Freewheeling diode causing error in Full-Bridge Inverter model

Hi, please see the attached Simulink model. Its a simple full-bridge inverter producing quasi-square alternating voltage at the load (resistor). The freewheeling diode, although it is standard in the design, is causing some numerical issue during simulation. The error stated is: "Derivative of state 'full_bridge.Diode.c1.vc' in block 'full_bridge/Diode' at time 0.000255 is not finite. The simulation will be stopped. There may be a singularity in the solution. If not, try reducing the step size (either by reducing the fixed step size or by tightening the error tolerances)".

I suspect the junction capacitance values of the diode is spiking at simulation initiation. Not sure why. Is there any obvious mistake that I am making?

Answer 1

[Sabin]

This model appears to be stiff and poses challenges to the solver. Running the model in fixed-step global solver is not the best way to simulate this model. If you want to simulate the model in fixed step it is better to enable Simscape local solver in the Solver Configuration block. Alternatively, you can run the model in continuous time variable step. Changing the parameterization may also help, for example by setting the diode junction capacitance to 0.