Add minus sign in front of dEgdT, sdm.py

[echedey-ls]

• Closes pvlib.ivtools.sdm.fit_desoto_sandia has incorrect sign for returned dEgdT #2321
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Fixes the typo in line 874 of sdm.py, where dEgdT = -0.0002677 instead of the same without the minus sign.

Inspired by today's AdventOfCode, I've regexed if this typo is everywhere else and I can confirm it isn't. Regex: (?<!-)0.0002677

Tests are passing locally. @cwhanse , should I create a test with a hella lot of precision to test this?

[cwhanse]

should I create a test with a hella lot of precision to test this?

I'd say no, it confirms the error is inconsequential, for practical purposes.

[RDaxini]

it confirms the error is inconsequential, for practical purposes.

This surprises me...
I haven't looked in detail yet at how the tests are constructed, but, a simple example:

import pandas as pd
from pvlib.pvsystem import calcparams_desoto, singlediode

ee = pd.Series([500, 800, 1000])
tc = pd.Series([40, 50, 60])
alphasc = 0.0004
aref = 1
ilref = 5
ioref = 1e-10
rshref = 2e3
rs = 1
egref = 1.1
degdt_pos = 0.0002677
degdt_neg = -0.0002677

sde_param1 = calcparams_desoto(ee, tc, alphasc, aref, ilref, ioref, rshref, rs,
                               egref, degdt_pos)
sde_param2 = calcparams_desoto(ee, tc, alphasc, aref, ilref, ioref, rshref, rs,
                               egref, degdt_neg)

output1 = singlediode(sde_param1[0], sde_param1[1], sde_param1[2],
                      sde_param1[3], sde_param1[4])
output2 = singlediode(sde_param2[0], sde_param2[1], sde_param2[2],
                      sde_param2[3], sde_param2[4])

returns different values between output1 and output2. Have I done something incorrectly here?

[cwhanse]

The error affects ivtools.sdm.fit_desoto_sandia, not pvsystem.calcparams_desoto and singlediode.

The tests for fit_desoto_sandia have a coarse tolerance, which could have been set because of this error.

pvlib-python/pvlib/tests/ivtools/test_sdm.py

Line 141 in 6af80da

assert np.allclose(modeled[params.keys()].values,