multiport dc-dc converter for renewable energy applications · a buck-boost converter with...

Multiport Dc-Dc Converter forRenewable Energy Applications

A. Lavanya1, J. Divya Navamani2

and K. Vijayakumar3

1 2 3EEE Department,SRM University, Kattankulathur,

Kancheepuram - 603203, [email protected]

[email protected] kvijay [email protected]

January 5, 2018

Abstract

Background/Objectives: Multisource dc-dc convertertopology, a promising concept for renewable energy systems.

Methods/Statistical analysis: In this paper the bidi-rectional dc-dc converters and the three port dc-dc convertersimulation results are obtained and investigated using MAT-LAB and PSIM software. Experimental procedure validatethe results

Findings: Two dc-dc converters bidirectional capabil-ity and different storage element placement is considered foranalysis and their performance is analysed and from the ca-parison a feasible converter for three port dc-dc converteris derived and considered for analysis. This converter con-sidered for analysis can be operated in both buck and boostmodes of operation.

Improvements/Applications: The three port con-verter is proficient for energy diversification from two energysources individually or simultaneously. This three port con-verter finds a suitable place in satellite applications.

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International Journal of Pure and Applied MathematicsVolume 118 No. 17 2018, 435-448ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version)url: http://www.ijpam.euSpecial Issue ijpam.eu

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Key Words: Multiport converter; dc-dc converter; Bidi-rectional converter; Satellite applications; renewable energy;Topology; PSIM.

1 Introduction

Power electronic multiport dc- dc converters are very much requiredfor air vehicle in the power supply, power distribution and on boardcharges.Alternative generation systems that utilize renewable en-ergy sources are gaining popularity due to their high operationefficiencies and low CO2 emission levels. Today, in the fields ofelectric power systems and power electronics a lot of research effortis being put into the development of alternative electricity gen-eration systems. Traditionally, individual converters are used toprovide interfaces for power inputs of the system. In principle,power converter for a fuel cell system can be designed from anybasic power electronics topology. In recent years, the advancementin power electronics has increased the growth of power convertersthat are capable of interfacing multiple renewable energy sources alltogether. Promising development in the field of multiport convert-ers are based on a integrated converter topology with many inputsthat are capable of interfacing with different sources, storages andloads. Instead of using many dc-dc converters and interconnecting,a single multiport converter can be utilised. This converter has theadvantages of requiring fewer components and having a lower costmore compact size and better performance.

Figure 1: Hybrid power system

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1.1 Bidirectional dc-dc converters

Non-isolated bi-directional converters have simple structure, betterefficiency, highly reliable with low cost. The basic non-isolatedconverter consists of a single switch and a single diode and mayhave one inductor and one capacitor as storage elements. Thereare other non-isolated converters having two switches, two diodesand additional energy storage elements.

Bidirectional converters can transfer power from both direc-tions. When source1 is actively transferring power, other side ofthe converter consuming the power acting as load and vice versa.They are essential in high-performance storage-backed generationsystems.

(a) (b)

(c)

Figure 2: Basic bidirectional topology: a)Boost half bridge (b)Three port converter combining dc-link and magnetic coupling(c)Boost full-bridge

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In many situations, a large voltage transfer ratio and electricalisolation are required when incorporating storage into a genera-tion system. This often leads to a converter topology with a high-frequency transformer. In the category of isolated bidirectional dc-dc converters, several full-bridge derived converter topologies havebeen proposed in the literature, with the aim to reduce switchingloss, minimize electro-magnetic interference (EMI), and increaseefficiency.

2 Comparison of cascaded dc-dc con-

verters

A buck-boost converter with cascading structure is proposed in theliterature for HEV and Fuel cell vehicles1 as shown in Fig. 3. Bidi-rectional converter acts in boost mode if the battery voltage droopsor if the dc bus voltage is greater. The voltages may overlap due tothis mode changes. Therefore converter used in this system shouldbe capable of handling these overlapping voltages. The same topol-ogy has been discussed in the literature 2,3,4 . Several differenttypes of bidirectional DC-DC converters along with their compar-ison appear in the literature 5,6. Main disadvantage in these con-verters are even though they have fewer components and simplecontrol techniques, but cannot provide bidirectional power flow ca-pability.

Table 1: Comparison of bidirectional dc dc converters

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2.1 Multiport dc-dc converters

Multiport converters, a promising concept for alternative energysystems, have attracted increasing research interest recently

Figure 3: Three port dc dc converter

A bi-directional cascaded DC-DC converter that can operate inboth modes i.e,buck and boost modes with a extensive range ofvoltage levels in either direction is necessary to achieve the objec-tive. The Single input topology 1 can also be used in the V2G modewith the battery pack and ultra-capacitor bank serving as multipleinput sources, and a DC external load connected across C4 at Voutin the circuit shown in Fig3 .

The Single input topology 1 and 2 with capacitor and inductorconverted to multiple input and/or multiple outputs is analyzedin the following. The duty cycles 2, 4 and 5 for the gate switchingsignals of 2, 4 and 5, respectively are as follows in equations[1][2][3]:

D2 = 1 − V CMV ε1

(1)

D4 = 1 − V CMV ε3

(2)

D5 = VoutV CM

(3)

where VCM is the intermediate stage voltage.Analysis of multiinput dc dc converter:

diL1

dt= −D1

L1Vcm + Vin1

L1(4)

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diL2

dt= −D3

L2Vcm + Vin2

L2(5)

diL2

dt= D6

L3Vcm + VC2

L3(6)

dVcmdt

= D1

CmiL1 + D6

CmiL2 (7)

dVc2dt

= 1C2iL2 − VC2

C2RL(8)

Multi input case in Single input topology 1 (b) 1 and 2 ¡ (Boostmode) and VCM ¿ (Buck mode). The topology 1 considered canalso be used in the G2V charging mode with the battery pack andultra-capacitor bank serving as multiple outputs. C4 then becomesthe charging port connected to a rectified DC source for chargingof battery or ultra-capacitor at the C1 and C2 ports. The topology2 can be used with one input and multiple outputs similar to thetopology 1.The duty cycles D4 and D6 for the gate switching signalsof S4 and S6.

2.2 Simulation results

In this section, two different single input dc dc converters is consid-ered and investigated using MATLAB in order to validate the per-formance of the proposed converter. Analyses were carried out withresistive load with 400 V and 200V input voltage. Fig 3 Cascadedbuck boost-CBB CIM converter simulated and output voltage Fig4 is obtained using MATLAB Simulink.

Figure 4: Single input topology 2 Figure 4(a): Output voltage

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Figure 5: Three port dc dc con-verter

Figure 5(b): output voltage wave-form

Figure 5(c): IL Inductor current waveform

Fig 6-12 shows the PSIM simulated circuit of Single input topol-ogy 1and 2 and the corresponding output voltage, gate pulses andinductor current waveforms for cascaded buck boost single with theenergy storage elements like inductor and capacitors are in the mid-dle of the converters and three port converter circuit and simulatedwaveforms.

Figure 6: Single input topology 1

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Figure 7: Input voltage waveform

Figure 8: Gate pulses for switches S1 and S2

Figure 9: Single input topology 2

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Figure 10: Inductor current waveform

Figure 11: Three port dc dc converter

Figure 12: Output voltage waveform

3 Experimental results

The hardware circuit diagram consists of two voltages sources, twoinductors, a capacitor, four switches and load. To verify the con-verter operation, the prototype is designed and results are obtained.The values of circuit parameters used in the simulation and exper-imental circuit are listed in Table 2.

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Table 2: Simulation parameters

Table 3: Experimental values

The experimental setup of the three port dc -dc converter isshown in Fig 8 followed by the gate pulse waveforms Fig 9 and alsothe output voltage waveform of the converter is shown to validatethe simulation results of the converter for boost mode of operationwith 36V input voltage.

Figure 13: Experimental setup

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(a) (b)

(c) (d)

Figure 14: (a) Gate pulse S1, S2 (b) Gate pulse S3,S4 (c) GateS5 (d) Output voltage waveform

Output voltage effects with load variation and line voltage vari-ation is depicted in the following graphs Fig 15 and Fig 16 for Threeport converter is analyzed.

Figure 15 : Load regulation Figure 16: Line regulation

4 Conclusion

The cascaded buck-boost DC-DC converter has an intermediatestage to store energy at a higher voltage level which allows theoverlap between battery voltage and DC bus voltage in the entire

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operating range. Using PSIM software two different single inputsimilar dc dc converter topologies are considered were simulatedand the output waveforms were shown. These converters can per-form boost and buck operation in both directions which is usefulin certain vehicle systems such as fuel cell electric vehicles. Threeport dc-dc converter derived from the single input dc-dc convertertopologies in the paper is simulated and hardware shown has bet-ter efficiency, compactness and decreased voltage stress across theswitches proves its suitability for satellite applications.

References

[1] Waffler, S.; Kolar, J.W., A Novel Low-Loss Modulation Strat-egy for High-Power Bidirectional Buck - Boost ConvertersPower Electronics, IEEE Transactions on , vol.24, no.6,pp.1589-1599, June 2009.

[2] F. Caricchi, F. Crescimbini, F. G. Capponi, L. Solero, Studyof bi-directional buck-boost converter topologies for applicationin electrical vehicle motor drives IEEE Appl. Power Electron.Conf. and Expo., APEC, vol.1, pp.287-293, Feb 1998.

[3] R.M. Schupbach; J.C. Balda, Comparing DC-DC convertersfor power management in hybrid electric vehicles Electric Ma-chines and Drives Conference, IEEE International, vol.3, pp.1369-1374, 1-4 June 2003.

[4] Yu Du; Xiaohu Zhou; Sanzhong Bai; Lukic, S.; Huang, A.,Review of non-isolated bi-directional DC-DC converters forplug-in hybrid electric vehicle charge station application at mu-nicipal parking decks Applied Power Electronics Conferenceand Exposition (APEC), 2010 Twenty-Fifth Annual IEEE,pp.1145-1151, Feb. 2010.

[5] Zhijun Qian, Osama Abdel-Rahman, Hussam Al-Atrash andIssa Batarseh, Modeling and Control of Three-Port DC/DCConverter Interface for Satellite Applications IEEE transac-tions on power electronics, vol. 25, NO. 3, MARCH 2010.

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[6] Edgar Cilio, Gavin Mitchell, Marcelo Schupbach, and Alexan-der B. Lostetter, SiC Intelligent Multi Module DC/DC Con-verter System for Space Applications IEEE Aerospace Confer-ence, Big Sky, Montana, March 9-13, 2009.

[7] P. Suresh and S. Karunakaran,On Chip SC DC-DC Converterwith Single Input Multiple Output Middle-East Journal of Sci-entific Research 23 (Sensing, Signal Processing and Security):97-101, 2015 ISSN 1990-9233.

[8] G. Ramu, Analysis and Design of a Isolated Bidirectional DC-DC Converter for Hybrid Systems Middle-East Journal of Sci-entific Research 19 (7): 960-965, 2014.

[9] Mehnaz Akhter Khan, Adeeb Ahmed, Iqbal Husain,YilmazSozerand Mohamed Badawy Performance Analysis of Bidirec-tional DCDC Converters for Electric Vehicles IEEE Trans-actions on Industry applications, vol. 51, no. 4, July/August2015.

[10] M. A. Khan, I. Husain, and Y. Sozer, A bidirectional dcdcconverter with overlapping input and output voltage ranges andvehicle to grid energy transfer capability IEEE J. Emerging Sel.Topics Power Electron., vol. 2, no. 3, pp. 507516, Sep. 2014.

[11] R. de Castro et al.,Robust dc-link control in EVs with multipleenergy storage systems, IEEE Transactions on Vehicle Tech-nology., vol. 61, no. 8, pp. 3553 3565, Oct. 2012.

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