JayA

Hi there
I am no expert on this but let me tell you my idea. AC coupling requires high voltage batteries and the cost of batteries are still to the roof. Just recently Voltronics (http://www.voltronicpower.com/oCart2/index.php?route=product/product&product_id=196) developed Axpert VMIII hybrid 5KVA/5KW output solar inverter for 48VDC systems, that can handle max PV input of 500Vdc, max 80A MPPT solar charger, max Solar Power 4000W. If your existing Grid-tied system has an existing two PV string of 500VDC each, then there is no need to rewire, all you need is to hook in one string to the inverter or you can invest to SATS (Solar Array DC Transfer Switch). You still have an option of keeping your grid-tie system working.
Another option is to purchase a 5500w Hybrid Solar inverter 48v 230vac PV input 500v , Grid tied solar +off grid form MPP solar (https://www.ebay.com.au/itm/5500w-Hybrid-Solar-inverter-48v-230vac-PV-input-500v-Grid-tied-solar-off-grid/132427185943). Check the details on the attached file. The same inverter is also made by Votronics InfiniSolar E 5.5KW (http://www.voltronicpower.com/oCart2/index.php?route=product/product&path=24&product_id=180). This has a multiple power operations: Grid-Tie with battery backup,Grid-Tie feedback or Off-Grid, Support Max Solar Power 6500w, Pure sine wave with max 5500w output, Supports parallel up to 6 units, 2 PV input,PV input up to 500Vdc each, Built-in Max 60A battery charger.
Axpert VM III_DS.pdf
InfiniSolar E_DS.pdf