simulation and implementation of high gain dc-dc converter ... · fig.2. pwm signal for the dc-dc...

Simulation and Implementation of HighGain DC-DC Converter for PV

Applications

S.Harika1, Dr.R.Seyezhai2,Research Scholar1, Associate Professor2,

Department of EEE, REC lab,SSN College of Engineering,

Chennai, [email protected],

[email protected]

May 11, 2018

Abstract

This This paper investigates a high gain DC-DC con-verter with low ripple content employing coupled inductorfor PV applications. It is highly preferable in boosting lowPV panel voltage to high voltage. The efficiency of theproposed converter is high and it is cost effective as it is ba-sically a transformer less topology. The proposed topologyis designed and implemented with multiple maxima searchMPPT algorithm interfaced with PV. Simulation studies ofthe converter and PV modeling with MPPT are carried outin MATLAB/SIMULINK. A hardware prototype is built tovalidate the simulation results

Key Words:Coupled inductor, Voltage gain, transformerless topology.

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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/

1 Introduction

In recent days, high gain converter plays a dominate role in caseof renewable energy resources. It has numerous advantage suchas low ripple content and high efficiency and hence finds applica-tion in solar system, UPS and automobile applications. The recentchange in the environmental conditions such as global warming andincreased electricity demand led to generation of electricity from re-newable energy resources (1). In that, solar energy has emerged tomeet the electricity demand to give a feasible solution to the abovementioned problem. Therefore, the DC/DC converters play an im-portant role for solar PV system. In addition, the design of highpower DC-DC converters and their controller plays an importantrole to regulate the output voltage.

To meet the existing power demand, PV power generation hasbecome increasingly important as it is a clean energy source dueto its environmentally friendly nature and practically unlimitedsource. Without any mechanical effort, solar panel delivers elec-trical energy when required number of cells connected in series andparallel (2). The great challenge of working with solar panel is itscost and efficiency. One best way to reduce the cost of PV panel(installation, generation and marketing) is to buy the solar panelwith low efficiency. And to increase the efficiency of PV panel is toimprove the efficiency of maximum power point tracking (MPPT)algorithm. In the literature, many power point tracking techniqueshas been explored to overcome the drawbacks of low conversionefficiency of PV panel (3 & 4). This paper focuses on multiplemaxima search MPPT algorithm to track the maximum operationpoint (OP) from multiple maxima points. During partial shadingcondition, conventional algorithm fails to track global maximumpoint. To overcome this, many MPPT algorithms is emerged andthe survey shows that multiple maxima search MPPT algorithmworks well during partial shading condition. It tracks as well ascontrols the pulse pattern of the converter switch (5).

Mostly, boost converter is chosen for high output voltage range,but the conventional boost converter suffers from high output volt-age ripple and low voltage gain. There are two types of converter:non-isolated and isolated converters, it is proven that the non-isolated can be more efficient than the isolated ones. The different

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International Journal of Pure and Applied Mathematics Special Issue

non-isolated dc-dc converters topologies are: classical boost, mod-ified boost, high gain boost, cascade, interleaved boost, high gaininterleaved boost and classic boost converter(6).For high voltageconversion ratio, traditional boost converter is not preferable sincethe conversion ratio of output voltage is limited to 5 times of the in-put voltage. Hence, high gain DC-DC boost converter is proposed(7). In this topology, the input inductor is replaced by coupled in-ductor to overcome problems such as high reverse recovery current,turn on and turn off losses, the leakage current and current stressin switching devices. High conversion gain is obtained at low valueof duty ratio.

The paper is organized as: Section II discusses about the pro-posed high gain DC-DC converter, Section III focuses on the simu-lation results, Section IV depicts the hardware results and sectionV finally concludes the paper.

2 HIGH GAIN DC-DC BOOST CON-

VERTER

The circuit diagram of high gain converter is shown in Fig.1.

Fig.1. Circuit diagram of high gain DC-DC boost converter

With the primary of the coupled inductor, current limiting in-ductor, two diodes and capacitor is connected to reduce the voltagestress across the switch. Moreover, LC filter is connected with cou-pled inductor to reduce the output voltage ripple. By varying the

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turns ratio of coupled inductor, high gain can be achieved in thistopology. The voltage gain of the converter is given by

V0 =n× Vs

1−D(1)

Where ’n’ is the turns ratio, ’D’ is the duty cycle and ’Vs’ is theinput voltage.

The pulses are generated to the converter by employing PWMtechnique, where a triangle waveform is used as a carrier wave andDC as the reference as shown in Fig.2.

Fig.2. PWM signal for the DC-DC converter

3 SIMULATION RESULTS

The high gain DC-DC boost converter is modeled and interfacedwith PV panel with multiple maxima search MPPT algorithm isshown in Fig.3.

Fig.3. Simulink diagram of high gain DC-DC boost converter

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Fig.4. Output voltage of the proposed topology

Fig.4 shows the output voltage boosted to 500V for an inputof 21V. The voltage across the diode, voltage across the inductor,voltage stress across the switch and inductor current is shown inFig.5 - Fig.8.

Fig.5. Diode voltage

Fig.6. Voltage across the inductor

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Fig.7. Current through the inductor

Fig.8. Voltage stress across the switch

The inductor current shape and voltage across the device de-picted in Fig.7 & 8, proves that current ripple and stress across thedevice is low.

From the simulation results, the performance analysis of pro-posed converter is done and compared with conventional boost con-verter, the results shows that the proposed converter has 2% outputvoltage ripple, 2.4% output current ripple and voltage gain of 24whereas traditional boost converter has 25 % output voltage ripple,25% output current ripple and voltage gain of 15. And it is proventhat the high gain boost converter with coupled inductor has lowvoltage ripple, low current ripple and high voltage gain comparedto traditional boost converter.

The converter switching loss is calculated using the equation (2)

Psw =1

2× |V | × |I| × (ton + toff )× fsw (2)

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The switching loss calculated is about 2.187W and diode loss is6.561W and the total loss is about 10.61W. The efficiency of theproposed high gain DC-DC boost converter with coupled inductoris 80%.

Fig.9. Duty ratio (D) Vs Voltage gain

Fig.10. Duty ratio (D) Vs Voltage ripple (V)

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Fig.11. Duty ratio (D) Vs Current ripple (I)

Fig.9 - Fig.11 shows the variation of voltage gain, voltage rip-ple and current ripple with different values of duty ratio. It isproven that the proposed high gain converter has high voltage gain,lower voltage ripple and lower current ripple compared to tradi-tional boost converter.

4 HARDWARE RESULTS

Practically, the VI and PV characteristics are observed for the 40Wsolar panel and the characteristics are shown in Fig.12. The pulsefor the proposed converter is generated using FPGA SPARTAN 3E.

Fig.12. VI and PV characteristics of 40W panel wit Voc = 21.4Vand Isc = 2.48

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Fig.13. Pulse generation for high gain DC-DC boost converter

In Fig.13, the triangular carrier wave is generated using SPAR-TAN 3E XILINX tools and compared with constant. The programis burned to the FPGA Processor and given to the optocouplerboard. The generated pulse pattern for high gain converter is shownin Fig.14.

Fig.14.Pulse pattern for high gain DC-DC boost converter

The parameters used for the prototype of the high gain DC-DCboost converter is listed in table -I.

TABLE I : Specifications of high gain boost converter

A prototype model of high gain DC-DC boost converter is de-veloped with input voltage of 6.3V and it is boosted to 218V isshown in Fig.15.

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Fig.15. A prototype of the proposed topology of DC-DC converter

In Fig.16, the proposed boost converter is interfaced with PVpanel through 12V,6A charge controller with input voltage of 12Vis boosted to 214V.

Fig.16. Prototype model of proposed converter interfaced with40W PV panel

Fig.17. Output voltage ripple content

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Fig.17, shows that the high gain converter has 0.8% ripple con-tent which validates the simulation results.

5 CONCLUSION

This paper has explored the significance of high gain DC-DC con-verter for PV applications. From the simulation results, it is notedthat this topology has resulted in high voltage gain, reduced ripplecompared to the classical boost converter. Further, a hardware pro-totype has been built and pulses have been generated using FPGA.The output voltage ripple have been measured using PQ analyzerand the results have been validated. Therefore, the proposed highgain converter will be highly beneficial for PV applications.

6 ACKNOWLEDGMENT

We authors wish to thank the SSN Management for providing thefinancial support in carrying out this research work.

References

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[7] Felinto S. F. Silva, Antnio A. A Freitas et.al, ” High GainDc-Dc Boost Converter With a Coupling Inductor ”, BrazilianPower Electronics Conference. pp. 486 - 492,2009

[8] P.V.Suresh, Dr. Arvind Mittal , Dr. Amit Ojha,” Review onHigh Gain DC/DC converters for Renewable Energy Applica-tions and their comparison with proposed converter”, IJETER,Vol. 3 No.6, pp : 471 - 476,(2015).

[9] A.Devipriya, Dr.S.Senthilkumar,” High Gain DC/DC Con-verter for Photovoltaic Applications”,IJPCSC, Vol 6. No.2 ,pp. 109-116, (Jan-March 2014).

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simulation and implementation of high gain dc-dc converter ... · fig.2. pwm signal for the dc-dc...

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