u/MindNo8679

Hello, I'm hoping someone can help me troubleshoot an issue I'm seeing while trying to solve a case in TARA.

I'm using a large power flow model that includes topology for all transmission buses, generators, loads, lines, etc. in the Western Interconnection (its a WECC base case model). I have this model as a .sav and .raw format. The .sav format solves easy in the PSS/E, no issue. The .raw file cannot converge in TARA. I've tried solving the .sav model in PSSE then converting it to .raw format, then trying it in TARA, but still same issue. This makes me think that something with TARA's solution parameters are creating the problem (or not accurately resolving it while the case is being solved).

TARA is saying there is a voltage control/convergence issue. There are 100+ switched shunts oscillating and hunting for their voltage target, but never able to reach them. I've tried solving the solution by disabling TAP adjustments and Shunt adjustments, but still seeing non-convergence. Further digging in, I believe that two of the buses effecting this voltage mismatch may be two 3-winding transformers, but I'm stuck on how to proceed from here.

I'm still pretty new to power flow solution parameters and troubleshooting, so any tips on what to try next would be greatly appreciated! Reason why I need TARA to solve the case as I'm using PowerGEMS tools to run Prop TrLim studies with these models. Thank you for any help that can be provided!

EDIT: Thank you to everyone that commented and provided your thoughts and suggestions! This is an awesome community. I found the issue and was able to solve the case in TARA. There were two, 3-winding transformers where one of the 3 windings' resistance value was too high. My thought process is that this high resistance caused a large MW loss which then resulted in large current flow and then voltage drop. Those voltage control devices tried to compensate but were not able to settle on a voltage (someone please correct me if my assumption is wrong here).