SImulation termination for SiC-base converter in simscape electriacal

I tried to use SIC MOSFET devices to build DAB converter, but it was difficult to converge. The model of the device I am using is CAS30012BM2 of Wolfspeed. Compared to ordinary MOSFETs, the characteristic is that the parasitic capacitance is very large. I cannot find a suitable solver configurtation to achieve stable operation. Even if I use discrete and open the local solver to run for a while, an error will be reported, and the waveform of the system will also be distorted. The reason why I think it is related to parasitic capacitance is because I can simulate correctly using the built-in MOSFET in Matlab under the default configuration of the solver. So I wonder how to set this simulation condition, because this circuit is not actually complicated. (I used the MATLAB version as 2020a). Thank you very much.

Answer 1

[Vishwa Uttam]

Hi Zhenyu,

I believe the model is working as expected. I used a global solver (ode23t) instead of a local solver. with a maximum time step of 1e-6 sec.

Below are a few suggestions that can help you increase simulation performance:

1. The allowed simulation time is insufficient for the converter to reach steady state. You can increase the simulation stop time to observe the steady-state waveforms.
2. Add DC blocking capacitance in series to avoid DC current flowing into the transformer windings.
3. Consider using MOSFET (Ideal, Switching) library blocks instead of high-fidelity N-Channel MOSFETs. This modification will help you avoid solver inconsistencies and make your simulation run faster.
4. Higher junction capacitance of the switch may require a larger dead time to transition from the on state to the off state reliably. Monitor the switching transitions to assess if more dead time is needed or not.

I hope you find the above information helpful.

Vishwa