====== Is there a control method to ensure zero export to the grid? ======
There are several branches in the behind-meter system. Some of them are chip-controllable, e.g. energy storage system, PV inverter. But the load is not. So the strategy is sampling the uncontrollable branches and controls the controllable branches, making the generated power is just equal to the consumed power. That is possible and practicable for stable loads. 

But we can't make sure the meter would be exactly zero, there must be some allowance.