pvl_est_single_diode_param

Uses a regression technique to fit the single diode equation to data for a single IV curve.

Contents

Syntax:

[Io Iph Rs Rsh n] = pvl_est_single_diode_param(I, V, NsVth)

Description

pvl_est_single_diode_param uses a regression technique based on [1] to fit the single diode equation to data for a single IV curve. Although values for each of the five parameters are returned, testing has shown only Rsh to be stable. Values for the parameters Rs, Io and n may be negative or imaginary even for IV curve data without obvious flaws. The method coded here uses a principal component transformation of (V,I) prior to regression to attempt to overcome effects of strong colinearity between V and I over much of the I-V curve.

Inputs

Outputs

Example

clearvars

% load IV curve data for a 36 cell Mitsubishi cSi module
load 'Desoto_demo.mat'

% Build structure for constants
Const.E0 = 1000; % W/m2
Const.T0 = 25; % C
Const.k = 1.38066E-23; % J/K
Const.q = 1.60218E-19; % c

i = 63; % randomly selected IV curve

Vth = Const.k/Const.q*(IVCurves(i).Tc+273.15);

% Clean up measured IV curve data
[I, V] = pvl_rectify_IV_curve(IVCurves(i).I, IVCurves(i).V, IVCurves(i).Voc, IVCurves(i).Isc);

% Estimate 5 parameters for the IV curve
[Io, Iph, Rs, Rsh, n] = ...
        pvl_est_single_diode_param(I, V, Specs.Ns*Vth);

% Compute IV curve associated with the 5 parameters
Result = pvl_singlediode(Iph, Io, Rs, Rsh, n*Specs.Ns*Vth, 100);

figure

plot(IVCurves(i).V,IVCurves(i).I,'k.')
hold on
plot(Result.V,Result.I,'r+')
xlabel('Voltage (V)')
ylabel('Current (A)')
title('Fitted IV Curve using regression method','FontSize',14)
xlim([0 21])
ylim([0 7])
text(2,6,['I_L = ' num2str(Iph)]);
text(2,5.5,['I_O = ' num2str(Io)]);
text(2,5,['R_{SH} = ' num2str(Rsh)]);
text(2,4.5,['R_S = ' num2str(Rs)]);
text(2,4,['n = ' num2str(n)]);
%

Sources

[1] A. Ortiz-Conde, F. Garci'a Sa'nchez, J. Murci, "New method to extract the model parameters of solar cells from the explict analytic solutions of their illuminated I-V characteristics", Solar Energy Materials and Solar Cells 90, pp 352-361, 2006.

[2] C. Hansen, Parameter Estimation for Single Diode Models of Photovoltaic Modules, Sandia National Laboratories Report SAND2015-2065.

See also

pvl_singlediode, pvl_rectify_IV_curve

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