Import_More Accurate Equivalent Circuit of PV Cell

International Journal of Advanced Technology & Engineering Research (IJATER)

ISSN No: 2250-3536 Volume 2, Issue 4, July 2012 73

DESIGN & SIMULATION OF PHOTOVOLTAIC

SYSTEM USING ADVANCE MPPT

M. K. Gupta1, Rohit Jain

2, Anjali Goswami

3

1Department of Electronic Instrumentation & Control Engineering, Jagannath Gupta Institute of Engg. & Technology, Jaipur-302022, Rajasthan, India

2Department of Physics, Jagannath Gupta Institute of Engg. & Technology, Jaipur-302022, Rajasthan, India

3Department of Mathematics, Jagannath Gupta Institute of Engg. & Technology, Jaipur-302022, Rajasthan, India

Abstract

This paper presents the design and simulation of a photovoltaic

system using advance maximum power point tracking (MPPT)

and MATLAB Simulation. It includes module BP SX 150S for

a solar photovoltaic. This module provides a maximum power of 150 W. The current-voltage (I-V) & power-voltage (P-V)

characteristics are obtained for various values of solar

irradiance keeping the cell temperature constant. The MPPT

algorithm, which is based on the perturb and observe (P & O)

method, is also described. The points indicating module voltage

Vmp and current Imp at maximum Power Pmax are obtained.

Keywords: Photovoltaic modules, MPPT,

MATLAB/Simulation, irradiance, perturb and observe method

I. Introduction

The entire world is facing a challenge to overcome the hurdle

of energy crisis. The diminishing deposits of non-renewable

energy resources such as coal, natural gas, fossil fuels etc. have

added to this worry. It is thus fairly evident that a need exist for

developing alternative energy sources. The immediate need

would be to vitiate the problems caused by depletion of oil and

natural gas, while the long term need would be to develop

means that can replace coal and fossil fuels. Rapid population

growth and industrialization, demands for an increased amount

of electrical energy. Solar energy is a renewable, inexhaustible and ultimate source of energy. If used in a proper way, it has a

capacity to fulfill numerous energy needs of the world. The

power from the sun intercepted by earth is approximately 1.8×

1011MW [1].This figure, being thousands of time larger than

the present consumption rate enables more and more research

in the field of solar energy so that the present and future energy

needs of the world can be met. The PV module represents the

fundamental power conversion unit of a PV generator system.

The output characteristics of PV module depends on the solar

irradiance, the cell temperature and output

voltage of PV module. Since PV module has nonlinear

characteristics, it is necessary to model it for the design and

simulation of (MPPT) for PV system applications. The

mathematical PV models used in computer simulation have

been built. [2-9]. However, the solar energy is a dilute source

of energy and its availability varies widely with time. So, it is

very necessary to make a complete utilization of solar energy in

available time. Many MPPT algorithms are available for a solar

panel in order to produce maximum output. It is very necessary

that it is operated consistently at the maximum power point.

The P & O method of MPPT is described here with its

maximum power point [10-14].

II. PV module

This model of a photovoltaic system is based in a MATLAB

model [5]. A simple model of a PV cell consist of an ideal

current source in parallel with an ideal diode is shown as an

equivalent circuit below Fig. 1.

Figure 1: The equivalent circuit of a simple PV cell [5]

The two key parameters most often used to

characterized a PV cell are its short circuit current (Isc) and its

open- circuit voltage (Voc) as shown in Fig. 1. The Module

manufacturer usually provides the values of these parameters in

their datasheets [15]. The output current (I) from the equivalent

circuit of a simple PV cell is found by applying the Kirchhoff’s

current Law (KCL) [5]

I = Isc - Id (1)

Where: Isc is the short-circuit current that is equal to the photon

generated current, and Id is the current shunted through intrinsic

diode. The diode current Id is given by the Shockley’s diode

equation:

Id= Io (eqV/kT-1) (2)

Where: Io is the reverse saturation current of diode (A); q is the

electron charge (1.602× 10-19C); V is the voltage across the PV cell (V); k is the Boltzmann’s constant (1.38×10-23 J/K); T is

the junction temperature in Kelvin (K). Combining the diode

equation with the equation of the output current of the PV cell

I = Isc - Io (eqV/kT - 1) (3)



The reverse saturation current of diode (Io) is constant

under the constant temperature, let I = 0 (no output current).

0 = Isc- Io (eqV/kT - 1)

Isc = Io (eqV/kT

- 1)

Io = Isc / (e

qV/kT - 1) (4)

There are a few things that have not been taken into account in

the simple model and that will affect the performance of a PV

cell in practice. In order to create more accurate model, series

resistance (Rs), parallel resistance (Rp), and recombination

must be factored into the equation as shown in Fig.2 [4].

Figure.2: More accurate equivalent circuit of PV cell

Taking into account these additional elements add to the

equation, the two diodes can be recombined to simplify the

equation to:

I=Isc-Io(eq(V+I×Rs)/(nkT)-1)-(V+I × Rs)/Rp (5)

Where: n is known as the idelity factor and takes the value

between 1and 2.

Figure 3: Equivalent circuit with diodes combined and Rp

= ∞

The equivalent circuit with didoes combined and Rp =

∞ is shown in Fig.3. The value of the photon generated current

Isc can be directly proportional to the irradiance, and the short

circuit current is given under standard test conditions,

Go=1000W/m2, which is provided on the data sheet [15].

Therefore the photon generated current at any other irradiance,

G(W/m2 is given by [4]

Isc × IG = Isc × IGo × (G/G0)) (6)

Where IG & IGo are the currents at irradiance G & Go respectely.

Since a single PV cell produces an output voltage of

less than 1 volt, it is necessary to string together a number of

PV cell in series to achieve a desired output voltage. Generally,

36 cells in series will provide a large enough voltage to charge

a 12 volt battery, and 72 cells would be suitable for a 24 volt

battery.

The BP SX 150 PV module, which contains 72 cells,

was selected for the purpose of this paper. The sheet for the BP

SX 150s provide the following information on the module [15].

Table I: parameters of BP SX 150s solar module (Go =

1KW/m2, 25oC)

Electrical Characteristics BP SX 150s

Max. Power (Pmax) 150W

Voltage at Pmax (Vmp) 34.5V

Current at Pmax (Imp) 4.35A

Warrented minimum Pmax 140W

Shortcircuit Current(Isc) 4.75A

Open Circuit Voltage(Voc) 43.5V

Temp. coeff. Of Isc (0.065 ± 0.05

)%/0C

Temp. coeff. Of Voc − (160 +20)

mv/0C

Temp. coeff. Of P − (0.5 ± 0.05)

%/0C

NOCT 47 ± 2 0C

Max. System Voltage 600V

III. Simulation of PV module in

MATLAB

The characteristic equations (3), (4), (5), & (6) for the PV

module is implemented in MATLAB. The parameters chosen

for modeling corresponds to the BP SX150s module as listed in

Table 1. The voltage V is considered varying from 0 to Voc

corresponding to the variation in current from Isc to 0. Fig.4, 5,

& 6 shows the V-I, P-V, and P-I curves at various module

temperatures simulated with the MATLAB model for BP SX

150s PV module [15].

Figure 4: I-V curves of BP SX 150s PV module at various

Temperatures simulated with the MATLAB

(1KW/m2, 250C)



Figure 5: P-V curves of BP SX 150s PV module at various


(1KW/m2,

250C)

Figure 6: P-I curves of BP SX 150s PV module at various


(1KW/m2, 250C)

IV. Maximum power point

Perturbation and Observe Method is an iterative

method used for obtaining the maximum power point (MPP)

[10-14]. It measures the PV array characteristics, and then it

perturbed the operating point of the PV generated to observe

the change direction. There are many adaptions of this method,

varying from simple to complex. The MPPT implemented

algorithm is depicted in Fig. 7.

Figure 7: MPPT algorithm

The output power of the solar PV module changes with change

in direction of the sun, change in solar irradiance level, and

change in temperature. Also there is a single maximum power

point in the PV characteristics of the PV module for a

particular operating condition. It is desired that the PV module

operates close to this point, i.e., output of the PV module

approaches near to MPP. The process of operating PV module

at this condition is called as maximum power point tracking (MPPT). Maximization of PV power improves the utilization

of the solar PV module. [10]

Many MPPT algorithms had been proposed in the past. The

most common algorithms nowadays are the P& O [13]. This

method offers the main advantage of providing high efficiency

under rapidly changing atmospheric conditions, so it has been

employed in the proposed model. Fig. 8 shows the P-V

characteristic for the BP SX150s module using P&O method

with maximum power tracking at different irradiance. The

Algorithm is implemented using MATLAB.

Figure 8: P-V curves for P & O Method at various

irradiance

Fig.9 shows the I-V characteristics for the BP SX150s module

using P&O method with maximum current and voltage tracking

at different irradiance.



Figure 9: I-V curves for P & O Method at various irradiance

Fig.10 shows the P-I characteristics for the BP SX150s module

using P&O method with maximum power and current tracking

at different irradiance.

Figure 10: P-I curves for P & O Method at various irradiance

Fig. 11, & 12 show the module voltage Vmp and Current Imp at

the maximum power Pmax

Figure 11: Module voltage at maximum power, Vmp

Figure 12: Module current at maximum power, Imp

V. Conclusion

The V-I and P-V characteristics of BP SX 150s module are obtained using the MATLAB/Simulation for different values of

irradiance.. It is observed that the characteristics obtained by P

& O method are better then simple PV characteristics of

module & theoretical Characteristics. Also the module voltage

Vmp and Current Imp at the maximum power Pmax are obtained

which are fairly same as indicated by the manufacturer of BP

SX150S solar panel. Thus the proposed simulation model in

conjunction with MPPT algorithm can be used with DC-DC

Boost converter to obtain the required dc voltage to supply the

dc load.

VI. References

[1] R. Messenger and J. Ventre, Photovoltaic Systems

Engineering, CRC Press, 2000, pp.41-51.

[2] S. W. Angrist, , Direct Energy Conversion, Allyn and

Bacon, Inc., 4th edition, 1982, pp. 177-227.

[3] O. Wasynczuk, “Dynamic behavior of a class of

photovoltaic power systems,” IEEE Transactions on

Power Apparatus and Systems, vol. PAS-102, no. 9, 1983,

pp. 3031-3037.

[4] Tyson Denherder, Design & Simulation of Photovoltaiv

Super System using Simulink, Senior Project EE

Department, Califonia Polytechnic State University, 2006.

[5] Oi, Akihiro Design & Simulation of photovoltaic water

pumping System Master’s Thesis, California Polytechnic

State University, Sn Luis Obispo, 2005

[6] Castañer, Luis & Santiago Silvestre Modelling

Photovoltaic Systems, Using PSpice John Wiley & Sons

Ltd, 2002

[7] Huan-Liang Tsai, Ci-Siang Tu, and Yi-Jie Su,

“Development of Generalized Photovoltaic Model Using

MATLAB/SIMULINK”, Proceedings of the World

Congress on Engineering and Computer Science 2008,

October 22 - 24, 2008, San Francisco, USA

[8] C. González-Morán, P. Arboleya, D. Reigosa, G. Díaz, J.

Gómez- Aleixandre “Improved model of photovoltaic

sources considering ambient temperature and solar

Irradiation” Principado de Asturias government (PCTI

2006-2009) under grant BP06-165, February 16, 2009.

[9] Chapin, D. M., C. S. Fuller, & G. L. Pearson, Bell

Telephone Laboratories, Inc., Murray Hill, New Jersey

“A New Silicon p-n Junction Photocell for Converting

Solar Radiation into Electrical Power” Journal of Applied

Physics, Volume 25, Issue 5, May 1954, page 676-677



[10] C. C. Hua and C. M. Shen, “Study of maximum power

tracking techniques and control of dc-dc converters for

photovoltaic power system,” Proceedings of 29th annual

IEEE Power Electronics Specialists Conference, vol. 1,

1998, pp. 86-93.

[11] M. Veerachary and K.S. Shinoy, “V2 based power

tracking for nonlinear PV sources,” IEE Proceedings

electrival Power Application vol. 152, no. 5, 2005, pp.

1263-1270.

[12] I. S. Kim, M. B. Kim, and M. J. Youn, “New maximum

power point tracker using sliding-mode observer for

estimation of solar array current in the grid-connected

photovoltaic system,” IEEE Transaction on Industrial

Electronics, vol. 53, no. 4, 2006, pp. 1027

[13] Hohm, D. P. & M. E. Ropp “Comparative Study of

Maximum Power Point Tracking Algorithms” Progress in

Photovoltaics: Research and Applications November

2002, page 47-62

[14] K. H. Hussein, I. Muta, T. Hoshino, and M. Osakada,

“Maximum photovoltaic power tracking: an algorithm for

rapidly changing atmospheric conditions,” IEE

Proceedings of Generation, Transmission and

Distribution, vol. 142, no. 1, 2005, pp. 953-959

[15] BP Solar BP SX 150-150Watt multicrystalline

photovoltaic module datasheet, 2001

Biographies

1. M. K. GUPTA Completed his B.E. Degree in

Electronic Instrumentation & Control Engineering

Branch in 1995 and M. E. Degree in Power System in 2009 from Engineering College Kota (RTU Kota)

Rajasthan, India and pursuing Ph.D. in Electronic

Communication Branch from Jagannath University

Jaipur Raj. India. Email: [email protected]

2. Dr. ROHIT JAIN Completed his M.Sc.in Physics in

1998 St.John’s college, Agra, Uttar-Pradesh, India and

M.Phil. and Ph.D.in Physics in 1991 and 2002 from

University of Rajasthan, Jaipur, Rajasthan,India.

Email: [email protected]

3. Dr. ANJALI GOSWAMI Completed her M.Sc. in

Mathematics in 2001 from University of Allahabad,

Allahabad, Uttar-Pradesh, India and Ph.D. in Mathematics in 2007 from University of

Rajasthan, Jaipur, Rajasthan, India.Email:

[email protected]

mailto:[email protected]



Import_More Accurate Equivalent Circuit of PV Cell

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