I asked and received the following information from a Bluetti after sales Engineer.
I am passing this information onto the Community.
If you were not aware, on the AC300 LCD screen, where you turn on the DC output or
AC output, where you also see the Grid load and AC Load, by pressing on the AC Load symbol, will give you further detail on the AC Load status.
Below is a list of the AC Load status and the sales engineer’s explanation:
Bypass Output-C (green led) means: When the AC connects to AC300, the power to loads only comes from the AC input and if the condition permits, the AC charges the battery too.
Bypass Output-D (green led) means: When the AC connects to AC300, the power to loads only comes from the AC input and the AC will not charge the battery.
Load Matching (orange led) means: When the AC connects to AC300, the power to loads only comes from the battery/inverter.
Inverter Output (orange led): Indicates that the power grid is abnormal and the AC Load is running off-grid (off-grid means not powering from the grid) with load. Such as the mains voltage and frequency exceed the input range or the power is cut off. And I may add maybe when input amperage is low and not sufficient to power the load.
So the AC300 runs on inverter mode.