Unexpected output from to_mpc()

[lefang16]

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Reproducible Example

import pandapower as pp
import pandapower.networks as pn
net=pn.case118()
pp.runpp(net)  # added 
pp.converter.to_mpc(net=net, filename="case118.mat")

Issue Description and Traceback

The produced .mat matrix contains more columns (zeros) than the standard mpc format case for bus, etc., the bus should have 13 columns for the version 2 matpower case.

Expected Behavior

should output a standard matpower case

Installed Versions

python : 3.9.20.final.0
python-bits : 64
OS : Darwin
OS-release : 24.1.0
pandas : 2.2.2
numpy : 1.26.4
pytz : 2024.1
dateutil : 2.9.0.post0
setuptools : 75.1.0
pip : 24.2
Cython : None
pytest : 8.3.3
IPython : 8.18.1
bottleneck : 1.3.7
matplotlib : 3.9.2
numba : 0.60.0
numexpr : 2.8.7
scipy : 1.13.1

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