Proposal and implementation of a novel perturb and observe algorithm using embedded software

1
Laboratory of Production engineering, Energy and Sustainable
Development (L.P.E.S.D.), higher school of technology, USMBA
University, Fez, Morocco
Proposal and Implementation of a novel perturb and observe
algorithm using embedded software
Authors :
Saad MOTAHHIR
Abdelaziz El Ghzizal
Souad Sebti
Aziz Derouich
IRSEC'15
3rd International Renewable and Sustainable Energy Conference
11/12/2015

2
Plan
1. Introduction
2. Modeling a photovoltaic panel
3. Implement MPPT using embedded software
4. Conclusion
Proposal and Implementation of a novel perturb and observe algorithm using embedded software11-12-2015

3
Introduction
33
Introduction Modeling a photovoltaic panel Implement MPPT using embedded software Conclusion

4
Modeling
Simulation and
validation of the
model
Datasheet
Model
Proposal and Implementation of a novel perturb and observe algorithm using embedded software
Present
the problematic
analogic
Load
Solution
Implement the
P&O algorithm
simulate the change
impact of
f
Modified
algorithm
by C
language
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555
Modeling a photovoltaic panel
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Cell model – Panel model - Problematic & Solution
𝐼,𝑐 = Iph,c −𝐼0, 𝑐 𝑒𝑥𝑝
𝑞 𝑉,𝑐 + 𝑅 𝑠, 𝑐 𝐼,𝑐
𝑎𝐾𝑇
− 1 −
(𝑉,𝑐 + 𝑅 𝑠, 𝑐 𝐼,𝑐)
𝑅 𝑠ℎ, 𝑐
Modeling Iph,c
(1)
Id,c
I,c
Ish,c
+
-
V,c
❑ Iph,c : The cell photocurrent;
❑ I0,c : The cell reverse saturation current of the diode;
❑ q : The electron charge;
❑ a : The ideality factor of the diode;
❑ K : The Boltzmann's constant;
❑ T :The junction temperature;
❑ V,c : The voltage across the cell;
❑ I,c : The current generated by the cell ;
❑ Rs,c : The series resistors of the cell;
❑ Rsh,c : The shunt resistors of the cell.
Rsh,c
Rs,c
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Cell model - Panel model - Problematic & Solution
෍
𝑘=1
𝑛
Cell Panel
The IV characteristic of this panel is represented by the following equations :
𝐼 = 𝐼 𝑝ℎ − 𝐼 𝑜 𝑒𝑥𝑝
𝑞 𝑉 + 𝑅 𝑠 𝐼
𝑎𝐾𝑇𝑁𝑠
− 1 −
(𝑉 + 𝑅 𝑠 𝐼)
𝑅 𝑠ℎ
Where:
𝐼 𝑝ℎ = 𝐼𝑠𝑐 + 𝐾𝑖 𝑇 − 298.15
𝐺
1000
𝐼0 =
𝐼𝑠𝑐 + 𝐾𝑖(𝑇 − 298.15)
exp
𝑞 𝑉𝑜𝑐 + 𝐾𝑣 𝑇 − 298.15
𝑎𝐾𝑇𝑁𝑠
− 1
(2)
(3)
(4)
❑ Ns : The number of cells connected in series;
❑ G : Sun irradiation in w/m2.
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" As a result, the complete physical behavior of the PV panel is
related to I0, Rs and Rsh on the one hand and with two
environmental parameters which are the solar irradiance and the
temperature on the other hand. "
Solarex MSX-60 is composed by 36 cells in series
Maximum power, Pmax 60W
Voltage at Pmax ,Vmp 17.1V
Current at Pmax , Imp 3.5A
Short-circuit current, Isc 3.8A
Open-circuit voltage, Vco 21.1V
Temperature coefficient of
open-circuit voltage Voc, Kv
-80mV/°C
Temperature coefficient of
short-circuit current Isc, Ki
2.4mA/°C
The number of cells 36
Table 1 : Typical Electrical Characteristics of Solarex MSX-60
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Based on the equations (1), (2) and (3), the modelization and simulation are obtained using Psim software as follow:
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Cell model - Panel model – Problematic & Solution
The power withdrawn from the PV panel depends on:
R1
R2
51W
Simulation of PV panel connected directly to the load (without control)
Irradiation Temperature Load
Rmax
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Cell model - Panel model – Problematic & Solution
α
I
V
MPPT command
Converter DC/DC
“ Insert between the PV panel and the load a converter DC/DC controlled by
an embedded system (Implement MPPT algorithm).”
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121212
Implement MPPT using embedded software

13Proposal and Implementation of a novel perturb and observe algorithm using embedded software
C1 C2
αV
L
R
𝐼 𝑜
The power electronic converter used is the Boost converter
𝑉𝑜 =
𝑉
1 − 𝛼
)𝐼 𝑜 = 𝐼(1 − 𝛼
(6)
(7)
Where, α, V and I, Vo and Io are respectively the duty cycle, PV input voltage and current, the output voltage and current of the
Boost converter.
The duty cycle α, is the output of the MPPT command.
DC/DC Converter - MPPT command
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The basic P&O algorithm is implemented using analog blocks :
Implementation
Basic Perturb and Observe
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The basic P&O algorithm simulated in PSIM software
“This method (P&O) generates oscillations of power
output therefore the efficiency is not at the requested
level (96.6%).”
Basic Perturb and Observe
11-12-2015

The novel P&O algorithm is designed in order to minimize the oscillation of power output
The proposed MPPT is based on the conventional Perturb & Observe algorithm with two proposed additions :
❑ The command of Boost converter alpha (α) will be modified every 5 periods;
❑ When the power increases or decreases by a value lower than the epsilon threshold ε (where ε is considered
as small positive real number), α keeps its value.
It is implemented using embedded C language. The reason lies
in the fact that once the MPPT is implemented using embedded
C language it can be implemented in cheap digital devices
(microcontroller, DSP…) because C language is portable and
machine independant.
Novel Perturb and Observe
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Implementation
11-12-2015

The proposed P&O algorithm using embedded C language simulated in PSIM software
“the oscillations of power output are decreasing. Also,
our system takes just 0.005s to stabilize around the
maximum power with an efficiency of 98.7%.”
11-12-2015

The simulation study was made to illustrate the response of the proposed method to rapid solar irradiance change:
“The system is stable, even at brutal change (from 800 to
500W/m²) the system presents the oscillations which last less
than 0.005 s.”
11-12-2015

The simulation study was made to change the temperature from 25°C to 35°C at 0.06 s :
“The increase in temperature causes a decrease of power;
however this decline lasts only 0.01s. After the embedded
software back the operating point and stabilizes it around the
MPP.”
11-12-2015

The simulation study was made to change the value of load from 50 Ω to 20 Ω :
“the decrease of load generates oscillations of power
output however after 0.035s the system converges to MPP.”
50Ω
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Conclusion and Perspectives
Introduction Modeling a photovoltaic panel Shading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power11-12-2015

232323
Conclusion :
❑ A good efficiency (98.7%) is obtained compared to the basic P&O algorithm implemented by analog blocks;
❑ The novel method presents a good response to temperature, solar irradiance and load change.
Perspective :
❑ Implement the novel method in cheap digital devices (microcontroller, DSP…).
Introduction Modeling a photovoltaic panel Shading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power11-12-2015

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Link of Paper:
https://ieeexplore.ieee.org/abstract/document/7455057
https://www.archives-ouvertes.fr/hal-01351499/
Link of Data:
https://data.mendeley.com/datasets/m5yv5r2d6k/3

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Please cite this work as:
Motahhir, S., El Ghzizal, A., Sebti, S., & Derouich, A. (2015, December). Proposal and
Implementation of a novel perturb and observe algorithm using embedded software.
In 2015 3rd International Renewable and Sustainable Energy Conference (IRSEC) (pp. 1-
5). IEEE.
For more papers and works please visit :
https://www.researchgate.net/profile/Saad_Motahhir

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