switching problem in circuit

Question

Hello,

I am simulating an ANPC inverter Modell. But an error occurs, said "Inconsistent source conditions after switching.", shown in the photo. It is interesting when I tried to reduce the switching frequency to 500Hz, the circuit works well. Or when I keep the switching frequency to 1000Hz, but change the amplitude from 1 to 0.99, the circuit works too. So what is the exact error for this circuit?Since I must set the switching frequency to more than 10kHz and amplitude firstly keeps 1 for a bench test, what should I do to make this circuit work?

Thanks for your help and the model is attached.

Best regards

Joy

Answer 1

Your modulator has a condition where there is a short circuit across the DC source.  You can place a small resistor in series with the lower DC source to suppress the error message and then observe the source current spiking at 0.015 seconds (and periodically after that).

The issue relates to the with the ">" vs the ">=" in your modulator for the neutral-connected switches. That's why it occurs only when your modulation index is exactly 1 - the carrier and the reference waveform are both exactly equal and your neutral-connected switches briefly toggle.  I didn't review the full modulation scheme, which you should do, but for the particular error message the highlighted component is the culprit (set to ">" from ">=".