I am building a model of a solar power system. In it, I connect a string of solar cells to a buck-boost converter. I use Simulink and Simscape Electrical to perform simulations. I am encountering an oscillation issue limited to a certain range of duty cycles.
By examining the oscillation closer, I can see that it has a frequency of about 125 kHz. However, I cannot see why the oscillation would be there in the first place. Looking at the input voltage trace, it can also be seen that it seems to be "capped" at a certain value.
I cannot explain why this happens; especially confusing is the fact that it only appears for a small range of duty cycles. For example, a duty cycle of 10% once again produces a clean trace. Therefore, I suspect that the model of the solar cells is at fault here. At the same time, it is extremely simple and does not include any parasitics.
What could be the cause of this oscillation? Is it a consequence of the simulation environment, or should I expect similar behavior in a real circuit?
I would appreciate any advice.