Impact of Partial Shading and bypass diode on PV panel Output Power

Impact of Partial Shading and bypass diode on PV panel Output Power

1. 1
Laboratory of Production engineering, Energy and Sustainable
Development, Smart Energy Systems and Information Processing
Research Team, higher school of technology, USMBA University,
Fez, Morocco
Impact of Partial Shading and bypass
diode on PV panel Output Power
Authors:
Saad MOTAHHIR
AbdelazizEl Ghzizal
SouadSebti
Aziz Derouich
WoISA'2015
Second Workshop On Imagery, Systems and Applications
31/10/2015
[email protected]

2. 2
Plan
1.Introduction
2.Modeling of photovoltaic panel
3.Shading and bypass diode impacts
4.Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power31-10-2015

3. 3
Introduction
33
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power31-10-2015

4. 4Impact of Partial Shading and bypass diode on PV panel Output Power
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Modeling
Simulation and
validation of the
model
Datasheet
Model
Simulatethe
effectof
Simulatethe effectof shading
Modelingof
shadingeffect
Simulatethe impact
of bypass diode
31-10-2015

5. 555
Modeling of photovoltaic panel
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power31-10-2015

6. 6
Cell model–Panel model -Effect of solar radiation variation
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power
??????
,??????=I
ph,
c−??????
0,
??????????????????�
�??????
,??????+??????
�,
????????????
,??????
??????????????????
−1−
(??????
,??????+??????
�,
????????????
,??????)
??????
�ℎ,
??????
Modeling
I
ph,c
(1)
I
d,c
I
,c
I
sh,c
+
-
V
,c
❑I
ph,c: The cellphotocurrent;
❑I
0,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: Currentgeneratedby the cell;
❑R
s,c: The series resistors of the cell;
❑R
sh,c: The shunt resistors of the cell.
R
sh,c
R
s,c
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7. 77
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Cell model-Panel model -Effect of solar radiation variation
෍
??????=1
�
Cell
Panel
The IV characteristic of this panel is represented by the following equations[1, 2]:
??????=??????
�ℎ−??????
�????????????�
�??????+??????
�??????
????????????????????????
�
−1−
(??????+??????
�??????)
??????
�ℎ
Where:
??????
�ℎ=(??????
�??????+??????
????????????−298.15)
??????
1000
??????
0=
??????
�??????+??????
??????(??????−298.15)
exp
�??????
�??????+??????
????????????−298.15
????????????????????????
�
−1
(2)
(3)
(4)
Impact of Partial Shading and bypass diode on PV panel Output Power
❑N
s: The number of cells connected in series;
❑G : Sun irradiation in w/m
2
.
31-10-2015

8. 8
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Cell model-Panel model -Effect of solar radiation variation
"As a result, the complete physical behavior of the PV panel is
related to I0, Rsand Rshon the one hand and with two
environmental parameters as the solar radiation and the
temperature on the other hand ."
SolarexMSX-60 is composed by 36 cells in series
Maximumpower,Pmax 60W
VoltageatPmax,Vmp 17.1V
CurrentatPmax,Imp 3.5A
Short-circuitcurrent,Isc 3.8A
Open-circuitvoltage,Vco 21.1V
Temperaturecoefficient of
open-circuit voltage Voc, Kv
-80mV/°C
Temperaturecoefficient of
short-circuit currentIsc, Ki
2.4mA/°C
Thenumberofcells 36
Table 1: TypicalElectricalCharacteristicsof Solarex MSX-60
Impact of Partial Shading and bypass diode on PV panel Output Power31-10-2015

9. 9
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Cell model-Panel model -Effect of solar radiation variation
Impact of Partial Shading and bypass diode on PV panel Output Power
I-VandP-Vcurvesfordifferentsolarradiation
“The PV panel current is highly dependent on
the irradiation. However, the voltage increases
by 1V when the irradiation increased from 400
W/m² to 1000 W/m².”
31-10-2015

10. 101010
Shading and bypass diode impact
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power31-10-2015

11. 11
Effect of shading -Mathematical modeling of the shading effect-Simulation
Introduction Modeling a photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power31-10-2015
Shading is when The PV panel is not completely exposed to light due to totrees, passing of clouds, neighboring
buildings and any other means.
❑Shading reduces energy production either by minimizing the energy supply of the shaded cells or by increasing the
energy loss in the shaded cells.

12. 12
Effect of shading -Mathematical modeling of the shading effect-Simulation
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power
Equivalent circuit of a PV panel consistsof 36 cellsin seriesunderpartial shading[3] :
❑Asetofilluminatedcellsisconnectedinserieswithanothersetofshadedcells;
❑ThephotoncurrentβI
phofshadedcellsislowerthanthephotoncurrentI
phofilluminatedcells;
❑IfthemodulecurrentI
msislowcomparedwithβI
phthen,thediodeD
sisforwardbiasedandthereisnorisk;
❑IfI
msisgreaterthanβI
ph,thediodecurrentI
Ds=I
phs-I
ms-IR
shs<0.Asaconsequence,thediodeisinthereversebiased;
ReversebiaseddiodeDsoffershighresistancewillconsumepowerandwillsignificantlyreducetheloadcurrentIitself.
Thiscausesadropintheoutputvoltage.Ifthedifferenceinilluminationlevelsishigh,Dsmaygetdamageddueto
overheating;
❑ThisphenomenoncalledHOTSPOTanditcancausepermanentdamagetothepanel.
❑Thesubscript‘i’and‘s’indicatetheparametersoffully
illuminatedcellsandshadedilluminatedcellsrespectively;
❑I
ph:thephotoncurrentofilluminatedcells;
❑βI
ph:Thephotoncurrentofshadedcells;
❑β:Theratioofthephotocurrentgeneratedbytheshaded
cellsandthecurrentgeneratedbytheilluminatedcells.
31-10-2015

13. 13
Effect of shading -Mathematical modeling of the shading effect-Simulation
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power31-10-2015
HOTSPOTphenomenon
❑Hot-spot heating occurs in a module when its operating current exceeds the reduced short-circuit current of a
shadowed cell or group of cells within it;
❑These hot spot mechanisms are the result of reverse biasing of cells which can lead to localized p-n junction
breakdown.

14. 14
Effect of shading -Mathematical modeling of the shading effect-Simulation
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power
Since the diode Ds is in the reverse biased so, V
Dstends to negative infinity. As a result, ????????????&#3627408477;(
????????????&#3627408480;
??????&#3627408481;&#3627408480;
)tends to zero. So, the equation
can be simplified as:
??????
&#3627408474;&#3627408480;=????????????
&#3627408477;ℎ+??????
0−
??????
&#3627408480;+??????
&#3627408474;&#3627408480;??????
&#3627408480;&#3627408480;
??????
&#3627408480;ℎ&#3627408480;
(7)
??????
&#3627408474;&#3627408480;=??????
??????=??????
&#3627408477;ℎ−??????
0????????????&#3627408477;
??????
????????????
??????
&#3627408481;??????
−1−
??????
????????????
??????
&#3627408480;ℎ??????
(5)
(6)
31-10-2015
??????
&#3627408474;&#3627408480;=????????????
=????????????
&#3627408477;ℎ−??????
0????????????&#3627408477;
??????
??????&#3627408480;
??????
&#3627408481;&#3627408480;
−1−
??????
??????&#3627408480;
??????
&#3627408480;ℎ&#3627408480;

15. 15
Effect of shading -Mathematical modeling of the shading effect-Simulation
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power
In order to prove the theory presented by (7), the simulation of the PV panel under shading is made and presented as follows :
“As is shown in simulation, once Imsis greater than Iphs, the curve I-V loses its
exponential characteristic like it is presented in the equation (7).”
??????
&#3627408474;&#3627408480;=????????????
&#3627408477;ℎ+??????
0−
??????
&#3627408480;+??????
&#3627408474;&#3627408480;??????
&#3627408480;&#3627408480;
??????
&#3627408480;ℎ&#3627408480;
ImpactofShading
(7)
“The power loss in the shaded cells is converted into heat which can lead to HOT SPOT
phenomenon causing permanent damage to the panel.”
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16. 16
Effect of shading -Mathematical modeling of the shading effect-Simulation
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power
Bypassdiode
“Under uniform insolation, the bypass diodes are
reverse biased and have no impact. However under
shades, the bypass diode is forward biased and the
current passes through the diode instead of the
shaded cells. Only those cells that are not influenced
by shadow generate power.”
“One method to protect the module against
hot-spot problem is when the bypass diodes
are connected in parallel with PV cells.”
31-10-2015
Inordertosimulatetheeffectofpartialshadingwithbypassdiodes,thestring1(18cells)isexposedby700W/m²
andstring2(18cells)by1000W/m²:

17. 17
Effect of shading -Mathematical modeling of the shading effect-Simulation
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power
Bypassdiode
Illustrate the effect of the bypass diode on the characteristics of the PV panel :
When Ims>Iphsthen, only the illuminated cells are functional. However, once
Ims<Iphsthen, all cells are functional. As a consequence there are two
maximum power points (MPP), point A (global) and point B (local).
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18. 181818
Conclusion and Perspectives
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power31-10-2015

19. 191919
Conclusion :
❑The work provides an idea about the effect of partial shading and bypass diode
on PV panel;
❑The conventional maximum power point tracking algorithms (i.e. P&O, IncCond
etc.) can fail to track the real MPP.
Perspectives :
❑Howitcanidentifytheglobalmaximum andlocalmaxima,willbestudiedin
thefuture.
❑Therearestillsomeoptimizationsandexperimentsneededtobedoneasthe
futurework.e.g.theproblemshowitcantracktheMPPinstantlywhenthe
weatherconditionischanging;
Introduction Modeling of photovoltaic panelShading and bypass diode impact Conclusion
Impact of Partial Shading and bypass diode on PV panel Output Power31-10-2015

20. 20
References:
1.SaadMOTAHHIR,AbdelazizElGhzizal,AzizDerouich,"Modélisationetcommanded’unpanneauphotovoltaïque
dansl’environnementPSIM",CongrèsInternationaldeGénieIndustrieletManagementdesSystèmes,2015.
2.SaadMOTAHHIR,AbdelazizElGhzizal,SouadSebti,AzizDerouich,Uneressourcepédagogiquepour
l'enseignementparsimulation:casdespanneauxphotovoltaïques,ProceedingsofInternationalWorkshopon
PedagogicApproaches&E-Learning(APEL2015).
3.SaadMOTAHHIR,AbdelazizElGhzizal,SouadSebti,AzizDerouich,"Shadingeffecttoenergywithdrawnfromthe
photovoltaicpanelandimplementationofDMPPTusingClanguage",Internationalreviewofautomaticcontrol,
Vol.9,No.2,2016,pp.88-94.
Appendix :
Please refer to the link below to download the data of this paper:
https://github.com/motahhir/PV-panel-under-shading-and-implementation-of-DMPPT

21. 21
Questions & Answers
[email protected]