Update whatsnew, example

pvlib · ajonesr · Jun 20, 2023 · Jun 21, 2023 · Jun 21, 2023 · Jun 21, 2023
commit 8cca7b7298bce3ee12bcc7d3b7b0fc8dc662a71c
diff --git a/docs/examples/iv-modeling/plot_mismatch.py b/docs/examples/iv-modeling/plot_mismatch.py
@@ -2,9 +2,30 @@
 Calculating a combined IV curve
 ===============================
 
-Example of combining IV curves in series, using the single diode model.
+Here we show how to use pvlib to combine IV curves in series.
+
+Differences in weather (irradiance or temperature) or module condition can
+cause two modules (or cells) to produce different current-voltage (IV)
+characteristics or curves. Series-connected modules produce a string-level IV
+curve, which can be obtained by combining the curves for the individual
+modules. Combining the curves involves modeling IV curves at negative voltage,
+because some modules (cells) in the series circuit will produce more
+photocurrent than others but the combined current cannot exceed that of the
+lowest-current module (cell).
 """
 
+# %%
+#
+# pvlib provides two functions to combine series-connected curves:
+#
+#* :py:func:`pvlib.ivtools.mismatch.prepare_curves` uses parameters for the
+#  single diode equation and a simple model for negative voltage behavior to
+#  compute IV curves at a common set of currents
+#
+#* :py:func:`pvlib.ivtools.mismatch.combine_curves` produces the combined IV
+#  curve from a set of IV curves with common current values.
+
+
 import numpy as np
 import matplotlib.pyplot as plt
 from scipy.constants import Boltzmann, elementary_charge
@@ -13,11 +34,13 @@
 
 
 # set up parameter array
+
 # the parameters should be in the order: photocurrent, saturation
 # current, series resistance, shunt resistance, and n*Vth*Ns
-vth = 298.15 * Boltzmann / elementary_charge
+# these are the parameters for the single diode function
 
 # example array of parameters
+vth = 298.15 * Boltzmann / elementary_charge
 params = np.array([[1.0, 3e-08, 1.0, 300, 1.3*vth*72],
                    [3, 3e-08, 0.1, 300, 1.01*vth*72],
                    [2, 5e-10, 0.1, 300, 1.1*vth*72]])
@@ -31,15 +54,19 @@
 combined_curve_dict = combine_curves(currents, voltages_array)
 
 # plot all curves and combined curve
-for v in voltages_array:
-    plt.plot(v, currents)
+for idx in range(len(voltages_array)):
+    v = voltages_array[idx]
+    plt.plot(v, currents, label=f"Panel {idx+1}")
 
 plt.plot(combined_curve_dict['v'], combined_curve_dict['i'],
          label="Combined curve")
 
+# plot vertical line at breakdown voltage (used in simplified
+# reverse bias model)
+plt.vlines(brk_voltage, ymin=0.0, ymax=combined_curve_dict['i_sc'], ls='--',
+           color='k', linewidth=1, label="Breakdown voltage")
+
 plt.xlabel("Voltage [V]")
 plt.ylabel("Current [A]")
-plt.vlines(brk_voltage, ymin=0.0, ymax=combined_curve_dict['i_sc'], ls='--',
-           color='k', label="Breakdown voltage")
 plt.legend()
 plt.show()
diff --git a/docs/sphinx/source/whatsnew/v0.10.0.rst b/docs/sphinx/source/whatsnew/v0.10.0.rst
@@ -92,10 +92,6 @@ Enhancements
   tolerance and number of iterations can be set.
   (:issue:`1249`, :pull:`1764`)
 * Improved `ModelChainResult.__repr__` (:pull:`1236`)
-* Added a new module :py:mod:`pvlib.ivtools.mismatch` to contain functions for
-  combining IV curves. Added functions 
-  :py:func:`pvlib.ivtools.mismatch.prepare_curves` and 
-  :py:func:`pvlib.ivtools.mismatch.combine_curves`. (:pull:`1781`)
 * Improved ``ModelChainResult.__repr__`` (:pull:`1236`)
 * Exposes several functions useful for bifacial and shading calculations (:pull:`1666`):
 
@@ -169,7 +165,6 @@ Contributors
 * Adam R. Jensen (:ghuser:`AdamRJensen`)
 * Echedey Luis (:ghuser:`echedey-ls`)
 * Cliff Hansen (:ghuser:`cwhanse`)
-* Abigail Jones (:ghuser:`ajonesr`)
 * Cédric Leroy (:ghuser:`cedricleroy`)
 * Jean-Baptiste Pasquier (:ghuser:`pasquierjb`)
 * Mark Mikofski (:ghuser:`mikofski`)

diff --git a/docs/sphinx/source/whatsnew/v0.10.2.rst b/docs/sphinx/source/whatsnew/v0.10.2.rst
@@ -15,6 +15,10 @@ Enhancements
   :py:func:`pvlib.iotools.get_pvgis_hourly`, :py:func:`pvlib.iotools.get_cams`,
   :py:func:`pvlib.iotools.get_bsrn`, and :py:func:`pvlib.iotools.read_midc_raw_data_from_nrel`.
   (:pull:`1800`)
+* Added a new module :py:mod:`pvlib.ivtools.mismatch` to contain functions for
+  combining IV curves. Added functions 
+  :py:func:`pvlib.ivtools.mismatch.prepare_curves` and 
+  :py:func:`pvlib.ivtools.mismatch.combine_curves`. (:pull:`1781`)
 
 
 Bug fixes
@@ -36,3 +40,4 @@ Requirements
 Contributors
 ~~~~~~~~~~~~
 * Adam R. Jensen (:ghuser:`AdamRJensen`)
+* Abigail Jones (:ghuser:`ajonesr`)