Ali Karimpour & Reza Bakhshi 2016 2 0 1 6 Photovoltaic systems engineering Photovoltaic Systems Engineering Reza Bakhshi Ph.D. student Ferdowsi University of Mashhad Ali Karimpour Associate Professor Ferdowsi University of Mashhad
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Photovoltaic systems engineering
Photovoltaic Systems
Engineering
Reza Bakhshi
Ph.D. student
Ferdowsi University of Mashhad
Ali Karimpour
Associate Professor
Ferdowsi University of Mashhad
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Lecture 5
The principles of grid connected
PV systems designing
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The definition of GCPV system designing
Consider a PV array with the specific brand and size as well as the
inverter brand. The “designing of a GCPV system” defines as the
inverter size determination and configuration selection. In
configuration selection, the number of PV panels in each string,
number of string connected to the inverter input and number of
used input should be calculated. These electrical constraints should
be checked in order to:
3
Maximum available output energy extraction (work in MPP)
Safe performance of inverter in different weather conditions
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Solar inverter Grid
Np
Ns
The definition of GCPV system designing
Design targetThe determination of:
N : number of inverters
N : the number of PV panels in each
string
N : number of string connected to the
inverter input
number of used input
inv
p
s
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The principles (Rule 1)
Inverter sizing
Sizing factor = nominal DC power of PV array / nominal output power of inverter
Inverter number Sizing factor Suitable for high radiation levels
Inverter number Sizing factor Suitable for low radiation levels
Too much inverters results in non economic performance
Low inverter numbers results in inverter disconnection
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The principles (Rule 1)
Inverter sizing
Sizing factor = nominal DC power of PV array / nominal output power of inverter
This parameter should be limited to 0.8 and 1.2 (some cases in tighter interval).
In most designs, small tolerance for the PV array size can be considered in order
to find the feasible designs.
This tolerance can be 2% of the nominal power.
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The principles (Rule 2)
Inverter protection against over voltage
The lower number of series panel is limited so that even in the lowest
temperature (Vpv,OCmax), the string highest voltage, i.e. open–circuit
voltage (VOC), does not exceed the inverter maximum input voltage
(Vinv,max):
max,
max,
OCpv
inv
SV
VN
)](1[ ,min,,max, STCCCOCOCSTCpvOCpv TTVV
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The principles (Rule 3)
Inverter protection against over current
The total output current of inverter input is limited so that it is protected
from overcurrent. The worst case for string current, i.e. the most at the
maximum radiation level (Ipv,max) can be calculated as follows:
),min( max,
max,
max,
p
pv
inv
p NI
IN
STC
STCpvpvS
SII max
,max,
Maximum strings
equipped for each input
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The principles (Rule 4)
Inverter operation in MPP
An important goal of electrical constraints is to guarantee the optimal
performance of the solar system, or in other words PV array MPP voltage
optimum allocation in the inverter MPP voltage interval. This should be
done, especially in conditions of high radiation level that mostly coincides
with high temperature. To do this, the string MPP voltage of the mth input
should be greater than the lowest MPP voltage interval of the inverter
(Vinv,MPPmin):
min,
min,
MPPpv
MPPinv
SV
VN
)](1[ ,max,,min, STCCCMPPMPPSTCpvMPPpv TTVV
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The summary
For a specific PV array size:
1. Determine the inverter numbers due to the sizing factor limitation
2. Divide the PV panels to the inverters
3. Calculate the minimum MPP voltage and maximum OC voltage of
PV module as well as maximum PV current
4. Determine the minimum and maximum series panel in each string
5. Determine the maximum parallel strings
6. Find Ns and Np so that Ns×Np equals to the PV panels per inverter
7. If you fail in (6), Try to change the inverter numbers and find another
Ns and Np
8. If you fail in (7), Try to change the PV array size and find Ns and Np
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GCPV system design
Growatt 10000UE
Example 6.1: Design a 20 kWp GCPV system with the following PV
panel and inverter. The site location is Bojnourd with -20 °C, 45 °C and
1100 W/m as the lowest ambient temperature, highest ambient temperature
and maximum available irradiance.
2
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GCPV system design
Yingli 255W
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GCPV system design
Solution:
Initially, we should calculate the maximum open-circuit voltage, minimum
MPP voltages as well as the maximum MPP current.
)](1[ min,,max, STCCVOCSTCpvOCpv TTVVOC
VV OCpv 3.409.14.38)]253020()01.033.0(1[4.38max,
)](1[ max,,min, STCCVMPPSTCpvMPPpv TTVVOC
VV MPPpv 4.252.54.30)]253045()01.033.0(1[4.30min,
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GCPV system design
Solution:
Initially, we should calculate the maximum open-circuit voltage, minimum
MPP voltages as well as the maximum MPP current.
STC
MPPSTCpvMPPpvS
SII max
,max,
AI MPPpv 06.91000
110024.8max,
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GCPV system design
Them ,the limitations on the series panel and string number should be
computed:
12 24
2
3.40
1000
4.25
300SN
06.9
20PN
06.9
20PN
3.40
1000
4.25
300SN
max,
max,
min,
min,
OCpv
inv
S
MPPpv
MPPinv
V
VN
V
V
max,
max,
MPPinv
inv
PI
IN
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GCPV system design
By considering the allowable sizing factor, the feasible designs will be as
follows:
Npv Np Ns Ppv (W) Ninv Pinv (W) Sizing factor
63 3 21 16065 2 20000 0.8032
76 4 19 19380 2 20000 0.9690
80 4 20 20400 2 20000 1.0200
94 4 23, 24 23970 2 20000 1.1985
The inverter number should be 2.
Suppose we can change the PV module numbers to achieve different sizing
factor values.
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GCPV system design
...
...
23
24
...
...
23
24
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GCPV system design
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GCPV system design
Example 6.2: Design a 650 kWp GCPV system with the following PV
panel and inverter. The site location lowest ambient temperature, highest
ambient temperature and maximum available irradiance are -14°C, 36°C
and 1250 W/m.2
Yaskawa–Solectria Solar PVI 28TL
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GCPV system design
Trina Solar TSM-PD14 310W
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GCPV system design
Solution:
Initially, we should calculate the maximum open-circuit voltage, minimum
MPP voltages as well as the maximum MPP current.
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GCPV system design
Solution:
Initially, we should calculate the maximum open-circuit voltage, minimum
MPP voltages as well as the maximum MPP current.
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GCPV system design
Them , the limitations on the series panel and string number should be
computed:
16 21
4
Min (4,4)=4
Per tracker
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GCPV system design
By considering the allowable sizing factor, we have:
Npv Np Ns Ppv (W) Ninv Pinv (W) Sizing factor
2100 5 21 651,000 20 560,000 1.162
2070 5 18 641,700 23 644,000 0.996
2080 5One with 20
Others with 18644,800 23 644,000 1.00
.
.
.
The feasible designs will be as follows:
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GCPV system design
...
20
...
5
...
18
...
5
One with 20 series panel 22 with 20 series panel
One inverter with 20 series panel 22 inverters with 18 series panel
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GCPV system design
Real project was installed in Oklahoma City (USA) at 2015.
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GCPV system design
Example 6.3: Design a 40 kWp GCPV system with the following PV
panel and inverter. The site location is somewhere with -40 °C, 30 °C and
1100 W/m as the lowest ambient temperature, highest ambient temperature
and maximum available irradiance.
2
Powador 20.0 TL3 (Kaco)
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GCPV system design
TSM-PA05 - Trina Solar
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GCPV system design
Solution:
Initially, we should calculate the maximum open-circuit voltage, minimum
MPP voltages as well as the maximum MPP current.
)](1[ min,,max, STCCVOCSTCpvOCpv TTVVOC
VV OCpv 366.41166.42.37)]253040()01.032.0(1[2.37max,
)](1[ max,,min, STCCVMPPSTCpvMPPpv TTVVOC
VV MPPpv 02.2628.33.29)]253030()01.032.0(1[3.29min,
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GCPV system design
Solution:
Initially, we should calculate the maximum open-circuit voltage, minimum
MPP voltages as well as the maximum MPP current.
STC
MPPSTCpvMPPpvS
SII max
,max,
AI MPPpv 833.81000
110003.8max,
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GCPV system design
Them , the limitations on the series panel and string number should be
computed:
8 24
2
366.41
1000
02.26
470SN
03.8
6.18PN
03.8
6.18PN
366.41
1000
02.26
470SN
max,
max,
min,
min,
OCpv
inv
S
MPPpv
MPPinv
V
VN
V
V
max,
max,
MPPinv
inv
PI
IN
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GCPV system design
For Psys=40 kWp the panel number (Npv) are 40 kWp÷235Wp=170
Also, by considering the allowable sizing factor, we have: Ninv=2
We have two inverters, so each one should have 170÷2=85 panels.
For 4 available strings, 85÷4=21.25 panels should be considered to
every string.
To have a feasible design we connect 21 panels in 6 strings (4 strings of
1st inverter and one MPPT of the 2nd inverter) and 22 panels for
remained strings (2nd MPPT of the 2nd inverter)
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GCPV system design
To have a feasible design we
connect 21 panels in 6 strings
(4 strings of 1st inverter and one
MPPT of the 2nd inverter) and
22 panels for remained strings
(2nd MPPT of the 2nd inverter)...
...
21
24
...
...
21
22
22
...
...
21
24
...
...
21
21
21
1st inverter 2nd inverter
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Exercise
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5.1 Present at least two designs for 30 kWp GCPV system with
following equipment:
Q Cells Q.Pro BFR-G3 250 and SMA Sunny Boy 9000TL-US
5.2 Design at least two configurations for 270 kWp GCPV system
with following equipment:
Canadian Solar CS6X-305P and Fronius Symo 24.0-3 480
5.3 Design a 5 MWp GCPV system with following equipment:
Hanwha HSL 72 305 and Eaton Power Xpert Solar 1670
Of course you need to download the datasheets from internet.
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References
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Bakhshi R., Sadeh J., Mosaddegh H–R., “Optimal economic designing of
grid-connected photovoltaic systems with multiple inverters using linear and
nonlinear module models based on Genetic Algorithm”, Renewable Energy,
Vol. 72, pp. 386–394, December 2014.
A. Kornelakis and Y. Marinakis, “Contribution for optimal sizing of grid-
connected PV-systems using PSO”, Renewable Energy, vol. 35, no. 6, pp.
1333–1341, June 2010.
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