v0.9.1b1 - Breaking change - grid inversion

Release Notes

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v0.9.1b1

Issues: #302

We apologise for this one. The Grid Export Power and Grid Import Power sensors have had
their values swapped since they were introduced, meaning every user has been seeing export
labelled as import and vice versa. The bug was in the formula that splits the signed grid power
value into its two always-positive halves — the positive and negative parts were extracted into
the wrong sensors. The signed Grid Power sensor and all daily energy sensors were unaffected
because they use a different code path. We only caught it because a user noticed the symptom
on a hybrid inverter where both directions are active (Issue #302). Grid-tied string inverter
users (MIN, MID, MIC) were also affected but the symptom was less obvious — those inverters
only export during the day, so Grid Export Power silently read zero while Grid Import Power
carried the export value. Both are now correct.

⚠️ BREAKING CHANGE — affects all users.
Grid Export Power and Grid Import Power were swapped in all previous versions.
After upgrading, these sensors will read the opposite value to before.
If you have automations, dashboards, or energy dashboard slots referencing either sensor,
you must swap them. The signed Grid Power sensor and all daily energy sensors are unaffected.
Users with Invert Grid Power enabled should also disable it (Settings → Devices &
Services → Growatt Modbus → Configure) — it was incorrectly set by auto-detection in
previous versions and is no longer needed for standard inverters.

• Breaking fix: grid_export_power and grid_import_power swapped on all profiles (Issue #302):
  The two always-positive derived power sensors had their formulas inverted in all previous
  versions. grid_export_power was extracting the import portion of the signed grid power
  value and grid_import_power was extracting the export portion — the opposite of their names.
  On hybrid profiles (SPH, MOD, WIT) the symptom was visible: during grid import,
  grid_export_power showed the import magnitude while grid_import_power read zero. On
  grid-tied string inverters (MIN, MIC, MID) the inverter only exports, so grid_export_power
  silently read zero and grid_import_power showed the export value under the wrong name.
  The signed grid_power sensor and the daily energy sensors (Energy to Grid Today,
  Grid Import Energy Today) were unaffected — they read from separate register addresses.

• Fix: invert_grid_power auto-detection was inverting the wrong case:
  The setup wizard's grid orientation detection returned the wrong result — it enabled inversion
  when it detected positive = export (the correct convention) and disabled it when it detected
  negative = export (the case that actually needs correction). This caused some users to have
  invert_grid_power incorrectly set to True, which negated the signed grid_power sensor
  so it showed negative while exporting. Auto-detection is now correct. Existing users with
  the flag incorrectly enabled should disable it via Configure.

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