Simulation and Experimental Analysis ofHybrid DC-DC Converter for Electric

Vehicle Applications

R.Elavarasu1, and C.Christober Asir Rajan2

1Department of EEE, Rajalakshmi Institute of Technology,Chennai, India.

2Department of EEE, Pondicherry Engineering College,Puducherry, India

May 9, 2018

Abstract

This proposal presents a Hybrid DC-DC converter forelectric vehicle applications. This converter is designed withtwo input sources (Solar PV), a bidirectional storage port(Battery) and an output port. The proposed converter issame as that of three phase inverter. The proportional in-tegral controller used for control the output dc voltage ofthe system. The proposed test for sudden change in loadingconditions, sudden change in reference conditions, changein irradiance conditions. Simulation results and hardwareresults are presented for justify the proposed work.

Key Words:Hybrid converter, DC-DC converter, PIcontroller.

1 Introduction

In recent years, greenhouse gas emissions have increased with ad-vances in technology, leading to global warming and climate change.

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International Journal of Pure and Applied MathematicsVolume 118 No. 24 2018ISSN: 1314-3395 (on-line version)url: http://www.acadpubl.eu/hub/Special Issue http://www.acadpubl.eu/hub/

The energy technology industry continues to be heavily dependenton fossil fuels and is unable to handle this stringent environment [1,2]. Therefore, the use of green energy has become the core of majoreconomic strategies and is a key focus in world politics, especiallybecause reducing greenhouse gas emissions and conserving energyare the main global concerns at present. In general, because of thelarge difference between the output voltage of green energy appara-tus and the operating voltage of DC bus, a high step-up converteris always required for connecting these two stages. A conventionalboost converter should operate with an extremely high duty ratio toprovide high step-up voltage. In particular, its maximum step-upratio is limited by the parasitic elements of the circuit components.The existence of parasitic components [3] and the reverse recoverytime of diode [4] reduce the converter efficiency. Consequently, theuse of conventional boost converters in the field of green energy islimited. Recently, to achieve a high step-up ratio, the use of a se-ries boost converter, the voltage-lift technique, a coupled inductor,and a cascade circuit structure has been proposed [511]. When theswitch of the boost converter is open, a large current flows throughthe power components, and therefore, power components with highcurrent stress are required, which implies high cost and conductionenergy loss. The conventional flyback converter and forward con-verter have also been proposed for achieving high step-up voltages.However, because the leakage inductance of the transformer in theseones can lead to high reverse voltage across the switch, a passivesnubber circuit or an active clamp is required to suppress such areverse voltage. A passive snubber circuit has a resistance that de-pletes the excess energy of the leakage inductance, thereby reducingthe circuit efficiency. By contrast, an active clamp results in manycomponents being added to the circuit, which not only increasescost but also renders inverter control difficult. In [12], a topologywas proposed for solving the leakage inductance problem; however,the remaining disadvantageslarge circuit size and high costpersist.

For the reasons mentioned above, in this paper we propose anovel hybrid bidirectional DC/DC converter. When the energy sup-plied by the PV modules is sufficient, the converter can not onlystep up the output of the PV modules, but also provide energyto the DC bus and charge the battery simultaneously. However,when the energy supplied is insufficient, the converter can step up

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the output of the battery and provide energy to the DC bus. Anyexcess energy in the DC bus is used to charge the battery, imply-ing that the proposed topology can perform both high step-up andhigh step-down functions. The topology proposed is isolated, andthe DC -blocking capacitor on the high-voltage side can reduce thevoltage on the transformer, facilitating the operation of the systemin the high step-down mode. An improved three phase inverteris used on the low-voltage side of the PV modules to step up theoutput of the PV modules for charging the battery and providingenergy to the DC bus. The proposed topology consists of threeoperational modes, which reduce the cost and size of the systemconsiderably. Furthermore, the converter can perform synchronousrectification and recycle energy from the leakage inductor simulta-neously functions increase the overall efficiency of the system con-siderably.

2 Hybrid DC-DC converter for electric

vehicle application

The block diagram of hybrid DC-DC converter for electric vehicleapplications is shown in the Figure 1. The system consist of twosolar PV system, one bidirectional battery storage system, threephase inverter system, step up transformer, diode bridge rectifier,filter, load, proportional integral controller, and switching and logiccircuits. The output voltage is compared with reference voltage andthen it is processed via proportional integral controller. The PIcontroller is produces control signal for switching and logic circuitsand it drive the inverter circuits and it tracks the reference voltage.The parameter of the proportional integral controller is tuned usingtrial and error method.

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Fig.1. Hybrid DC-DC converters

3 Simulink model and results

The rating of the solar panel and battery in shown in Table 1. Theoverall simulink model is created in MATLAB 2015b 64 bit versionwith 1.7 GHz PC. Figure 2 shows the overall simulink model of thehybrid DC-DC converter.

Table.1. Specification of solar PV and Battery

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Fig.2. Simulink model of the hybrid DC-DC converter

The proposed sytem is tested for different reference voltage condi-tions and change in load conditions. Figure 3 shows the voltageresponse for different reference voltage conditions, load change inconditions. By examin the voltage response, it is track the refer-ence voltage settings. And also, no changes in the voltage responseduring sudden load change in conditions. From these results, itis ascetained that the proposed sustem is suitable for the electricvehicle applications. In order to justify the effectiveness of the pro-posed system, experimental verfication of the proposed system isexplained in the next section.

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Fig.3. Simulation results, a) Voltage response at reference voltage100, b) Voltage response at reference voltage 200, c) Voltage

response for load change from 0.2 amps to 0.5 amps, d) Voltageresponse for load change from 0.5 amps to 0.2 amps

4 Experimental setup and results

To verify the effectiveness of the proposed system, simplified ex-perimental setup block diagram is shown in Figure 4. Snap shot ofreal time experimental setup is shown in Figure 5.

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Fig.4. simplified block diagram of the experimental setup ofhybrid DC-DC converter

Fig.5. Snap shot of real time hardware setup of hybrid DC-DCconverter

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Fig.6. Hardware results of the proposed system

Figure 6 shows the hardware results of the proposed system andresponses are similar to the simulation results. Performance pa-rameter comparisons of the simulation results and hardware resultsare shown in Table 2.

Table.2. Comparisons of the simulation and hardware results

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5 Conclusions

In this paper, hybrid DC-DC converter system is proposed for elec-tric vehicle applications. The overall system is created and simu-lated in MATLAB / Simulink. The proposed system is tested withdifferent operating conditions. Finally, the proposed system is ver-ified experimentally and compared with simulation results. Fromthese results analyze, it is ascertained that the proposed hybrid DCDC converter is suitable for electric vehicle applications.

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