It would help considerably if you signal your intended use for this....Yes, your turn for not enough info
If you want to transport the full 12000 watts down the line, then grid tie, you could buy a HV inverter and run 600dc direct to the inverter.
If you want to transport the full 12000 watts down the line to charge a monster battery bank...., or use 12000 watts (good lord why), then your in the pain territory Chris has outlined. Invert at the panels, batts at the panels, and transformer transmit to your chosen load and transform down again... expensive every which way.
If you want to run a house and charge a 700ah battery bank.... use 48volt system, not 24v......now we'll find out why......
For this application, you will likely need to transport only 5kw-6kw max I would suggest.... full charge and load of 2kw should do it.
The best equipment for this will be the SMA range of inverter chargers, and SMA grid tie inverters.
I can now confirm that the fellow who came here today, uses the hv dc to the grid tie inverters. They directly parallel the output from the SMA 240vac 48v inverter driving the house..... yes it is that simple I'm afraid. .... He lives 500 miles away, and monitors it all on his phone with 30 channels of logging...... all facets of the system.... so I saw it in real time from way over here.
The grid tie units will power your house AND charge the batteries through the house inverter at their proper settings for the bank size etc. including equalise if needed. No other mppt controllers or gadgets required.
Sounds too good to be true... soooooo........ I couldn't help it...
I got my no-name inverter 48v 70amp charger 18000 watt surge, and decided to put my money where his mouth was.
I hooked the grid tie units I have (I bought a pallet of them for peanuts 1.5kw CEHE units) straight onto the output of the inverter, and then stood back and waited for the grid tie units to log on and start....... not sweating much I might add.....much.
I figured I could rebuild the output stage of the big inverter if it all turned to mush, and I have plenty of grid tie inverters (I really bought them for the S/Steel box they are in... ).. so if anyone should try this at home, I guessed I was it.
The output stage circuitry for this big inverter is available on the net, so a rebuild should be straight forward. The charger power and battery type is programmable for 8 different types of technologies, and then equalise if wanted.... and it is up to 70 amps (you get to set A max).... Thats why we want 48v. The current limit is for either 24 or 48v versions.... so 48v wins easily, as can charge at twice the power as the 24v versions.
Well I turned on some loads so the grid ties would have something to work into, and all went as expected, and as Chris has seen too.
But because of the H bridge output design, as I turned off the loads, and watched the amp gauge on the battery to inverter rail... I saw it slowly move from discharging the batteries, to charging the batteries... even with 500 watts of load still on line.
I took it up to 20 amps battery charging before I decided enough was enough for 1 day..... and I was running out of solar, darn clouds came back over, but I had 1.5kw from the panels into the load AND the batteries........ Hmmmm looks promising.
Dont try this at home unless your prepared to kill an inverter (I doubt it, but I don't want folks to blow up their stuff until we know more about this.)
All worked as advertised, and should work for all inverter chargers using big output transformers and H bridge outputs ( should be all).
Also, I prefer the heavy transformer galvanically isolated grid tie units.... more flexibility and because I do.
So The next and only problem is where does the power go when the batteries are full, or the load drops off and the batteries are near float etc etc.
We know the grid mppt controls the power from the panels by running up the va curve until they are happy with their Pmax... so that stops excess power coming from the panels.... but below this level
For the SMA range, it is simple and seamless, no work required apparently. It simply shifts the Hz a fraction, the grid ties see it, and runs up the VA curve further to limit the current.. that simple and Auto.
For the rest of us:
Simply turn on a 240vac pwm load of up to 4kw (hot water then radiators) to act as a dump load till we figure something better. Maybe drop off a grid tie if the battery hits float voltage... Need to monitor the system set up like this to find what parameters will give us the best switch points to isolate the grid ties in sequence if no dump loads are used.
We also need to research the SMA inverter chargers to see just how they do as I am told they do.... but the system works as is, but as the kw of the panel goes up, the SMA looks the best set and forget system out there at this stage.
I don't think Xantrex has this facility... so is a non starter.
..................oztules