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Comparative Analysis of Buck Converter and

Modified Interleaved Buck Converter for

Standalone Wind Energy System

Ashwini A. Patil

1

, D. S. Chavan

2

1,2Department of Electrical Engineering, Bharati Vidyapeeth Deemed University College of Engineering, Pune, India

ABSTRACT

This paper presents comparative analysis of buck converter and interleaved buck converter for standalone wind energy system. The comparisons of both converters are on the basis of harmonics, power factor, efficiency and output voltage. As compare to buck converter the modified interleaved buck converter is better. Because the disadvantages of buck converter are more. In buck converter switching losses inductor ac losses are more also efficiency is less. Power density is also less. Power factor of buck converter is less as compare to modified interleaved converter. Also there are disadvantages of conventional interleaved buck converter like less efficiency, high switching losses, high cost. In Modified interleaved buck converter switches are connected in series also capacitor provides power path. As the modified interleaved buck converter works in continuous conduction mode so the current stress is less. The voltage stress across switches is half of input voltage before switch on and switch off conditions. So the switching losses are less and efficiency is also high. Control logic is implemented for controlling the buck converter. Proportional integral derivative controller is used in modified interleaved buck converter. Simulation results verify the difference between buck converters modified interleaved buck converter. By using MATLAB/ SIMULINK the proposed system is modeled.

Keywords: Buck converter, Efficiency, Harmonics, Modified interleaved buck converter and Power factor

I. INTRODUCTION

There are various types of converters like buck, boost, buck boost and interleaved buck converter. Buck converter is used to step down the voltage i.e. buck converter gives output voltage less than input voltage. In all the devices switch as a power device used. Suja A et.al [1] Presented modified interleaved buck converter which consist of inferior inductor ripple current and high step down conversion ratio. When switching frequency is more and duty ratio is less than 50% then proposed buck converter is used. The benefits of proposed converter are inductor current and output current is very low. Morteza esteki et.al [2] Presented four phase interleaved buck converter for less voltage stress and high step down ratio . Proposed converter can be used for reducing switching and conduction losses and efficiency improvement. The benefits of proposed converter are low output current ripple and uninterrupted input current. D. Lakshmi et.al [3] Presented enhanced step down interleaved buck converter. There are various advantages of interleaved buck converter like small switching losses, more efficiency and less switching stress. As compared to conventional interleaved buck converter proposed interleaved buck converter is better. From simulation and experimental results it is confirmed that proposed interleaved buck converter has greater step down conversion ratio also inductor ripple current is small. Krishna P.S. [4] presented comparative analysis of conventional buck converter and modified buck converter. It is concluded that modified interleaved buck converter is better when the duty ratio is below 50%.Current and voltage ripple are very less in modified interleaved buck converter.

II. BUCK CONVERTER

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Buck converter is a step down converter which gives output voltage less than input voltage. Buck Converter is simple in construction but the efficiency of buck converter is less than modified interleaved buck converter. Also the total harmonic distortion is high in buck converter. To reduce size and weight of the converters must work at high switching frequencies. But as the switching Frequency increases, switching loss, noise, and stress during turn-on and turn-off transitions also increase. These drawbacks decrease power conversion efficiency and powering capability, which in turn seriously deteriorate in system performance.

III. MODIFIEDINTERLEAVEDBUCK CONVERTER

As shown in fig two active switches are connected in series whereas capacitor provide power path. At 180 phase angle active switches are driven and by maintaining duty ratio is below 50% at switching frequency output voltage can be regulated. Current stress is less when interleaved buck converter operates in continuous conduction mode. When converter is in steady state voltage stress becomes half of input voltage after switch off and before switch on .Capacitor starts discharging and switching losses decreases.

Figure 2 Modified Interleaved Buck Converter

Figure.3 Operating circuit of modified interleaved buck converter at mode 1

Figure 4 Operating circuit of modified interleaved buck converter at mode 2 or mode 4

Figure 5 Operating circuit of modified interleaved buck converter at mode 3

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Mode 2 [t1 –t2]: When Q1 is switched off at t1then mode 2 starts. Then, from diode D1 and D2 current and flow, respectively. Both and turn into the negative VO, and therefore, and reduce linearly. During this mode, the voltage and current equations are as follows, (8)

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Mode 3 [t2 –t3 ]: When Q2 is switched on at t2 then mode 3 starts and D2 is switched off. Then flows through D1 and from D1, CB, Q2 , and L2 flows. Thus, voltage across CB is discharged. The voltages and currents can be expressed at mode 3 are as follows. (13)

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IV. SIMULATION

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Simulation of standalone wind battery hybrid system by using buck converter consists of squirrel cage induction generator, buck converter, battery for back up. Subsystem consists of wind turbine squirrel cage induction generator and rectifier. As wind passes through wind turbine, turbine rotate and rotational energy is converted into mechanical energy. Generator converts mechanical energy into electrical energy. Through the rectifier AC power is converted into DC. Buck converter is also DC-DC converter gives DC voltage. Constant DC voltage is obtained at load. When the wind is not available the battery is used as a backup.

Figure 7 Simulation of wind battery hybrid system by using Modified interleaved buck converter

Standalone wind energy system by using interleaved buck converter consists of interleaved buck converter, PID controller and subsystem. There are various advantages of interleaved buck converter like high efficiency reliable, better thermal performance and high power density. Subsystem consist of wind turbine, squirrel cage induction generator and rectifier.

V. RESULTS

The results obtained from the MATLAB simulation carried out in sequential manner, are as follows,

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Total harmonic distortion is 72.49% at 50 Hz by using buck converter. The total harmonic distortion is more in buck converter.

Figure 9 Total Harmonic Distortion at 50 Hz by using Interleaved Converter

The total harmonic distortion is 31.04% at 50 Hz by using Modified Interleaved Converter as shown in fig 9. As compare to buck converter the total harmonic distortion is less in Modified interleaved buck converter.

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Total Harmonic Distortion at 60 Hz by using Buck Converter is 76.32% as shown in fig 10

Figure 11Total Harmonic Distortion at 60 Hz by using Modified interleaved Buck Converter

The total harmonic distortion at 60 Hz by using buck converter is 54.95% as shown in fig 9.6 Power factor

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The power factor obtained by using buck converter is 0.8719 as shown in fig 12

Figure 13 Power Factor of Buck Converter

The power factor obtained by using interleaved buck converter is 0.9853  Buck converter efficiency calculation

For buck converter Output voltage =60V Output current= 6.5 A Input voltage= 250V Input current= 5A

The efficiency of buck converter is 31% For Interleaved buck converter

Output voltage =60V Output current= 6.5 A Input voltage= 250V Input current= 3A

The efficiency of modified interleaved buck converter is 52%

CONCLUSION

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REFERENCES

[1]. Suja A , Sivakumar S and Ramkumar P.S “Modified Interleaved Buck Converter Implementation for Higher Step-Down Conversion Ratio” International Conference on Innovations in Information Embedded and Communication Systems,2015. [2]. Morteza Esteki , Behzad Poorali, Ehsan Adib, Hosein Farzanehfard “High step-down interleaved buck converter with low voltage

stress” IET Power Electron., 2015, Vol. 8, Iss. 12, pp. 2352–2360.

[3]. D.Lakshmi , S.Zabiullah, Dr. Venu gopal. N “ Improved Step down Conversion in Interleaved Buck Converter and Low Switching Losses” International Journal Of Engineering And Science ,Vol.4, Issue 3(March 2014), PP 15-24.

[4]. Krishna P.S, Jubin Eldho Paul and Hari kumar R “Study and analysis of conventional and modified interleaved buck converter”International journal of research and general science , vol.3, issue6, Nov-Dec,2015.

[5]. Huang-Hua Chiu, Ming-Fa Tsai, Chung-Shi Tseng, and Shu-Yi Yen “A Novel Interleaved and Isolated Buck Converter with High Voltage Ratio” IEEE conference on in Power Electronics ,2010. PP 2715-2721.

[6]. Mohamed. A. Shrud, Ahmad Kharaz, Ahmed. S. Ashur, Mustafa Shater and Ismail Benyoussef “A Study of Modeling and Simulation for Interleaved Buck Converter” IEEE International Conference in Power Electronic & Drive Systems & Technologies 2010. PP 28-35

[7]. Guoen Cao, Arsalan Ansari and Hee-Jun Kim “An Interleaved Buck Converter With Reduced Reverse-Recovery Problems” Industrial Technology (ICIT), 2014. IEEE International Conference on Feb. 26 - Mar. 1, 2014, pp. 312-317

[8]. Cheng-Tao Tsai and Chih-Lung Shen ,“A High Step-Down Interleaved Buck Converter with Active-Clamp Circuits for Wind Turbines” Energies 2012

[9]. Y. M. Chen, S. Y. Teseng, C. T. Tsai, and T. F. Wu, “Interleaved buck converters with a single-capacitor turn-off snubber ,” IEEE Trans. Aerosp.Electron. Syst., vol. 40, no. 3, pp. 954–967, Jul. 2004.

[10]. C. T. Tsai and C. L. Shen, “Interleaved soft-switching coupled-buck converter with active-clamp circuits,” in Proc. IEEE Int. Conf. PowerElectron. Drive Syst., 2009, pp. 1113–1118

Figure

Figure 7 Simulation of wind battery hybrid system by using Modified interleaved buck converter
Figure 10 Total Harmonic Distortion at 60 Hz by using Buck Converter
Figure 11Total Harmonic Distortion at 60 Hz by using Modified interleaved Buck Converter
Figure 13 Power Factor of Buck Converter

References

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