Good afternoon. I’m having a really hard time trying to simulate a 3-level grid-connected NPC inverter. It’s giving me this cyclic behavior during switching error, and I have no idea how to solve it. I’ve tried everything but nothing has worked. I’m using the 3-level NPC leg module, the symmetrical PWM and the 3-level modulator blocks.
Hi Paulo, Without a model this will be difficult to debug. One can only provide generic advice, per this link. There are several NPC models in the PLECS demo model library. Please post your model for more specific suggestions.
Inversor - NPC.plecs (244.8 KB)
I think I’ve solved that problem, but then others appear. Like, the line voltage of the 3-level converter shouldn’t be like this, right? And the output current completely destabilizes when I increase the DC bus voltage by 10%.
Like, the line voltage of the 3-level converter shouldn’t be like this, right?
What kind of waveform are you expecting? Looking at the line-to-line voltage there’s 5-levels… In the future please post a graphic.
And the output current completely destabilizes when I increase the DC bus voltage by 10%.
You’ll notice even before the step change in Vdc_ref, the DC voltages start to diverge. The neutral point voltage is not correctly balanced. Also there is a possibility for instability in LCL output filters if there is not sufficient active or passive damping. These are conventional control challenges that PLECS is well suited to help you analyze!