fix(plan): don't offer Freeze Export for inverters that always charge from PV surplus (#4207)

Alternative to the stale #4425 (which patched the prediction model instead
- reworking it here per that PR's own follow-up discussion): on an inverter
with inverter_can_charge_during_export=true (the default), PV surplus
charges the battery regardless of what mode Predbat has commanded, so
Freeze Export (hold SoC flat, export the rest) can never actually be
achieved - it collapses to identical behaviour as Idle. Rather than teach
the prediction model to simulate a distinction that doesn't exist in
reality, stop the optimiser offering/selecting freeze for these inverters
in the first place:

- optimise_export(): allow_freeze is now also forced off when the inverter
  can charge during export, alongside the existing set_export_freeze check.
- optimise_solar() ("Export more solar"): sets export limits to 99.0
  (freeze) directly, bypassing optimise_export()'s search entirely, so it
  needs the same gate independently or it reintroduces the bug through the
  back door.

No prediction.py or kernel changes needed - this is purely a search-space
restriction, not a modelling change, so no parity bump or binary rebuild.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: 2 people

apps/predbat/plan.py

@@ -2158,7 +2158,11 @@ def optimise_export(self, window_n, record_charge_windows, try_charge_limit, cha
         export_step = 5
         export_step_large = 15
 
-        if not self.set_export_freeze:
+        if not self.set_export_freeze or self.inverter_can_charge_during_export:
+            # An inverter that charges the battery from surplus PV regardless of what it's been told
+            # (inverter_can_charge_during_export) can't actually achieve a frozen SoC - it behaves
+            # identically to idle in that case, so offering freeze as a distinct option is pointless
+            # and would mislabel the plan (#4207/#4425).
             allow_freeze = False
 
         # loop on each export option
@@ -3080,8 +3084,10 @@ def optimise_solar(self, best_metric, best_cost, best_keep, best_cycle, best_car
         """
         curr = self.currency_symbols[1]
 
-        # Freeze export slots only have an effect when export freeze is enabled
-        if not self.calculate_best_export or not self.set_export_freeze or not self.export_window_best:
+        # Freeze export slots only have an effect when export freeze is enabled, and only mean anything
+        # distinct from idle when the inverter can actually hold SoC flat - see optimise_export()'s
+        # matching gate (#4207/#4425) for why inverter_can_charge_during_export rules it out too.
+        if not self.calculate_best_export or not self.set_export_freeze or not self.export_window_best or self.inverter_can_charge_during_export:
             return best_metric, best_cost, best_keep, best_cycle, best_carbon, best_import
 
         pv_forecast_minute_step = self.prediction.pv_forecast_minute_step

apps/predbat/tests/test_optimise_solar.py

@@ -32,6 +32,7 @@ def run_optimise_solar(
     expect_export_start=None,
     car_charging_slots=None,
     car_charging_from_battery=False,
+    inverter_can_charge_during_export=False,
 ):
     print("Starting optimise solar test {}".format(name))
     failed = False
@@ -41,6 +42,7 @@ def run_optimise_solar(
     my_predbat.calculate_best_export = calculate_best_export
     my_predbat.set_export_freeze = set_export_freeze
     my_predbat.set_charge_freeze = True
+    my_predbat.inverter_can_charge_during_export = inverter_can_charge_during_export
     my_predbat.export_more_solar_threshold = threshold
     my_predbat.soc_max = battery_size
     my_predbat.soc_kw = battery_soc
@@ -161,6 +163,20 @@ def run_optimise_solar_tests(my_predbat):
         set_export_freeze=False,
     )
 
+    # An inverter that charges the battery from surplus PV regardless of command can't actually hold
+    # SoC flat, so freeze is no different from idle for it (#4207/#4425) - feature is a no-op here too,
+    # same outcome as freeze_disabled above but via the capability gate instead of the switch
+    failed |= run_optimise_solar(
+        "freeze_pointless_when_inverter_always_charges",
+        my_predbat,
+        export_window_best=export_window_best,
+        export_limits_best=[100.0, 100.0, 100.0],
+        expect_export_limit=[100.0, 100.0, 100.0],
+        pv_amount=3.0,
+        threshold=100.0,
+        inverter_can_charge_during_export=True,
+    )
+
     # An already active export window (limit 0) is left untouched, only idle ones are converted
     failed |= run_optimise_solar(
         "skip_active_window",