feat(converter): import OpenDSS RegControl as a tap controller

CHANGELOG.rst

@@ -5,6 +5,7 @@ Change Log
 -------------------------------
 - [FIXED] restored ``OpenDSSDirect.py`` to the ``all``/``dev`` extras so the OpenDSS converter is exercised (and its coverage reported) in CI again; it was dropped in #3062 because installing it alongside ``pytest~=9.1`` crashed the pytest process on Windows. Root cause (see `dss-extensions/OpenDSSDirect.py#148 <https://github.com/dss-extensions/OpenDSSDirect.py/issues/148>`_): pytest enables Python's ``faulthandler`` by default, which intercepts a first-chance Windows structured exception that OpenDSSDirect.py's native backend raises -- and normally handles itself -- during import, and misreports it as fatal. Bracketing the import with ``faulthandler.disable()``/``.enable()`` avoids the false crash while leaving ``faulthandler`` protecting the rest of the test run; the converter now runs on Windows instead of merely skipping there.
 - [ADDED] OpenDSS converter: series (bus-to-bus) ``Reactor`` elements are now imported as a fixed-impedance ``line``, the pattern some feeder libraries (e.g. EPRI's Ckt5/Ckt7) use to model the substation's Thevenin-equivalent source impedance instead of a ``Transformer``.
+- [ADDED] OpenDSS converter: ``from_opendss`` imports a transformer's tap changer (``tap_pos``/``tap_min``/``tap_max``/``tap_step_percent``/``tap_neutral``) instead of baking the solved ratio into ``vn_hv_kv``/``vn_lv_kv``, and can import each ``RegControl`` as a ``DiscreteTapControl`` via the new ``import_controllers`` option (default False).
 
 [3.5.4] - 2026-07-08
 -------------------------------

doc/converter/opendss.rst

@@ -9,9 +9,15 @@ feeder into a **balanced (positive-sequence)** pandapower net. It reads the circ
 through ``OpenDSSDirect.py`` (an optional dependency, ``pip install pandapower[opendss]``),
 mapping buses, lines (with their LineCode carried through as ``std_type``),
 series (bus-to-bus) reactors (the pattern some feeder libraries use to model the
-substation's source impedance), two-winding transformers (at their solved tap),
+substation's source impedance), two-winding transformers (with their tap changer
+imported as an explicit ``tap_pos`` rather than baked into ``vn_hv_kv``/``vn_lv_kv``),
 center-tapped split-phase service transformers (collapsed to a two-winding
-equivalent), loads, shunt capacitors, switches and the source.
+equivalent), loads, shunt capacitors, switches and the source. With
+``import_controllers=True``, each ``RegControl`` is additionally imported as a
+``DiscreteTapControl``, so the tap responds to bus voltage during
+``pandapower.control.run_control`` instead of staying pinned at the OpenDSS
+operating point; line-drop compensation, reverse-mode regulation and time delays
+are not modeled and are reported as warnings when encountered.
 
 Positive-sequence is exact for symmetric (e.g. European 3-phase 4-wire) feeders and
 a documented approximation for unsymmetrical North-American topology (single-phase