Adding vectorgroup dynyn to 3w-transformer

[nis-bucr]

Problem

The vectorgroup Dynyn was currently not supported for shortcircuit calculations of three winding transformers

Fix

Added the vectorgroup. Also fixed bug with vectorgroup Ynyy.

[vogt31337]

@nis-bucr thanks for this patch. Could you by any chance update the changelog?

[codecov]

Codecov Report

Attention: Patch coverage is 22.22222% with 7 lines in your changes missing coverage. Please review.

Project coverage is 76.45%. Comparing base (2698f7e) to head (dabe912).
Report is 114 commits behind head on develop.

Files with missing lines	Patch %	Lines
pandapower/pd2ppc_zero.py	22.22%	7 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2283      +/-   ##
===========================================
- Coverage    76.47%   76.45%   -0.02%     
===========================================
  Files          281      281              
  Lines        32580    32587       +7     
===========================================
  Hits         24915    24915              
- Misses        7665     7672       +7     

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[nis-bucr]

@vogt31337 Thank you for the review. I added the changelog message to upcoming release, hope this is correct.

[vogt31337]

@nis-bucr thanks for updating. CodeCov reported that there is no test covering your changes/additions. Could you by any chance add a simple test for your dynyn 3w transformer?

[nis-bucr]

@vogt31337 I added a test to test_1ph.py for the dynyn vectorgroup. Could you please verify the values with your commercial calculating tool used for the other vectorgroups?

[vogt31337]

@nis-bucr, thanks for updating!
@pawellytaev, could you verify this calculation with PF?