Add logical meter formula for EV power

Create a formula engine from the component graph for
calculating total EV Chargers power.

Signed-off-by: Daniel Zullo <[email protected]>

Author: daniel-zullo-frequenz

RELEASE_NOTES.md

@@ -13,7 +13,7 @@
 <!-- Here goes the main new features and examples or instructions on how to use them -->
 
 * A new class `OrderedRingBuffer` is now available, providing a sorted ring buffer of datetime-value pairs with tracking of any values that have not yet been written.
-
+* Add logical meter formula for EV power.
 
 ## Bug Fixes
 

src/frequenz/sdk/timeseries/logical_meter/_formula_generators/__init__.py

@@ -6,6 +6,7 @@
 from ._battery_power_formula import BatteryPowerFormula
 from ._battery_soc_formula import BatterySoCFormula
 from ._ev_charger_current_formula import EVChargerCurrentFormula
+from ._ev_charger_power_formula import EVChargerPowerFormula
 from ._formula_generator import (
     ComponentNotFound,
     FormulaGenerationError,
@@ -26,6 +27,7 @@
     "GridPowerFormula",
     "BatteryPowerFormula",
     "BatterySoCFormula",
+    "EVChargerPowerFormula",
     "PVPowerFormula",
     #
     # Current formula generators

src/frequenz/sdk/timeseries/logical_meter/_formula_generators/_ev_charger_power_formula.py

@@ -0,0 +1,53 @@
+# License: MIT
+# Copyright © 2023 Frequenz Energy-as-a-Service GmbH
+
+"""Formula generator from component graph for Grid Power."""
+
+import logging
+
+from .....sdk import microgrid
+from ....microgrid.component import ComponentCategory, ComponentMetricId
+from .._formula_engine import FormulaEngine
+from ._formula_generator import NON_EXISTING_COMPONENT_ID, FormulaGenerator
+
+logger = logging.getLogger(__name__)
+
+
+class EVChargerPowerFormula(FormulaGenerator):
+    """Create a formula engine from the component graph for calculating grid power."""
+
+    async def generate(self) -> FormulaEngine:
+        """Generate a formula for calculating total EV power from the component graph.
+
+        Returns:
+            A formula engine that calculates total EV charger power values.
+        """
+        builder = self._get_builder("ev-power", ComponentMetricId.ACTIVE_POWER)
+        component_graph = microgrid.get().component_graph
+        ev_chargers = [
+            comp
+            for comp in component_graph.components()
+            if comp.category == ComponentCategory.EV_CHARGER
+        ]
+
+        if not ev_chargers:
+            logger.warning(
+                "Unable to find any EV Chargers 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 EV Chargers, we have to send 0 values as 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.
+            await builder.push_component_metric(
+                NON_EXISTING_COMPONENT_ID, nones_are_zeros=True
+            )
+            return builder.build()
+
+        for idx, comp in enumerate(ev_chargers):
+            if idx > 0:
+                builder.push_oper("+")
+
+            await builder.push_component_metric(comp.component_id, nones_are_zeros=True)
+
+        return builder.build()

src/frequenz/sdk/timeseries/logical_meter/_logical_meter.py

@@ -27,6 +27,7 @@
     BatteryPowerFormula,
     BatterySoCFormula,
     EVChargerCurrentFormula,
+    EVChargerPowerFormula,
     FormulaGenerator,
     GridCurrentFormula,
     GridPowerFormula,
@@ -224,6 +225,18 @@ async def ev_charger_current(self) -> FormulaReceiver3Phase:
             "ev_charger_current", EVChargerCurrentFormula
         )
 
+    async def ev_charger_power(self) -> FormulaReceiver:
+        """Fetch the cumulative EV charger power for the microgrid.
+
+        If a formula engine to calculate EV charger power is not already
+        running, it will be started. Else, we'll just get a new receiver
+        to the already existing data stream.
+
+        Returns:
+            A *new* receiver that will stream ev_charger_power values.
+        """
+        return await self._get_formula_stream("ev_charger_power", EVChargerPowerFormula)
+
     async def battery_power(self) -> FormulaReceiver:
         """Fetch the cumulative battery power in the microgrid.
 

tests/timeseries/test_logical_meter.py

@@ -460,3 +460,47 @@ async def test_3_phase_formulas(self, mocker: MockerFixture) -> None:
 
         await mockgrid.cleanup()
         await engine._stop()  # pylint: disable=protected-access
+
+    async def test_ev_power(  # pylint: disable=too-many-locals
+        self,
+        mocker: MockerFixture,
+    ) -> None:
+        """Test the battery power and pv power formulas."""
+        mockgrid = MockMicrogrid(grid_side_meter=False)
+        mockgrid.add_ev_chargers(5)
+        request_sender, channel_registry = await mockgrid.start(mocker)
+        logical_meter = LogicalMeter(
+            channel_registry,
+            request_sender,
+            microgrid.get().component_graph,
+        )
+
+        main_meter_recv = await self._get_resampled_stream(
+            logical_meter,
+            channel_registry,
+            request_sender,
+            mockgrid.main_meter_id,
+            ComponentMetricId.ACTIVE_POWER,
+        )
+        grid_power_recv = await logical_meter.grid_power()
+        ev_power_recv = await logical_meter.ev_charger_power()
+
+        await self._synchronize_receivers(
+            [grid_power_recv, main_meter_recv, ev_power_recv]
+        )
+
+        ev_results = []
+        for _ in range(10):
+            grid_pow = await grid_power_recv.receive()
+            ev_pow = await ev_power_recv.receive()
+            main_pow = await main_meter_recv.receive()
+
+            assert grid_pow is not None and grid_pow.value is not None
+            assert ev_pow is not None and ev_pow.value is not None
+            assert main_pow is not None and main_pow.value is not None
+            assert isclose(grid_pow.value, ev_pow.value + main_pow.value)
+
+            ev_results.append(ev_pow.value)
+
+        await mockgrid.cleanup()
+        assert len(ev_results) == 10