Merge pull request #28 from nzweibaum/master

add quadratic term to breakdown and add new contrib folder

pvmismatch/contrib/tetris_reference_module.py

@@ -0,0 +1,56 @@
+"""
+This script uses default Tetris module configuration and cell parameters to
+calculate performance and generate IV and PV curves.
+"""
+
+from pvmismatch import *
+import numpy as np
+from matplotlib import pyplot as plt
+
+if __name__ == "__main__":
+
+    # Model parameters
+    NPTS=5000  # Because of the high cell breakdown voltage, NPTS must be >1000
+
+    # Cell parameters
+    RS = 0.0181123  # [ohm] series resistance
+    RSH = 58.082  # [ohm] shunt resistance
+    ISAT1_T0 = 2.9885E-11  # [A] diode one saturation current
+    ISAT2 = 1.6622E-07  # [A] diode two saturation current
+    ISC0_T0 = 1.437  # [A] reference short circuit current
+    ARBD = 9.0E-4  # reverse breakdown coefficient 1
+    BRBD = -0.056  # reverse breakdown coefficient 2
+    VRBD_ = -25.1  # [V] reverse breakdown voltage
+    NRBD = 4.0  # reverse breakdown exponent
+    EG = 1.166  # [eV] band gap of cSi
+    ALPHA_ISC = 0.0003551  # [1/K] short circuit current temperature coefficient
+    TCELL = 298.15  # [K] cell temperature
+    CELLAREA = np.float64(38.064)  # [cm^2] cell area used for efficiency calculation
+
+    # Module parameters
+    VBYPASS = np.float64(-0.885)  # [V] trigger voltage of bypass diode
+    NUMBERCOLS = 6  # number of hypercells per module
+
+    # System parameters
+    NUMBERMODS = 1  # number of modules per string
+    NUMBERSTRS = 1  # number of strings in parallel
+
+    # System definition
+    tetrisCell = pvcell.PVcell(Rs=RS, Rsh=RSH, Isat1_T0=ISAT1_T0, Isat2=ISAT2,
+                    Isc0_T0=ISC0_T0, aRBD=ARBD, VRBD=VRBD_, bRBD=BRBD, 
+                    nRBD=NRBD, Eg=EG, alpha_Isc=ALPHA_ISC,
+                    Tcell=TCELL)
+    tetrisModule = pvmodule.PVmodule(cell_pos=pvmodule.PCT492, pvcells=tetrisCell,
+                    Vbypass=VBYPASS, cellArea=CELLAREA)  # Tetris module with no cross-tiling
+    tetrisSystem = pvsystem.PVsystem(pvconst=pvconstants.PVconstants(npts=NPTS),
+                    pvmods=tetrisModule, numberStrs=NUMBERSTRS, numberMods=NUMBERMODS)
+
+    print 'Imp = ' + str(tetrisSystem.Imp) + ' A'
+    print 'Vmp = ' + str(tetrisSystem.Vmp) + ' V'
+    print 'Pmp = ' + str(tetrisSystem.Pmp) + ' W'
+    print 'Isc = ' + str(tetrisSystem.Isc) + ' A'
+    print 'Voc = ' + str(tetrisSystem.Voc) + ' V'
+    print 'FF = ' + str(100*tetrisSystem.FF) + ' %'
+    print 'Efficiency = ' + str(100*tetrisSystem.eff) + ' %'
+    figure = tetrisSystem.plotSys()
+    plt.show()

pvmismatch/pvmismatch_lib/pvcell.py

@@ -17,7 +17,8 @@
 ISAT2 = 1.117455042372326E-6  # [A] diode two saturation current
 ISC0_T0 = 6.3056  # [A] reference short circuit current
 TCELL = 298.15  # [K] cell temperature
-ARBD = 1.036748445065697E-4  # reverse breakdown coefficient
+ARBD = 1.036748445065697E-4  # reverse breakdown coefficient 1
+BRBD = 0.  # reverse breakdown coefficient 2
 VRBD_ = -5.527260068445654  # [V] reverse breakdown voltage
 NRBD = 3.284628553041425  # reverse breakdown exponent
 EG = 1.1  # [eV] band gap of cSi
@@ -33,7 +34,8 @@ class PVcell(object):
     :param Isat1_T0: first saturation diode current at ref temp [A]
     :param Isat2: second saturation diode current [A]
     :param Isc0_T0: short circuit current at ref temp [A]
-    :param aRBD: reverse breakdown coefficient
+    :param aRBD: reverse breakdown coefficient 1
+    :param bRBD: reverse breakdown coefficient 2
     :param VRBD: reverse breakdown voltage [V]
     :param nRBD: reverse breakdown exponent
     :param Eg: band gap [eV]
@@ -44,7 +46,7 @@ class PVcell(object):
     :type pvconst: :class:`~pvmismatch.pvmismatch_lib.pvconstants.PVconstants`
     """
     def __init__(self, Rs=RS, Rsh=RSH, Isat1_T0=ISAT1_T0, Isat2=ISAT2,
-                 Isc0_T0=ISC0_T0, aRBD=ARBD, VRBD=VRBD_,
+                 Isc0_T0=ISC0_T0, aRBD=ARBD, bRBD=BRBD, VRBD=VRBD_,
                  nRBD=NRBD, Eg=EG, alpha_Isc=ALPHA_ISC,
                  Tcell=TCELL, Ee=1., pvconst=PVconstants()):
         # user inputs
@@ -53,7 +55,8 @@ def __init__(self, Rs=RS, Rsh=RSH, Isat1_T0=ISAT1_T0, Isat2=ISAT2,
         self.Isat1_T0 = Isat1_T0  #: [A] diode one sat. current at T0
         self.Isat2 = Isat2  #: [A] diode two saturation current
         self.Isc0_T0 = Isc0_T0  #: [A] short circuit current at T0
-        self.aRBD = aRBD  #: reverse breakdown coefficient
+        self.aRBD = aRBD  #: reverse breakdown coefficient 1
+        self.bRBD = bRBD  #: reverse breakdown coefficient 2
         self.VRBD = VRBD  #: [V] reverse breakdown voltage
         self.nRBD = nRBD  #: reverse breakdown exponent
         self.Eg = Eg  #: [eV] band gap of cSi
@@ -166,8 +169,10 @@ def calcCell(self):
         fRBD = 1. - Vdiode / self.VRBD
         # use epsilon = 2.2204460492503131e-16 to avoid "divide by zero"
         fRBD[fRBD == 0] = np.finfo(np.float64).eps
-        fRBD = self.aRBD * fRBD ** (-self.nRBD)
-        Icell = Igen - Idiode1 - Idiode2 - Ishunt * (1. + fRBD)
+        Vdiode_norm = Vdiode / self.Rsh / self.Isc0_T0
+        fRBD = self.Isc0_T0 * fRBD ** (-self.nRBD)
+        IRBD = (self.aRBD * Vdiode_norm + self.bRBD * Vdiode_norm ** 2) * fRBD 
+        Icell = Igen - Idiode1 - Idiode2 - Ishunt - IRBD
         Vcell = Vdiode - Icell * self.Rs
         Pcell = Icell * Vcell
         return Icell, Vcell, Pcell

pvmismatch/tests/test_pvcell.py

@@ -57,11 +57,18 @@ def test_calc_series():
     i, v = pvconst.calcSeries(icells, vcells, isc.mean(), i_at_vrbd.max())
     iv = np.loadtxt(os.path.join(BASE_DIR, 'calc_series_test_iv.dat'))
     # noinspection PyTypeChecker
-    ok_(np.all(i == iv[0]))
+    ok_(np.allclose(i, iv[0]))
     # noinspection PyTypeChecker
-    ok_(np.all(v == iv[1]))
+    ok_(np.allclose(v, iv[1]))
     return i, v
 
 
+def test_pvcell_calc_rbd():
+    pvc1 = PVcell(bRBD=0.)
+    ok_(isinstance(pvc1, PVcell))
+    pvc2 = PVcell(bRBD=-0.056)
+    ok_(isinstance(pvc2, PVcell))
+
+
 if __name__ == "__main__":
     test_calc_series()