Energy Comparison of MPPT Techniques Using Cuk Converter

International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163
Volume 1 Issue 6 (July 2014) http://ijirae.com
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© 2014, IJIRAE- All Rights Reserved Page - 277
Energy Comparison of MPPT Techniques Using Cuk Converter
R.B.Wankhede1
PROF.U.B.Vaidya2
1
Student of M.Tech(EMS), RCERT, Chandrapur. 2
Professor, Electrical Department, RCERT, Chandrapur
Abstract--In this paper the energy comparison of two MPPT, P&O and Incremental conductance is done using cuk
convertor. For comparison such as voltage, current and power output for each different combination has been recorded.
MATLAB simulink tools have been used for performance evaluation on energy point.
Key words--Maximum power point tracking MPPT, photovoltaic cell PV, P&O, incremental conductance IC, CUK convertor
I.INTRODUCTION
Photovoltaic (PV) generation is becoming increasingly important as a renewable source since it offers many advantage such as
incurring no fuel cost, not being polluted, requiring little maintenance, and emitting no noise among others.[1] PV module
still have relatively low conversion efficiency, therefore, controlling maximum power point tracking (MPPT) for the solar array
is essential in a PV system. The optimum operating changes with solar radiation and cell temperature. In general, there is a
unique point on V-I or V-P characteristic curve, called maximum power point (MPP) at which entire PV system operates with
maximum efficiency and produces its maximum power output.[2] Therefore Maximum Power Point Tracking (MPPT)
techniques are needed to maintain the PV array operating point at its MPP.A variety of maximum power point tracking (MPPT)
are developed. These techniques vary between then in many aspects including simplicity, convergence, speed, hardware
maintenance, sensor required, cost range effectiveness. Perterb and observance[3] and increamental conductance technique[4]
using cuk convertor with resistive load is studied in this paper.
II.PV EQUIVALENT CIRCUIT
Solar cells are connected in series and parallel to set up the solar array. Solar cell will produce dc voltage when it is exposed to
sunlight. Fig.1 shows the equivalent circuit model for a solar cell. Solar cell can be regarded as a non-linear current source.[5] Its
generated current depends on the characteristic of material, age of solar cell, irradiation and cell temperature.
Fig.1:-Equivalent circuit model for a solar cell
III. CUK CONVERTER
When proposing an MPP tracker, the major job is to choose and design a highly efficient converter, which is supposed to operate
as the main part of the MPPT. The efficiency of switch-mode dc–dc converters is widely discussed in [7]. Most switching-mode
power supplies are well designed to function with high efficiency. Among all the topologies available, both Cuk and buck–boost
converters provide the opportunity to have either higher or lower output voltage compared with the input voltage. Although the
buck–boost configuration is cheaper than the Cuk one, some disadvantages, such as discontinuous input current, high peak
currents in power components, and poor transient response,make it less efficient.On the other hand the Cuk convertor has low
switching losses and the hieghest efficiency amond non isolated dc-dc convertor. It can also provide a better output-current
characteristic due to the inductor on the output stage. Thus, the Cuk configuration is a proper converter to be employed in
designing the MPPT. Figs. 2 and 3 show a Cuk converter and its operating modes, which is used as the power stage interface
between the PV module and the load. The Cuk converter has two modes of operation. The first mode of operation is when the
switch is closed (ON), and it is conducting as a short circuit. In this mode, the capacitor releases energy to the output. The
equations for the switch conduction mode are as follows:
L1= (1)
2=− 1 – 2 (2)

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1= 2 (3)
2= 2 − 2/ (4)
make it less efficient. On the other hand, the Cuk converter has low switching losses and the highest efficiency among non
isolated dc–dc converters.
Fig. 2 Electrical circuit of the Cuk converter used as the PV power-stage interface
Fig.3.Cuk converters with (a) switch ON and (b) switch OFF
On the second operating mode when the switch is open (OFF), the diode is forward-biased and conducting energy to the output.
Capacitor C1 is charging from the input. The equations for this mode of operation are as follows:
L1= – 1 (5)
vL2=− 2 (6)
1= 1 (7)
2= 2− 2/ (8)
The principles of Cuk converter operating conditions state that the average values of the periodic inductor voltage and capacitor
current waveforms are zero when the converter operates in steady state. The relations between output and input currents and
voltages are given in the following:
/ = − ( /1− ) (9)
/ = − ( /1− ) (10)
IV.PERTURB AND OBSERVE (P&O)
In this algorithm a slight perturbation is introduce system [8]. This perturbation causes the power of the solar module changes. If
the power increases due to the perturbation then the perturbation is continued in that direction [8]. After the peak power is
reached the power at the next instant decreases and hence after that the perturbation reverses. When the steady state is reached
the algorithm oscillates around the peak point. In order to keep the power variation small the perturbation size is kept very small.
A PI controller then acts moving the operating point of the module to that particular voltage level. It is observed that there some
power loss due to this perturbation also the fails to track the power under fast varying atmospheric conditions. But still this
algorithm is very popular and simple.
Fig. 4: Graph Power versus Voltage for Perturb and Observe Algorithm [3]

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Fig. 5: Flow chart of the Perturb and Observe Algorithm [3]
V.INCREAMENTAL CONDUCTANCE (IC)
The disadvantage of the perturb and observe method to track the peak power under fast varying atmospheric condition is
overcome by IC method [3].
Fig.6: Graph Power versus Voltage for IC algorithm
Fig 7 :-Flow chart of incremental conductance method

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The IC can determine that the MPPT has reached the MPP and stop perturbing the operating point. If this condition is not met,
the direction in which the MPPT operating point must be perturbed can be calculated using the relationship between dl/dV and –
I/V [9 This relationship is derived from the fact that dP/dV is negative when the MPPT is to the right of the MPP and positive
when it is to the left of the MPP. This algorithm has advantages over P&O in that it can determine when the MPPT has reached
the MPP, where P&O oscillates around the MPP. Also, incremental conductance can track rapidly increasing and decreasing
irradiance conditions with higher accuracy than perturb and observe [3]. One disadvantage of this algorithm is the increased
complexity when compared to P&O [3].
VI. GRAPHICAL ENVIRONMENT MATLAB SIMULINK ENVIRONMENT
Fig 8:- Simulink model of Incremental conductance MPPT with resistive load.
Fig 9:- Simulink model of PO MPPT with resistive load
C ontinuous
powergui
v
+
-
Voltage Measurement1
v+
-
Voltage Measurement
V1
To Workspace4
P1
To Workspace3
I
To Workspace2
V
To Workspace1
P
To Workspace
Step
Series RLC Branch
Scope8
Scope6
Scope5
Scope4
Scope3
Scope2
Scope1
ScopeSaturation
In RMS
RMS4
InRMS
RMS2
InRMS
RMS1
Product1
Product
VrefD
PWM Generator
ISO
+V
-V
PVG1
V
I
Vref
MPPT
i+
-
Current Measurement1
i+
-
Current Measurement
PWM
+V
-V
V+
V-
Cuk
|u|
Abs1
|u|
Abs
v
pv
pp
Discrete,
Ts = 5e-006 s.
powergui
pi
p
id
PWM
+V
-V
V+
V-
cuk
v
+
-
Vm1
v
+
-
Vm
Transport
Delay
I1
To Workspace2
P1
To Workspace1
V1
To Workspace
Subtract
In1
Out1
Out2
Subsystem
Step
Saturation1
Saturation
InS/H
Sample
and Hold1
RL
Product1
Product
ISO
+V
-V
PVG
InRMS
Discrete
RMS value6
InRMS
Discrete
RMS val ue5
InRMS
Discrete
RMS val ue4
In RMS
Discrete
RMS val ue3
In RMS
Discrete
RMS val ue2
InRMS
Discrete
RMS value1
>= 0
Compare
To Constant2
i
+
-
Cm1
i
+
-
Cm
|u|
Abs2
|u|
Abs1
|u|
Abs

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Fig 10:- Simulink model of with ought IC and P&O MPPT with resistive load
VII. RESULT
Result of comparison of o/p current, voltage and power with and without Perturb and observe method and Incremental
conductance method is shown in figure below
Fig. 11. Comparison diagram of o/p current, voltage & power without P&O and Incremental conductance method
Continuo us
powergui
v+
-
Voltage Measurement1
v
+
-
Voltage Measurement
I
To Workspace2
V
To Workspace1
P
To Workspace
Step
Series RLC Branch
Scope5
Scope3
Scope2
Scope1
ScopeSaturation
In RMS
RMS5
InRMS
RMS2
In RMS
RMS1
Product1
Product Power
VrefD
PWM Generator
ISO
+V
-V
PVG1
i+
-
C urrent Measurement1
i
+
-
Current Measurement
PWM
+V
-V
V+
V-
Cuk
0.465
Constant1
|u|
Abs1
|u|
Abs
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
0
1
2
3
4
5
6
Time
current
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5
0
10
20
30
40
50
60
Time
voltage
0 1 2 3 4 5 6
x 10
4
0
50
100
150
200
250
300
time
power

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Fig. 12. Comparison diagram of o/p current, voltage & power with Incremental conductance method
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
1
2
3
4
5
6
7
8
9
Time
current
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
20
40
60
80
100
Time
voltage
0 1 2 3 4 5 6 7 8 9
x 10
5
0
100
200
300
400
500
600
700
800
time
power
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
0.5
1
1.5
2
2.5
Time
current

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Fig. 14:- Comparison diagram of o/p current, voltage & power with perturb & observe method
VIII. CONCLUSION
This paper has presented a comparison of two most popular MPPT controller, Perturb and Observe Controller with Incremental
Conductance Controller. One simple solar panel that has standard value of insolation and temperature has been included in the
simulation circuit. From all the cases, the best controller for MPPT is incremental conductance controller. This controller gives a
better output value for cuk converter.
REFERENCES
[1] Sohan Lal, Rohtash Dhiman, Mr.S.K.Sinha, “Analysis Different MPPT Techniques for Photovoltaic System”
International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 6, December 2012
[2] Jay Patel, Vishal sheth, Gaurang Sharma,“Design & Simulation Of Photovoltaic System Using Increamental MPPT
Algorithm” International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering Vol. 2,
Issue 5, May 2013
[3] Hairul Nissah Zainudin, Saad Mekhilef,”Comparison Study of Maximum Power Point Tracker Techniques for PV Systems”
Proceedings of the 14th International Middle East Power Systems Conference (MEPCON’10), Cairo University, Egypt,
December 19-21, 2010, Paper ID 278.
[4] Saravana Selvan. D,” Modeling and Simulation of Incremental Conductance MPPT Algorithm for Photovoltaic
Applications” International Journal of Scientific Engineering and Technology (ISSN : 2277- 1581) Volume No.2, Issue
No.7, pp : 681-685 1 July 2013
[5] M.Lokanadham, K.Vijaya Bhaskar,” Incremental Conductance Based Maximum Power Point Tracking (MPPT) for
Photovoltaic System” International Journal of Engineering Research and Applications (IJERA), Vol. 2, Issue 2,Mar-Apr
2012, pp.1420-1424
[6] Divya Teja Reddy Challa, I. Raghavendar,”Implementation of Incremental Conductance MPPT with Direct Control Method
Using Cuk Converter,”International Journal of Modern Engineering Research (IJMER),Vol.2, Issue.6, Nov-Dec. 2012 pp-
4491-4496 ISSN: 2249-6645
[7] R.-J. Wai, W.-H. Wang and C.-Y. Lin, ―”High-performance stand-alone Photovoltaic generation system,‖ IEEE Trans. Ind.
Electron.” vol. 55, no. 1, pp. 240–250, Jan. 2008.
[8] Ch.Kiran Kumar, T.Dinesh, S.Ganesh Babu,”Design and Modelling of PV system and Different MPPT algorithms”
International Journal of Engineering Trends and Technology (IJETT) – Volume 4 Issue 9- Sep 2013
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
5
10
15
20
25
Time
voltage
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
0
10
20
30
40
50
60
Time
power

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