The following are my code for simple pv modules, I keep getting the same plot for different irradiance values. Can someone help?

Even after changing the values of Gn and S in code 1 and code 2 resp. I keep getting the same plot.

Code 1 for a simple Pv module with one diode and one resistor:

clc;

clear all;

K= 1.38065e-23; %Boltsman constant

q= 1.602e-19; %charge of electron

Iscn= 8.21; %nominal SC current

Vocn= 32.9; %nominal OC voltage

Kv= -0.123; %temp. voltage constant

Ki= 0.0032; %temp current constant

Ns= 54; %No. of series connected cells

T= 25+273; %operating temp.

Tn= 25+273 %nominal temp.

Gn= 1000; %nominal irradiance

a= 1.3; %diode ideality constant

Eg= 1.12; %band gap of silicon at 25 degree celcius

G= 800; %actual irradiation

Rs= 0.221;

Rp= 415.405;

tic

Vtn= Ns*(K*Tn/q);

Ion = Iscn/((exp(Vocn/(a*Vtn)))-1)

Io= Ion*((Tn/T)^3)*exp(((q*Eg/(a*K)*((1/Tn)-(1/T)))));

Ipvn = Iscn;

Ipv= (Ipvn + Ki*(T-Tn)*(G/Gn))

Vt = Ns*(K*T/q);

I= zeros(330,1);

i=1;

I(1,1)=0;

for V= 32.9:-0.1:0

I_part = Io*(exp((V+(I(i,1)*Rs))/(Vt*a))-1) + ((V+(Rs*I(i,1)))/Rp);

I(i+1)= Ipv -I_part;

V1(i)= V;

P(i)= V*I(i);

i=i+1;

end

time_elapsed=toc;

V1(i) = V1(i-1);

P(i) = P(i-1);

V1=transpose(V1);

%subplot(3,1,1)

%plot(V1,I);

%subplot(3,1,2)

plot(V1,P);

%subplot(3,1,3)

%plot(V1, I_part);

Code 2 is basically the same as code 1 but uses more complex equations and give better and faster solutions:

clc;

clear all;

Pmpp = 50; %Max Power

Vmpp = 17.98; %Vol at Pmax

Impp = 2.77; %Current at Pmax

Isc= 3; %Short-circuit current

Voc= 22; %Open Circuit Voltage

a= 0.0004; %Temp coeff. of Isc

b= -0.0033; %Temp coeff. of Voc

T = 30;

Tref= 25;

S= 800;

Sref= 1000;

Rs= 0.085;

V= 30;

kref= (1-(Impp/Isc))^(1/(((Vmpp+Rs*Impp)/Voc)-1));

Vo = Voc*(1+ a*log(S/Sref)+ b*(T-Tref));

I= zeros(330,1);

for i = 1:330

V(i)= (i-1)*0.1;

Is = Isc*(1+a*(T-Tref))*(S/Sref);

I(i)= Isc*(1-kref.^((V(i)-Voc+Rs*I(i))/Voc));

end

plot(V,I),grid;

xlabel('Voltage'),ylabel('Current');

Answer 1

[Edoardo_a]

Hi!

For what I have seen in the code 1, the plot doesn't change because you set the value of T and Tn to be identical.

Therefore the expression for Ipv= (Ipvn + Ki*(T-Tn)*(G/Gn)) never change regardless on the value of Gn.

In code 2 the plot is always the same because the expression of I(i) inside the for loop is obtained using parameters that are not dependent on S! I think you would include instead the Is value calculated inside the loop, probably instead of I(i).

[Aryan Sharma]

Thanks bro, your answer helped me...for the 2nd code but for the 1st one I changed the value of T and made G as zero but it still gave a plot

[Edoardo_a]

I don't know what is the physial meaning of this formula:

Ipv= (Ipvn + Ki*(T-Tn)*(G/Gn))

However the reason why it keeps gving problems is that

G = 0
Ipv = Ipvn

which is exactly the same result you get whenT=Tn.

If any of the 3 terms in the second part of the equation goes to 0, Ipv will be always the same value

% When Ki = 0
% or   T-Tn = 0
% or   G/Gn = 0
--> Ipv = Ipvn