Bug fix: simplify_network.py (simplify_links) - By adding preceding converter removal

doc/release_notes.rst

@@ -78,6 +78,8 @@ Upcoming Release
 
 * Bugfix: demand for ammonia was double-counted at current/near-term planning horizons when ``sector['ammonia']`` was set to ``True``.
 
+* Bugfix: Bug when multiple DC links are connected to the same DC bus and the DC bus is connected to an AC bus via converter. In this case, the DC links were wrongly simplified, completely dropping the shared DC bus. Bug fixed by adding preceding converter removal. Other functionalities are not impacted.
+
 PyPSA-Eur 0.13.0 (13th September 2024)
 ======================================
 

scripts/simplify_network.py

@@ -374,6 +374,44 @@ def find_closest_bus(n, x, y, tol=2000):
         return None
 
 
+def remove_converters(n: pypsa.Network) -> pypsa.Network:
+    """
+    Remove all converters from the network and remap all buses that were originally connected to the
+    converter to the connected AC bus. Preparation step before simplifying links.
+
+    Parameters:
+        n (pypsa.Network): The network object.
+
+    Returns:
+        n (pypsa.Network): The network object with all converters removed.
+    """
+    # Extract converters
+    converters = n.links.query("carrier == ''")[["bus0", "bus1"]]
+    converters["bus0_carrier"] = converters["bus0"].map(n.buses.carrier)
+    converters["bus1_carrier"] = converters["bus1"].map(n.buses.carrier)
+
+    converters["ac_bus"] = converters.apply(
+        lambda x: x["bus1"] if x["bus1_carrier"] == "AC" else x["bus0"], axis=1
+    )
+
+    converters["dc_bus"] = converters.apply(
+        lambda x: x["bus1"] if x["bus1_carrier"] == "DC" else x["bus0"], axis=1
+    )
+
+    # Dictionary for remapping
+    dict_dc_to_ac = dict(zip(converters["dc_bus"], converters["ac_bus"]))
+
+    # Remap all buses that were originally connected to the converter to the connected AC bus
+    n.links["bus0"] = n.links["bus0"].replace(dict_dc_to_ac)
+    n.links["bus1"] = n.links["bus1"].replace(dict_dc_to_ac)
+
+    # Remove all converters from network.links and associated dc buses from network.buses
+    n.links = n.links.loc[~n.links.index.isin(converters.index)]
+    n.buses = n.buses.loc[~n.buses.index.isin(converters["dc_bus"])]
+
+    return n
+
+
 if __name__ == "__main__":
     if "snakemake" not in globals():
         from _helpers import mock_snakemake
@@ -391,6 +429,8 @@ def find_closest_bus(n, x, y, tol=2000):
     linetype_380 = snakemake.config["lines"]["types"][380]
     n, trafo_map = simplify_network_to_380(n, linetype_380)
 
+    n = remove_converters(n)
+
     n, simplify_links_map = simplify_links(n, params.p_max_pu)
 
     busmaps = [trafo_map, simplify_links_map]