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Improve BatteryPool's SoC accuracy at the edges #843

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Merged
merged 2 commits into from
Jan 15, 2024
Merged

Improve BatteryPool's SoC accuracy at the edges #843

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ea42350
Adjust BatteryPool's SoC to 100.0 when it `isclose` to 100.0
shsms Jan 15, 2024
3c17ac3
Use floating point constants in floating point calculations
shsms Jan 15, 2024
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27 changes: 16 additions & 11 deletions src/frequenz/sdk/timeseries/battery_pool/_metric_calculator.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,12 +5,14 @@


import logging
import math
from abc import ABC, abstractmethod
from collections.abc import Mapping, Set
from datetime import datetime, timezone
from typing import Generic, TypeVar

from ... import timeseries
from ..._internal import _math
from ...actor.power_distributing._component_managers._battery_manager import (
_get_battery_inverter_mappings,
)
Expand Down Expand Up @@ -361,9 +363,9 @@ def calculate(
Return None if there are no component metrics.
"""
timestamp = _MIN_TIMESTAMP
usable_capacity_x100: float = 0
used_capacity_x100: float = 0
total_capacity_x100: float = 0
usable_capacity_x100: float = 0.0
used_capacity_x100: float = 0.0
total_capacity_x100: float = 0.0

for battery_id in working_batteries:
if battery_id not in metrics_data:
Expand Down Expand Up @@ -395,26 +397,29 @@ def calculate(
# Therefore, the variables are named with a `_x100` suffix.
usable_capacity_x100 = capacity * (soc_upper_bound - soc_lower_bound)
soc_scaled = (
(soc - soc_lower_bound) / (soc_upper_bound - soc_lower_bound) * 100
(soc - soc_lower_bound) / (soc_upper_bound - soc_lower_bound) * 100.0
)
# we are clamping here because the SoC might be out of bounds
soc_scaled = min(max(soc_scaled, 0), 100)
soc_scaled = min(max(soc_scaled, 0.0), 100.0)
timestamp = max(timestamp, metrics.timestamp)
used_capacity_x100 += usable_capacity_x100 * soc_scaled
total_capacity_x100 += usable_capacity_x100

if timestamp == _MIN_TIMESTAMP:
return Sample(datetime.now(tz=timezone.utc), None)

# When the calculated is close to 0.0 or 100.0, they are set to exactly 0.0 or
# 100.0, to make full/empty checks using the == operator less error prone.
pct = 0.0
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I would add a comment about the intention of pct being literally 0.0 and 100.0 on the edges, just in case anyone feels tempted to simplify the code.

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done

# To avoid zero division error
if total_capacity_x100 == 0:
return Sample(
timestamp=timestamp,
value=Percentage.from_percent(0.0),
)
if not _math.is_close_to_zero(total_capacity_x100):
pct = used_capacity_x100 / total_capacity_x100
if math.isclose(pct, 100.0):
pct = 100.0

return Sample(
timestamp=timestamp,
value=Percentage.from_percent(used_capacity_x100 / total_capacity_x100),
value=Percentage.from_percent(pct),
)


Expand Down