Add method to fit PVsyst SDM to IEC 61853 data

[kandersolar]

We have developed a method for determining parameter values for the PVsyst single diode model using IEC 61853-1 matrix measurements. The method produces useful fits on a range of IEC 61853 datasets without resorting to numerical optimization. A journal article describing the method is nearing readiness for submission. Once that manuscript is submitted, we plan to submit a PR to add the method to pvlib.

We already have pvlib.ivtools.sdm.fit_pvsyst_sandia, which calculates SDM parameters based on I-V curves. Perhaps new functions along these lines should encode the data source in their name, so this function could be called fit_pvsyst_iec61853_sandia or similar.

Note that such a method does not constitute a "PAN file generator" as it addresses only the electrical portion of a PAN file.

See also:

• Add converters between single diode models #1935
• Add method to fit SAPM array model #2001