Add a Fuse class and use it in Grid

This commit introduces a class to represent fuses. Fuses have just one
property representing their rated max current. If the current flowing
through a fuse is greater than this limit, then the fuse will break the
circuit.

This commit also introduces using a Fuse object to represent the allowed
max current at a grid connection point.

Signed-off-by: Tiyash Basu <[email protected]>

Author: tiyash-basu-frequenz

RELEASE_NOTES.md

@@ -92,9 +92,12 @@ This release replaces the `@actor` decorator with a new `Actor` class.
 
 - `Actor`: This new class inherits from `BackgroundService` and it replaces the `@actor` decorator.
 
-- Calling `microgrid.initialize()` now also initializes the microgrid's grid connection point as a singleton object of a newly added type `Grid`. This object can be obtained by calling `microgrid.grid.get()`. This object exposes the max current that can course through the grid connection point, which is useful for the power distribution algorithm. The max current is provided by the Microgrid API, and can be obtained by calling `microgrid.grid.get().max_current`.
+- Calling `microgrid.initialize()` now also initializes the microgrid's grid connection point as a singleton object of a newly added type `Grid`. This object can be obtained by calling `microgrid.grid.get()`. This object exposes the max current that can course through the grid connection point, which is useful for the power distribution algorithm. The max current is provided by the Microgrid API, and can be obtained by calling `microgrid.grid.get().fuse.max_current`.
   Note that a microgrid is allowed to have zero or one grid connection point. Microgrids configured as islands will have zero grid connection points, and microgrids configured as grid-connected will have one grid connection point.
 
+- A new class `Fuse` has been added to represent fuses. This class has a member variable `max_current` which represents the maximum current that can course through the fuse. If the current flowing through a fuse is greater than this limit, then the fuse will break the circuit.
+
+
 ## Bug Fixes
 
 - Fixes a bug in the ring buffer updating the end timestamp of gaps when they are outdated.

src/frequenz/sdk/microgrid/__init__.py

@@ -8,7 +8,7 @@
 """
 
 from ..actor import ResamplerConfig
-from . import _data_pipeline, client, component, connection_manager, grid
+from . import _data_pipeline, client, component, connection_manager, fuse, grid
 from ._data_pipeline import battery_pool, ev_charger_pool, logical_meter
 from ._graph import ComponentGraph
 
@@ -37,6 +37,7 @@ async def initialize(host: str, port: int, resampler_config: ResamplerConfig) ->
     "component",
     "battery_pool",
     "ev_charger_pool",
+    "fuse",
     "grid",
     "logical_meter",
 ]

src/frequenz/sdk/microgrid/fuse.py

@@ -0,0 +1,16 @@
+# License: MIT
+# Copyright © 2023 Frequenz Energy-as-a-Service GmbH
+
+"""Fuse data class."""
+
+from dataclasses import dataclass
+
+from ..timeseries import Current
+
+
+@dataclass(frozen=True)
+class Fuse:
+    """Fuse data class."""
+
+    max_current: Current
+    """Rated current of the fuse."""

src/frequenz/sdk/microgrid/grid.py

@@ -11,20 +11,18 @@
 from dataclasses import dataclass
 from typing import Iterable, Optional
 
+from ..timeseries import Current
 from .component import Component
 from .component._component import ComponentCategory
+from .fuse import Fuse
 
 
 @dataclass(frozen=True)
 class Grid:
-    """A grid connection point.
+    """A grid connection point."""
 
-    Attributes:
-        max_current: The maximum current that can course through the grid
-            connection point, in Amperes.
-    """
-
-    max_current: float
+    fuse: Fuse
+    """The fuse protecting the grid connection point."""
 
 
 _GRID: Optional[Grid] = None
@@ -60,7 +58,8 @@ def initialize(components: Iterable[Component]) -> None:
         )
     else:
         max_current = grid_connections[0].metadata.max_current  # type: ignore
-        _GRID = Grid(max_current)
+        fuse = Fuse(Current.from_amperes(max_current))
+        _GRID = Grid(fuse)
 
 
 def get() -> Optional[Grid]:

tests/microgrid/test_grid.py

@@ -7,7 +7,9 @@
 
 from frequenz.sdk import microgrid
 from frequenz.sdk.microgrid.component import Component, ComponentCategory, GridMetadata
+from frequenz.sdk.microgrid.fuse import Fuse
 from frequenz.sdk.microgrid.grid import Grid
+from frequenz.sdk.timeseries import Current
 
 
 async def test_grid() -> None:
@@ -53,7 +55,11 @@ async def test_grid() -> None:
     microgrid.grid.initialize(components)
 
     grid = microgrid.grid.get()
-    assert grid == Grid(max_current=123.0)
 
-    max_current = grid.max_current
-    assert max_current == 123.0
+    expected_fuse_current = Current.from_amperes(123.0)
+    expected_fuse = Fuse(expected_fuse_current)
+
+    assert grid == Grid(fuse=expected_fuse)
+
+    fuse_current = grid.fuse.max_current
+    assert fuse_current == expected_fuse_current