Coefficient error in the CEC Performance Model with User entered Specifications

We are receiving some form of this module coefficient error with a number of user-defined panels. I would appreciate a general solution for when we encounter this error. I have attached the details (.sam file, datasheet) on a specific model, the Solaria POWERX-400R-4T bifacial panel. The error message is "Could not solve, sanity check failed (-33): abs((P - Pmp) / Pmp) > 0.015".

 

Hi Jeff,SAM's module library is generated from module datasheet parameters using the coefficient calculator described in the following publication: Dobos, A. P. (2012). An Improved Coefficient Calculator for the CEC Photovoltaic Module Model . ASME Journal of Solar Energy Engineering. 6pp. Volume 134 No.2. The source code for the calculator is on GitHub: [url] github.com/NREL/ssc/blob/patch/shared/lib_cec6par.cpp [/url] The problem is that the method described in the paper does not work for some modules, particularly ones with high current ratings. We've investigated and improved it some, for example see   github.com/NREL/ssc/pull/172  and [url] github.com/NREL/ssc/pull/480 [/url]. We think that we'll need to use a completely different algorithm to fix this problem, but don't currently have funding to do that work.

In the meantime, I did some experimenting with the parameters for the Solaria POWERX-400R-4T module, and found that the coefficient calculator's solver works using parameters from the datasheet with modified values for Vmp and Imp: Vmp = 32.22 and Imp = 12.42. These should result in a reasonable I-V curve for modeling a PV system based on this module.

Here is a screenshot from the file you attached showing the results with these parameters:

 

Best regards,
Paul.

Hi Paul, I appreciate the quick response. We figured it was an issue with the solver. It's helpful to know that the general fix for now is to slightly modify parameters.

For the other modules that we will need to do this for, is there any rhyme or reason to adjusting parameters? Or is it guess-and-check?

Hi Jeff,

I used "guess and check" to come up with these. I wrote the attached LK script to try different values of Imp and Vmp.

To run the script, start SAM and on the File menu click Open script. Then click Run at the top of the script editor.

For more about LK, see sam.nrel.gov/lk-script.html .

Best regards,
Paul.