fix: restore correct assigned countries for virtual tyndp nodes (#794)

* fix: restore correct assigned countries for virtual tyndp nodes in base_network.py

* doc: add release note

* feat: generalise adding virtual nodes in build_tyndp_network.py

* doc: clarify docstring

Author: daniel-rdt

doc/release_notes.md

@@ -41,6 +41,8 @@
 
 * Extend `tyndp-archive` support to integrate three new datasets (`desnz_electricity_consumption`, `jrc_energy_atlas`, `ons_lad`) and two new versions (`nitrogen_statistics`, `synthetic_electricity_demand`) ([#758](https://github.com/open-energy-transition/open-tyndp/pull/758)).
 
+* Restore correct assigned countries for virtual TYNDP nodes ([#794](https://github.com/open-energy-transition/open-tyndp/pull/794)).
+
 
 **Documentation**
 

scripts/base_network.py

@@ -42,6 +42,7 @@
     get_snapshots,
     set_scenario_config,
 )
+from scripts.build_tyndp_network import AC_VIRTUAL_NODES_IT
 
 PD_GE_2_2 = parse(pd.__version__) >= Version("2.2")
 
@@ -560,6 +561,25 @@ def prefer_voltage(x, which):
     return buses
 
 
+def _restore_virtual_node_countries_tyndp(
+    n: pypsa.Network, buses: pd.DataFrame
+) -> None:
+    """
+    Restore the declared country of TYNDP virtual nodes instead of coordinate-based country assignment
+    from `_set_countries_and_substations`.
+
+    Parameters
+    ----------
+    n : pypsa.Network
+        Network whose `buses` country assignment is corrected in place.
+    buses : pd.DataFrame
+        Buses as loaded in `_load_buses`, holding the countries declared in
+        build_tyndp_network before the coordinate-based reassignment.
+    """
+    nodes = n.buses.index.intersection(AC_VIRTUAL_NODES_IT)
+    n.buses.loc[nodes, "country"] = buses.loc[nodes, "country"]
+
+
 def _replace_b2b_converter_at_country_border_by_link(n):
     # Affects only the B2B converter in Lithuania at the Polish border at the moment
     buscntry = n.buses.country
@@ -752,6 +772,8 @@ def base_network(
 
     _set_countries_and_substations(n, config, country_shapes, offshore_shapes)
 
+    _restore_virtual_node_countries_tyndp(n, buses)
+
     _set_links_underwater_fraction(n, offshore_shapes)
 
     _replace_b2b_converter_at_country_border_by_link(n)

scripts/build_tyndp_network.py

@@ -78,6 +78,11 @@
     "UK": "GB",
 }
 
+AC_VIRTUAL_NODES_IT = {
+    "ITCO": "FR15",
+    "ITVI": "ITSI",
+}
+
 IBFI_COORD = (63.0, 25.0)
 
 
@@ -223,6 +228,41 @@ def build_shapes(
     return bidding_shapes, country_shapes
 
 
+def _add_virtual_node(
+    target_gdf: gpd.GeoDataFrame,
+    new_bus: str,
+    ref_bus: str,
+    source_gdf: gpd.GeoDataFrame | None = None,
+    **overrides,
+) -> None:
+    """
+    Add a virtual node to target Dataframe as a copy of an existing reference bus.
+
+    The virtual node inherits every attribute of the reference bus and takes its
+    own name as ``station_id`` and ``tags``. Any remaining attribute is set
+    through ``overrides``.
+
+    Parameters
+    ----------
+    target_gdf : gpd.GeoDataFrame
+        Bus GeoDataFrame the virtual node is appended to, modified in place.
+    new_bus : str
+        Name of the virtual node.
+    ref_bus : str
+        Name of the reference bus whose attributes are copied.
+    source_gdf : gpd.GeoDataFrame, optional
+        Bus GeoDataFrame holding the reference bus. Defaults to None in which case ``target_gdf`` is used.
+    **overrides, optional
+        Attribute values overriding those inherited from the reference bus.
+    """
+    source_gdf = target_gdf if source_gdf is None else source_gdf
+    target_gdf.loc[new_bus] = (
+        source_gdf.loc[[ref_bus]]
+        .assign(station_id=new_bus, tags=new_bus, **overrides)
+        .loc[ref_bus]
+    )
+
+
 def build_buses(
     buses_fn: str,
     countries: list[str],
@@ -281,14 +321,10 @@ def build_buses(
 
     # Manually add Italian virtual nodes  # TODO Refine assumptions
     if "IT" in countries:
-        buses.loc["ITCO"] = (
-            buses.loc[["FR15"]]
-            .assign(station_id="ITCO", country="IT", tags="ITCO")
-            .loc["FR15"]
-        )
-        buses.loc["ITVI"] = (
-            buses.loc[["ITSI"]].assign(station_id="ITVI", tags="ITVI").loc["ITSI"]
-        )
+        for node, location in AC_VIRTUAL_NODES_IT.items():
+            _add_virtual_node(
+                target_gdf=buses, new_bus=node, ref_bus=location, country="IT"
+            )
 
     buses_h2 = (
         country_shapes[["node", "x", "y"]]
@@ -309,23 +345,23 @@ def build_buses(
 
     # Manually add IBIT and IBFI nodes  # TODO Refine assumptions
     if "IT" in countries:
-        buses_h2.loc["IBIT H2"] = (
-            buses.loc[["ITN1"]]
-            .assign(station_id="IBIT H2", voltage=None, dc="f", tags="IBIT H2")
-            .loc["ITN1"]
+        _add_virtual_node(
+            target_gdf=buses_h2,
+            new_bus="IBIT H2",
+            ref_bus="ITN1",
+            source_gdf=buses,
+            voltage=None,
+            dc="f",
         )
     if "FI" in countries:
         ibfi_lat, ibfi_long = IBFI_COORD
-        buses_h2.loc["IBFI H2"] = (
-            buses_h2.loc[["FI H2"]]
-            .assign(
-                station_id="IBFI H2",
-                tags="IBFI H2",
-                x=ibfi_long,
-                y=ibfi_lat,
-                geometry=Point(ibfi_long, ibfi_lat),
-            )
-            .loc["FI H2"]
+        _add_virtual_node(
+            target_gdf=buses_h2,
+            new_bus="IBFI H2",
+            ref_bus="FI H2",
+            x=ibfi_long,
+            y=ibfi_lat,
+            geometry=Point(ibfi_long, ibfi_lat),
         )
 
     return buses, buses_h2