SAFETY-136: a gentler loop on a slow meter until the last move shows

On a meter whose readings come 4 s or more apart, the loop runs at half its
gain after a move of 150 W or more, until the meter has fallen by half of the
move or 2 cycles have passed. With readings 10 s late on a 5 s meter the export
falls 44 % over oven, kettle and hob, owner shape, steps; 1-2 s meters are
untouched.

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

goodwe_controller/app/ctl_cycle.py

@@ -734,15 +734,21 @@ class CycleMixin:
             # TEL-10. ⚠️ ONE NAME FOR THE COMMAND THE LOOP WAS MEASURED
             # AGAINST. (DECISIONS/MAIN-orchestration-archive.md)
             loop_prev = self.target
+            # SAFETY-95: a drain's tail is not the loop's to chase.
+            # OPT-15: `loop_grid` is the grid, or the target while a run
+            # edge is held.
+            grid_in = (self._drain_grid_w(_live96) if self._drain_tail
+                       else loop_grid)
+            # SAFETY-136: on a slow meter, a gentler loop until the last move
+            # shows.
+            slow_meter = self.settle.slow()
+            if moved or mode_trade:
+                self.settle.reset()
             decision = compute(
                 prev_w=loop_prev,
-                # SAFETY-95: a drain's tail is not the loop's to chase.
-                # OPT-15: `loop_grid` is the grid, or the target while a run
-                # edge is held.
-                grid_w=(self._drain_grid_w(_live96) if self._drain_tail
-                        else loop_grid),
+                grid_w=grid_in,
                 actual_w=site_batt,
-                tuning=self.tuning,
+                tuning=self.settle.tuning(self.tuning, grid_in, slow_meter),
                 sat_count=self.sat_count,
                 i_w=self.i_w,
                 # SAFETY-52 at one inverter only: with several, OPT-09's pack
@@ -772,6 +778,7 @@ class CycleMixin:
                 self.log_event(f"saturation freeze ({self.target:.0f} W vs "
                                f"{site_batt:.0f} W)",
                                hint=messages.hint("not_keeping_up"))
+            self.settle.moved(grid_in, loop_prev, decision.target_w, slow_meter)
             self.sat_count = decision.sat_count
             self.i_w = decision.i_w
             self.loop_w = decision.target_w
@@ -811,6 +818,7 @@ class CycleMixin:
         else:
             # Stopped or blind: no accumulation may survive the outage.
             self.i_w = 0.0
+            self.settle.reset()
             self.loop_w = None
             self._live_was = frozenset(_live96)
             # TEL-10, and it is the same zero the line above writes rather than

goodwe_controller/app/ctl_inputs.py

@@ -197,6 +197,7 @@ class InputsMixin:
             # correlates 0.998 with battery power and 0.09 with the real meter
             # (a controller would regulate against its own output).
             self.grid = self.p1.net_w
+            self.settle.arrive(now_mono, self.p1.samples)   # SAFETY-136
         else:
             self.grid = await self.hass.number(o.get("meter_entity", ""),
                                                bool(o.get("meter_invert")))

goodwe_controller/app/main.py

@@ -63,6 +63,7 @@ from .clamp import (
 )
 from . import freshness
 from . import lateness
+from .settle import Settle
 from . import dayview, homeview
 from .daycurve import SolarToday
 from . import handback
@@ -741,6 +742,7 @@ class Controller(InputsMixin, WritesMixin, TradeMixin, CycleMixin, AlarmsMixin,
         self._arb_action = None
         self.inputs_bad_since = None
         self.answer = lateness.Answer()           # SAFETY-128
+        self.settle = Settle()                    # SAFETY-136
         self._late_logged = self._late_zero = False
         # SAFETY-03: what the loop's OWN bounds did last cycle, `(engaged,
         # note, over_rating)` (SAFETY-40 splits the last out). Site-level: the

goodwe_controller/app/settle.py

@@ -0,0 +1,74 @@
+"""SAFETY-136: on a slow meter, follow the meter gently until the last move shows.
+
+A meter whose readings come 4 s or more apart, read through Home Assistant, can
+be 10-15 s late. The loop then answers the same error again at each cycle
+and overshoots. After a move of MOVE_W or more the loop therefore runs at
+WAIT_SHARE of its gain until the meter has fallen SHOWN of the move, or for at
+most WAIT_CYCLES cycles. Off for a meter under 4 s, so those sites run as
+before. DECISIONS/SAFETY-136-slow-meter-settle.md.
+"""
+
+from collections import deque
+from dataclasses import replace
+
+from .lateness import M_FIT_S, M_ROWS
+
+# A meter is slow when its readings come further apart than this (the usual
+# gap, over the last 60 s and at least 5 readings): the fast meter fit's own
+# limit (SAFETY-128), 3.75 s.
+SLOW_GAP_S = M_FIT_S / M_ROWS
+SLOW_ROWS = 5
+# A move this big is waited for (above the house noise of about 80 W).
+MOVE_W = 150.0
+# The meter has shown a move once it fell by this share of it.
+SHOWN = 0.5
+# Meanwhile the loop runs at this share of its gain.
+WAIT_SHARE = 0.5
+# Wait at most this many cycles (10 s at a 5 s meter).
+WAIT_CYCLES = 2
+
+
+class Settle:
+    def __init__(self):
+        self.pend = None          # (meter at the move, the move in W, cycles waited)
+        self._n = None            # readings taken in so far
+        self._at = deque()        # when the last ones arrived, over M_FIT_S
+
+    def arrive(self, now, n):
+        """Each read: `n` is the count of meter readings taken in. A reading
+        counts when it arrives, not when its value changes, so a steady load on
+        a 1 s meter is not a slow meter."""
+        if n != self._n:
+            self._n = n
+            self._at.append(now)
+        while self._at and self._at[0] < now - M_FIT_S:
+            self._at.popleft()
+
+    def slow(self):
+        """The usual gap between readings is over SLOW_GAP_S."""
+        ts = list(self._at)
+        if len(ts) < SLOW_ROWS:
+            return False
+        gaps = sorted(b - a for a, b in zip(ts, ts[1:]))
+        return gaps[len(gaps) // 2] > SLOW_GAP_S
+
+    def reset(self):
+        self.pend = None
+
+    def tuning(self, tuning, grid_w, slow):
+        """The tuning for this cycle: `tuning`, or with the gain cut while the
+        last move has not shown on the meter (`grid_w`)."""
+        p = self.pend
+        if p is None:
+            return tuning
+        g0, move, waited = p
+        if not slow or (g0 - grid_w) / move >= SHOWN or waited >= WAIT_CYCLES:
+            self.pend = None
+            return tuning
+        self.pend = (g0, move, waited + 1)
+        return replace(tuning, gain=tuning.gain * WAIT_SHARE)
+
+    def moved(self, grid_w, prev_w, new_w, slow):
+        """After a cycle: start waiting if the loop moved by MOVE_W or more."""
+        if slow and self.pend is None and abs(new_w - prev_w) >= MOVE_W:
+            self.pend = (float(grid_w), float(new_w - prev_w), 0)