Clarification on the Use of beta_Voc_pc Parameter in the official PV Array Module

Question 1:

In the official PV array module, there is a parameter beta_Voc_pc (Temperature coefficient of Voc), but I couldn't find where this parameter is specifically applied within the internal model. Could you please explain where the beta_Voc_pc parameter is used inside the module, and what is the exact formula used when applying this parameter in the model?

Question 2:

The value of beta_Voc_pc is restricted between -1 and -0.1, but I want to simulate perovskite solar cells, which have a positive temperature coefficient of Voc. This value exceeds the allowable range for the parameter. How can I address this issue? Are there any alternative solutions or workarounds?

Answer 1

[Kothuri]

Hi jinxia zhang,

Answer 1:

• In the official PV array module within MATLAB/Simulink, the “beta_Voc_pc” parameter, which stands for the “temperature coefficient of the open-circuit voltage (Voc)”, is used to adjust the Voc based on temperature changes.
• The parameter is defined in units of %/°C, representing the percentage change in open-circuit voltage per degree Celsius change in temperature.

You can refer the below link on “Temperature coefficient of Voc”

https://www.mathworks.com/help/sps/powersys/ref/pvarray.html?&s_tid=srchtitle_support_results_2_pv%20array#mw_8ea21103-bc40-42da-b8c5-a9713d2bf7da

Answer 2:

The default “beta_Voc_pc” parameter is restricted between -1 and -0.1 (negative values) because traditional silicon-based solar cells typically exhibit a negative temperature coefficient for Voc​. However, perovskite solar cells can exhibit a positive temperature coefficient for Voc​, which is outside the allowable range.

So, for positive temperature coefficient of Voc in PV array, you can try the below steps:

• Create a custom PV module model in Simulink that allows for a positive temperature coefficient.
• Implement the Voc temperature dependency as a “lookup table” based on experimental data or theoretical models for perovskite solar cells. This allows greater flexibility and avoids the limitations of the built-in “beta_Voc_pc” parameter.

If you want to retain the built-in PV module but bypass the parameter range restriction:

• Scale the positive temperature coefficient to fit within the allowable range.
• Apply a scaling factor outside the module to revert to the original positive coefficient.
• Use a "Simulink Function" block to implement the Voc adjustment formula with your desired coefficient. This block can then be integrated into your existing PV array model.

You can refer the below documentation links for more info on

Lookup table - https://www.mathworks.com/help/simulink/slref/ndlookuptable.html?&s_tid=srchtitle_support_results_3_lookup%20table

Simulink Function block - https://www.mathworks.com/help/simulink/slref/simulinkfunction.html?&s_tid=srchtitle_support_results_1_simulink%20function