May 25, 2020 - 03:06 PM
It seems like the ON resistance of both your IGBTs and reverse diodes are below the default threshold where the EMTDC calculation engine will model them as ideal branches. Depending on the gate signal of the IGBT when the simulation starts the small loop of ideal branches can cause some confusion for the algorithm and lead to this error. As a solution you can either a) increase the ON resistance of the IGBT or reverse diodes above 0.0005 Ohms, b) Change the level where EMTDC will treat a branch as ideal (Project Settings -> Simulation ->Network Solution Accuracy -> Use ideal branches for resistances under XXXX Ohms), or c) Disable ideal branches.
You can find more information under the help documentation by searching for “Use Ideal Branches for Resistances Under” or “Ideal branches”