Design and Develfor Ph

Syafrudin Masri1, NSc

Eng Seri Am

syaf@eng.us

Abstract—This paper presents the design anDC-DC buck converter for photovoltaic intention in designing DC-DC buck converter iand high performance power point trackintermediate between supply source and loadsimulated using Power Electronic Simulationprocedure in terms of selection of componedemonstrated. The experimental results shconstant input voltage of 80V, the buck coproduce 164W with average 60 percent efficien

Keywords-buck; photovoltaic; psim; conmode

I. INTRODUCTION In recent decades, research on the use of

alternative source of energy has become pfield of electrical engineering [1]. A typenergy system compromises DC value at its are a promising technology and future enesustainable and environmentally friendly way

Photovoltaic, (PV) is made up of cells (sowired together into a module. A number of arranged together to produce a much higsurface area of a cell and the intensity of thpanel determine the amount of current produc

A number of modules can be arranged parallel or in series. The amount of DC voltaarrangement of modules. For instance, four275F can reach out 300Watt when connected value of its output voltage is high. Due to theand the need to provide a lower voltage withregulator or converter is required in most Porder to step-down the output voltage that addition, PV modules require an intermedtracker as their v-i characteristics are nonlinea

The proposed topology in this work converter which has the voltage output lowThe system was later simulated using Simulation (PSIM 9.0) software. In order tomethodology, the experimental work has beeThe result has shown that the prototype efachieved at an average of 60 percent with power produced of 164W at a constant voltashows an overview of the system.

opment of DC-DC Buchotovoltaic ApplicationNorizah Mohamad2, Muhammad Hafeez Mohamed

hool of Electrical & Electronic Engineering gineering Campus Universiti Sains Malaysia, mpangan, 14300 Nibong Tebal, Penang, Malaysia sm.my1, norizah@eng.usm.my2, aphieez@yahoo.com3

nd development of application. The

is to provide robust ker acting as an d. The system was n (PSIM 9.0). The ents has also been how that with a

onverter is able to ncy.

ntinous conduction

photovoltaic as an prominence in the pical photovoltaic output side. They

ergy demand in a y.

olar cell) which are these cells can be

gher voltage. The he light hitting the ced [2].

together either in age depends on the r PV modules BP in parallel and the

e load specification h high efficiency, a PV applications in

they generate. In diate power point ar [3].

is DC-DC buck wer than the input.

Power Electronic o verify the design n tested for 300W. fficiency has been

maximum output age of 80V. Fig. 1

Figure 1: A general schem

II. BUCK

In a buck converter, the avthan the input voltage , hepopular DC regulator for PV diagram of a buck is illustrated

Figure 2: Circuit diag

ck Converter n

d Hariri3

matic diagram of the system.

K CONVERTER verage output voltage is less ence the name ‘Buck’, a very

application. The typical circuit d in Fig. 2.

gram of a buck converter.

G6 IEEE Conference on Power Engineering and Renewable Energy 20123-5 July 2012, Bali, Indonesia

978-1-4673-2470-0/12/$31.00@2012 IEEE

A. Principle of Operation A buck converter consists of two opera

are continuous conduction mode (CCM) aconduction mode (DCM). Usually CCM tecfor efficient power conversion while the DCpower and stand-by application [4].

For the CCM, the inductor current neduring one switching cycle as illustrated insmooth input current because an inductor is cwith the power source [5]. The operation of bdivided into two modes where; for mode 1 wand mode 2 when switch is off as shownrespectively.

Figure 3: Waveform of voltage and

1) Mode 1: Switch, S is ON

Figure 4: Switch, S in ON mo

When switch, S is ON, the input current, inductor , filter capacitor and load resistoKirchhoff’s voltage law, the inductor voltage

and

Integrating with respect to leads to; ∆

where , , k and ∆ are supply sourcduty cycle and value of inductor current durespectively.

ating modes which and discontinuous chnique is applied CM is for a lower

ever reaches zero n Fig. 3. It has a connected in series buck circuit can be

when switch is on n in Fig. 4 and 5

d current.

ode.

flows through the or . By applying e is given by: 1

2

3

ce, output voltage, uring the ON state

2) Mode 2: Switch, S is OF

Figure 5: Switch

When switch, S is OFF, thconducted due to the energy inductor current continues to fD. Therefore:

and

Integrating with respect to ∆ where is the value of volta∆ is the value of inductor

3) Steady State Operation

During the steady state operatio∆ ∆and

therefore, by solving Eq. 8 give

4) Continuous Inductor Cu

For the system to conduct cuminimum inductor current m 0from [6], the minimum inductais given by:

and 1

FF

h, S in OFF mode.

he freewheeling diode, gets

stored in the inductor and the flow through L, C, R, and diode 4

5

leads to;

1 6

age across the capacitor C and r current during OFF state.

on, ∆ 0 7

1 0 8

es the output voltage ; 0 1 9

urrent and Capacitor Voltage

urrent in continuous mode, the must be higher or equal to zero 0 10

ance and capacitance

1 2 11

116 12

B. Selection of Components The selection of components plays an

order for the system to operate at its full capa 1) Electronic Switch The power transistors can be broadly cl

categories which are; BJTs, MOSFETs, SCOOLMOS [6]. Transistors are normallymedium power applications. Meanwhile voltage-controlled device which is suitable high frequency converters, whereas, IGBTs ihigh power application. The design specificasize, speed and thermal requirements are vitato be considered in choosing the most suitadesign.

2) Inductor The minimum value of an inductor in orde

design to operate in CCM is 0.2mH as calcToroid inductor value of 1mH has been cho

is ten times higher than ). Saturbe taken into account before making use of tinductor is a component that can standapplication.

3) Capacitor Output capacitance is required to mini

overshoot and ripple present at the outpuconverter. Another important considerationseries resistance or ESR. Since ESR affectslow ESR capacitance would be used for best

4) Diode Diode reverse voltage rating is the main

selecting the freewheeling diode aside from the required off-state voltage stress. In sufficient peak and reverse current handling switching.

The important simulation parameters are These parameters will be later used later in dconverter.

TABLE I. BUCK CONVERTER CALCULATE

Components VSwitch IR

Inductor Diode M

Output Capacitor 2Load

Frequency switching, 2

important role in acity.

lassified into five SITs, IGBTs and

y used in low to MOSFET is a

in low-power and is more suitable in ation, cost, losses, al factors that need able switch for the

er for the proposed culated by Eq. 11. osen (for practical, ration level should the device. Toroid

d high frequency

imize the voltage ut of a step-down n is its equivalent s the efficiency, a performance.

n consideration for its ability to block addition, it have capability and fast

listed in Table 1. designing the buck

ED PARAMATERS

Value RF540N

1mH MUR 860

220uF 16Ω

20kHz

III. SIM

The simulations were perfoview on the characteristics ofSeveral simulations have been poperation of the proposed desigout using PSIM 9.0 softwareproposed buck converter is show

Figure 6: Circuit diagr

The simulation results of thk= 0.7 are shown in Fig. 7 (a) a

Figure 7: Simulation resu

IV. RESULT A

PWM signal is generated from PIC is then amplified usinit is connected directly to thegenerated from PIC is shown in

MULATION ormed in order to obtain an early f the proposed buck converter. prepared in order to illustrate the gn. The simulations were carried e. The circuit diagram of the wn in Fig. 6.

ram of a buck converter

he buck converter at k= 0.5 and and (b) respectively.

(a)

(b)

ults: a) at k=0.5 and b) at k=0.7

AND DISCUSSION using PIC16F877. 5V signal

ng CA3140 opto-coupler before e gate pin at MOSFET. PWM n Fig. 8.

Figure 8: PWM signal from PIC16F877

Several experimental trials have been conducted in order to fulfill the objective of the research. Three independent variables, which consist of the input voltages, , switching frequency, f and duty cycle, k were varied at fixed resistive load of 16 ohm. In Table II shows the data from the experimental trials.

TABLE II. EXPERIMENT DATA

Input Voltage

(V)

Input Current

(A)

Input Power (W)

Duty cycle

Output Voltage

(V)

Output Current

(A)

Output Power

(W)

80

0.14

11.2

0.1

8.23

0.51

4.23

80

0.20

16.0

0.2

15.00

0.94

14.6

80

0.45

36.0

0.3

21.74

1.36

29.54

80

0.90

72.0

0.4

29.70

1.86

55.13

80

2.13

170.4

0.5

34.17

2.13

72.97

80

2.90

232.0

0.6

38.37

2.39

92.02

80

3.15

252.0

0.7

41.01

2.56

105.12

80

3.35

268.0

0.8

49.69

3.10

154.32

80

3.61

288.8

0.9

51.24

3.20

164.10 Figures 9, 10 and 11 show the outcomes of the experimental setup.

Figure 9: Efficiency η versus Input Voltage

Figure 10: Efficiency η versus Frequency switching

Figure 11: Efficiency η versus Duty cycle From the experimental results, it can be apparently seen

that the efficiency of the system decreases as the input supply varied from 0 to 80V at a fixed duty cycle, k, frequency switching, f and load, R. In the second section, the efficiency of the proposed design was decreased as the frequency switching, f varies from 5 kHz to 35 kHz. The proposed design was able to produce 164 Watt with an average of 60 percent efficiency with the constant input voltage of 80V at 20 kHz switching frequency, f and 16 Ohm constant load. There are a number of assumptions which can be made based on the particular outcome. The climb-down in efficiency of the system is largely due to the losses occurred at MOSFET and free-wheeling diode. In addition, saturation of inductor that may hold the inductor current at saturation level and the thickness of copper track on the printed circuit board could also affect the reliability of the system.

V. CONCLUSION A robust, efficient and high performance buck converter as

an intermediate between the supply source and load can be achieve by carefully choosing a suitable component for the system and reduce the power loss caused by each element in order to increase the converter’s efficiency.

ACKNOWLEDGMENT The authors would like to acknowledgement Universiti

Sains Malaysia for providing the research grant to undertake this research.

REFERENCES [1] P. C. M. Bernardo, Z. M. A. Peixoto, L. V. B. Machado Neto, “A high

efficient micro-controlled buck converter with maximum power point tracking for photovoltaic systems”, International Conference on Renewable Energies and Power Quality (ICREPQ’09) Spain, April 2009.

[2] V. Meksarik, S. Masri, S. Taib, C. M. Hadzer, “Development of high efficiency boost converter for photovoltaic application”, National Power & Energy Conference (PECon) 2004 Proceedings, 2004.

[3] M. Veerachary, “Fourth-order buck converter for maximum power point tracking applications,” IEEE Trans. On Aerospace and Electronic Systems, vol. 47, NO. 2, April 2011.

[4] S. Khader, “Design and simulation of a chopper circuits energized by photovoltaic modules”, 2011 IEEE GCC Conference and Exibition (GCC) United Arab Emirates, February 2011.

[5] R.W. Erickson, D. Maksimovic, Fundamental of Power Electronic, Kluver Academic Publisher, University of Colorado, USA, 2005.

[6] M. H. Rashid, “Power Electronics: Circuits, Devices and Applications”, Prentice-Hall, NJ07458, 2004.