Re a Multiplus 2 when in ESS mode, when the grid operator send out the Ripple control signals the inverter will pull up to and extra 1000watts of power when the loads are running at less than 100 watts. the ripple control frequency is in the range of 375 or 500 and up to 1000 Hz in New Zealand.
I though the inverter would have some sort of 1st fundamental filter, so to block all other frequencies , so the inverter can't pull more power very odd fault to react to the ripple control signals, sometimes this can go,on for more than 5 min. 2 or 4 times a day.
The ripple control signal is making the inverter self consume power.
Note: a inverter should not do this !!! a Flaw in the design?