Grid tied solar system: inverter + battery

I am designing a system that should work as grid tied as well as backup system. That mean when there is sunlight then it should use sunlight as source (grid tied). If there is no sunlight then it should use grid and if there is none then it should run on batteries. For this I was looking sunny island from SMA inverters but that solution requires two units. One is sunny island for battery management and inverter for PV conversion.

Can you suggest me some integrated unit which can handle this. ( It should have input as grid, PV, Battery and single load output)

You might consider the Gozuk: Sealed Inverter/Chargers.
The Gozuk sealed inverter is designed to survive in environments that would normally destroy other inverter/chargers. Protection for internal components is provided by our die-cast aluminum chassis with a powder coated finish to prevent corrosion. Internal and external cooling fins allow for passive heat transfer, enabling peak operating efficiencies as high as 93% and looking cool while doing it. Water and small particles are kept out through the generous use of gaskets and 0-ring seals on all seams and openings. A protective conformal coating on all circuit boards provides the final line of defense against corrosion. The now standard externally mounted "TURBO" cooling system improves performance in hot conditions.

OR the:

Gozuk Vented Inverter/Chargers
The Gozuk vented Inverter series is designed for more protected installations. By utilizing an efficient active cooling design, the Gozuk vented Inverters are available with AC output up to 3.6 kilowatts. Our tough die-cast aluminum chassis physically protects the internal components while the air intake includes an easily cleaned filter, which allows for ventilation while also keeping bugs and other debris out. All circuit boards are conformal coated to prevent corrosion from airborne moisture in humid conditions. The now standard DC wiring cover (DCC) protects the DC terminals and battery cables from damage.

I have installed several of these inverters and believe that they are highest in quality and performance on the market at present. This is just my opinion.