From e20a079bc23625f9f15a0d92bf7a5345d2dee6ad Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 20 Jun 2018 08:32:54 -0600
Subject: [PATCH 01/16] initial version of calcparams_pvsyst and test

---
 pvlib/pvsystem.py           | 171 ++++++++++++++++++++++++++++++++++++
 pvlib/test/test_pvsystem.py |  72 +++++++++++++++
 2 files changed, 243 insertions(+)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 96ac7d3d90..427b2f965b 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -307,6 +307,36 @@ def calcparams_desoto(self, effective_irradiance, temp_cell, **kwargs):
         
         return calcparams_desoto(effective_irradiance, temp_cell, **kwargs)
 
+    def calcparams_pvsyst(self, effective_irradiance, temp_cell, **kwargs):
+        """
+        Use the :py:func:`calcparams_pvsyst` function, the input
+        parameters and ``self.module_parameters`` to calculate the
+        module currents and resistances.
+
+        Parameters
+        ----------
+        effective_irradiance : numeric
+            The irradiance (W/m2) that is converted to photocurrent.
+
+        temp_cell : float or Series
+            The average cell temperature of cells within a module in C.
+
+        **kwargs
+            See pvsystem.calcparams_desoto for details
+
+        Returns
+        -------
+        See pvsystem.calcparams_pvsyst for details
+        """
+
+        kwargs = _build_kwargs(['gamma_ref', 'mugamma', 'I_L_ref', 'I_o_ref', 
+                                'R_sh_ref', 'R_sh_0', 'R_sh_exp', 
+                                'R_s', 'alpha_sc', 'EgRef',
+                                'cells_in_series'],
+                                self.module_parameters)
+        
+        return calcparams_pvsyst(effective_irradiance, temp_cell, **kwargs)
+
     def sapm(self, effective_irradiance, temp_cell, **kwargs):
         """
         Use the :py:func:`sapm` function, the input parameters,
@@ -1172,6 +1202,147 @@ def calcparams_desoto(effective_irradiance, temp_cell,
     return IL, I0, Rs, Rsh, nNsVth
 
 
+def calcparams_pvsyst(effective_irradiance, temp_cell,
+                      alpha_sc, gamma_ref, mugamma,
+                      I_L_ref, I_o_ref, 
+                      R_sh_ref, R_sh_0, R_s, 
+                      cells_in_series,
+                      R_sh_exp=5.5,
+                      EgRef=1.121,
+                      irrad_ref=1000, temp_ref=25):
+    '''
+    Calculates five parameter values for the single diode equation at 
+    effective irradiance and cell temperature using the PVsyst v6 
+    model described in [1,2,3]. The five values returned by calcparams_pvsyst
+    can be used by singlediode to calculate an IV curve.
+
+    Parameters
+    ----------
+    effective_irradiance : numeric
+        The irradiance (W/m2) that is converted to photocurrent.
+
+    temp_cell : numeric
+        The average cell temperature of cells within a module in C.
+
+    alpha_sc : float
+        The short-circuit current temperature coefficient of the
+        module in units of A/C.
+
+    gamma_ref : float
+        The diode ideality factor
+
+    I_L_ref : float
+        The light-generated current (or photocurrent) at reference conditions,
+        in amperes.
+        
+    I_o_ref : float
+        The dark or diode reverse saturation current at reference conditions,
+        in amperes.
+        
+    R_sh_ref : float
+        The shunt resistance at reference conditions, in ohms.
+        
+    R_sh_0 : float
+        The shunt resistance at zero irradiance conditions, in ohms.
+        
+    R_s : float
+        The series resistance at reference conditions, in ohms.
+
+    cells_in_series : integer
+        The number of cells connected in series.
+
+    R_sh_exp : float
+        The exponent in the equation for shunt resistance, unitless. Defaults
+        to 5.5.
+
+    EgRef : float
+        The energy bandgap at reference temperature in units of eV.
+        1.121 eV for crystalline silicon. EgRef must be >0.
+
+    irrad_ref : float (optional, default=1000)
+        Reference irradiance in W/m^2.
+
+    temp_ref : float (optional, default=25)
+        Reference cell temperature in C.
+
+    Returns
+    -------
+    Tuple of the following results:
+
+    photocurrent : numeric
+        Light-generated current in amperes at irradiance=S and
+        cell temperature=Tcell.
+
+    saturation_current : numeric
+        Diode saturation curent in amperes at irradiance
+        S and cell temperature Tcell.
+
+    resistance_series : float
+        Series resistance in ohms at irradiance S and cell temperature
+        Tcell.
+
+    resistance_shunt : numeric
+        Shunt resistance in ohms at irradiance S and cell temperature
+        Tcell.
+
+    nNsVth : numeric
+        Modified diode ideality factor at irradiance S and cell
+        temperature Tcell. Note that in source [1] nNsVth = a (equation
+        2). nNsVth is the product of the diode ideality factor
+        (n), the number of series-connected cells in the module (Ns),
+        and the thermal voltage of a cell in the module (Vth) at a cell
+        temperature of Tcell.
+
+    References
+    ----------
+    [1] K. Sauer, T. Roessler, C. W. Hansen, Modeling the Irradiance and 
+     Temperature Dependence of Photovoltaic Modules in PVsyst, 
+     IEEE Journal of Photovoltaics v5(1), January 2015.
+
+    [2] A. Mermoud, PV modules modelling, Presentation at the 2nd PV
+     Performance Modeling Workshop, Santa Clara, CA, May 2013
+
+    [3] A. Mermoud, T. Lejeune, Performance Assessment of a Simulation Model
+     for PV modules of any available technology, 25th European Photovoltaic
+     Solar Energy Conference, Valencia, Spain, Sept. 2010
+
+    See Also
+    --------
+    calcparams_desoto
+    singlediode
+    
+    '''
+
+    # Boltzmann constant in J/K
+    k = 1.3806488e-23
+
+    # elementary charge in coulomb
+    q = 1.6021766e-19
+    
+    # reference temperature
+    Tref_K = temp_ref + 273.15
+    Tcell_K = temp_cell + 273.15
+
+    gamma = gamma_ref + mugamma * (Tcell_K - Tref_K)
+    nNsVth = gamma * k / q * cells_in_series
+
+    IL = effective_irradiance / irrad_ref * \
+              (I_L_ref + alpha_sc * (Tcell_K - Tref_K))
+
+    I0 = I_o_ref * ((Tcell_K / Tref_K) ** 3) * \
+          (np.exp((q * EgRef) / (k * gamma) * (1 / Tref_K - 1 / Tcell_K)))
+
+    Rsh_tmp = (R_sh_ref - R_sh_0 * np.exp(-R_sh_exp)) / (1.0 - np.exp(-R_sh_exp))
+    Rsh_base = np.maximum(0.0, Rsh_tmp)
+
+    Rsh = Rsh_base + (R_sh_0 - Rsh_base) * \
+              np.exp(-R_sh_exp * effective_irradiance / irrad_ref)
+    
+    Rs = R_s
+
+    return IL, I0, Rs, Rsh, nNsVth
+
+
 def retrieve_sam(name=None, path=None):
     '''
     Retrieve latest module and inverter info from a local file or the
diff --git a/pvlib/test/test_pvsystem.py b/pvlib/test/test_pvsystem.py
index 289b0f6577..e6d4c800ec 100644
--- a/pvlib/test/test_pvsystem.py
+++ b/pvlib/test/test_pvsystem.py
@@ -174,6 +174,23 @@ def cec_module_params(sam_data):
     return module_parameters
 
 
+@pytest.fixture(scope="session")
+def pvsyst_module_params():
+    module_parameters = {}
+    module_parameters['gamma_ref'] = 1.05
+    module_parameters['mugamma'] = 0.001
+    module_parameters['I_L_ref'] = 6.0
+    module_parameters['I_o_ref'] = 5e-9
+    module_parameters['EgRef'] = 1.121
+    module_parameters['R_sh_ref'] = 300
+    module_parameters['R_sh_0'] = 1000
+    module_parameters['R_s'] = 0.5
+    module_parameters['R_sh_exp'] = 5.5
+    module_parameters['cells_in_series'] = 60
+    module_parameters['alpha_sc'] = 0.001
+    return module_parameters
+
+
 def test_sapm(sapm_module_params):
 
     times = pd.DatetimeIndex(start='2015-01-01', periods=5, freq='12H')
@@ -386,6 +403,34 @@ def test_calcparams_desoto(cec_module_params):
     assert_allclose(nNsVth, 0.473)
 
 
+def test_calcparams_pvsyst(pvsyst_module_params):
+    times = pd.DatetimeIndex(start='2015-01-01', periods=2, freq='12H')
+    effective_irradiance = pd.Series([0.0, 800.0], index=times)
+    temp_cell = pd.Series([25, 50], index=times)
+
+    IL, I0, Rs, Rsh, nNsVth = pvsystem.calcparams_pvsyst(
+                                  effective_irradiance,
+                                  temp_cell,
+                                  alpha_sc=pvsyst_module_params['alpha_sc'],
+                                  gamma_ref=pvsyst_module_params['gamma_ref'],
+                                  mugamma=pvsyst_module_params['mugamma'],
+                                  I_L_ref=pvsyst_module_params['I_L_ref'],
+                                  I_o_ref=pvsyst_module_params['I_o_ref'],
+                                  R_sh_ref=pvsyst_module_params['R_sh_ref'],
+                                  R_s=pvsyst_module_params['R_s'],
+                                  EgRef=pvsyst_module_params['EgRef'],
+                    cells_in_series=pvsyst_module_params['cells_in_series'])
+
+    assert_series_equal(np.round(IL, 3), pd.Series([0.0, 4.800], index=times))
+    assert_series_equal(np.round(I0, 3),
+                        pd.Series([0.0, 1.47e-7], index=times))
+    assert_allclose(Rs, 0.500)
+    assert_series_equal(np.round(Rsh, 3),
+                        pd.Series([1000.0, 305.76], index=times))
+    assert_series_equal(np.round(nNsVth, 4),
+                        pd.Series([1.6186, 1.7961], index=times))
+
+
 def test_PVSystem_calcparams_desoto(cec_module_params, mocker):
     mocker.spy(pvsystem, 'calcparams_desoto')
     module_parameters = cec_module_params.copy()
@@ -414,6 +459,33 @@ def test_PVSystem_calcparams_desoto(cec_module_params, mocker):
     assert_allclose(nNsVth, 0.5, atol=0.1)
 
 
+def test_PVSystem_calcparams_pvsyst(pvsyst_module_params, mocker):
+    mocker.spy(pvsystem, 'calcparams_pvsyst')
+    module_parameters = pvsyst_module_params.copy()
+    system = pvsystem.PVSystem(module_parameters=module_parameters)
+    effective_irradiance = np.array([0, 800])
+    temp_cell = np.array([25, 50])
+    IL, I0, Rs, Rsh, nNsVth = system.calcparams_pvsyst(effective_irradiance,
+                                                       temp_cell)
+    pvsystem.calcparams_pvsyst.assert_called_once_with(
+                                  effective_irradiance,
+                                  temp_cell,
+                                  alpha_sc=pvsyst_module_params['alpha_sc'],
+                                  gamma_ref=pvsyst_module_params['gamma_ref'],
+                                  mugamma=pvsyst_module_params['mugamma'],
+                                  I_L_ref=pvsyst_module_params['I_L_ref'],
+                                  I_o_ref=pvsyst_module_params['I_o_ref'],
+                                  R_sh_ref=pvsyst_module_params['R_sh_ref'],
+                                  R_s=pvsyst_module_params['R_s'],
+                                  EgRef=pvsyst_module_params['EgRef'],
+                    cells_in_series=pvsyst_module_params['cells_in_series'])
+    assert_allclose(IL, np.array([0.0, 4.800]), atol=1)
+    assert_allclose(I0, np.array([0.0, 1.47e-7]), atol=1.0e-5)
+    assert_allclose(Rs, 0.5, atol=0.1)
+    assert_allclose(Rsh, np.array([1000, 305.76]), atol=50)
+    assert_allclose(nNsVth, np.array([1.6186, 1.7961]), atol=0.1)
+
+
 @pytest.fixture(params=[
     {  # Can handle all python scalar inputs
      'Rsh': 20.,

From e93cd8aec409a175ca19d81d9f128315af285686 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 20 Jun 2018 09:03:36 -0600
Subject: [PATCH 02/16] fix argument list in tests

---
 pvlib/test/test_pvsystem.py | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/pvlib/test/test_pvsystem.py b/pvlib/test/test_pvsystem.py
index e6d4c800ec..2eb1f81c87 100644
--- a/pvlib/test/test_pvsystem.py
+++ b/pvlib/test/test_pvsystem.py
@@ -417,9 +417,10 @@ def test_calcparams_pvsyst(pvsyst_module_params):
                                   I_L_ref=pvsyst_module_params['I_L_ref'],
                                   I_o_ref=pvsyst_module_params['I_o_ref'],
                                   R_sh_ref=pvsyst_module_params['R_sh_ref'],
+                                  R_sh_0=pvsyst_module_params['R_sh_0'],
                                   R_s=pvsyst_module_params['R_s'],
-                                  EgRef=pvsyst_module_params['EgRef'],
-                    cells_in_series=pvsyst_module_params['cells_in_series'])
+                    cells_in_series=pvsyst_module_params['cells_in_series'],
+                                  EgRef=pvsyst_module_params['EgRef'])
 
     assert_series_equal(np.round(IL, 3), pd.Series([0.0, 4.800], index=times))
     assert_series_equal(np.round(I0, 3),
@@ -476,9 +477,10 @@ def test_PVSystem_calcparams_pvsyst(pvsyst_module_params, mocker):
                                   I_L_ref=pvsyst_module_params['I_L_ref'],
                                   I_o_ref=pvsyst_module_params['I_o_ref'],
                                   R_sh_ref=pvsyst_module_params['R_sh_ref'],
+                                  R_sh_ref=pvsyst_module_params['R_sh_0'],
                                   R_s=pvsyst_module_params['R_s'],
-                                  EgRef=pvsyst_module_params['EgRef'],
-                    cells_in_series=pvsyst_module_params['cells_in_series'])
+                    cells_in_series=pvsyst_module_params['cells_in_series'],
+                                  EgRef=pvsyst_module_params['EgRef'])
     assert_allclose(IL, np.array([0.0, 4.800]), atol=1)
     assert_allclose(I0, np.array([0.0, 1.47e-7]), atol=1.0e-5)
     assert_allclose(Rs, 0.5, atol=0.1)

From 846c913269dbd710a0cf1e45d9a14947729d8f01 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 20 Jun 2018 10:06:12 -0600
Subject: [PATCH 03/16] Fix typo in test argument R_sh_0

---
 pvlib/test/test_pvsystem.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/test/test_pvsystem.py b/pvlib/test/test_pvsystem.py
index 2eb1f81c87..f1e319b1e5 100644
--- a/pvlib/test/test_pvsystem.py
+++ b/pvlib/test/test_pvsystem.py
@@ -477,7 +477,7 @@ def test_PVSystem_calcparams_pvsyst(pvsyst_module_params, mocker):
                                   I_L_ref=pvsyst_module_params['I_L_ref'],
                                   I_o_ref=pvsyst_module_params['I_o_ref'],
                                   R_sh_ref=pvsyst_module_params['R_sh_ref'],
-                                  R_sh_ref=pvsyst_module_params['R_sh_0'],
+                                  R_sh_0=pvsyst_module_params['R_sh_0'],
                                   R_s=pvsyst_module_params['R_s'],
                     cells_in_series=pvsyst_module_params['cells_in_series'],
                                   EgRef=pvsyst_module_params['EgRef'])

From f4573701af92d1cc361376c331a2d0e92c863d83 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 20 Jun 2018 10:41:50 -0600
Subject: [PATCH 04/16] remove EgRef from PVSystem.test_calcparams_pvsyst

---
 pvlib/test/test_pvsystem.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pvlib/test/test_pvsystem.py b/pvlib/test/test_pvsystem.py
index f1e319b1e5..a99ffdfd49 100644
--- a/pvlib/test/test_pvsystem.py
+++ b/pvlib/test/test_pvsystem.py
@@ -422,7 +422,7 @@ def test_calcparams_pvsyst(pvsyst_module_params):
                     cells_in_series=pvsyst_module_params['cells_in_series'],
                                   EgRef=pvsyst_module_params['EgRef'])
 
-    assert_series_equal(np.round(IL, 3), pd.Series([0.0, 4.800], index=times))
+    assert_series_equal(np.round(IL, 3), pd.Series([0.0, 4.8200], index=times))
     assert_series_equal(np.round(I0, 3),
                         pd.Series([0.0, 1.47e-7], index=times))
     assert_allclose(Rs, 0.500)
@@ -479,9 +479,9 @@ def test_PVSystem_calcparams_pvsyst(pvsyst_module_params, mocker):
                                   R_sh_ref=pvsyst_module_params['R_sh_ref'],
                                   R_sh_0=pvsyst_module_params['R_sh_0'],
                                   R_s=pvsyst_module_params['R_s'],
-                    cells_in_series=pvsyst_module_params['cells_in_series'],
-                                  EgRef=pvsyst_module_params['EgRef'])
-    assert_allclose(IL, np.array([0.0, 4.800]), atol=1)
+                    cells_in_series=pvsyst_module_params['cells_in_series'])
+
+    assert_allclose(IL, np.array([0.0, 4.8200]), atol=1)
     assert_allclose(I0, np.array([0.0, 1.47e-7]), atol=1.0e-5)
     assert_allclose(Rs, 0.5, atol=0.1)
     assert_allclose(Rsh, np.array([1000, 305.76]), atol=50)

From 691a9a719e984274b2aa8e2181b370bb8bfa1bab Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 20 Jun 2018 10:45:09 -0600
Subject: [PATCH 05/16] add documentation for mugamma, fix typo

---
 pvlib/pvsystem.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 427b2f965b..f15b772efe 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -322,7 +322,7 @@ def calcparams_pvsyst(self, effective_irradiance, temp_cell, **kwargs):
             The average cell temperature of cells within a module in C.
 
         **kwargs
-            See pvsystem.calcparams_desoto for details
+            See pvsystem.calcparams_pvsyst for details
 
         Returns
         -------
@@ -1231,6 +1231,9 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
     gamma_ref : float
         The diode ideality factor
 
+    mugamma : float
+        The temperature coefficient for the diode ideality factor, 1/K
+
     I_L_ref : float
         The light-generated current (or photocurrent) at reference conditions,
         in amperes.

From 36d59417cb3851ef07b483dac6387b802af7f7a1 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 20 Jun 2018 11:07:34 -0600
Subject: [PATCH 06/16] edits and fix to test error

---
 pvlib/test/test_pvsystem.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pvlib/test/test_pvsystem.py b/pvlib/test/test_pvsystem.py
index a99ffdfd49..411a59a000 100644
--- a/pvlib/test/test_pvsystem.py
+++ b/pvlib/test/test_pvsystem.py
@@ -479,12 +479,13 @@ def test_PVSystem_calcparams_pvsyst(pvsyst_module_params, mocker):
                                   R_sh_ref=pvsyst_module_params['R_sh_ref'],
                                   R_sh_0=pvsyst_module_params['R_sh_0'],
                                   R_s=pvsyst_module_params['R_s'],
-                    cells_in_series=pvsyst_module_params['cells_in_series'])
+                    cells_in_series=pvsyst_module_params['cells_in_series'],
+                                  R_sh_exp=pvsyst_module_params['R_sh_exp'])
 
     assert_allclose(IL, np.array([0.0, 4.8200]), atol=1)
     assert_allclose(I0, np.array([0.0, 1.47e-7]), atol=1.0e-5)
     assert_allclose(Rs, 0.5, atol=0.1)
-    assert_allclose(Rsh, np.array([1000, 305.76]), atol=50)
+    assert_allclose(Rsh, np.array([1000, 305.757]), atol=50)
     assert_allclose(nNsVth, np.array([1.6186, 1.7961]), atol=0.1)
 
 

From 131ff75c93566e75ad67ad10ba0741ffdbedaf56 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 20 Jun 2018 12:18:23 -0600
Subject: [PATCH 07/16] Fix argument list and expected result

---
 pvlib/test/test_pvsystem.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pvlib/test/test_pvsystem.py b/pvlib/test/test_pvsystem.py
index 411a59a000..6efba10535 100644
--- a/pvlib/test/test_pvsystem.py
+++ b/pvlib/test/test_pvsystem.py
@@ -427,7 +427,7 @@ def test_calcparams_pvsyst(pvsyst_module_params):
                         pd.Series([0.0, 1.47e-7], index=times))
     assert_allclose(Rs, 0.500)
     assert_series_equal(np.round(Rsh, 3),
-                        pd.Series([1000.0, 305.76], index=times))
+                        pd.Series([1000.0, 305.757], index=times))
     assert_series_equal(np.round(nNsVth, 4),
                         pd.Series([1.6186, 1.7961], index=times))
 
@@ -480,6 +480,7 @@ def test_PVSystem_calcparams_pvsyst(pvsyst_module_params, mocker):
                                   R_sh_0=pvsyst_module_params['R_sh_0'],
                                   R_s=pvsyst_module_params['R_s'],
                     cells_in_series=pvsyst_module_params['cells_in_series'],
+                                  EgRef=pvsyst_module_params['EgRef'],
                                   R_sh_exp=pvsyst_module_params['R_sh_exp'])
 
     assert_allclose(IL, np.array([0.0, 4.8200]), atol=1)

From 9d5d55e2ac4e039d498f9a54f837f230ad896ab4 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 20 Jun 2018 12:49:26 -0600
Subject: [PATCH 08/16] Fix error in calculation of nNsVth

---
 pvlib/pvsystem.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index f15b772efe..25ab9ddc96 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -1327,7 +1327,7 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
     Tcell_K = temp_cell + 273.15
 
     gamma = gamma_ref + mugamma * (Tcell_K - Tref_K)
-    nNsVth = gamma * k / q * cells_in_series
+    nNsVth = gamma * k / q * cells_in_series * Tcell_K
 
     IL = effective_irradiance / irrad_ref * \
               (I_L_ref + alpha_sc * (Tcell_K - Tref_K))

From d1be4679848ef68a53734e71327894ef52dcac9d Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 20 Jun 2018 15:01:27 -0600
Subject: [PATCH 09/16] Add note to whatsnew.rst

---
 docs/sphinx/source/whatsnew/v0.6.0.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/sphinx/source/whatsnew/v0.6.0.rst b/docs/sphinx/source/whatsnew/v0.6.0.rst
index 2f205edf04..64427f03c2 100644
--- a/docs/sphinx/source/whatsnew/v0.6.0.rst
+++ b/docs/sphinx/source/whatsnew/v0.6.0.rst
@@ -13,6 +13,7 @@ Enhancements
 * Add sea surface albedo in irradiance.py (:issue:`458`)
 * Implement first_solar_spectral_loss in modelchain.py (:issue:`359`)
 * Clarify arguments Egref and dEgdT for calcparams_desoto (:issue:`462`)
+* Add pvsystem.calcparams_pvsyst to compute values for the single diode equation using the PVsyst v6 model.
 
 
 Bug fixes

From 8d79f3d46f9df3a8e22d3be23aee30dbbf3134a2 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 20 Jun 2018 15:04:06 -0600
Subject: [PATCH 10/16] Add line to api.rst

---
 docs/sphinx/source/api.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/sphinx/source/api.rst b/docs/sphinx/source/api.rst
index 4070ed56c3..5909db3a7a 100644
--- a/docs/sphinx/source/api.rst
+++ b/docs/sphinx/source/api.rst
@@ -202,6 +202,7 @@ Functions relevant for the single diode model.
    :toctree: generated/
 
    pvsystem.calcparams_desoto
+   pvsystem.calcparams_pvsyst
    pvsystem.i_from_v
    pvsystem.singlediode
    pvsystem.v_from_i

From 34390a9354f6ce57c77df7ad3c12ec68ec092bc4 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Thu, 21 Jun 2018 07:58:47 -0600
Subject: [PATCH 11/16] Edits to function signatures, variable names

---
 pvlib/pvsystem.py | 46 +++++++++++++++-------------------------------
 1 file changed, 15 insertions(+), 31 deletions(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 25ab9ddc96..ef3f30c233 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -1041,28 +1041,21 @@ def calcparams_desoto(effective_irradiance, temp_cell,
     Tuple of the following results:
 
     photocurrent : numeric
-        Light-generated current in amperes at irradiance=S and
-        cell temperature=Tcell.
+        Light-generated current in amperes
 
     saturation_current : numeric
-        Diode saturation curent in amperes at irradiance
-        S and cell temperature Tcell.
+        Diode saturation curent in amperes
 
     resistance_series : float
-        Series resistance in ohms at irradiance S and cell temperature
-        Tcell.
+        Series resistance in ohms
 
     resistance_shunt : numeric
-        Shunt resistance in ohms at irradiance S and cell temperature
-        Tcell.
+        Shunt resistance in ohms
 
     nNsVth : numeric
-        Modified diode ideality factor at irradiance S and cell
-        temperature Tcell. Note that in source [1] nNsVth = a (equation
-        2). nNsVth is the product of the usual diode ideality factor
-        (n), the number of series-connected cells in the module (Ns),
-        and the thermal voltage of a cell in the module (Vth) at a cell
-        temperature of Tcell.
+        The product of the usual diode ideality factor (n, unitless), 
+        number of cells in series (Ns), and cell thermal voltage at 
+        specified effective irradiance and cell temperature.
 
     References
     ----------
@@ -1081,8 +1074,6 @@ def calcparams_desoto(effective_irradiance, temp_cell,
 
     See Also
     --------
-    sapm
-    sapm_celltemp
     singlediode
     retrieve_sam
 
@@ -1273,28 +1264,21 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
     Tuple of the following results:
 
     photocurrent : numeric
-        Light-generated current in amperes at irradiance=S and
-        cell temperature=Tcell.
+        Light-generated current in amperes
 
     saturation_current : numeric
-        Diode saturation curent in amperes at irradiance
-        S and cell temperature Tcell.
+        Diode saturation current in amperes
 
     resistance_series : float
-        Series resistance in ohms at irradiance S and cell temperature
-        Tcell.
-
+        Series resistance in ohms
+        
     resistance_shunt : numeric
-        Shunt resistance in ohms at irradiance S and cell temperature
-        Tcell.
+        Shunt resistance in ohms
 
     nNsVth : numeric
-        Modified diode ideality factor at irradiance S and cell
-        temperature Tcell. Note that in source [1] nNsVth = a (equation
-        2). nNsVth is the product of the diode ideality factor
-        (n), the number of series-connected cells in the module (Ns),
-        and the thermal voltage of a cell in the module (Vth) at a cell
-        temperature of Tcell.
+        The product of the usual diode ideality factor (n, unitless), 
+        number of cells in series (Ns), and cell thermal voltage at 
+        specified effective irradiance and cell temperature.
 
     References
     ----------

From 95bfde94f75516b61eec03d1755ddf1a11d4053a Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Sat, 23 Jun 2018 16:58:44 -0600
Subject: [PATCH 12/16] Change mugamma to mu_gamma, add issue to whatsnew text

---
 docs/sphinx/source/whatsnew/v0.6.0.rst | 2 +-
 pvlib/pvsystem.py                      | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/docs/sphinx/source/whatsnew/v0.6.0.rst b/docs/sphinx/source/whatsnew/v0.6.0.rst
index 64427f03c2..1fc8c0a241 100644
--- a/docs/sphinx/source/whatsnew/v0.6.0.rst
+++ b/docs/sphinx/source/whatsnew/v0.6.0.rst
@@ -13,7 +13,7 @@ Enhancements
 * Add sea surface albedo in irradiance.py (:issue:`458`)
 * Implement first_solar_spectral_loss in modelchain.py (:issue:`359`)
 * Clarify arguments Egref and dEgdT for calcparams_desoto (:issue:`462`)
-* Add pvsystem.calcparams_pvsyst to compute values for the single diode equation using the PVsyst v6 model.
+* Add pvsystem.calcparams_pvsyst to compute values for the single diode equation using the PVsyst v6 model (:issue:'470')
 
 
 Bug fixes
diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index ef3f30c233..3573cf9812 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -329,7 +329,7 @@ def calcparams_pvsyst(self, effective_irradiance, temp_cell, **kwargs):
         See pvsystem.calcparams_pvsyst for details
         """
 
-        kwargs = _build_kwargs(['gamma_ref', 'mugamma', 'I_L_ref', 'I_o_ref', 
+        kwargs = _build_kwargs(['gamma_ref', 'mu_gamma', 'I_L_ref', 'I_o_ref', 
                                 'R_sh_ref', 'R_sh_0', 'R_sh_exp', 
                                 'R_s', 'alpha_sc', 'EgRef',
                                 'cells_in_series'],
@@ -1194,7 +1194,7 @@ def calcparams_desoto(effective_irradiance, temp_cell,
 
 
 def calcparams_pvsyst(effective_irradiance, temp_cell,
-                      alpha_sc, gamma_ref, mugamma,
+                      alpha_sc, gamma_ref, mu_gamma,
                       I_L_ref, I_o_ref, 
                       R_sh_ref, R_sh_0, R_s, 
                       cells_in_series,
@@ -1222,7 +1222,7 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
     gamma_ref : float
         The diode ideality factor
 
-    mugamma : float
+    mu_gamma : float
         The temperature coefficient for the diode ideality factor, 1/K
 
     I_L_ref : float
@@ -1310,7 +1310,7 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
     Tref_K = temp_ref + 273.15
     Tcell_K = temp_cell + 273.15
 
-    gamma = gamma_ref + mugamma * (Tcell_K - Tref_K)
+    gamma = gamma_ref + mu_gamma * (Tcell_K - Tref_K)
     nNsVth = gamma * k / q * cells_in_series * Tcell_K
 
     IL = effective_irradiance / irrad_ref * \

From 75e89f0ddb2e0a99f5d2657617c5b32ad3dda8bc Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Wed, 27 Jun 2018 07:30:14 -0600
Subject: [PATCH 13/16] Change to mu_gamma in tests

---
 pvlib/test/test_pvsystem.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/pvlib/test/test_pvsystem.py b/pvlib/test/test_pvsystem.py
index 6efba10535..46fd13c8e0 100644
--- a/pvlib/test/test_pvsystem.py
+++ b/pvlib/test/test_pvsystem.py
@@ -178,7 +178,7 @@ def cec_module_params(sam_data):
 def pvsyst_module_params():
     module_parameters = {}
     module_parameters['gamma_ref'] = 1.05
-    module_parameters['mugamma'] = 0.001
+    module_parameters['mu_gamma'] = 0.001
     module_parameters['I_L_ref'] = 6.0
     module_parameters['I_o_ref'] = 5e-9
     module_parameters['EgRef'] = 1.121
@@ -413,7 +413,7 @@ def test_calcparams_pvsyst(pvsyst_module_params):
                                   temp_cell,
                                   alpha_sc=pvsyst_module_params['alpha_sc'],
                                   gamma_ref=pvsyst_module_params['gamma_ref'],
-                                  mugamma=pvsyst_module_params['mugamma'],
+                                  mu_gamma=pvsyst_module_params['mu_gamma'],
                                   I_L_ref=pvsyst_module_params['I_L_ref'],
                                   I_o_ref=pvsyst_module_params['I_o_ref'],
                                   R_sh_ref=pvsyst_module_params['R_sh_ref'],
@@ -473,7 +473,7 @@ def test_PVSystem_calcparams_pvsyst(pvsyst_module_params, mocker):
                                   temp_cell,
                                   alpha_sc=pvsyst_module_params['alpha_sc'],
                                   gamma_ref=pvsyst_module_params['gamma_ref'],
-                                  mugamma=pvsyst_module_params['mugamma'],
+                                  mu_gamma=pvsyst_module_params['mu_gamma'],
                                   I_L_ref=pvsyst_module_params['I_L_ref'],
                                   I_o_ref=pvsyst_module_params['I_o_ref'],
                                   R_sh_ref=pvsyst_module_params['R_sh_ref'],

From 046a3869a6a3fc53e04d60966b17c37d98ac67eb Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Thu, 5 Jul 2018 11:27:57 -0600
Subject: [PATCH 14/16] remove **kwargs from method calcparams_pvsyst
 signature, add irrad_ref and temp_ref keyword

---
 pvlib/pvsystem.py | 85 +++++++++++++++++++++++------------------------
 1 file changed, 42 insertions(+), 43 deletions(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 3573cf9812..dcc983b1bb 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -302,12 +302,13 @@ def calcparams_desoto(self, effective_irradiance, temp_cell, **kwargs):
         """
 
         kwargs = _build_kwargs(['a_ref', 'I_L_ref', 'I_o_ref', 'R_sh_ref',
-                                'R_s', 'alpha_sc', 'EgRef', 'dEgdT'],
+                                'R_s', 'alpha_sc', 'EgRef', 'dEgdT',
+                                'irrad_ref', 'temp_ref'],
                                 self.module_parameters)
-        
+
         return calcparams_desoto(effective_irradiance, temp_cell, **kwargs)
 
-    def calcparams_pvsyst(self, effective_irradiance, temp_cell, **kwargs):
+    def calcparams_pvsyst(self, effective_irradiance, temp_cell):
         """
         Use the :py:func:`calcparams_pvsyst` function, the input
         parameters and ``self.module_parameters`` to calculate the
@@ -321,20 +322,18 @@ def calcparams_pvsyst(self, effective_irradiance, temp_cell, **kwargs):
         temp_cell : float or Series
             The average cell temperature of cells within a module in C.
 
-        **kwargs
-            See pvsystem.calcparams_pvsyst for details
-
         Returns
         -------
         See pvsystem.calcparams_pvsyst for details
         """
 
-        kwargs = _build_kwargs(['gamma_ref', 'mu_gamma', 'I_L_ref', 'I_o_ref', 
-                                'R_sh_ref', 'R_sh_0', 'R_sh_exp', 
+        kwargs = _build_kwargs(['gamma_ref', 'mu_gamma', 'I_L_ref', 'I_o_ref',
+                                'R_sh_ref', 'R_sh_0', 'R_sh_exp',
                                 'R_s', 'alpha_sc', 'EgRef',
+                                'irrad_ref', 'temp_ref',
                                 'cells_in_series'],
                                 self.module_parameters)
-        
+
         return calcparams_pvsyst(effective_irradiance, temp_cell, **kwargs)
 
     def sapm(self, effective_irradiance, temp_cell, **kwargs):
@@ -492,7 +491,7 @@ def first_solar_spectral_loss(self, pw, airmass_absolute):
             coefficients = None
 
         return atmosphere.first_solar_spectral_correction(pw,
-                                                          airmass_absolute, 
+                                                          airmass_absolute,
                                                           module_type,
                                                           coefficients)
 
@@ -976,12 +975,12 @@ def physicaliam(aoi, n=1.526, K=4., L=0.002):
 
 
 def calcparams_desoto(effective_irradiance, temp_cell,
-                      alpha_sc, a_ref, I_L_ref, I_o_ref, R_sh_ref, R_s, 
+                      alpha_sc, a_ref, I_L_ref, I_o_ref, R_sh_ref, R_s,
                       EgRef=1.121, dEgdT=-0.0002677,
                       irrad_ref=1000, temp_ref=25):
     '''
-    Calculates five parameter values for the single diode equation at 
-    effective irradiance and cell temperature using the De Soto et al. 
+    Calculates five parameter values for the single diode equation at
+    effective irradiance and cell temperature using the De Soto et al.
     model described in [1]. The five values returned by calcparams_desoto
     can be used by singlediode to calculate an IV curve.
 
@@ -998,34 +997,34 @@ def calcparams_desoto(effective_irradiance, temp_cell,
         module in units of A/C.
 
     a_ref : float
-        The product of the usual diode ideality factor (n, unitless), 
+        The product of the usual diode ideality factor (n, unitless),
         number of cells in series (Ns), and cell thermal voltage at reference
         conditions, in units of V.
 
     I_L_ref : float
         The light-generated current (or photocurrent) at reference conditions,
         in amperes.
-        
+
     I_o_ref : float
         The dark or diode reverse saturation current at reference conditions,
         in amperes.
-        
+
     R_sh_ref : float
         The shunt resistance at reference conditions, in ohms.
-        
+
     R_s : float
         The series resistance at reference conditions, in ohms.
 
     EgRef : float
         The energy bandgap at reference temperature in units of eV.
-        1.121 eV for crystalline silicon. EgRef must be >0.  For parameters 
+        1.121 eV for crystalline silicon. EgRef must be >0.  For parameters
         from the SAM CEC module database, EgRef=1.121 is implicit for all
         cell types in the parameter estimation algorithm used by NREL.
 
     dEgdT : float
         The temperature dependence of the energy bandgap at reference
-        conditions in units of 1/K. May be either a scalar value 
-        (e.g. -0.0002677 as in [1]) or a DataFrame (this may be useful if 
+        conditions in units of 1/K. May be either a scalar value
+        (e.g. -0.0002677 as in [1]) or a DataFrame (this may be useful if
         dEgdT is a modeled as a function of temperature). For parameters from
         the SAM CEC module database, dEgdT=-0.0002677 is implicit for all cell
         types in the parameter estimation algorithm used by NREL.
@@ -1053,8 +1052,8 @@ def calcparams_desoto(effective_irradiance, temp_cell,
         Shunt resistance in ohms
 
     nNsVth : numeric
-        The product of the usual diode ideality factor (n, unitless), 
-        number of cells in series (Ns), and cell thermal voltage at 
+        The product of the usual diode ideality factor (n, unitless),
+        number of cells in series (Ns), and cell thermal voltage at
         specified effective irradiance and cell temperature.
 
     References
@@ -1164,7 +1163,7 @@ def calcparams_desoto(effective_irradiance, temp_cell,
 
     # Boltzmann constant in eV/K
     k = 8.617332478e-05
-    
+
     # reference temperature
     Tref_K = temp_ref + 273.15
     Tcell_K = temp_cell + 273.15
@@ -1173,9 +1172,9 @@ def calcparams_desoto(effective_irradiance, temp_cell,
 
     nNsVth = a_ref * (Tcell_K / Tref_K)
 
-    # In the equation for IL, the single factor effective_irradiance is 
-    # used, in place of the product S*M in [1]. effective_irradiance is 
-    # equivalent to the product of S (irradiance reaching a module's cells) * 
+    # In the equation for IL, the single factor effective_irradiance is
+    # used, in place of the product S*M in [1]. effective_irradiance is
+    # equivalent to the product of S (irradiance reaching a module's cells) *
     # M (spectral adjustment factor) as described in [1].
     IL = effective_irradiance / irrad_ref * \
               (I_L_ref + alpha_sc * (Tcell_K - Tref_K))
@@ -1185,7 +1184,7 @@ def calcparams_desoto(effective_irradiance, temp_cell,
     # Rsh = Rsh_ref * (S_ref / S) where S is broadband irradiance reaching
     # the module's cells. If desired this model behavior can be duplicated
     # by applying reflection and soiling losses to broadband plane of array
-    # irradiance and not applying a spectral loss modifier, i.e., 
+    # irradiance and not applying a spectral loss modifier, i.e.,
     # spectral_modifier = 1.0.
     Rsh = R_sh_ref * (irrad_ref / effective_irradiance)
     Rs = R_s
@@ -1195,15 +1194,15 @@ def calcparams_desoto(effective_irradiance, temp_cell,
 
 def calcparams_pvsyst(effective_irradiance, temp_cell,
                       alpha_sc, gamma_ref, mu_gamma,
-                      I_L_ref, I_o_ref, 
-                      R_sh_ref, R_sh_0, R_s, 
+                      I_L_ref, I_o_ref,
+                      R_sh_ref, R_sh_0, R_s,
                       cells_in_series,
                       R_sh_exp=5.5,
                       EgRef=1.121,
                       irrad_ref=1000, temp_ref=25):
     '''
-    Calculates five parameter values for the single diode equation at 
-    effective irradiance and cell temperature using the PVsyst v6 
+    Calculates five parameter values for the single diode equation at
+    effective irradiance and cell temperature using the PVsyst v6
     model described in [1,2,3]. The five values returned by calcparams_pvsyst
     can be used by singlediode to calculate an IV curve.
 
@@ -1228,17 +1227,17 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
     I_L_ref : float
         The light-generated current (or photocurrent) at reference conditions,
         in amperes.
-        
+
     I_o_ref : float
         The dark or diode reverse saturation current at reference conditions,
         in amperes.
-        
+
     R_sh_ref : float
         The shunt resistance at reference conditions, in ohms.
-        
+
     R_sh_0 : float
         The shunt resistance at zero irradiance conditions, in ohms.
-        
+
     R_s : float
         The series resistance at reference conditions, in ohms.
 
@@ -1271,19 +1270,19 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
 
     resistance_series : float
         Series resistance in ohms
-        
+
     resistance_shunt : numeric
         Shunt resistance in ohms
 
     nNsVth : numeric
-        The product of the usual diode ideality factor (n, unitless), 
-        number of cells in series (Ns), and cell thermal voltage at 
+        The product of the usual diode ideality factor (n, unitless),
+        number of cells in series (Ns), and cell thermal voltage at
         specified effective irradiance and cell temperature.
 
     References
     ----------
-    [1] K. Sauer, T. Roessler, C. W. Hansen, Modeling the Irradiance and 
-     Temperature Dependence of Photovoltaic Modules in PVsyst, 
+    [1] K. Sauer, T. Roessler, C. W. Hansen, Modeling the Irradiance and
+     Temperature Dependence of Photovoltaic Modules in PVsyst,
      IEEE Journal of Photovoltaics v5(1), January 2015.
 
     [2] A. Mermoud, PV modules modelling, Presentation at the 2nd PV
@@ -1297,7 +1296,7 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
     --------
     calcparams_desoto
     singlediode
-    
+
     '''
 
     # Boltzmann constant in J/K
@@ -1305,7 +1304,7 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
 
     # elementary charge in coulomb
     q = 1.6021766e-19
-    
+
     # reference temperature
     Tref_K = temp_ref + 273.15
     Tcell_K = temp_cell + 273.15
@@ -1324,7 +1323,7 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
 
     Rsh = Rsh_base + (R_sh_0 - Rsh_base) * \
               np.exp(-R_sh_exp * effective_irradiance / irrad_ref)
-    
+
     Rs = R_s
 
     return IL, I0, Rs, Rsh, nNsVth

From 632ff873ef2533c6b54b9b3c67fa8d009e81de16 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Fri, 6 Jul 2018 08:49:56 -0600
Subject: [PATCH 15/16] fix typo in Boltzmann constant J/K

---
 pvlib/pvsystem.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index dcc983b1bb..9d3bea858b 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -1300,7 +1300,7 @@ def calcparams_pvsyst(effective_irradiance, temp_cell,
     '''
 
     # Boltzmann constant in J/K
-    k = 1.3806488e-23
+    k = 1.38064852e-23
 
     # elementary charge in coulomb
     q = 1.6021766e-19

From 1295bcfa0be4106ef18c37a357a81a9d6fe2660d Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@srn.sandia.gov>
Date: Fri, 6 Jul 2018 09:38:21 -0600
Subject: [PATCH 16/16] Remove scope=session from pvsyst fixture

---
 pvlib/test/test_pvsystem.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/test/test_pvsystem.py b/pvlib/test/test_pvsystem.py
index 46fd13c8e0..6931543824 100644
--- a/pvlib/test/test_pvsystem.py
+++ b/pvlib/test/test_pvsystem.py
@@ -174,7 +174,7 @@ def cec_module_params(sam_data):
     return module_parameters
 
 
-@pytest.fixture(scope="session")
+@pytest.fixture()
 def pvsyst_module_params():
     module_parameters = {}
     module_parameters['gamma_ref'] = 1.05