id summary reporter owner description type status priority milestone component version resolution keywords cc 4535 Structural singularity related to electric ground placement Pierre Haessig Lennart Ochel "I've been trying to model three phase inverters (AC-DC converters, similar to the MSL example Modelica.Electrical.PowerConverters.Examples.DCAC.MultiPhaseTwoLevel.MultiPhaseTwoLevel_RL, but using discrete MSL Electrical.Analog and Electrical.Ideal components). I've been hit by Symbolic Warning that some equation sub-system is '''structurally or numerically singular''', and indeed the simulation fails at time 0.0 (unable to solve linear system). I've created a minimal example to reproduce the issue (cf. QuickRInverterSingle.mo file). It has the topology of a single phase inverter, but using resistors instead of switches (to remove any source of error coming from non linear elements). The key aspect is that the AC side is made of '''two inductors with the ground connected between the two'''. This may looks weird, but this mimics the typical three-phase case when the ground is connected to the neutral point. This means that some state variables (inductor currents) are algebraically coupled. Simulation of this model fails, unless the ground is placed somewhere else. Maybe I'm missing something, but I believe that the system should have a solution no matter the placement of the ground. I'm using OpenModelica 1.12.0~dev.alpha1 on Debian stretch." defect new high Future Backend v1.12.0 Patrick Täuber Volker Waurich