Photovoltaic By-Pass Diodes

1. Photovoltaic By-Pass Diodes
(LTspice IV)
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 1

2. Contents
1. Solar Module Model and Specification
2. Bypass Diode Model
3. Modules without the Bypass Diodes
4. Modules with the Bypass Diodes
5. Solar Module Field with the Bypass Diodes
Library Files and Symbol Files Location
Simulation Index
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 2

3. 1. Solar Module Model and Specification
• The specification of Showa Shell's solar module SC75-RT-A are shown in the table.
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 3
Parameter, SOL is added
as normalized incident
radiation, where SOL=1 for
AM1.5 conditions
Parameter, SOL is added
as normalized incident
radiation, where SOL=1 for
AM1.5 conditions
No. SC75-RT-A
Maximum power(Pmax) 75(W)
Voltage at Pmax(Vmp) 40.5(V)
Current at Pmax(Imp) 1.85(A)
Short-circuit current(Isc) 2.20(A)
Open-circuit voltage(Voc) 55.5(V)
Fig.1 A single solar module part number SC75-RT-A

4. 2. Bypass Diode Model
• Shottky diode is used as a bypass. I-V characteristic of the diode is shown in the
graph.
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 4
Bypass DiodesBypass Diodes
IF-VF Characteristic:
.model Dbypass D
+ IS=10.134E-6 N=1.1371 RS=12.648E-3
Fig.2 A bypass diode is connected to the solar module. Fig.3 Shottky diode I-V characteristics.

5. 3. Modules without the Bypass Diodes
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 5
SOL=1
SOL=0.2 (under shade)
SOL=1
SOL=0.2 (under shade)
Current
Power
Under shade,
incident radiation
drops to 20%
Under shade,
incident radiation
drops to 20%
Simulation ResultSimulation Circuit
• Simulate 3 solar modules that are connected in series without bypass diode when
one module is in shade. the simulation result shows how the power and current are
lowered.
Current is limited by
an inactive module
Current is limited by
an inactive module

6. 4. Modules with the Bypass Diodes
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 6
SOL=1
SOL=0.2 (under shade)
SOL=1
SOL=0.2 (under shade)
Current
Power
Under shade,
incident radiation
drops to 20%
Under shade,
incident radiation
drops to 20%
Simulation ResultSimulation Circuit
• With the bypass diode when one module is in shade. the simulation result shows that
the output of the active modules can flow past an inactive module.
Current flow past
an inactive module
Current flow past
an inactive module

7. 5. Solar Module Field with the Bypass Diodes
Simulate solar field that’s built from 30 solar modules in series with bypass diode across
group of 10 modules when one group is in shade.
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 7
Activated Bypass DiodeActivated Bypass Diode
Current Flow
Under shade,
incident radiation
drops to 20%
Under shade,
incident radiation
drops to 20%

8. 5. Solar Module Field with the Bypass Diodes
The graphs show I-V and P-V with bypass diodes across groups of 10 modules.
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 8
Current
Power
SOL=1
SOL=0.2 (under shade)
SOL=1
SOL=0.2 (under shade)

9. Library Files and Symbol Files Location
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 9
…Photovoltaic By-Pass Diodes
C:Program FilesLTCLTspiceIVlibsub
C:Program FilesLTCLTspiceIVlibsym
Copy/
Paste
into
Copy/
Paste
into
Copy/
Paste
into
Copy/
Paste
into
1. Copy the library files (.lib) from the folder …Photovoltaic By-Pass Diodes.sub, then paste into the
folder C:Program FilesLTCLTspiceIVlibsub
2. Copy the symbol files(.asy) from the folder …Photovoltaic By-Pass Diodes.asy, then paste into
the folder C:Program FilesLTCLTspiceIVlibsym

10. Simulation Index
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011 10
Simulations Folder name
1. Bypass Diode Model............................................
2. Modules without the Bypass Diodes.....................
3. Modules with the Bypass Diodes..........................
4. Solar Module Field with the Bypass Diodes..........
...SimulationBypass-Diode
...SimulationCase1Type-A
...SimulationCase1Type-B
...SimulationCase2