Cliff Hansen

I see the point. There's a helper function [here](https://github.com/pvlib/pvlib-python/blob/72f3783bd0ca874e78ece7922938f6f3c652a428/pvlib/ivtools/sdm.py#L956) so pvlib has the same calculation twice. I'm open to ideas to improve this. Under what conditions is Rsh@G=1000 not equal...

I get the same results, unsurprisingly. What's odd is the magnitude of the Rsh_0 in that PAN file, and the departure from the default of 5.5 for the exponent. If...

Helper functions would be an improvement, but let's make sure they are traceable to a specific module performance model (and possibly to a version of that model).

> After rereading this long-forgotten thread, I wonder whether @cwhanse got any clarification or confirmation from Bruno and/or Ken... I didn't get any further clarification about v6. I haven't asked...

@markcampanelli I'd say yes. It would be necessary to bring some of the PAN and OND files for test purposes, and to explicitly state the Pvsyst versions for which this...

> 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.

I'm sure that Loutzenhiser's notation is `I_{d}` sky diffuse on a surface tilted at `d`, and `I_{d0}` is sky diffuse on a horizontal surface. But that's not helpful documentation here....

> Also, does it make sense for the Loutzenhiser reference to be listed first? Seems like it ought to be a secondary reference if it's included at all. Although Loutzenhiser...

+1. This [reference](https://www.sciencedirect.com/science/article/abs/pii/S0038092X96001375) might be relevant.

@kanderso-nrel have you located a copy of the 1958 T-J paper?