Why the simulation of the half bridge inverter doesn't finish in reasonable time?

Question

Hello,

I have attempted to made a simulation of the current control loop of the half bridge inverter (please see the attachment). In case I start the simulation it doesn't finish in reasonable time (five minutes). I have noticed that in case I break the control loop i.e. the duty cycle is set to fix value the simulation offers correct outcomes. Please can you tell me how to get the control loop simulation up and running? Thanks in advance.

Answer 1

You disabled the solver's "Max. number of consecutive zero-crossings" limit, likely because you were getting an error message. The error message is pointing to the fact that your PI output is changing faster than your carrier wave, leading to multiple comparator events per period. The result is an effective switching frequency much higher than you intended (100's of GHz).  Disabling the zero-crossing limit simply masks the underlying issue and results in the long simulation times.

The solution is to fix the control scheme with an appropriately tuned PI controller.  You can also insert a zero-order hold before the modulator to prevent multiple comparator events per period, but you will see the general control issue still remains, with the PI output toggling between the high and low limits.

Comments

Bryan Lieblick thank you for your response. Do I understand correctly your idea that the root cause of my problem is in inappropriate constants of the PI controller? In case I find correct values I can set the Max. number of consecutive zero-crossings to its original value and the simulation should work?

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Yes, exactly. In this particular case it's probably because you did not account for the voltage to duty cycle conversion, leading to much higher effective gains and more restrictive duty cycle limits than you are expecting...