You can't write equations like that. It would basically be translated to either assigning to Voc_real or not assigning to anything, which means this if-equation is 0 or 1 scalar equations and the equation count will not work.

It sounds more like you want to use when/reinit or limiting Voc_real when it is calculated or you need to introduce some additional variable.

tmp = ... // What calculated Voc_real before

Voc_real = if ... then tmp else iVoc_real

This is my full code.
How do i change it?


Isc_real =  Isc * (G_real / Gstc) * (1 + (Ki * (T_real - Tstc)));  // eqn 2.27
   
IL =  Isc_real + ((Isc_real * Rs) / Rsh_real);  //eqn 2.29
   Voc_real =  Voc * (1 + Kv * (T_real - Tstc)) + ns * Vt * log(G_real / Gstc); //eqn 2.30

     for count1 in 1:maxlim2 loop
          iVoc_real =  Wcor * Voc_real + (1 - Wcor) * (ns * Vt * log((IL * Rsh_real - Voc_real) / (I0 * Rsh_real)) * (1 + Kv * (T_real - Tstc)));

         if  G_real < 0.001 then
           Voc_real =  0;
         else

             if  abs((iVoc_real - Voc_real) / Voc_real) < accuracy then
              Voc_real =  iVoc_real;
             else
         end if;
       end if;
    end for;

Rewrite your code to an algorithm-section (eqn 2.30 and the for-loop as an algorithm calculating Voc_real and iVoc_real). You are writing to the same scalar variable multiple times in a for-loop which will cause problems further down the line. Modelica enforces single-assignment for equations...

I am using dymola and i still dont understand what you mean. Do i need to include a function in this model?

http://www.ida.liu.se/~mohto/OO_Modelic … ctions.pdf

ok. thanx. but this is a Model that I am making. How do i include an algorithm in this? can you show an example?

model Photovoltaic
extends SinglePhase.Interfaces.OnePortGrounded;

  import Modelica.ComplexMath.'abs';
parameter Real Gstc = 1000;
    parameter Integer maxlim2= 1000;
    parameter Integer matrixsize = 10000;
    parameter Real Impp_real, Pout_max, iVoc_real, Tstc=298,iIr, Vr, Ir;
    parameter Integer   count2, count3;
    parameter Integer  Vout_GranTurismo[:] = zeros( matrixsize);
    parameter Integer   Iout_GranTurismo[:] = zeros( matrixsize);
    parameter Integer Pout_GranTurismo[:] = zeros(matrixsize);
    input Real  Ki, Kv,  T_real;
    input Integer G_real;

equation

     if  G_real == 0 then   //to avoid division by 0
     Rsh_real =  100000000000000;   //close to infinite
   else
     Rsh_real =  Rsh * (Gstc / G_real); //eqn 2.28
     end if;

   Isc_real =  Isc * (G_real / Gstc) * (1 + (Ki * (T_real - Tstc))); // eqn 2.27
   IL =  Isc_real + ((Isc_real * Rs) / Rsh_real); //eqn 2.29
   Voc_real= Voc * (1 + Kv * (T_real - Tstc)) + ns * Vt * log(G_real / Gstc); //eqn 2.30

     for count1 in 1:maxlim2 loop
          iVoc_real=     Wcor * Voc_real + (1 - Wcor) * (ns * Vt * log((IL * Rsh_real - Voc_real) / (I0 * Rsh_real)) * (1 + Kv * (T_real - Tstc)));
         if G_real < 0.001 then
           Voc_real =   0;
         else

             if  abs((iVoc_real - Voc_real) / Voc_real) < accuracy then
              Voc_real =     iVoc_real;
             else
         end if;

         end if;

    end for;
   I0_GranTurismo =  (Isc_real - (Voc_real - Isc_real * Rs) / Rsh_real) * exp(-Voc_real / (ns * Vt)); //eqn 2.23
   Ir =  Isc_real;

     count2 =  0;
       for Vr in 0:Voc_real / (matrixsize - 1):Voc_real loop
              count3 =  1;
              count2 =  count2 + 1;
          for count3 in 1:maxlim2 loop
       iIr =  Wcor * Ir + (1 - Wcor) * (IL -  I0_GranTurismo * (exp((Vr + Ir * Rs) / (ns * Vt)) - 1) - (Vr + Ir * Rs) / Rsh_real);

       if  abs(iIr - Ir) < accuracy then
        Iout_GranTurismo[count2] =  iIr;
        else

       end if;

       Ir =  iIr;
       Iout_GranTurismo[count2] =  iIr;
      count3 =  count3+1; //counter to limit number of iterations
     end for;

     Vout_GranTurismo[count2] =  Vr;
   end for;
   Pout_max =  0;

       if  G_real < 0.0001 then
        Vmpp_GranTurismo =  0;
        Impp_real =  0;
      else
        for count4 in 1:count2 loop
          Pout_GranTurismo[count4] =  Vout_GranTurismo[count4] * Iout_GranTurismo[count4];
          if  Pout_GranTurismo[count4] > Pout_max then
            Vmpp_GranTurismo =  Vout_GranTurismo[count4];
            Impp_real =  Iout_GranTurismo[count4];
            else
          end if;
        end for;
       end if;

end Photovoltaic;

Unable to expand if-statement:
if (firstOrder.y > 0.0001 and Throttle > 0.01 and currentGear < floor( upshiftTable.y[1])) then
shiftBegin = (if GearNumber < floor(upshiftTable.y[1]) then true else false);
shiftEnd = (if GearNumber < floor(upshiftTable.y[1]) then false else (if GearNumber == floor(upshiftTable.y[1]) then true else false));
elseif (firstOrder.y < -0.0001 or currentGear > floor(downshiftTable.y[1])) then
shiftBegin = (if GearNumber > floor(downshiftTable.y[1]) then true else false);
shiftEnd = (if GearNumber > floor(downshiftTable.y[1]) then false else (if GearNumber == floor(downshiftTable.y[1]) then true else false));
else
// No equations
end if;

Not able to rectify the problem. please help me