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DEVELOPMENT OF ADAPTIVE PERTURB AND OBSERVE TECHNIQUE FOR GLOBAL MAXIMUM POWER POINT TRACKING S SAKTHINATHAN School of Electrical Engineering (SELECT) Vellore Institute of Technology Vellore, India [email protected]

Abstract— To enable the Solar PV module to deliver maximum power at all weather conditions, MPPT techniques are being used. But the presence of partial shading of some PV cells in a panel, not only affects the output of the particular panel but also affects the entire system. Hence it has to be avoided. So, in order to avoid this condition byepass diodes are used in parallel across the panels for the purpose of providing way for the excess current to pass and thereby preventing these conditions. In order to obtain the maximum power from the given irradiation, we are using adaptive perturb and observe technique to determine the duty cycle corresponding to the maximum power obtained from the PV panel and the major disadvantage of this P&O technique occurs in the partial shading conditions, where two or more peak duty ratios are obtained and hence to determine the accurate global maximum power point we are using adaptive PNO technique for the case of 4 s*2p and 4 s*2p model PV panel. Keywords—Boost dc-dc converter, Photovoltaic, Maximum power point tracking, Perturb and Observe I. INTRODUCTION

G VARSHITH School of Electrical Engineering (SELECT) Vellore Institute of Technology Vellore, India [email protected]

Renewable energy is one of the recent trends in the energy sector of our country. This is due to the fact that availability of fossil fuels are decreasing day by day and there is an urgent to find an alternate solution and one such solution is solar power. Solar is the principle of harnessing electricity from the radiations from the sun. The main advantage of solar is that it is environment friendly and produces less CO2 gases which are released into the environment by the fossil fuels. The solar panel can be made to provide maximum output when the irradiation is constant. But in practical use the value of irradiation is not constant across the entire panel and there by affecting the entire system. The maximum output from the PV panel can be extracted using a number of algorithms. The main objective of MPPT is to improve the total efficiency of the panel. There are numerous MPPT methods are available and each varies according to the number sensors, cost of implementation and complexity.

They are

are connected in parallel or series it makes a PV module.

1) Perturb and Observe 2) Incremental conductance method 3) Fractional short-circuit current method 4) Fractional open circuit current method 5) Soft computing techniques such as fuzzy and ANN Each of the above methods have their own approach in determining the maximum power point. But one of the main drawback is due to the presence of the partial shading. Which emerges a condition where there are two or more peaks which results in the identification of the local maxima instead of the global maxima.

In fig 2 the model of a single of a PV module is shown. In the fig 3a, the IV curve is shown, where V oc, I sc, V mpp, I mpp, are open circuit voltage across PV, short circuit current through PV panel, voltage at the global maximum power point, current at the global maximum power point respectively. From these IV curves, we can see the nonlinear nature of the PV source because the output of PV system depends on the load. Fig 3b shows the PV curve, where Pmax is the maximum power. The Isc changes with the change in the irradiation which is shown in the fig 3c, as the irradiation decreases the value of the Isc decreases.

Out of all the algorithms, conventional PNO algorithm is extensively used for the commercial purpose, so in this paper Adaptive P&O has been tested in MATLAB under various conditions and their results are plotted and validated.

Fig 2 : Simulink topology of single PV module

Fig 1: Block diagram of PV system with boost converter II. CHARACTERISTICS MODULE

OF

PV

The solar PV cell is a nonlinear source, so understanding the characteristics of the solar module are required to track the global maximum power point. A basic PV cell is a photodiode, when an n number of PV cells

Fig 3a : IV curve of PV Module

I V CHARACTERISTICS FOR DIFFERENT IRRIDIANCE (SM55)

1000w/m2

3.5

800w/m2

X: 4.453 Y: 3.424

600w/m2

3

400w/m2

CURRENT

2.5

2

1.5

1

0.5

0

0

5

10

15

20

VOLTAGE

Fig 3b : P-V curve of PV module

III. CHARACTERISTICS OF PV ARRAY UNDER PARTIAL SHADING CONDITIONS The uneven exposure of solar panels to the irradiation is the cause of partial shading. These changes in irradiation are due to various environmental factors like a passage of clouds, birds dropping & shade of the building.

Fig3c:IV curve irradiation

for

different

the cell is specifically relative to the yield of the present source. A sun powered cell in a perfect model can be essentially displayed by a present source in parallel with the p-n intersection which is related with photo carriers created. Brightening current parameter related with the photoelectric impact current is the invert inclination immersion current for the diode and n, the diode perfect factor.

Under the partial shading condition, multiple peaks will be occurring in the PV curve due to the change in the IV characteristics of the respective PV modules. It happens because the current pass through the diode which is connected in anti-parallel to each panel. Fig 6 shows the 4X2 array. From the fig7a-7b different partial shading conditions are discussed and their respective shading patterns are shown in the table1a -1c for the 4X2 array. IV. MODELING OF PV CELL In single diode model diode is parallel to the current source. Where the light falling on

Fig 4: Model of PV cell

The equations for this model are I= I pv –Id I D  I S (e KB

qv nK BT

…. (1)

I  I pv  I D  I sh

…………… (4)

 1) ……. (2)

is knowns as Boltzmann constant

q is the charge of the electron

I  I pv  I S (e

q ( v  IRS ) nK S T

 1) 

v  IRs Rsh … (5)

T is the temperature of the p-n junction of the diode V is the output voltage from the panel. The solar irradiance and solar cell active area are proportional to the illumination current associated with the photoelectric effect. The accuracy of the model is improved by adding a series resistance. Series resistance with a solar cell is known as a 1M4P model (four parameters, single mechanism), takes into account the influence of contacts by means of a series resistance Rs. The unknown parameters of this model are Rs, Ipv, Is, n.

The new diode current expression after introducing diode expression is given by

I D  I S (e

q ( v  IRS ) nK BT

 1)

…………(3)

These models are not precise enough, as they do not consider real factor such as partial shading conditions. In realistic a solar cell with series and shunt are used which are commonly called as 1M5P model (Five Parameters, Single Mechanism), leakage currents are taken into account by parallel shunt resistor Rush, Ipv, Is, n, Rs and Rsℎ are the five parameters of this model current equation 4-5 of this model is given by

Fig 5: Practical single diode model Single-diode model of a solar cell the series resistance increases with increase in the shadow rate. In contrast due to shading, the shunt resistance presents a clear reduction, therefore, the leakage current and the voltage drop in the contacts will be higher when the shadow rate increases. When the Rsh value decreases the probability of hot spot apparition increases since its working as a load in reverse bias. It is seen that reduction of output power as a result of shading is due to series resistance dissipating 50 percent of PV module output power adjusts the duty cycle of the boost dc-dc converter.

Fig 6a: IV CURVES

1a-UNIFORM IRRADIATION

1b-WEAK SHADE

Fig 6b: PV CURVES

1c-STRONG SHADE

Table 1: For different shades V.

SIMULATION UNDER UNIFORM SHADING

Fig 7: Simulation diagram of the PV system in Uniform shading with MPPT

VI.

SIMULATION RESULTS

Fig 8a: Plot for duty cycle for Uniform shading

VII.

Fig 8b: Plot for Duty cycle Under uniform shading using Proposed method

SIMULATION UNDER PARTIAL SHADING

Fig 9: Simulation diagram of the PV system in Partial shading with MPPT

VIII. SIMULATION RESULTS

Fig 10a: Plot for duty cycle for Partial shading

IX.

CONCLUSION

This paper throws a limelight in the following areas PV panel design using single diode model, partial shading and maximum power point tracking and determination of global maximum under the partial shading condition. This paper also compares the conventional perturb and observe technique with the adaptive method of perturb and observe method and it is seen that the time taken to achieve the global maximum in a reduced interval. X.

REFERENCES

1)J. Prasanth Ram, T. Sudhakar Babu, N. Rajasekar, A comprehensive review on solar PV maximum power point tracking techniques, Renewable and Sustainable Energy Reviews, Volume 67, 2017, Pages 826-847, ISSN 1364-0321 2) J.Prasanth Ram, N. Rajasekar, Masafumi Miyatake, Design and overview of maximum power point tracking techniques

Fig 10b: Plot for duty cycle under Partial shading using proposed method

in wind and solar photovoltaic systems: A review, Renewable and Sustainable Energy Reviews, Volume 73, 2017, Pages 11381159, ISSN 1364-0321 3) J. Prasanth Ram, T. Sudhakar Babu, N. Rajasekar, A comprehensive review on solar PV maximum power point tracking techniques, Renewable and Sustainable Energy Reviews, Volume 67, 2017, Pages 826-847, ISSN 1364-0321 4) A. Rezaee Jordehi, Maximum power point tracking in photovoltaic (PV) systems: A review of different approaches, Renewable and Sustainable Energy Reviews, Volume 65, 2016, Pages 11271138, ISSN 1364-0321 5)Haithem Chaieb, Anis Sakly, A novel MPPT method for photovoltaic application under partial shaded conditions ,Solar Energy, Volume 159, 2018, Pages 291-299