ATTAINMENT OF IMPROVED PERFORMANCE BY …ATTAINMENT OF IMPROVED PERFORMANCE BY USING MODIFIED SEPIC CONVERTER Anitha M1, ashaswiniT2, Prema V,33 Assistant professors, SVCE , Bengaluru

ATTAINMENT OF IMPROVEDPERFORMANCE BY USING

MODIFIED SEPIC CONVERTER

Anitha M1, ashaswiniT2, Prema V,33

Assistant professors, SVCE , Bengaluru.anitha [email protected]

May 24, 2018

Abstract

Renewable energy resources plays main role in this erawhere large number of dc to dc converters are being usedto convert one level of dc voltage to another. In last fewdecades many number direct current converters are beingused. SEPIC converters are to be special by its uniquenessby making the technique of conversion by using a semi con-ductor device as a switch and provide wide range of outputvoltage as per requirement.

1 INTRODUCTION

Single ended Primary inductor converter is the proposed type whereMOSFET is being used as a switching device. It is known that itoperates on very high frequency with pulse width modulation tech-nique were width of the triggering input is being varied to get stepup, step down or same voltage as that of the input.

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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/

2 SEPIC model

It consist of an input source, input inductor and an input couplingcapacitor, semiconductor switch, a diode, output load, output filtercapacitor and an output inductor. The assumption made here isbecause of the output capacitor the ripple at the output is very low,zero diode voltage drop, only inductors and capacitors are beingused so resistances are assumed to be very low and the possibility ofcontinuous conduction mode of operation were the inductor currentat the input never becomes zero.

Fig.1. SEPIC converter model

3 SEPIC operation

It has an advantage of achieving non inverted output which is ob-tained by a series capacitor C1which is acting as a coupling capac-itor between input and the output. During steady-state operation,the mean value of the voltage across the input capacitor is equalto the voltage given to the source which is to be processed. As weknow that capacitor blocks DC, so DC current is blocked by thecapacitor and mean value of IC1 is zero. Hence current throughthe L2 is same as the output current independent of the processingvoltage.

VIN = VL1 + Vc1 + VL2

Since the average voltage ofVc1 = VIN

VL1 = −VL2

As voltages are equal in magnitude, and opposite in directiontheir mutual inductance effect will be zero and the ripple currents of

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International Journal of Pure and Applied Mathematics Special Issue

the two inductors will be equal in magnitude. The average currentscan be summed as follows:

ID1 = IL1 − IL2

When switch SW1 is supplied with the gate signal, current inthe input inductor increases and the current IL2 increases in thenegative direction. The energy to increase the current IL1 comesfrom the input source. Since SW1 is closed short while and theinstantaneous voltage VC1 is approximately VIN , the voltage VL2 isapproximately VIN , therefore, the capacitor C1 supplies the energyto increase the magnitude of the current in IL2 and thus increasethe energy stored in L2. When switch SW1 is turned off, the currentIC1 becomes the same as the current IL1, as the inductors will notallow instantaneous changes in current. Current IL2 will continuein the negative direction, in fact it never goes in reverse direction.It can be seen from the diagram that a negative IL2 will add tothe current IL1 to increase the current delivered to the load. Byapplying KCL,

ID1 = IC1 − IL2

So, while SWI is off, power is delivered to the load from bothL2 and L1. Coupling capacitor (C1), is charged by L1 during thisoff cycle, and will recharge L2 during the on cycle. The boost/buckcapabilities of the SEPIC are possible because of capacitor C1 andinductor L2. Inductor L1 and switch SW1 create a standard boostconverter, which generates a voltage that is higher than VIN.

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4 Simulation model of SEPIC converter

5 Simulation results

Result( i): Current and voltage waveforms for 25% duty cycle.

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Result (ii): Current and voltage waveforms for 50% duty cycle

Result( iii): Current and voltage waveforms for 75% duty cycle.

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Result( IV): Current and voltage waveform of 95% duty cycle

6 Modified SEPIC Converter

Dc requirement is being increased day by day were it is of led lampera were in house hold application s or in street as street light onlyLED lamps are being used. So modified SEPIC converter increasesthe output gain double times than that of SEPIC converters.

Fig. 2: Modified SEPIC Coverter

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7 Modified SEPIC Converter operation:

Gain of the regular SEPIC converter can be doubled by using twoextra component in the available circuit. (i.e.) Diode D2 is be-ing connected between drain terminal of the switch to inductor L2ending end and capacitor is being connected between cathode of D2and source terminal of the semiconductor switch. When the switchSW1 is turned ON diode D1 and D2 are blocked and L1 and L2store energy. VIN is applied to L1 and voltage across the inductorL2 will be VC1 − VC2.When the MOSFET switch is turned off energy stored in L1 istransferred to the output through the capacitor C1 and diode andalso transferred to the C2 through D2. Switching voltage is equal toC2 Voltage. Energy stored in the inductor L2 is transferred to theoutput through the diode D1. By this way the final output acrossthe resistance is double than that of the normal SEPIC converter.The circuit has been simulated and results are shown.

8 Modified SEPIC Converter MATLAB

Simulation

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Result (i): Current and voltage waveforms for 25% duty cycle


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9 Component details

10 Comparison of SEPIC and Modified

SEPIC Converter results:

11 Conclusion

From the simulation result the following points has been executedand results were found 1. By varying the duty cycle of the switchingsignal output across the resistance is being varied. 2. In the tableshown static gain of the modified SEPIC converter is Doubled thanthe traditional SEPIC converter.

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References

[1] J. Leema Rose and B. Sankaragomathi, Design, Modeling,Analysis and Simulation of a SEPIC Converter:

[2] SubramaniSaravanan, Neelakandan Ramesh Babu, A modifiedhigh step-up non-isolated DC-DC converter for PV applica-tion:

[3] OnurKIRCIOLU, Murat NL, Sabri AMUR, Modeling andAnalysis of DC-DC SEPIC Converterwith Coupled Inductors:

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Documents

ATTAINMENT OF IMPROVED PERFORMANCE BY …ATTAINMENT OF IMPROVED PERFORMANCE BY USING MODIFIED SEPIC CONVERTER Anitha M1, ashaswiniT2, Prema V,33 Assistant professors, SVCE , Bengaluru