC and DC/DC converter for plug-in hybrid electric vehicles, IEEE Trans. Veh. Technol., vol. 58, no. 5, pp , Oct [13] B. W. Williams, Basic DC-to-DC converters, IEEE Trans. Power Electron., vol. 23, no. 1, pp , Jan

9 [14] B. Sahu and G. A. Rincon-Mora, A low voltage, dynamic, noninverting, synchronous buck-boost converter for portable applications, IEEE Trans. Power Electron., vol. 19, no. 2, pp , Mar [15] P. C. Huang, W. Q. Wu, H. H. Ho, and K. H. Chen, Hybrid buck-boost feedforward and reduced average inductor current techniques in fast line transients and high-efficiency buck-boost converter, IEEE Trans. Power Electron., vol. 25, no. 3, pp , Mar [16] S. Waffler and J. W. Kolar, A novel low-loss modulation strategy for high-power bidirectional buck + boost converters, IEEE Trans. Power Electron., vol. 24, no. 6, pp , Jun [17] M. B. Camara, H. Gualous, F. Gustin, A. Berthon, and B. Dakyo, DC/DC converter design for supercapacitor and battery power management in hybrid vehicle applications Polynomial control strategy, IEEE Trans. Ind. Electron., vol. 57, no. 2, pp , Feb [18] M. C. Ghanem, K. Al-Haddad, and G. Roy, A new control strategy to achieve sinusoidal line current in a cascade buck-boost converter, IEEE Trans. Ind. Electron., vol. 43, no. 3, pp , Jun [19] M. Gabriault and A. Notman, A high efficiency, non-inverting, buckboost DC-DC converter, in Proc. IEEE 19th Annu. Appl. Power Electron. Conf. Expo., Anaheim, CA, Feb. 2004, vol. 3, pp [20] P. Midya, K. Haddad, and M. Miller, Buck or boost tracking power controller, IEEE Trans. Power Electron., vol. 2, no. 4, pp , Dec [21]

Dual power flow Interface for EV, HEV, and PHEV Applications

International Journal of Engineering Inventions e-issn: 2278-7461, p-issn: 2319-6491 Volume 4, Issue 4 [Sep. 2014] PP: 20-24 Dual power flow Interface for EV, HEV, and PHEV Applications J Ranga 1 Madhavilatha