create a bus for every unique coordinate, not only substations (closes #699)

rules/postprocess.smk

@@ -45,7 +45,7 @@ if config["foresight"] != "perfect":
             (
                 LOGS
                 + "plot_power_network/elec_s{simpl}_{clusters}_l{ll}_{opts}_{sector_opts}_{planning_horizons}.log"
-            )
+            ),
         benchmark:
             (
                 BENCHMARKS
@@ -74,7 +74,7 @@ if config["foresight"] != "perfect":
             (
                 LOGS
                 + "plot_hydrogen_network/elec_s{simpl}_{clusters}_l{ll}_{opts}_{sector_opts}_{planning_horizons}.log"
-            )
+            ),
         benchmark:
             (
                 BENCHMARKS
@@ -102,7 +102,7 @@ if config["foresight"] != "perfect":
             (
                 LOGS
                 + "plot_gas_network/elec_s{simpl}_{clusters}_l{ll}_{opts}_{sector_opts}_{planning_horizons}.log"
-            )
+            ),
         benchmark:
             (
                 BENCHMARKS

scripts/base_network.py

@@ -555,6 +555,7 @@ def _set_countries_and_substations(n, config, country_shapes, offshore_shapes):
     for b, df in product(("bus0", "bus1"), (n.lines, n.links)):
         has_connections_b |= ~df.groupby(b).under_construction.min()
 
+    buses["onshore_bus"] = onshore_b
     buses["substation_lv"] = (
         lv_b & onshore_b & (~buses["under_construction"]) & has_connections_b
     )

scripts/build_bus_regions.py

@@ -135,7 +135,13 @@ if __name__ == "__main__":
         c_b = n.buses.country == country
 
         onshore_shape = country_shapes[country]
-        onshore_locs = n.buses.loc[c_b & n.buses.substation_lv, ["x", "y"]]
+        onshore_locs = (
+            n.buses.loc[c_b & n.buses.onshore_bus]
+            .sort_values(
+                by="substation_lv", ascending=False
+            )  # preference for substations
+            .drop_duplicates(subset=["x", "y"], keep="first")[["x", "y"]]
+        )
         onshore_regions.append(
             gpd.GeoDataFrame(
                 {

scripts/simplify_network.py

@@ -611,6 +611,7 @@ if __name__ == "__main__":
         "symbol",
         "tags",
         "under_construction",
+        "onshore_bus",
         "substation_lv",
         "substation_off",
         "geometry",