Improve pv power formula

We are using the new dfs, in the component graph, to search for pv power
components.
That fixes this formula in several graphs, especially nested graphs and
graphs with more then one grid meter.

Signed-off-by: Matthias Wende <[email protected]>

Author: matthias-wende-frequenz

src/frequenz/sdk/timeseries/_formula_engine/_formula_generators/_pv_power_formula.py

@@ -6,7 +6,6 @@
 from __future__ import annotations
 
 import logging
-from collections import abc
 
 from ....microgrid import connection_manager
 from ....microgrid.component import ComponentCategory, ComponentMetricId
@@ -33,14 +32,20 @@ def generate(self) -> FormulaEngine[Power]:
             "pv-power", ComponentMetricId.ACTIVE_POWER, Power.from_watts
         )
 
-        pv_components = self._get_pv_power_components()
+        component_graph = connection_manager.get().component_graph
+        pv_components = component_graph.dfs(
+            self._get_grid_component(),
+            set(),
+            component_graph.is_pv_chain,
+        )
+
         if not pv_components:
             _logger.warning(
-                "Unable to find any PV inverters in the component graph. "
+                "Unable to find any PV components in the component graph. "
                 "Subscribing to the resampling actor with a non-existing "
                 "component id, so that `0` values are sent from the formula."
             )
-            # If there are no PV inverters, we have to send 0 values at the same
+            # If there are no PV components, we have to send 0 values at the same
             # frequency as the other streams.  So we subscribe with a non-existing
             # component id, just to get a `None` message at the resampling interval.
             builder.push_component_metric(
@@ -50,11 +55,15 @@ def generate(self) -> FormulaEngine[Power]:
 
         builder.push_oper("(")
         builder.push_oper("(")
-        for idx, comp_id in enumerate(pv_components):
+        for idx, component in enumerate(pv_components):
             if idx > 0:
                 builder.push_oper("+")
 
-            builder.push_component_metric(comp_id, nones_are_zeros=True)
+            # should only be the case if the component is not a meter
+            builder.push_component_metric(
+                component.component_id,
+                nones_are_zeros=component.category != ComponentCategory.METER,
+            )
         builder.push_oper(")")
         if self._config.formula_type == FormulaType.PRODUCTION:
             builder.push_oper("*")
@@ -65,31 +74,3 @@ def generate(self) -> FormulaEngine[Power]:
             builder.push_clipper(0.0, None)
 
         return builder.build()
-
-    def _get_pv_power_components(self) -> abc.Set[int]:
-        """Get the component ids of the PV inverters or meters in the component graph.
-
-        Returns:
-            A set of component ids of the PV inverters or meters in the component graph.
-
-        Raises:
-            RuntimeError: if the grid component has no PV inverters or meters as successors.
-        """
-        component_graph = connection_manager.get().component_graph
-        grid_successors = self._get_grid_component_successors()
-
-        if len(grid_successors) == 1:
-            successor = next(iter(grid_successors))
-            if successor.category != ComponentCategory.METER:
-                raise RuntimeError(
-                    "Only grid successor in the component graph is not a meter."
-                )
-            grid_successors = component_graph.successors(successor.component_id)
-
-        pv_meters_or_inverters: set[int] = set()
-
-        for successor in grid_successors:
-            if component_graph.is_pv_chain(successor):
-                pv_meters_or_inverters.add(successor.component_id)
-
-        return pv_meters_or_inverters