Solar-PV und KNX: Fronius Symo Modbus-Integration zur Eigenverbrauchsoptimierung

Aktivieren von Modbus TCP am Fronius-Wechselrichter

1. Connect to inverter webserver: http://<inverter-IP>
   (default IP shown on inverter display → Settings → Network)

2. Navigate to: Settings > Modbus
   Enable Modbus TCP: ON
   TCP port: 502 (default, leave unchanged)
   SunSpec model: enabled

3. Key holding registers (read-only):
   Register 40070 → AC power output     (int16, W)
   Register 40080 → AC energy today     (uint32, Wh)
   Register 40225 → Grid power          (int16, W, Gen24 with smart meter)
                    Positive = import, Negative = export
   Register 40493 → Battery SOC         (Gen24 Plus only, 0–100%)
   Register 40495 → Battery power       (Gen24 Plus only, int16, W)

4. Fronius smart meter must be installed and paired
   for grid power register 40225 to report correctly

Eigenverbrauchs-Prioritätslogik

Trigger condition: GA 9/0/1 (Grid Power) < −1000W
  → surplus export greater than 1 kW

Priority sequence (activate in order, release in reverse):
  1. Heat pump SG Ready (State 3 encouraged mode)
     → KNX binary output → heat pump S1/S2 terminals
  2. EV charger current increase (via EVCC/OCPP)
     → increase from 6A minimum toward surplus limit
  3. Immersion heater ON
     → KNX binary output → 3kW immersion contactor

Deactivation: GA 9/0/1 > −200W (export below 200W)
  → release loads in reverse priority order
  → 60-second hysteresis to prevent rapid cycling

Batteriebewusste Eigenverbrauchsbedingungen

GA 9/1/0 (Battery SOC) conditions:

  SOC < 20%:
    → Pause all controllable loads
    → Prioritise battery charging from PV
    → SG Ready → State 2 (normal, don't add extra heat pump load)

  SOC > 80% AND GA 9/0/1 (Grid Power) < −500W:
    → Activate controllable loads (battery sufficiently full)
    → Standard priority sequence applies

  Battery power (GA 9/1/1):
    → Negative = battery charging (absorbing PV surplus)
    → Positive = battery discharging (supplying building)
    → Use to calculate net PV available for controllable loads:
       Available = PV power − battery charging power

SMA Sunny Boy Modbus TCP Einrichtung

Enable in SMA webserver:
  Settings > External communication > Modbus > ON
  TCP port: 502

Key registers (read-only, unit ID 3):
  30775 → AC power output   (uint32, W, 2 registers)
  30517 → Daily yield       (uint32, Wh, 2 registers)
  30513 → Total yield       (uint32, kWh × 1000)
  30521 → Operating status  (uint32, enum)

Note: SMA registers are uint32 (2×16-bit), big-endian.
Configure IN701KNX signal type as 32-bit unsigned integer.
SMA does not provide a signed grid power register without
a separate SMA Energy Meter — add SMA Energy Meter for
grid flow monitoring (registers 30865/30867 on Meter unit ID).

KPI-Formeln für Gira X1 oder IP-Symcon

Self-consumed power (W):
  = PV power (GA 9/0/0) − max(0, −Grid power (GA 9/0/1))
  (PV output minus what is being exported)

Self-consumption rate (%):
  = Self-consumed power / PV power × 100
  Target: > 70% with EV + heat pump controllable loads

Self-sufficiency rate (%):
  = Self-consumed power / Total building demand × 100
  Total demand = PV power − grid export + grid import
               = GA 9/0/0 + max(0, GA 9/0/1)

Annual self-consumption: log daily GA 9/0/2 (Energy today Wh)
  → accumulate in IP-Symcon variable → annual total kWh
  → self-consumption rate = annual self-consumed / annual yield

Solar.web API vs. lokales Modbus TCP

Solar.web REST API (api.solarweb.com):
  Latency: 1–5 minutes (cloud polling cycle)
  Use for: BREEAM energy reports, historical analysis,
           CSV export for energy assessors
  Poll: daily at 23:59 from IP-Symcon or ARISTO BewO
  Output: daily/monthly kWh → CSV → energy assessor

Local Modbus TCP (Fronius register 40070/40225):
  Latency: < 1 second (direct LAN poll at 10s interval)
  Use for: ALL real-time self-consumption control
           SG Ready triggers, EV current adjustment,
           export limiting, immersion heater switching

NEVER use cloud API for real-time control —
  1–5 minute latency makes load shifting ineffective

Inbetriebnahme-Prüfsequenz

1. PV data verification (by 10:00 on a sunny day):
   ETS6 Group Monitor → watch GA 9/0/0
   → confirms PV Power W > 0 and rising with irradiance
   → compare with Fronius webserver display (should agree ±2%)

2. Grid flow verification:
   GA 9/0/1 should be negative when PV > building consumption
   GA 9/0/1 should be positive when PV < building consumption
   Turn off major loads, re-check sign changes

3. SG Ready functional test (without waiting for solar surplus):
   ETS6 Group Monitor → write −4000 to GA 9/0/1 (simulate export)
   → confirm Logic Module condition fires (GA 9/0/1 < −1000)
   → confirm SG Ready relay activates (State 3: S1=0, S2=1)
   → confirm with heat pump display (mode indicator changes)
   → restore: write 0 to GA 9/0/1 → relay deactivates

4. Battery SOC check (Gen24 Plus):
   GA 9/1/0 value should match Fronius webserver battery SOC %

5. Export limit test:
   Write 50 to power limit register via Group Monitor write
   → confirm Fronius webserver shows 50% power limit active