Re: How can I fix the error that produces this peak in Bode plot?

On Wed, Oct 14, 2020 at 7:02 AM Beginner1 via Help-octave <
[email protected]> wrote:

> Hi,
> I am plotting a Bode diagram of a simple resonant control function for a RL
> load and there is a 'sharp peak' around the target frequency on both the
> magnitude and the phase diagrams. This sharp peak should not appear and
> without it, the bode plot would be correct. Could you please give me an
> intuition on where the problem is? I know that it has nothing to do with
> the kp_1 and ki_1 parameters, since this peak appears for the complete
> range
> of them. I think there is something wrong on how Matlab treats some
> integrators but I am not sure. Here is my code:
>
>  Ub=400/sqrt(3);
> Ib=3.3;%
> w_b=2*pi*50;
> Zbase=(Ub)^2/(sqrt(3)*Ub*Ib);
> Lbase=Zbase/w_b;
> Td=0.00015;
> Rf=0.1;
> Lf=0.0018;
> R=Rf/Zbase;
> L=Lf/Lbase;
> w=2*pi*50;
> kp_1=2*pi*1000*Lf;
> ki_1=(Rf/Lf)*kp_1;
> s=tf('s');
> G_pwm=(1-(Td/2)*s)/(1+(Td/2)*s);
>  G_i_1=kp_1+ki_1*s/(s^2+w^2);
> sys_1_vd=(G_i_1*G_pwm)^2/((L*s+R+G_i_1*G_pwm)*(G_i_1*G_pwm+L*s+R-(1-G_i_1)*G_pwm));
>
> bode(sys_1_vd,'r');
> grid on;
> <https://octave.1599824.n4.nabble.com/file/t372684/Bode2.jpg>
>
>
>
>
> --
> Sent from:
> https://octave.1599824.n4.nabble.com/Octave-General-f1599825.html
>
>
> First ---->  this is not a matlab group.

second :
   did you know that you have a zero at +13333.33?
use the rlocus(sys) command to see.


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