Support ideal PV devices (#324) (#340)

* Add draft i_from_v_alt function with tests

* Better comments and more explicit typing

* Use transform from shunt resistance to shunt conductance

* Add v_from_i_alt() with initial tests and use np.where

* Use test fixtures

* Add @requires_scipy to test fixtures

* More current_sum_at_diode_node() tests and using fixture

* Naming, documentation, and formatting

* Deprecate replaced functions and flake8

* Add release documentation and flake8 again

* Replace deprecated function usages and update test_singlediode_series_ivcurve

* Conform to existing API

* Run flake8

* Implement some code quality suggestions

* Remove extraneous print statements

* Better docstrings

* Fix parameter ranges in docstrings

* Add test that overflows lambertw arg

* Add test for mixed solution types logic

* Use broadcast_arrays for cleaner code

* One more simplification

* Better use of broadcast_arrays

Author: Mark Campanelli

docs/sphinx/source/api.rst

@@ -201,10 +201,10 @@ Functions relevant for the single diode model.
 .. autosummary::
    :toctree: generated/
 
-   pvsystem.singlediode
    pvsystem.calcparams_desoto
-   pvsystem.v_from_i
    pvsystem.i_from_v
+   pvsystem.singlediode
+   pvsystem.v_from_i
 
 SAPM model
 ----------

docs/sphinx/source/whatsnew/v0.5.1.rst

@@ -16,18 +16,35 @@ Bug fixes
 Enhancements
 ~~~~~~~~~~~~
 * Improve clearsky.lookup_linke_turbidity speed. (:issue:`368`)
+* Ideal devices supported in single diode model, e.g.,
+  resistance_series = 0 and/or resistance_shunt = numpy.inf (:issue:`340`)
+* `pvsystem.v_from_i` and `pvsystem.i_from_v` computations for near ideal
+  devices are more numerically stable. However, very, very near ideal
+  resistance_series and/or resistance_shunt may still cause issues with the
+  implicit solver (:issue:`340`)
+
+API Changes
+~~~~~~~~~~~
+* `pvsystem.v_from_i` and `pvsystem.i_from_v` functions now accept
+  resistance_series = 0 and/or resistance_shunt = numpy.inf as inputs
+  (:issue:`340`)
 
 Documentation
 ~~~~~~~~~~~~~
 * Doc string of modelchain.basic_chain was updated to describe args
   more accurately
+* Doc strings of `singlediode`, `pvsystem.v_from_i`, and `pvsystem.i_from_v`
+  were updated to describe acceptable input arg ranges
 
 Testing
 ~~~~~~~
 * Changed test for clearsky.haurwitz to operate on zenith angles
+* Significant new test cases added for `pvsystem.v_from_i` and
+  `pvsystem.i_from_v` (:issue:`340`)
 
 Contributors
 ~~~~~~~~~~~~
 * Cliff Hansen
 * KonstantinTr
 * Will Holmgren
+* Mark Campanelli

pvlib/atmosphere.py

@@ -380,7 +380,7 @@ def first_solar_spectral_correction(pw, airmass_absolute, module_type=None,
         The module used to calculate the spectral correction
         coefficients corresponds to the Mult-crystalline silicon
         Manufacturer 2 Model C from [3]_. Spectral Response (SR) of CIGS
-        and a-Si modules used to derive coefficients can be found in [4]_ 
+        and a-Si modules used to derive coefficients can be found in [4]_
 
     coefficients : None or array-like, default None
         allows for entry of user defined spectral correction