Output Fluctuation at Output of Multiple Connected Converters

I am using the Simscape Electrical Specialized Power System to create a model of a grid-connected PV and battery system based on some schematic diagram provided to me. The problem is that the output current of the battery has very large fluctuations. Can anybody help me to troubleshoot this? Thank you!

Answer 1

[Joel Van Sickel]

The primary issue with your model is that the step size is too large. You have multiple PWM generators generating 10kHz switching signals. Since you are using a fixed step, you need to make your fixed step size at least 1/100 of your switching frequency. This means you need to set your powergui step size to 1 us and your simulink configuration step size to 1us. This will likely slow your model down by a factor of 50. Since it looks like you want to simulate for 100 seconds, this will be an incredibly slow simulation. I see that you are already using a VSC for the inverter. You should use the built in converters to make all of your power electronics average mode and remove all of the PWM generators so that you can have a faster simulation. You can always add the PWM back in later if you want a higher fidelity simulation.

[John Carlo Perion]

Thank you for your response. I will try your suggestion.

I originally plan to use average mode for the converters. However, I do not know how to implement the same controller (one is driven with a duty cycle while the other has zero duty cycle) for the bidirectional converter. If I can learn how to implement that, I will be using the average mode for both converters.