Error: Incorrect use of '=' operator. To assign a value to a variable, use '='. To compare values for equality, use '=='.

Error evaluating 'InitFcn' callback of block_diagram 'DFIG_SMC'. Callback string is '% Parametrs for DFIG with SMC

% Parametrs for DFIG with SMC
f=50;                                 
Ps=2e6;                             
n=1500;                             
Vs=690;                             
Is=1760;                            
Tem=12732;                      

Vr=2070;                           
p=2;                                  
u=1/3;                              
smax=1/3;                        
Vr_stator=(Vr*smax)*u;     
Rs=2.6e-3;                        
Ls=2.587e-3;                     
Rr'=26.1e-3;                      
Lr'=2.587e-3;                     
Lm=2.51e-3;
Rm=1.0805e6;                     
Vbus=Vr_stator*sqrt(2);    
sigma=(1-Lm^2)/(Ls*Lr);
Vs=690*sqrt(2/3);
ws=f*2*pi;
J=127/2;                              
D=1e-3;                             

fsw=4e3;                            
Ts=1/fsw/50;                      

F=0.058;

%% Maximum and Minimum wind speeds

wt_nom=18;
wt_min=9;

%% Three Blade wind turbine model

N=100;                                                 
Radio=42;                                             
ro=1.225;                                              

%% Cp and Ct curves

beta=0;                                                    
ind2=1;

%% Kopt for MPPT

Cp_max=0.44;
lambda_opt=7.2;
Kopt=((0.5*rho*pi(Radio^5)*Cp_max)/(lambda_opt^3));
%% Torque and speed inputs

Temm=Torque/N;                                      
wmm=wt*(50/2/pi)*N;
sss=(1500-wmm)/1500; 

%% Grid side converter

Cbus=80e-3;                                                
Cg=20e-6;                                                     
Lg=400e-6;                                                   
Kpg=1/(1.5*Vs*sqrt(2/3));
Kqg=-Kpg;

%% Mechanical Inputs
Theta=20;
Speed=1500;

Caused by:

• Error: Incorrect use of '=' operator. To assign a value to a variable, use '='. To compare values for equality, use '=='.

[MANSOOR SOOMRO]

plz help me in resolving the error.

[John D'Errico]

You cannot name a variable Rr' or Lr'. The resulution? Don't try to use that variable name. Pick some legal variable name.

What more resolution do you think you need?

[MANSOOR SOOMRO]

Thanks John for your prompt response.

I find this problem now.

% Parametrs for DFIG with SMC

f=50;

Ps=2e6;

n=1500;

Vs=690;

Is=1760;

Tem=12732;

Vr=2070;

p=2;

u=1/3;

smax=1/3;

Vr_stator=(Vr*smax)*u;

Rs=2.6e-3;

Ls=2.587e-3;

Rr=26.1e-3;

Lr=2.587e-3;

Lm=2.51e-3;

Rm=1.0805e6;

Vbus=Vr_stator*sqrt(2);

sigma=(1-Lm^2)/(Ls*Lr);

Vs=690*sqrt(2/3);

ws=f*2*pi;

J=127/2;

D=1e-3;

fsw=4e3;

Ts=1/fsw/50;

F=0.058;

%% Maximum and Minimum wind speeds

wt_nom=18;

wt_min=9;

%% Three Blade wind turbine model

N=100;

Radio=42;

rho=1.225;

%% Cp and Ct curves

beta=0;

ind2=1;

%% Kopt for MPPT

Cp_max=0.44;

lambda_opt=7.2;

Kopt=((0.5*rho*pi(Radio^5)*Cp_max)/(lambda_opt^3));

%% Grid side converter

Cbus=80e-3;

Cg=20e-6;

Lg=400e-6;

Kpg=1/(1.5*Vs*sqrt(2/3));

Kqg=-Kpg;

Caused by:

• Too many input arguments.

[John D'Errico]

What can I say? You need to learn to use MATLAB. You need to write your code a bit more carefully.

And when you get an error, read the ENTIRE error message. If you ask a question on answers, report the ENTIRE ERROR MESSAGE. Thus EVERYTHING IN RED.

Here, for example, you got the error message:

Error using pi
Too many input arguments. 

That should give you the hint that maybe you are using pi improperly. So now, look at your code. READ THE CODE YOU WROTE! I see this line:

ws=f*2*pi;

There, pi clearly has no arguments. So look further.

Kopt=((0.5*rho*pi(Radio^5)*Cp_max)/(lambda_opt^3));

We see pi here. Now, you need to understand that MATLAB does not allow implicit multiplication. It does not understand that when you write the expression

pi(radio^5)

that your intention is to write the PRODUCT of pi and the value radio^5.

MATLAB cannot read your mind to infer that. Instead, it ssumes that pi is a function or a vector or array. What is pi?

exist('pi')
ans =
     5

In turn, this tells us that pi is an existing MATLAB function. In fact, pi is a function that accepts NO input arguments.

Now, what did you do? You effectively tried to execute the FUNCTION pi, passing in the argument radio^5. That is how MATLAB sees it. So you effectively called the function pi with an input argument.

Error using pi
Too many input arguments. 

Yes, you just forgot to put in a * there to denote multiplication. MATLAB assumes you know what you are doing, at least until it becomes clear that MATLAB has no idea what you are telling it to do. Then it throws out an error.

The error message told you what you needed to know. You had to read the ENTIRE error message, and think about what the message told you.

[Azariah Seblu]

Thank you @John D'Errico for the excellent, detailed response. You are very good with MATLAB! Hope to see you around the forum in the future!

Answer 1

[Walter Roberson]

Rr'=26.1e-3;                      

Apostrophe cannot be part of a variable name in MATLAB Function Block or Callbacks.

[MANSOOR SOOMRO]

thanks walter for your response.

Answer 2

[John D'Errico]

A simple rule in MATLAB: You cannot assign a result to a result.

What is Rr' then? This is the conjugate transpose of the array or vector Rr. MATLAB does not truly care that Rr is apparently a scalar.

Rr'=26.1e-3;                      
Lr'=2.587e-3;                     

My guess is you wanted to name a variable like that. Sorry, but Rr' is not a valid variable name. So, what error arises? MATLAB thinks the left hand side is the conjugate transpose of something called Rr, that is, it sees the result of an operation. Therefore, it thinks you may want to compare the two results for equality, thus the error message.

[MANSOOR SOOMRO]

thanks John for the explanation.