fix recombination args in pvsystem.maximum_power_point (#1733)

* fix recombination args in pvsystem.maximum_power_point

* d2mutau and NsVbi were hardcoded instead of passing through the
  arguments to the function

* fix stickler

* Update docs/sphinx/source/whatsnew/v0.9.6.rst

remove "fix" from whatsnew

Co-authored-by: Cliff Hansen <[email protected]>

* Apply suggestions from code review

---------

Co-authored-by: Cliff Hansen <[email protected]>
Co-authored-by: Kevin Anderson <[email protected]>

Author: 3 people

docs/sphinx/source/whatsnew/v0.9.6.rst

@@ -53,6 +53,8 @@ Bug fixes
 ~~~~~~~~~
 * `data` can no longer be left unspecified in
   :py:meth:`pvlib.modelchain.ModelChain.run_model_from_effective_irradiance`. (:issue:`1713`, :pull:`1720`)
+* ``d2mutau`` and ``NsVbi`` were hardcoded in :py:func:`pvlib.pvsystem.max_power_point` instead of
+  passing through the arguments to the function. (:pull:`1733`)
 
 Testing
 ~~~~~~~

pvlib/pvsystem.py

@@ -2918,8 +2918,7 @@ def max_power_point(photocurrent, saturation_current, resistance_series,
     """
     i_mp, v_mp, p_mp = _singlediode.bishop88_mpp(
         photocurrent, saturation_current, resistance_series,
-        resistance_shunt, nNsVth, d2mutau=0, NsVbi=np.Inf,
-        method=method.lower()
+        resistance_shunt, nNsVth, d2mutau, NsVbi, method=method.lower()
     )
     if isinstance(photocurrent, pd.Series):
         ivp = {'i_mp': i_mp, 'v_mp': v_mp, 'p_mp': p_mp}

pvlib/tests/test_pvsystem.py

@@ -20,6 +20,8 @@
 from pvlib import temperature
 from pvlib._deprecation import pvlibDeprecationWarning
 from pvlib.tools import cosd
+from pvlib.singlediode import VOLTAGE_BUILTIN
+from pvlib.tests.test_singlediode import get_pvsyst_fs_495
 
 
 @pytest.mark.parametrize('iam_model,model_params', [
@@ -1246,6 +1248,43 @@ def test_mpp_floats():
         assert np.isclose(v, expected[k])
 
 
+def test_mpp_recombination():
+    """test max_power_point"""
+    pvsyst_fs_495 = get_pvsyst_fs_495()
+    IL, I0, Rs, Rsh, nNsVth = pvsystem.calcparams_pvsyst(
+        effective_irradiance=pvsyst_fs_495['irrad_ref'],
+        temp_cell=pvsyst_fs_495['temp_ref'],
+        alpha_sc=pvsyst_fs_495['alpha_sc'],
+        gamma_ref=pvsyst_fs_495['gamma_ref'],
+        mu_gamma=pvsyst_fs_495['mu_gamma'], I_L_ref=pvsyst_fs_495['I_L_ref'],
+        I_o_ref=pvsyst_fs_495['I_o_ref'], R_sh_ref=pvsyst_fs_495['R_sh_ref'],
+        R_sh_0=pvsyst_fs_495['R_sh_0'], R_sh_exp=pvsyst_fs_495['R_sh_exp'],
+        R_s=pvsyst_fs_495['R_s'],
+        cells_in_series=pvsyst_fs_495['cells_in_series'],
+        EgRef=pvsyst_fs_495['EgRef'])
+    out = pvsystem.max_power_point(
+        IL, I0, Rs, Rsh, nNsVth,
+        d2mutau=pvsyst_fs_495['d2mutau'],
+        NsVbi=VOLTAGE_BUILTIN*pvsyst_fs_495['cells_in_series'],
+        method='brentq')
+    expected_imp = pvsyst_fs_495['I_mp_ref']
+    expected_vmp = pvsyst_fs_495['V_mp_ref']
+    expected_pmp = expected_imp*expected_vmp
+    expected = {'i_mp': expected_imp,
+                'v_mp': expected_vmp,
+                'p_mp': expected_pmp}
+    assert isinstance(out, dict)
+    for k, v in out.items():
+        assert np.isclose(v, expected[k], 0.01)
+    out = pvsystem.max_power_point(
+        IL, I0, Rs, Rsh, nNsVth,
+        d2mutau=pvsyst_fs_495['d2mutau'],
+        NsVbi=VOLTAGE_BUILTIN*pvsyst_fs_495['cells_in_series'],
+        method='newton')
+    for k, v in out.items():
+        assert np.isclose(v, expected[k], 0.01)
+
+
 def test_mpp_array():
     """test max_power_point"""
     IL, I0, Rs, Rsh, nNsVth = (np.array([7, 7]), 6e-7, .1, 20, .5)