DC-DC Converter with Coupled Inductor and Multiplier Cells ... · gain is also improved by using a...

DC-DC Converter with CoupledInductor and Multiplier Cells for High

Voltage Gain Applications

Shyni S.M, Abitha Memala W, Bhuvaneswari CDepartment of Electrical and Electronics Engineering

Sathyabama Institute of Science and Technology,Chennai, India [email protected],

[email protected], bhuns [email protected]

July 6, 2018

Abstract

In this paper, a high voltage gain DC-DC converter us-ing coupled inductor and two voltage multiplier cells is an-alyzed and simulated. The proposed converter operates inZero-Voltage Switching (ZVS) mode where the reasonableleakage inductances of the coupled inductors alleviate thereverse recovery problem of diodes. The converter used re-duces the conduction losses and the voltage stress on theswitch, thereby improving the efficiency. A prototype cir-cuit with 21-V input voltage, 260-V output voltage is imple-mented to verify the performance of the proposed converter.

Key Words:DCDC converter; singlecoupled inductor;high voltage gain; voltage multiplier cells (VMCs); zero-voltage switching (ZVS); low voltage stress.

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International Journal of Pure and Applied MathematicsVolume 120 No. 6 2018, 7123-7135ISSN: 1314-3395 (on-line version)url: http://www.acadpubl.eu/hub/Special Issue http://www.acadpubl.eu/hub/

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1 INTRODUCTION

Various DC DC converters like Boost converter, Buck converter,Buck Boost converter, Cuk converter, Zeta converter, SEPIC con-verter, etc. are been used for obtaining high voltage. Among thisBoost Converters are used in wide applications due to its perfor-mance, efficiency, design and control.

The voltage gain DC DC converters is used in industrial ap-plications such as battery backup systems, Switched Mode PowerSupply (SMPS), distributed photovoltaic (PV) generation systems,high intensity discharge lamp ballasts for automobile headlamps,traction control of electric vehicles and in biomedical applications.It is used to reduce voltage stress on the main switches and recyclethe output by leakage inductance energy. This converter achieveshigh voltage gain at 100% duty cycle.

A high voltage gain is generated using boost converters withdual coupled inductors and a voltage multiplier module in [1]. Theproposed converter has advantages of low ripple voltage and re-duced voltage stress in switches as they switch in ZCS Conditionwith reduced reverse recovery problem of diodes. This converter isnot effective for reduced duty cycle under the interleaved control.This drawback can be overcome by a DC-DC Converter using PIController where the converter can be operated with less duty cycle[2]. The maximum overshoot response which is obtained by a PIController is avoided in [3] by using a Fuzzy Logic Controller. Highvoltage is generated by charging and discharging the capacitor inparallel and in series respectively. PI Controller when used withFuzzy Logic has minimum overshoot and constant output voltage.

An integrated converter with a single conversion stage is used onthree-state communication cell for battery charging [4]. Howeverthe conduction losses and efficiency are challengeable. A Switchwith low resistance is adapted with the converter to reduce theconduction loss, thus improving the efficiency [5]. Two Interleavedthree level module is used with Pulse Width Modulation to sharethe load current and to reduce the ripple current[6].A quadraticboost converter with coupled inductor, a voltage doubler cell and

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diodecapacitor techniques alleviates the problem of potential reso-nance improving efficiency [7].

A Switched Capacitor Inductor converter is more advantageouswith renewable energy sources [8]. The circuit improves the effi-ciency and reduces the voltage stress as the inductors and capaci-tors are switched in a parallel-series configuration. Two inductors ofsame inductance, when charged in parallel and discharged in seriesproves to be efficient for Diesel Generation Systems along with PVSystems[9].A high output voltage at the rate of 30 to 50 times theinput voltage is generated with an isolated inductor. The switchingpeak current is also minimized by the inductor [10]. [11] Has useda diode capacitor combination at the secondary side of the coupledinductor. Switches of low voltage rating are used and the leakageenergy of the inductor is recycled to obtain high efficiency.

A DC-DC Converter is designed by using voltage multiplier cellsand three state switching cells [12]. This in turn increases the volt-age gain to double and reduces the duty cycle loss. The voltagegain is also improved by using a parallel input output series boostconverter [13]. This DC-DC Converter makes use of two coupledinductors and a voltage multiplier cell. A three phase interleavedDC-DC converter is proposed to improve voltage gain for photo-voltaic applications [14].A quadratic boost converter and voltagemultiplier cell are combined to design a non-isolated DC-DC Con-verter [15]. Hence the voltage gain can be improved by using mul-tiplier cells.

The drawbacks discussed in the literature regarding high voltagestress across the switch and diodes, switching losses and decreasein efficiency with increase in duty ratio can be obtained by DC-DCConverter integrated with Single Coupled Inductor and two Volt-age Multiplier cells. This Paper gives a brief explanation of variousparts of High Voltage Gain DC-DC Converter and its modes of op-eration.

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2 HIGH VOLTAGE GAIN DC DC CON-

VERTER

The block diagram of a high voltage gain DC-DC Converter isshown in figure 1.which consists of a boost converter, coupled in-ductor and voltage multiplier cells. A low voltage is given as aninput to the boost converter, which steps up the given voltage andis fed to the coupled inductor. The output from the coupled induc-tor is directed to the voltage multiplier cells where the voltage getsmultiplied to many times according to the requirement.

Fig.1.High voltage gain dc-dc converter

A. Boost ConverterBoost converter is a type of step-up converter in which the inputvoltage is increased to a higher value. The main advantage of thisconverter is low operating duty cycles. Boost converters are used inconjunction with much renewable energy like photovoltaic energy,wind energy, etc., to obtain maximum power and higher efficiency.Boost converters can be used for inductive or non-inductive solu-tions. This paper proposes inductive interleaved boost converterwith voltage multiplier cell. The voltage ripples in the output ofboost converter can be removed by using filters.

B. Coupled Inductor

Two inductors coupled magnetically are called as coupled In-ductors. The input to one inductor will result as an output onboth inductors. The magnetic field of two inductors attached to

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two different circuits together, the inductors can transfer energyfrom one to the other.

C. Voltage Multiplier CellsA Voltage Multiplier cell increases the voltage from a lower levelto higher level. The Voltage level can be increased to two times,three times or many a times depending upon the application andaccordingly multiplier cells can also be stacked. Here the outputof the converter is given to voltage multiplied cells to increase thevoltage level.

3 MODES OF OPERATION

The proposed DC-DC converter comprises of a boost converter,coupled inductor and voltage multiplier Cells. The equivalent cir-cuit of the DC-DC converter has a magnetizing inductor Lm, leak-age inductor Lk, and an ideal transformer. The primary winding Np

of the transformer is parallel to the magnetizing inductor Lm andthis combination is connected in series with the leakage inductorLk. An input voltage of 21V is given to obtain an output voltage of260V. The operation of the proposed converter is discussed in fivedifferent stages.

A. Mode 1When the power switch S is turned ON, while diodes D2 and D4

are turned ON and diodes D1 and D3 are turned OFF, as shownin figure 2.The dc source, Vi magnetizes Lm through switch S. Thesecondary winding of the coupled inductor is in parallel with capac-itor C2 through diode D2. The secondary winding current of thecoupled inductor decreases linearly with the increase in the cur-rent of leakage inductor Lk. The output capacitor CO supplies therequired energy for the load RL. This mode continues until thesecondary current of the coupled inductor becomes zero say t = t1.

B. Mode 2Att = t1, the switch S remains turned ON while the diode D3 getsturned ON and the diodes D1, D2,and D4 are turned OFF. During

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this stage, there is a linear increase in current of both leakage induc-tor Lk and magnetizing inductor Lm. The capacitor C3 is chargedand the secondary winding current of coupled inductor decreases.This interval ends when switch S is turned OFF, say at t = t2. Fig-ure 3 explains the second operation mode of high voltage DCDCconverter.

Fig.2. First mode of operation

Fig.3. Second mode of operation

C. Mode 3Third mode of operation starts from time t = t2. At this mode, theswitch S is turned OFF, meanwhile the diodes D1andD3 are turnedON and diodesD2andD4 are turned OFF. The energy stored in thecapacitor C2 charges the capacitor C1. The secondary current ofthe coupled inductor increases linearly with the decrease in the cur-rent of leakage inductor Lk.DiodeD3 charges the capacitor C3. Thismode exists until the currents of leakage inductor and magnetizinginductor are equal say at t = t3, which is represented in figure 4.

D. Mode 4The switch S remains turned OFF condition even after third modeof operation. During this stage, diodes D1andD4 are turned ONand diodes D2andD3 are turned OFF. The clamp capacitor C1is

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charged by the capacitor C2. There is a decrease in the currentsof the leakage inductor Lkand magnetizing inductor Lm. The mag-netizing inductor Lm transfers a part of the stored energy to thesecondary side of the coupled inductor. This interval continues un-til the diode D1 is turned OFF say at t = t4. Figure 5 Shows thecurrent flow path of fourth mode.

E. Mode 5During this stage, the switch remains in OFF position. The diodesD2andD4 are turned ON and diodes D1andD3 are turned OFF. Itis observed that the currents of the leakage inductor and magnetiz-ing inductor decreases linearly. Diode D2 charges the capacitorC2.This interval ends when switch S is turned ON. The current flowpath of this stage is shown in figure 6.

Fig.4. Third mode of operation

Fig.5. Fourth mode of operation

Fig.6. Fifth mode of operation

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Table 1 explains the various modes of operation of high voltage gainDCDC converter in brief.

Table 1: Modes of Conduction

4 SIMULATION ANALYSIS

The proposed circuit can be divided into two parts, namely modifiedboost converter and a voltage multiplier cell using single coupledinductor as shown in figure 7. This circuit improves the voltagegain by reducing the output voltage ripple and voltage stresses.The double independent inductors in the modified boost converterare separately replaced by the primary windings of single coupledinductors that are employed as energy storage and filtering devices.The secondary winding of the single coupled inductors and a volt-age multiplier cell are connected in series to which is stacked withthe modified converter to get high voltage gain.

Fig.7. Simulation circuit for proposed converter

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Figure 8 and figure 9 represent the input and output voltage wave-forms respectively. A low input voltage of 21V is boosted to a veryhigh output voltage of 260V. The output voltage settles to a steadyvalue of 265V.The output graph is obtained by plotting time in x-axis and voltage in y-axis. As the output voltage is obtained inthe positive axis, it is a ripple free waveform. The output voltagetaken with a time period of 1ms, the settling time of output voltageis 0.08ms which is very less. The proposed converter gives a highvoltage gain with reduced voltage distortion.

Fig.8. Input Voltage Waveform for the Converter.

Fig.9. Output Voltage Waveform for the Converter.

5 CONCLUSION

The DC-DC converter using integrated coupled inductor with volt-age multiplier is designed to obtain high voltage gain. Further-more, the proposed work reduces the voltage stress on the main

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power switch. The performance of the converter is improved byrecycling the energy stored in the leakage inductor. Hardware im-plementation has also been done to convert 21V input voltage to260V output voltage and the feasibility of the proposed converterhas been verified.

References

[1] Xuefeng Hu, Chunying Gong, A High Gain Input-ParallelOutput-Series DC/DC Converter with Dual Coupled Induc-tors, IEEE Transactions on Power Electronics, vol. 30, pp.13061317, April 2014.

[2] Sujith M, Neelan S, et al., A Novel PI Converter based HighVoltage Gain DC DC Converter, International Journal of Ad-vanced Research in Electrical Electronics and InstrumentationEngineering, vol. 3, pp. 13575-13576, Dec 2014.

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[6] Bor-Ren Lin, Chia-Hung Chao, Analysis of an InterleavedThree-Level ZVS Converter with Series-Connected Transform-ers, IEEE Transactions on Power Electronics, vol. 28, pp. 3088-3099, July 2013.

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[7] Xuefeng Hu and Chunying Gong, A High Voltage Gain DCDCConverter Integrating Coupled-Inductor and DiodeCapacitorTechniques, IEEE Transactions on Power Electronics, vol. 29,pp. 789-800, Feb 2014.

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[15] J. Divya Navamani, K. Vijayakumar, R. Jegatheesan, Non-isolated high gain DC-DC converter by quadratic boost con-verter and voltage multiplier cell, Ain Shams Engineering Jour-nal, Oct 2016.

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