Add fitting function for Anton's inverter model

[Peque]

pvlib includes de inverter.adr() model, but it still does not provide a way to infer the required parameter for the model given, for example, some known datasheet parameters. The fitting function would be a great addition to be able to work with Anton's model.

I think @adriesse had a MATLAB implementation, so this issue is to discuss its addition and track progress when/if Anton finds some time to implement the fitting function in Python. 😊

[adriesse]

I have finally taken some time to work in this topic, which has been at the bottom of my to-do list for too long. You can now find a ready-to-use function to convert from Sandia inverter model parameters to ADR inverter model parameters here:

https://github.com/adriesse/pvpltools-python

There are also helper functions that can be used with suitable measured data, the CEC matrix, or other tabulated specifications.

Related issue: #317.

[adriesse]

Does this seem useful to anyone?

[cwhanse]

Does this seem useful to anyone?

For this specific issue, the two fit_xxx functions in power_conversion.py would be valuable to add to pvlib.inverter if you are offering that code.

[adriesse]

It's written with pvlib in mind, but I'm still thinking about some improvements.