remake expected test output, add kwargs

Author: cwhanse

pvlib/ivtools/convert.py

@@ -19,17 +19,6 @@
 CONSTANTS = {'E0': 1000.0, 'T0': 25.0, 'k': constants.k, 'q': constants.e}
 
 
-IEC61853_plus = pd.DataFrame(
-    columns=['effective_irradiance', 'temp_cell'],
-    data=np.array(
-        [[100, 100, 100, 100, 200, 200, 200, 200, 400, 400, 400, 400,
-          600, 600, 600, 600, 800, 800, 800, 800, 1000, 1000, 1000, 1000,
-          1100, 1100, 1100, 1100],
-         [15, 25, 50, 75, 15, 25, 50, 75, 15, 25, 50, 75, 15, 25, 50, 75,
-          15, 25, 50, 75, 15, 25, 50, 75, 15, 25, 50, 75]]).T,
-    dtype=np.float64)
-
-
 IEC61853 = pd.DataFrame(
     columns=['effective_irradiance', 'temp_cell'],
     data=np.array(
@@ -88,8 +77,10 @@ def _pvsyst_objfun(pvs_mod, cec_ivs, ee, tc, cs):
     return mean_abs_diff
 
 
-def convert_cec_pvsyst(cec_model, cells_in_series, method='Nelder-Mead',
-                       options=None):
+
+def convert_cec_pvsyst(cec_model, cells_in_series, initial=None,
+                       method='Nelder-Mead',
+                       bounds=None, options=None):
     r"""
     Convert a set of CEC model parameters to an equivalent set of PVsyst model
     parameters.
@@ -106,16 +97,21 @@ def convert_cec_pvsyst(cec_model, cells_in_series, method='Nelder-Mead',
         'R_sh_ref', 'R_s', 'Adjust'
     cell_in_series : int
         Number of cells in series.
+    initial : ndarray, optional
+        Initial guess for CEC model parameters. See Notes for parameter order.
     method : str, default 'Nelder-Mead'
         Method for scipy.optimize.minimize.
+    bounds : sequence or Bounds, optional
+        Initial guess for CEC model parameters. See Notes for parameter order.
+        See documentation for scipy.optimize.minimize for details.
     options : dict, optional
         Solver options passed to scipy.optimize.minimize.
 
     Returns
     -------
     dict with the following elements:
         alpha_sc : float
-            Short-circuit current temperature coefficient [A/C] .
+            Short-circuit current temperature coefficient [A/C].
         I_L_ref : float
             The light-generated current (or photocurrent) at reference
             conditions [A].
@@ -159,6 +155,27 @@ def convert_cec_pvsyst(cec_model, cells_in_series, method='Nelder-Mead',
     .. [2] "IEC 61853-3 Photovoltaic (PV) module performance testing and energy
        rating - Part 3: Energy rating of PV modules". IEC, Geneva, 2018.
     """
+    if initial is None:
+        # initial guess at PVsyst parameters
+        # Order in list is alpha_sc, gamma_ref, mu_gamma, I_L_ref, I_o_ref,
+        # Rsh_mult = R_sh_0 / R_sh_ref, R_sh_ref, R_s
+        gamma_ref = cec_model['a_ref'] / (cells_in_series * 0.025)
+        initial = [cec_model['alpha_sc'], gamma_ref, 0.001,
+                   cec_model['I_L_ref'], cec_model['I_o_ref'],
+                   12, 1000, cec_model['R_s']]
+
+    if bounds is None:
+        # bounds for PVsyst parameters
+        b_alpha = (-1, 1)
+        b_gamma = (1, 2)
+        b_mu = (-1, 1)
+        b_IL = (1e-12, 100)
+        b_Io = (1e-24, 0.1)
+        b_Rmult = (1, 20)
+        b_Rsh = (100, 1e6)
+        b_Rs = (1e-12, 10)
+        bounds = [b_alpha, b_gamma, b_mu, b_IL, b_Io, b_Rmult, b_Rsh, b_Rs]
+
     if options is None:
         options = {'maxiter': 5000, 'maxfev': 5000, 'xatol': 0.001}
 
@@ -169,23 +186,6 @@ def convert_cec_pvsyst(cec_model, cells_in_series, method='Nelder-Mead',
         **cec_model)
     cec_ivs = singlediode(*cec_params)
 
-    # initial guess at PVsyst parameters
-    # Order in list is alpha_sc, gamma_ref, mu_gamma, I_L_ref, I_o_ref,
-    # Rsh_mult = R_sh_0 / R_sh_ref, R_sh_ref, R_s
-    initial = [0, 1.2, 0.001, cec_model['I_L_ref'], cec_model['I_o_ref'],
-               12, 1000, cec_model['R_s']]
-
-    # bounds for PVsyst parameters
-    b_alpha = (-1, 1)
-    b_gamma = (1, 2)
-    b_mu = (-1, 1)
-    b_IL = (1e-12, 100)
-    b_Io = (1e-24, 0.1)
-    b_Rmult = (1, 20)
-    b_Rsh = (100, 1e6)
-    b_Rs = (1e-12, 10)
-    bounds = [b_alpha, b_gamma, b_mu, b_IL, b_Io, b_Rmult, b_Rsh, b_Rs]
-
     # optimization to find PVsyst parameters
     result = optimize.minimize(
         _pvsyst_objfun, initial,
@@ -242,7 +242,9 @@ def _cec_objfun(cec_mod, pvs_ivs, ee, tc, alpha_sc):
     return mean_diff
 
 
-def convert_pvsyst_cec(pvsyst_model, method='Nelder-Mead', options=None):
+def convert_pvsyst_cec(pvsyst_model, initial=None, method='Nelder-Mead', 
+                       bounds=None, options=None,
+                       EgRef=1.121, dEgdT=-0.0002677):
     r"""
     Convert a set of PVsyst model parameters to an equivalent set of CEC model
     parameters.
@@ -258,14 +260,31 @@ def convert_pvsyst_cec(pvsyst_model, method='Nelder-Mead', options=None):
         Must include keys: 'alpha_sc', 'I_L_ref', 'I_o_ref', 'EgRef', 'R_s',
         'R_sh_ref', 'R_sh_0', 'R_sh_exp', 'gamma_ref', 'mu_gamma',
         'cells_in_series'
-    method : str, default 'Nelder-Mead'
+    initial : ndarray, optional
+        Initial guess for CEC model parameters. See Notes for parameter order.
+    method : str or callable, default 'Nelder-Mead'
         Method for scipy.optimize.minimize.
+    bounds : sequence or Bounds, optional
+        Initial guess for CEC model parameters. See Notes for parameter order.
+        See documentation for scipy.optimize.minimize for details.
     options : dict, optional
         Solver options passed to scipy.optimize.minimize.
+    EgRef : float, default 1.121
+        The energy bandgap at reference temperature [eV].
+        1.121 eV for crystalline silicon. EgRef=1.121 is implicit for all
+        cell types in the SAM CEC module database, and is imposed by the
+        CEC parameter estimation algorithm in SAM.
+    dEgdT : float, default -0.0002677
+        The temperature dependence of the energy bandgap at reference
+        conditions [1/K]. dEgdT=-0.0002677 is implicit for all cell
+        types in the SAM CEC module database, and is imposed by the
+        CEC parameter estimation algorithm in SAM.
 
     Returns
     -------
     dict with the following elements:
+        alpha_sc : float
+            The input short-circuit current temperature coefficient [A/C].
         I_L_ref : float
             The light-generated current (or photocurrent) at reference
             conditions [A].
@@ -284,16 +303,21 @@ def convert_pvsyst_cec(pvsyst_model, method='Nelder-Mead', options=None):
             The adjustment to the temperature coefficient for short circuit
             current, in percent.
         EgRef : float
-            The energy bandgap at reference temperature [eV].
+            The input energy bandgap at reference temperature [eV].
         dEgdT : float
-            The temperature dependence of the energy bandgap at reference
+            The input temperature dependence of the energy bandgap at reference
             conditions [1/K].
 
     Notes
     -----
     Reference conditions are irradiance of 1000 W/m⁻² and cell temperature of
     25 °C.
 
+    Notes
+    -----
+    The order of the parameters in the initial guess and bounds:
+    [I_L_ref, I_o_ref, a_ref, R_sh_ref, R_s, Adjust]
+
     See Also
     --------
     pvlib.ivtools.convert.convert_cec_pvsyst
@@ -307,6 +331,25 @@ def convert_pvsyst_cec(pvsyst_model, method='Nelder-Mead', options=None):
     .. [2] "IEC 61853-3 Photovoltaic (PV) module performance testing and energy
        rating - Part 3: Energy rating of PV modules". IEC, Geneva, 2018.
     """
+    # initial guess
+    # order must match arguments of _cec_objfun
+    # order : [I_L_ref, I_o_ref, a_ref, R_sh_ref, R_s, alpha_sc, Adjust]
+
+    if initial is None:
+        nNsVth = pvsyst_model['gamma_ref'] * pvsyst_model['cells_in_series'] \
+            * 0.025
+        initial = [pvsyst_model['I_L_ref'], pvsyst_model['I_o_ref'],
+                   nNsVth, pvsyst_model['R_sh_ref'], pvsyst_model['R_s'], 0]
+
+    if bounds is None:
+        # bounds for CEC parameters
+        b_IL = (1e-12, 100)
+        b_Io = (1e-24, 0.1)
+        b_aref = (1e-12, 1000)
+        b_Rsh = (100, 1e6)
+        b_Rs = (1e-12, 10)
+        b_Adjust = (-100, 100)
+        bounds = [b_IL, b_Io, b_aref, b_Rsh, b_Rs, b_Adjust]
 
     if options is None:
         options = {'maxiter': 5000, 'maxfev': 5000, 'xatol': 0.001}
@@ -318,33 +361,11 @@ def convert_pvsyst_cec(pvsyst_model, method='Nelder-Mead', options=None):
         **pvsyst_model)
     pvsyst_ivs = singlediode(*pvs_params)
 
-    # set EgRef and dEgdT to CEC defaults
-    EgRef = 1.121
-    dEgdT = -0.0002677
-
-    # initial guess
-    # order must match _pvsyst_objfun
-    # order : [I_L_ref, I_o_ref, a_ref, R_sh_ref, R_s, alpha_sc, Adjust]
-    nNsVth = pvsyst_model['gamma_ref'] * pvsyst_model['cells_in_series'] \
-        * 0.025
-    initial = [pvsyst_model['I_L_ref'], pvsyst_model['I_o_ref'],
-               nNsVth, pvsyst_model['R_sh_ref'], pvsyst_model['R_s'],
-               0]
-
-    # bounds for PVsyst parameters
-    b_IL = (1e-12, 100)
-    b_Io = (1e-24, 0.1)
-    b_aref = (1e-12, 1000)
-    b_Rsh = (100, 1e6)
-    b_Rs = (1e-12, 10)
-    b_Adjust = (-100, 100)
-    bounds = [b_IL, b_Io, b_aref, b_Rsh, b_Rs, b_Adjust]
-
     result = optimize.minimize(
         _cec_objfun, initial,
         args=(pvsyst_ivs, IEC61853['effective_irradiance'],
               IEC61853['temp_cell'], pvsyst_model['alpha_sc']),
-        method='Nelder-Mead',
+        method=method,
         bounds=bounds,
         options=options)
 

tests/ivtools/test_convert.py

@@ -6,24 +6,24 @@ def test_convert_cec_pvsyst():
     cells_in_series = 66
     trina660_cec = {'I_L_ref': 18.4759, 'I_o_ref': 5.31e-12,
                     'EgRef': 1.121, 'dEgdT': -0.0002677,
-                    'R_s': 0.159916, 'R_sh_ref': 113.991, 'a_ref': 1.59068,
+                    'R_s': 0.159916, 'R_sh_ref': 113.991, 'a_ref': 1.8,
                     'Adjust': 6.42247, 'alpha_sc': 0.00629}
     trina660_pvsyst_est = convert.convert_cec_pvsyst(trina660_cec,
                                                      cells_in_series)
-    pvsyst_expected = {'alpha_sc': 0.007478218748188788,
-                       'I_L_ref': 18.227679597516214,
-                       'I_o_ref': 2.7418999402908e-11,
-                       'EgRef': 1.121,
-                       'R_s': 0.16331908293164496,
-                       'R_sh_ref': 5267.928954454954,
-                       'R_sh_0': 60171.206687871425,
-                       'R_sh_exp': 5.5,
-                       'gamma_ref': 1.0,
-                       'mu_gamma': -6.349173477135307e-05,
-                       'cells_in_series': 66}
+    pvsyst_expected = {'alpha_sc': 0.0096671,
+                   'I_L_ref': 18.19305,
+                   'I_o_ref': 6.94494e-12,
+                   'EgRef': 1.121,
+                   'R_s': 0.16318,
+                   'R_sh_ref': 1000.947,
+                   'R_sh_0': 8593.35,
+                   'R_sh_exp': 5.5,
+                   'gamma_ref': 1.0724,
+                   'mu_gamma': -0.00074595,
+                   'cells_in_series': 66}
 
     assert np.all([np.isclose(trina660_pvsyst_est[k], pvsyst_expected[k],
-                              rtol=1e-3)
+                              rtol=1e-4, atol=0.)
                    for k in pvsyst_expected])
 
 
@@ -34,15 +34,17 @@ def test_convert_pvsyst_cec():
                        'R_sh_exp': 5.5, 'gamma_ref': 1.002, 'mu_gamma': 1e-3,
                        'cells_in_series': 66}
     trina660_cec_est = convert.convert_pvsyst_cec(trina660_pvsyst)
+
     cec_expected = {'alpha_sc': 0.0074,
-                    'I_L_ref': 18.05154226834071,
-                    'I_o_ref': 2.6863417875143392e-14,
+                    'I_L_ref': 18.09421,
+                    'I_o_ref': 2.46522e-14,
                     'EgRef': 1.121,
                     'dEgdT': -0.0002677,
-                    'R_s': 0.09436341848926795,
-                    'a_ref': 1.2954800250731866,
-                    'Adjust': 0.0011675969492410047}
+                    'R_s': 0.098563,
+                    'R_sh_ref': 268.508,
+                    'a_ref': 1.2934,
+                    'Adjust': 0.0065145}
 
     assert np.all([np.isclose(trina660_cec_est[k], cec_expected[k],
-                              rtol=1e-3)
+                              rtol=1e-4, atol=0.)
                    for k in cec_expected])