IRJET - Maximum Power Extraction by Introducing P&O Technique in PV Grid

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 07 Issue: 02 | Feb 2020 www.irjet.net p-ISSN: 2395-0072
© 2020, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 2298
Maximum Power Extraction by Introducing P&O Technique in PV Grid
Meenakshi Ojha1, Dashrath Kumar2
1PG Student [Power System], Dept. of EEE, Maharishi University of Information Technology, Lucknow, U.P., India 1
2Assistant Professor, Dept. of EEE, Maharishi University of Information Technology, Lucknow, U.P., India 1
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Abstract - The Maximum Power Point Tracking (MPPT)
is a technique used in power electronic circuits to extract
maximum energy from the Photovoltaic (PV) Systems. This
paper elaborates overview of a photovoltaic (PV) system
model, and compares the attributes of different
conventional and improved incremental conductance
algorithms, perturbation and observation techniques, and
other maximum power point tracking (MPPT) algorithms in
normal and partial shading conditions. One of the most
widely used techniques is the perturb & observe algorithm,
which periodically perturbs the operating point of the PV
array, sometime with an adaptive perturbation step, and
compares the PV power before and after the perturbation.
Key Words: MPPT, Photo Voltaic Cell, Perturb & Observe,
partial shading conditions, performance evaluation etc.
1. INTRODUCTION
Fossil fuels like gas and oil are not renewable, unclean and
non eco-friendly source of energy. Solar energy is one of
the most important renewable energy sources. PV system
is divided into two categories: Stand-alone and Grid
connected PV system. For places that are away from the
utility grid, stand-alone PV systems are used at those
places. In these systems, the performance of a PV system
relies on the operating conditions. The maximum power
extracted from the PV source depends strongly on three
factors such as irradiation, load profile and temperature
[Salas, 2006]. A place where utility grid is easily available,
grid-connected PV system is used there. Amongst all RES,
solar energy is well-thought-out one of the probable
sources to resolve the crunch as it is accessible in plenty
and free of cost [1].
Photovoltaic (PV) power generation has acknowledged
major attention from scientists over the last few years to
reduce the environmental pollution inherently associated
with traditional electric generators. The economic
convenience of PV generation is directly connected to the
cost of the cells and the amount of energy that the arrays
are capable of supplying over their life. The former is
influenced mainly by the price of the feedstock for the PV
industry and the improvement of fabrication technologies.
PV systems have the main drawback that the power
output is dependent on direct sunlight, about 10-25% is
lost if a tracking system is not used, since the cell will not
be directly facing the sun at all times [2]. Dust, clouds, and
other hindrances in the atmosphere also reduce the power
output. [3][4]
The latter is connected to the efficiency of the power
conversion system, which is normally necessary when PV
arrays are used for power generation. At the present state
of the art, the control algorithms used for the
maximization of the power extracted from PV arrays are
widely known as maximum power point tracking (MPPT)
algorithms. These power conditioners guarantee that PV
arrays operate close to their point of maximum efficiency
under any weather conditions. This is particularly
important for variable irradiation levels, because the
efficiency of the PV modules is very small when the
operating point is far from the maximum power point.
Figure 1: Working of Photovoltaic cell
Maximum power point tracking (MPPT) scheme is used to
extract maximum power from solar PV cells. various types
of MPPT schemes are projected by researchers [5] namely
open circuit, short circuit, perturb and observe (P&O)/hill
climbing, incremental conductance, and so forth.

Figure 2: Block diagram of Typical MPPT system.
This paper proposes a limited search space based on
improved P&O algorithm integrated with a solar tracker.
Solar tracker makes sure the maximum coupling of the
irradiance with the solar panel by keeping the panel always
normal to the sun. The proposed algorithm first divides the
power curve into three regions: Area 1 and area 3 are the
left and right regions to the MPP respectively. Area 2 is the
intermediate region of the power curve containing 10%
area of the power curve and MPP lies in this area 2. This
reduction in the search space reduces the step response
time to reach the maximum power and the steady-state
oscillations at the maximum power point.
Figure 3: I-V and P-V characteristics of solar PV cell
Figure 4: Standard equivalent circuit of the PV cell
Figure 5: Block diagram of the MPPT system
There are different techniques used to track the
maximum power point are:
1) Perturb and observe (hill climbing method)
2) Incremental Conductance method
3) Fractional short circuit current
4) Fractional open circuit voltage
5) Neural networks
6) Fuzzy logic
1.1 Methodology (Perturb-and-Observe):
Doubly The most commonly used and modest MPPT
algorithm is Perturb-and-Observe (P&O) method. Both Hill
climbing (HC) and P&O methods have same logic and can
be said to be two dissimilar means of visualizing the same
method. In HC method duty ratio of the power converter
used is perturbed and in P&O method the working voltage
of the PV array is perturbed. Since a power converter is
generally used with a PV array, so perturbing its duty ratio
will automatically perturb the working voltage and thus
both the methods are almost same. The logical flowchart
of P&O method is shown in figure 6.
Figure 6: Flowchart of P&O MPPT technique
V(k) and I(k) is the PV panel voltage and current at kth
iteration. C is the length of voltage perturbation and choice

of its value is very important. Small C results in slow
tracking and large C gives fast tracking but the oscillation
near the peak is large. The solution for this problem is the
use of varying value of C, such that its value is large when
the system is far from the MPP and its value approaches
zero as the system reaches MPP. Here, it is shown that a
fast convergence speed and almost no oscillation around
the MPP can be attained by taking the value of C at kth
iteration i.e. C (k) according to following equation.
Figure 7: Basics of MPPT Technique
As shown in Figure 7 the first block is sourcing i.e. Solar
Panel. There are some materials, which are photo sensitive
and they find a place in photo voltaic conversion. A junction
of materials, which have dissimilar electrical properties
semiconductors are used in solar cells, provides the
electrical field in most solar cells. Semiconductors are a
class of materials with conductivity somewhere between
metals and insulators. Solar cells are manufactured from
monocrystalline materials. Low cost cells are round
because they are made from sheets, which are cut from
monocrystalline rods as they are pulled from the melt.
Joining p and n type material in to a single crystal makes
the cross section of a silicon solar cell.
1.1.1 Oscillation near MPP:
In most online MPPT schemes, power losses are mainly due
to steady-state oscillations in the vicinity of the MPP [6].
The use of a large step size in a fixed duty cycle to increase
tracking speed causes many oscillations around the MPP of
PV panels [7]. These power oscillations can be extreme if
the conventional algorithm (P&O) continues to search for
the operating point on the P-V curve, although the MPP is
tracked in advance [6]. A function-based modified MPPT
method is implemented to track a current MPP with less
steady-state oscillations to remain close to the MPP
compared with the variable step size INC algorithm [8]. All
improved and hybrid MPPT algorithms are employed to
curb the oscillations adjacent the maximum power point in
the dynamics.
1.1.2 Tracking Performance:
In conventional algorithms, the tracking accuracy is found
to be higher when using soft computing, moderate with
P&O algorithms and lower when used with constant
voltage or current methods. In the P&O technique, tracking
accuracy is reduced if the tracking speed and perturbation
size are increased to track the MPP [9]. In the conventional
INC MPPT method, the fixed step size is the main constraint
in achieving high tracking performance for the PV system.
Thus, the variable INC algorithm is introduced to improve
the tracking efficiency, but it has an inversely proportional
effect on steady-state oscillations and tracking speed. Fast
and accurate tracking speed is attainable by calculating the
distance from the operating point to MPP in combination
with an automated tuning of the duty cycle step size [10].
MPPT
Technique
Speed Complex
ity
Reliab
ility
Implemen
tation
Fractional
Voc
Medium Low Low Digital/Ana
log
Incremental
Conductance
Varies Medium Mediu
m
Digital
Hill
Climbing(P &
O)
Varies Low Mediu
m
Digital/Ana
log
Fuzzy Logic Fast High Mediu
m
Digital
Neural
Network
Fast High Mediu
m
Digital
Table I: Comparison of common MPPT methods
1.2 Perturb and observe:
In this method the controller adjusts the voltage by a small
amount from the array and measures power; if the power
increases, further adjustments in that direction are tried
until power no longer increases. This is called perturb and
observe method and is most common, although this
method can result in oscillations of power output. It is
referred to as a hill climbing method, because it depends
on the rise of the curve of power against voltage below the
maximum power point, and the fall above that point.
Perturb and observe is the most commonly used MPPT
method due to its ease of implementation. Perturb and
observe method may result in top-level efficiency,
provided that a proper predictive and adaptive hill
climbing strategy is adopted.
1.2.1 Modified Perturb and Observe
method:

This method is an improved method of perturb and
observe (P&O) method. P&O is unable to track the power
during load changes and rapid variation of environmental
condition. MP&O method can meet the desired shape
which is ineffective in case of P&O method. Although
response time is improved, but power oscillation still
pertains in case of MP&O algorithm.
That presents the idea to focus on ANN and fuzzy logic
controller.
Advantages:
1. Simplicity: This algorithm solves one linear equation.
Therefore, it does not consume much computational
power.
2. It can be implemented as analog or digital circuits.
3. Since temperature varies slowly with time, there are no
steady-state oscillation and instability.
4. Low cost: temperature sensors are usually very cheap.
5. Robust against noise.
Disadvantages:
1. Estimation error might not be negligible for low
irradiation levels (e.g. below 200 W/m²).
3. Conclusions:
This paper analyses the most suitable perturbation step to
optimize maximum power point tracking performance and
suggests a design criterion to select the parameters of the
controller. Using this proposed adaptive step, the MPPT
perturb & observe algorithm achieves an excellent
dynamic response by adapting the perturbation step to the
actual operating conditions of the PV array. The proposed
algorithm has been validated and tested in a laboratory
using a dual input inductor push-pull converter. This
particular converter topology is an efficient interface to
boost the low voltage of PV arrays and effectively control
the power flow when input or output voltages are
variable. [11]
4. References:
1. K. Solanki, S. Chetan. Solar Photovoltaics:
Fundamentals, Technologies and Applications,
New Delhi, PHI, 2012.
2. Bushong, Steven. "Advantages and disadvantages
of a solar tracker system". Solar Power World.
Retrieved 20 August 2016.
3. Grid connect solar power FAQ - Energy Matters.
Available at:
https://www.energymatters.com.au/residential-
solar/home-solar-faqs/[accessed 14 June 2018].
4. "Cloud Cover and Solar Radiation" (PDF).
Scool.larc.nasa.gov. Available at:
https://www.nasa.gov/pdf/135641main_clouds_t
rifold21.pdf [accessed 14 June 2018].
5. Nasr, Ali & Saied, Mohamed & Mostafa, M.Z. &
Abdel-Moneim, T.M.. (2012). “A survey of
maximum PPT techniques of PV systems”,2012
IEEE Energytech, Energytech 2012. 1-17.
10.1109/EnergyTech.2012.6304652.
6. Sher, H.A.; Murtaza, A.F.; Noman, A.; Addoweesh,
K.E.; Al-Haddad, K.; Chiaberge, M. A New
sensorless hybrid MPPT algorithm based on
fractional short circuit current measurement and
P&O MPPT. IEEE Trans. Sustain. Energy 2015, 6,
1426–1434.
7. Babu, T.S.; Rajasekar, N.; Sangeetha, K. Modified
particle swarm optimization technique based
maximum power point tracking for uniform and
under partial shading condition. Appl. Soft
Comput. 2015, 34, 613–624.
8. Tousi, S.R.; Moradi, M.H.; Basir, N.S.; Nemati, M. A
function-based maximum power point tracking
method for photovoltaic systems. IEEE Trans.
Power Electron. 2016, 31, 2120–2128.
9. Verma, D.; Nema, S.; Shandilya, A.; Dash, S.K.
Maximum power point tracking (MPPT)
techniques: Recapitulation in solar photovoltaic
systems. Renew. Sustain. Energy Rev. 2016, 54,
1018–1034.
10. Karami, N.; Moubayed, N.; Outbib, R. General
review and classification of different MPPT
Techniques. Renew. Sustain. Energy Rev. 2017,
68, 1–18.
11. Piegari Luigi ; Rizzo Renato; Spina Ivan; Tricoli
Pietro, Optimized Adaptive Perturb and Observe
Maximum Power Point Tracking Control for
Photovoltaic Generation.
12. Pandey Arti; Srivastava Sumati, Perturb &
Observe MPPT Technique used for PV System
Under different Environmental Conditions,
International Research Journal of Engineering and
Technology (IRJET), Volume: 06 Issue: 04 | Apr
2019, e ISSN: 2395-0056 p-ISSN: 2395-0072.

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