My take on that device is that it will stop your inverter seeing the high grid voltage and shutting down. 
It won’t help with the solar harvest being fed back into the grid,  but will reduce your power consumption as the household continues to be powered from the solar rather that the solar inverter going offline and resulting in 100% of your consumption coming from the grid while its offline. 
Steve
				
			 
			
		 
			
				
			
			
				1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
1988 120 with rust and potential
1999 300tdi 130 single cab - "stock as bro"
2003 D2a Td5 - the boss's daily drive
			
			
		 
	
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