Implement Powermeter TQ EM

[tomquist]

Summary

• Implemented a new TQEMPowermeter to interact with the TQ Energy Manager JSON API, supporting optional authentication and power calculation
• Documented the TQ Energy Manager configuration in the README, including setup instructions
• Added configuration example for TQ_EM in the sample config file
• Updated the configuration loader to create TQ_EM powermeter instances based on the new section

Testing

• pytest -q

---

Fixes #133

[TheItschi]

Code is much nicer but returns wrong value(s) ;-)

The power is always reported in two different values (e.g. one for the power coming from the grid and one for the power that is fed to the grid). To get a signed total you need to calculate the value by subtracting the power that is fed to the grid from the power that is drawn from the grid. At least one of those values will always be zero. Note sure why you extract the phase power as well, but you would need to calculate the total phase power accordingly.

"tq_tm.py" needs to be changed as follows:

    # OBIS codes
    _TOTAL_TO_GRID = 0
    _TOTAL_FROM_GRID = 1

    _TOTAL_KEYS = (
        "1-0:1.4.0*255",   # Σ active power (from grid) 
        "1-0:2.4.0*255",   # Σ active power (to grid)
    )

    _TOTAL_TO_GRID_L1 = 0
    _TOTAL_FROM_GRID_L1 = 1
    _TOTAL_TO_GRID_L2 = 2
    _TOTAL_FROM_GRID_L2 = 3
    _TOTAL_TO_GRID_L3 = 4
    _TOTAL_FROM_GRID_L3 = 5

    _PHASE_KEYS = (
        "1-0:21.4.0*255",  # L1 active power (from grid)
        "1-0:22.4.0*255",  # L1 active power (to grid)
        "1-0:41.4.0*255",  # L2..
        "1-0:42.4.0*255",
        "1-0:61.4.0*255",  # L3..
        "1-0:62.4.0*255"
    )

...

    def get_powermeter_watts(self) -> List[float]:
        self._ensure_session()

        try:
            data = self._read_live_json()
        except _SessionExpired:
            self._login()
            data = self._read_live_json()

        if len([element for element in self._TOTAL_KEYS if element in data]) == len(self._TOTAL_KEYS):
            return [float(data[self._TOTAL_KEYS[self._TOTAL_TO_GRID]])-float(data[self._TOTAL_KEYS[self._TOTAL_FROM_GRID]])]
        else:
            raise RuntimeError("Required OBIS values missing in payload")