Error using diff Difference order N must be a positive integer scalar.

I got this error from trying to use the Newton-Raphson method to extract pv parameters. I was trying to follow the flowchart atttached below

% %

Error using diff

Difference order N must be a positive integer scalar.

Error in Esram (line 56)

g(a+1) = g(a) - (Isc-I0*(exp(1)*(q*((Vmp+(Imp*Rs))/n))-1) - ((Vmp+(Imp*Rs))/(n*k*T))) / (-I0*((q/(n*k*T))*(1 + diff(I, V)*Rs)*exp(1)*(q*(V+(I*Rs)/(n*k*T)))))-(1/Rsh)*(1 + diff(I, V)*Rs);

here is the updated program

clc

close all

clear

% Data provided

load('SD_Test_Data_01.mat', 'voltage')

load('SD_Test_Data_01.mat', 'current')

I = current;

V = voltage;

P = I.*V; % To find the P-V curve

Pmaxcurve = max(P);

% Graphs

figure(1);

plot (V, I,'b:')

xlabel('Voltage (V)'), ylabel('Current (A)')

title('I-V Curve')

figure(2);

plot(V, P,'r--');

xlabel('Voltage(V)'), ylabel('Power (W)')

title('P-V Curve')

figure(3);

plot (V, I,'--')

title('Combine Plots')

hold on

plot(V, P, 'r:');

hold off

%At the standard test conditions (STC)

[Pmax, index_of_Pmax] = max(P);

Imp = I(index_of_Pmax); %(A)

Vmp = V(index_of_Pmax); %(v)

%We know that

Isc = max(I); %(A)

Voc = max(V); %(V)

q = 1.6022e-19; %q is the electron charge

k = 1.3806e-23; % k is the Boltzmann constant in (J/k)

% if the solar cells inside a solar module reach 65?C

T = 25; % T the module temperature in celcius

% Initializing Rs the series resistance and the shunt resistance Rsh and n

Rsh = (Vmp/(Isc- Imp))- ((Voc-Vmp)/Imp);

Rs = 0;

n= 1.2;

% Taking an assumption that Rsh>>Vo

I0 = Isc/(exp(1)*(q*(Voc/(n*k*T)))-1);

Nmax = 1000; %maximum number of interations

g(1) = 0.5; %first approximation

g = zeros(1, Nmax);

for a = 1:Nmax-1

g(a+1) = g(a) - (Isc-I0*(exp(1)*(q*((Vmp+(Imp*Rs))/n))-1) - ((Vmp+(Imp*Rs))/(n*k*T))) / (-I0*((q/(n*k*T))*(1 + diff(I, V)*Rs)*exp(1)*(q*(V+(I*Rs)/(n*k*T)))))-(1/Rsh)*(1 + diff(I, V)*Rs);

end

plot(g, 'r.')

Answer 1

[VBBV]

Replace the term

%if true
  % code
%end
(1+diff(I,V)*Rs)

To

%if true
  % code
% end
(1+diff(I,1)*Rs)

In all the occurances. Since diff calculates derivative. You have specified the second argument as vector instead of differentiating variable.

Answer 2

[Joanan Destin]

I get this error now.

Error using *

Incorrect dimensions for matrix multiplication. Check that the number of columns in the first matrix matches the number of rows in the second matrix. To perform elementwise multiplication, use '.*'.

Error in Esram (line 56)

g(a+1) = g(a) - (Isc-I0*(exp(1)*(q*((Vmp+(Imp*Rs))/n))-1) - ((Vmp+(Imp*Rs))/(n*k*T))) / (-I0*((q/(n*k*T))*(1 + diff(I, V)*Rs)*exp(1)*(q*(V+(I*Rs)/(n*k*T)))))-(1/Rsh)*(1 + diff(I, V)*Rs);