My smart meter Holley DTZ541 is installed and sealed as a basic one direction consumption meter by my utility company.
A reverse flow towards the grid occurs occasionally witch active solar panels, feeding the grid for free. That is OK, but I want to know about the magnitude of the reverse flow in order to switch additional loads.
The meter sends SML /MQTT data every 10 seconds by means of a IR-Head.:
SENSOR = {"Time":"2023-03-15T12:41:38","SML":{"total_kwh":870.3787,"curr_w":84}}
No other readings are available. Unfortunately, the power value is absolute, disregarding the actual flow direction.
In order to detect the flow direction, I make use of the power reading: If the power increases between two measurement intervals, the flow is inbound. A reverse flow does not alter the energy reading (remember the meter is not mend to measure reverse flow).
This allows for a simple detector. The detection becomes ambiguous with very low power readings (0 to 36 W), an increase of the power cannot be measured due to the limited power resolution of 1/10 Wh. This may result in an unwanted oscillation:
I could program a smoothing filter, but at the expense of time resolution.
Is there any alternate approach I should be aware of?