Why am i getting the following error?

Hello!

im currently working on a Simscape alk electrolyzer project, I have the code below, and it is only coded for voltage for now.

component (Propagation = blocks) alk

nodes
    % Electrodes
    p = foundation.electrical.electrical; % +
    n = foundation.electrical.electrical; % -
end

parameters
    N_cell       = {12,    '1'     }; % Number of cells in stack
    area_cell    = {0.01,   'm^2'  }; % Cell area
    P_stack      = {7,     'bar'   };% 

end
% Parameter checks
equations
    assert(N_cell > 0)
    assert(area_cell > 0)
end

% Internal parameters
parameters (Access = protected)
    % Constants
    r1 = {7.3255e-1,    'V*m^2*A^-1'};
    r2 = {-4.6800e-6,    'V*K^-1*m^2*A^-1'};%'V*K^-1*m^2*A^-1
    d1 = {double(-7.3077e-1),    'V*m^2*A^-1'};
    d2 = {double(-1.8500e-5),    'V*bar^-1*m^2*A^-1'};
    s = {double(9.3603e-2),    'V'};
    t1 = {16.497,    'm^2*A^-1'};
    t2 = {-1.1318e4,    'K*m^2*A^-1'};
    t3 = {-1.9538e6,    'K^2*m^2*A^-1'};
    V_rev = {1.23,    'V'};
    uno = {1,    '1'};
    T_stack = {75,    'K'};
end

variables (ExternalAccess = observe)
    i = {0, 'A' }; % Current (positive in)
    v = {0, 'V' };
end

branches
    i : p.i -> n.i;
 
end

intermediates

    i_cell = if ge(i, 0), i/area_cell else 0 end; % Cell current density
    v_cell = V_rev + ((r2*T_stack + r1) + (d1 + d2*P_stack))*i_cell + s*log(((t1 + (t2/T_stack) + (t3/(T_stack)^2))*i_cell) + uno)  ; %V_rev + (((r1 + r2*T_stack)) + (d1 + d2*P_stack))*i_cell + s*log((t1 + (t2/T_stack) + (t3/(T_stack)^2))*i_cell + uno);

end

annotations
    [v, v_cell]                                             : LoggingUnit = 'V';
    i_cell                                                  : LoggingUnit = 'A/m^2';

end

equations
    % Stack voltage
    v == p.v - n.v; % Voltage
    v == N_cell * v_cell  ; 

end

end

This component is modeled with a solar charge profile.But when the simulation runs, this error is presented: "At time 18014.354000, one or more assertions are triggered. See causes for specific information.Argument of log must be positive". I really don't know where my mistake is, and i really dont know why i cant run this empirical model in simscape.

Thanks!!

Answer 1

[Sabin]

This error points out to the log function which is used to compute v_cell,i.e,

s*log(((t1 + (t2/T_stack) + (t3/(T_stack)^2))*i_cell) + uno)

It might be that the argument of log is getting to some small negative values. Probably best to double check if this can be the case with your parameterization. Also, you can try an add some mechanism to protect against negative values. The simulation seems to be running for 5 hours before it errors out. I hope this helps.