# National Instruments Circuit Design Community Blog

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## New Models for Photovoltaic Cells in Multisim

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NI Multisim is a powerful tool used to simulate and prototype power electronics circuit designs. Multisim has large database of configurable power component models along with existing SPICE models from various semiconductor manufacturers. The simulation capabilities in Multisim enable the evaluation of different power circuits of different ratings at an early design stage.

This is the first of a series of blog posts about new power electronics models specifically developed for simulations renewable energy applications in NI Multisim. The models were developed in collaboration with the Virtual Instrumentation and Renewable Energy Laboratory at the Transilvania University of Brasov in Romania.

1. Basic PV Cell

this model represents the ideal and most simplistic case of a PV cell model. the solar cell is modeled using an ideal current source in parallel with a diode and a load resistance.

The model is available in the Multisim file Testing the Solar Cell Modules_1.ms13 attached to this post. Connected to the model are two DC sources; Virrad representing the level of illumination where 1000V=1000W/m2 a, while Vbias allows the variation of the bias point to measure the output I-V characteristics. In a real world application, Vbias would be replaced by a load.

The internal parameters of the models are set based on a Si solar cell example:

• The reverse saturation current (Io = 10-11 A)
• The short circuit current (Isc = 0.034 A)
• The area of the solar cell (A = 1cm2)

These parameters could be viewed and altered simply by double-clicking the component on the schematic and clicking on Edit model in the Value tab:

Running a DC Sweep simulation in Multisim to evaluate the output current at different bias points as well as the output power, the below graph could be reproduced

2. Advanced PV Cell with Series and Shunt Resistance

This model is based on the single exponential model published in [1]. It add a shunt and series parameters to model the panel resistance.

The same Si solar cell example was used to set the following parameters:

• The constant material (B = 5.769*106 )
• The short circuit current (Isc = 0.034 A)
• The area of the solar cell (A = 1cm2)
• The energy bangap (Eg = 1.11eV)
• The series resistance (Rs = 0.1 Ω)
• The shunt resistance (Rsh = 10000 Ω)

In this advanced model the open circuit voltage of the solar cell depends on the material of the solar cell expressed in the material constant B and the energy band gap Eg. The material constant can be determined using the variation of the reverse saturation current function of the temperature and it theoretically derives from this relation:

While the values of the energy Bandgap for some important semiconductor materials are available in the table below:

 Semiconductor materials Energy bangap [eV] Si 1.11 CdTe 1.43 GaAs 1.45 InP 1.27 GaP 2.25

The model and the test circuit are available in the attachment Testing the Solar Cell Modules_2.ms13. Running a Nested DC Sweep yields the following I-V characteristics of the PV cell

This is a model of a PV panel based on a number of individual solar cells connected in series using one diode model with irradiance and temperature parameters. It is based on the physical parameters of the BP-MSX120 PV panel, however these parameters could be altered in the model to match other PV panels:

• The short circuit current (Isc = 3.87 A)
• The series resistance (Rs = 0.47 Ω)
• The shunt resistance (Rsh = 1365 Ω)
• The temperature coefficient of the power (kp = −0.5 ± 0. 05)
• The number of solar cells in series (ns = 72)
• The ideality factor of diode (A = 1.397)

The example testing circuit to validate this model is in the attached file Testing the Solar Cell Modules_3.ms13

A nested temperature sweep is performed to evaluate the I-V characteristics of the panel under different temperature conditions:

About the Virtual Instrumentation and Renewable Energy Laboratory - Transilvania University

Laboratory members:

Dr. Daniel Tudor COTFAS

The lab is integrated in the Electronics and Computers Department, Electronics and Computers Science Faculty, Transilvania University of Brasov. Transilvania University of Brasov was founded in 1948 and has now 18 faculties, offering bachelor, master and doctoral studies to over 22000 students. Advanced research is developed in 22 centers focusing on major topics of sustainable development: Renewable Energy Systems, novel Energy Efficiency in processes, advanced solutions for Energy Saving products and processes, Natural Resources preservation and use, Health and Life Quality, and Education, Culture, Communication and Economic Development.

There are many educational and industrial applications using the NI products at the University:

• Simulation of Physics labs using the graphical programming language LabVIEW
• SolarLab – educational and research system powered by NI LabVIEW and NI ELVIS II platform

• RELab (Renewable Energy Laboratory) – educational and research system powered by NI LabVIEW and NI ELVIS II and myDAQ platforms

• STNV 25120469 – research contract for development of drivers LabVIEW Ecochemie - Netherlands
• Weighing and monitoring system of Mass Distribution for S.C. IAR S.A. Brasov, Romania
• Management system for the utilities implemented at S.C. IAR S.A. Brasov, Romania

The ReLab system is a very good solution for the study of the renewable energy. The design of the entire RELab circuit was done using the NI Multism and NI Ultiboard. The RELab system was recognized as a break-through tool in education and won three awards at international competitions organized by National Instruments:

• Graphical System Design Achievement Awards - Education category - August 2013
• Graphical System Design Achievement Awards - Editors Choice Award - August 2013
• Graphical System Design Achievement Awards - NI Community’s Choice - August 2013.

References

1. 1.   D. T. Cotfas, P. A. Cotfas, S. Kaplanis: Methods to determine the dc parameters of solar cells: A critical review, Renewable and Sustainable Energy Reviews, vol. 28, 2013, pp. 588–596.
2. 3.   D. Sera, R. Teodorescu, PV panel model based on datasheet values, Industrial Electronics, 2007. ISIE 2007. IEEE International Symposium on, pp. 2392 – 2396, 2007
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I would like to use wind turbine generator instead of solar cell. could you guide me how to built it?

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Dear Mahmoud,

Thanks for sharing the examples files for the solar cell PV model.

I am trying to develope the PV model based on the double diode configuration. I would like to ask a few things regarding the material constant "B", you used in the above example.