add tests

Author: kandersolar

tests/ivtools/sdm/test_pvsyst.py

@@ -7,6 +7,8 @@
 
 from tests.conftest import requires_statsmodels, TESTS_DATA_DIR
 
+import pytest
+
 
 def _read_iv_curves_for_test(datafile, npts):
     """ read constants and npts IV curves from datafile """
@@ -198,3 +200,107 @@ def test_pvsyst_temperature_coeff():
         params['I_L_ref'], params['I_o_ref'], params['R_sh_ref'],
         params['R_sh_0'], params['R_s'], params['cells_in_series'])
     assert_allclose(gamma_pdc, expected, rtol=0.0005)
+
+
+@pytest.fixture
+def pvsyst_iec61853_table3():
+    # test cases in Table 3 of https://doi.org/10.1109/JPHOTOV.2025.3554338
+    parameters = ['alpha_sc', 'I_L_ref', 'I_o_ref', 'gamma_ref', 'mu_gamma',
+                  'R_sh_ref', 'R_sh_0', 'R_sh_exp', 'R_s', 'cells_in_series',
+                  'EgRef']
+    high_current = {
+        'true': [1e-3, 10, 1e-11, 1.0, -1e-4, 300, 1500, 5.5, 0.2, 60, 1.121],
+        'estimated': [9.993e-4, 9.997, 1.408e-10, 1.109, -1.666e-5, 543.7,
+                      6130, 5.5, 0.176, 60, 1.121]
+    }
+    high_voltage = {
+        'true': [1e-3, 1.8, 1e-9, 1.5, 1e-4, 3000, 10000, 5.5, 5.0, 108, 1.4],
+        'estimated': [9.983e-4, 1.799, 1.225e-8, 1.706, 2.662e-4, 4288, 47560,
+                      5.5, 4.292, 108, 1.4],
+    }
+    for d in [high_current, high_voltage]:
+        for key in d:
+            d[key] = dict(zip(parameters, np.array(d[key])))
+
+    return {
+        'high current': high_current, 'high voltage': high_voltage
+    }
+
+
+@pytest.fixture
+def iec61853_conditions():
+    ee = np.array([100, 100, 200, 200, 400, 400, 400, 600, 600, 600, 600,
+                   800, 800, 800, 800, 1000, 1000, 1000, 1000, 1100, 1100,
+                   1100], dtype=np.float64)
+    tc = np.array([15, 25, 15, 25, 15, 25, 50, 15, 25, 50, 75,
+                   15, 25, 50, 75, 15, 25, 50, 75, 25, 50, 75],
+                  dtype=np.float64)
+    return ee, tc
+
+
+@requires_statsmodels
+def test_fit_pvsyst_iec61853_sandia(pvsyst_iec61853_table3,
+                                    iec61853_conditions):
+    ee, tc = iec61853_conditions
+    for _, case in pvsyst_iec61853_table3.items():
+        true_params = case['true']
+        expected_params = case['estimated']
+
+        sde_params = pvsystem.calcparams_pvsyst(ee, tc, **true_params)
+        iv = pvsystem.singlediode(*sde_params)
+
+        fitted_params = sdm.fit_pvsyst_iec61853_sandia(
+            ee, tc, iv['i_sc'], iv['v_oc'], iv['i_mp'], iv['v_mp'],
+            true_params['cells_in_series'], EgRef=true_params['EgRef'],
+        )
+        for key in expected_params.keys():
+            assert np.isclose(fitted_params[key], expected_params[key],
+                              atol=0, rtol=1e-3)
+
+
+@requires_statsmodels
+def test_fit_pvsyst_iec61853_sandia_optional(pvsyst_iec61853_table3,
+                                             iec61853_conditions):
+    # verify that modifying each optional parameter results in different output
+    ee, tc = iec61853_conditions
+    case = pvsyst_iec61853_table3['high current']
+    true_params = case['true']
+    expected = case['estimated']
+    sde_params = pvsystem.calcparams_pvsyst(ee, tc, **true_params)
+    iv = pvsystem.singlediode(*sde_params)
+
+    main_inputs = dict(
+        effective_irradiance=ee, temp_cell=tc, i_sc=iv['i_sc'],
+        v_oc=iv['v_oc'], i_mp=iv['i_mp'], v_mp=iv['v_mp'],
+        cells_in_series=true_params['cells_in_series']
+    )
+
+    fitted_params = sdm.fit_pvsyst_iec61853_sandia(**main_inputs,
+                                                   EgRef=1.0)
+    assert not np.isclose(fitted_params['I_o_ref'], expected['I_o_ref'],
+                          atol=0, rtol=1e-3)
+
+    fitted_params = sdm.fit_pvsyst_iec61853_sandia(**main_inputs,
+                                                   alpha_sc=0.5e-3)
+    assert not np.isclose(fitted_params['alpha_sc'], expected['alpha_sc'],
+                          atol=0, rtol=1e-3)
+
+    fitted_params = sdm.fit_pvsyst_iec61853_sandia(**main_inputs,
+                                                   beta_mp=-1e-4)
+    assert not np.isclose(fitted_params['R_sh_ref'], expected['R_sh_ref'],
+                          atol=0, rtol=1e-3)
+
+    fitted_params = sdm.fit_pvsyst_iec61853_sandia(**main_inputs,
+                                                   r_sh_coeff=0.3)
+    assert not np.isclose(fitted_params['R_sh_ref'], expected['R_sh_ref'],
+                          atol=0, rtol=1e-3)
+    
+    fitted_params = sdm.fit_pvsyst_iec61853_sandia(**main_inputs,
+                                                   R_s=0.5)
+    assert not np.isclose(fitted_params['R_s'], expected['R_s'],
+                          atol=0, rtol=1e-3)
+
+    fitted_params = sdm.fit_pvsyst_iec61853_sandia(**main_inputs,
+                                                   min_Rsh_irradiance=500)
+    assert not np.isclose(fitted_params['R_sh_ref'], expected['R_sh_ref'],
+                          atol=0, rtol=1e-3)