Don't repeat zero commands to inverters

Signed-off-by: Sahas Subramanian <[email protected]>

Author: shsms

src/frequenz/sdk/microgrid/_power_distributing/_component_managers/_battery_manager.py

@@ -183,6 +183,9 @@ def __init__(
         )
         """The distribution algorithm used to distribute power between batteries."""
 
+        self._last_set_powers: dict[ComponentId, Power] = {}
+        """The last power value set to each battery's inverter."""
+
     @override
     def component_ids(self) -> collections.abc.Set[ComponentId]:
         """Return the set of component ids."""
@@ -638,8 +641,15 @@ async def _set_distributed_power(
                 api.set_power(inverter_id, power.as_watts())
             )
             for inverter_id, power in distribution.distribution.items()
+            if power != Power.zero()
+            or self._last_set_powers.get(inverter_id) != Power.zero()
         }
 
+        if not tasks:
+            if _logger.isEnabledFor(logging.DEBUG):
+                _logger.debug("Not repeating 0W commands to batteries.")
+            return Power.zero(), set()
+
         if _logger.isEnabledFor(logging.DEBUG):
             battery_distribution = {
                 self._inv_bats_map[inverter_id]: distribution.distribution[inverter_id]
@@ -727,6 +737,8 @@ def _parse_result(
             if failed:
                 failed_power += distribution[inverter_id]
                 failed_batteries.update(battery_ids)
+            else:
+                self._last_set_powers[inverter_id] = distribution[inverter_id]
 
         return failed_power, failed_batteries
 

tests/timeseries/_battery_pool/test_battery_pool_control_methods.py

@@ -551,3 +551,48 @@ async def test_case_4(self, mocks: Mocks, mocker: MockerFixture) -> None:
                 result, _power_distributing.Success
             ),
         )
+
+    async def test_no_resend_0w(self, mocks: Mocks, mocker: MockerFixture) -> None:
+        """Test that 0W command is not resent unnecessarily."""
+        set_power = typing.cast(
+            AsyncMock, microgrid.connection_manager.get().api_client.set_power
+        )
+        await self._patch_battery_pool_status(mocks, mocker)
+        await self._init_data_for_batteries(mocks)
+        await self._init_data_for_inverters(mocks)
+
+        battery_pool = microgrid.new_battery_pool(priority=5)
+        bounds_rx = battery_pool.power_status.new_receiver()
+
+        self._assert_report(
+            await bounds_rx.receive(), power=None, lower=-4000.0, upper=4000.0
+        )
+
+        # First send 0W command.  This should result in API calls.
+        await battery_pool.propose_power(Power.from_watts(0.0))
+
+        self._assert_report(
+            await bounds_rx.receive(), power=0.0, lower=-4000.0, upper=4000.0
+        )
+        await asyncio.sleep(1.0)  # Wait for the power to be distributed.
+        assert set_power.call_count == 4
+        assert sorted(set_power.call_args_list) == [
+            mocker.call(inv_id, 0.0) for inv_id in mocks.microgrid.battery_inverter_ids
+        ]
+
+        set_power.reset_mock()
+
+        # Sending 0W again should not result in any API calls.
+        await battery_pool.propose_power(Power.from_watts(0.0))
+        await asyncio.sleep(1.0)  # Wait for the power to be distributed.
+        assert set_power.call_count == 0
+
+        set_power.reset_mock()
+
+        # Sending a different power should result in API calls.
+        await battery_pool.propose_power(Power.from_watts(100.0))
+        await asyncio.sleep(1.0)
+        assert set_power.call_count == 4
+        assert sorted(set_power.call_args_list) == [
+            mocker.call(inv_id, 25.0) for inv_id in mocks.microgrid.battery_inverter_ids
+        ]