Dimitris "Jimi" Charalampidis

@ArtemGovorov 3 years later, maybe it's time to make this a priority.

LGTM. I checked your changes with mine also.

Just a friendly advice. Since this is a breaking change, if you are following [Semantic Versioning](https://semver.org/) the version number should be bumped to `2.0.0`.

From what I know, only file icon extensions and the client of the said extension, if that extension has a server service, are depending on the `language ids`. You may...

After some more code digging I believe the best way to resolve this is to add `"OPF_converged": False` in `create.py` after https://github.com/e2nIEE/pandapower/blob/v2.9.0/pandapower/create.py#L506

Not sure if it's necessary as the OP error was a `KeyError`, simply because the `OPF_converged` key was not in the dictionary. Adding it resolves all issues that may occur...

> it is added in line 56 of powerflow.py `_powerflow` in `powerflow.py` is not called if you run `runpp_3ph`. Instead `runpp_3ph` is called from `pf/runpp_3ph.py`. Also when the code-flow goes...

From my POV, if you add `OPF_converged` in `create.py` you can avoid blotting the code-base with initializing it in several places and it's set to `True` whenever it makes sense.

@elodin Issue has been fixed since 5c4c47561c059a8f7cf917f19959e3cd8e9ebd99 but I'm waiting for the release to close this issue. >During my testing, OPF_converged was initialized every time, because create_empty_network is always executed...

This fix has been released. Thanks.