I see that smaller values work, but I don’t see a sense in “crippling” this featzre.
I have 2 heatpumps with a separate tariff which are connected in a cascading fashion between grid and house (this tariff is significantly lower than the dynamic tarif, except for very few occasions in winter).
Hence, when battery SoC is too low to serve both, heatpumps plus house, I need to excempt the power drawn by the heatpumps from the coverage of the battery.
The only way to achieve that is to set the grid setpoint to a positive value (the power draw of the respective heatpump, which is value between 900w and 2.9kW in my case).
Edit: OK, I just tested a larger POSITIVE value (like +2500W) and this still works!!
However I still do not see the value in the way it is limited on the negative side.