As per my understanding, you are trying to maintain a constant DC bus voltage using closed loop voltage control. You are using the block "Thyristor Rectifier Voltage Controller (three phase)" for this purpose.
Upon investigating the simulink model attached by you, I found the model to be correct, but the PI controller performs well, only when you operate at discontinuous conduction mode. At continuous conduction mode, the performance of your PI controller is not good and therefore, you need to re-tune the parameters of PI controller. To demonstrate this, I provided a constant firing angle of (
) to the thyristor bridge. This roughly corresponds to the DC bus voltage of 243.7 V. I have used the below formulla to find this firing angle.
Below given are the waveforms captured on scope:
You can see that the results are as expected. (Note: the "I_out_ref" variable was set to value of 50 in the script).
As a next step, I simulated the system by re-tuning the gains of PI controller through some number of trial and errors.
Below given are the waveforms captured on scope.
You can see that the response is much improved as compared with the previous case and the waveforms are much closer to the expectations . Low frequency oscillation is witnessed in the inductor current, which is due to improper tuning of PI controller parameters. But, you can tune them in a proper way to achieve a better response.
I am attaching the modified "rectifier_setup.m" file with this answer.
I hope this answers your question !