Hi,
I would like to implement the following system at my home and would be extremely grateful if someone could confirm whether a Multiplus 2 system as depicted will provide me with the listed functionality.
Regards, and thank you in advance.
asked
3 Phase Multiplus 2 - Configuration
1. MP-II 3000 is not 3kW unit but 3000VA. It is 2.4kW.
2. If only 2.3kWp per phase, Fronius 8.2kW is better choice.
3. I would suggest to use LFP battery. It is less expensive in the long run.
4. If battery gets depleted at night and there is grid this system will not start-up in the morning.
Fronius being at the AC-out will not get micro-grid from MP-IIs since battery is discharged.
For this system to start in the morning without the grid, you need PV connected to DC side.
You need MPPT to charge battery and once is charged the MP-II will start inverting and Fronius will start.
You can also use generator to charge battery in this situation.
Hi marekp,
Thank you for your responses, much appreciated.
Just one clarification please, this is a grid-tied system, not off-grid, therefore, your comment relates to a situation where the batteries are fully depleted due to a long outage?
Would the issue be resolved if I connect the PV inverter to the input instead, as per attachment?
I know it is a grid-tie system.
My suggestion was only to point out that, there is a possibility that the system will not start up if there is no grid and battery is depleted even if Sun is shinning.
If you can live with that possibility it is up to you. Now you know of it.
Moving Fronius to the AC-in will not fix that situation, since no grid means Fronius is off.
Hi marekp,
Sorry, I'm just trying to get across system features and functionality, and I understand that if the batteries have been depleted to SOC or LVD, and the mains outage lasts until next morning, then the PV won't start. However, once mains is restored, PV will start up again right?
Mains outages in Sydney, Australia do not usually last very long, and I'm setting it up this way to provide backup for essential loads for rare occasions of mains fails. I intend on installing about >25KWH of battery backup, so scenario you described should be extremely rare.
Main objective of the system is to extend stored PV power usage into the evening, and perhaps mornings.
Thank you
And off-peak mains charging of batteries, to utiise during peak times.
Thanks
My ESS system works like this today (last 24 hours):
There was not much Sun day before so batteries were empty at night.
In the morning some energy come from sun and it continued during the day.
Now battery is supplying power and will continue until empty.
Hi
Yes that will work well, this is what i have installed in the past for Clients. The Fronius will need to be set up in micro grid mode so it can run on the output of the inverters when you lose the grid etc.
When the batteries are to flat to do a restart you could add a black start system to keep the battries and inverters alive in the worst case situation.
By adding a MPPT charger to the battery bank and to be controlled by the Cerbo, also this can be used to export surplus dc power to the grid as well.
Regards
Rob D
NZ
Hi Rob,
Thank you for the confirmation.
Do you know whether the Multiplus 2 is approved for anti-islanding in AUS/NZ without having to install an external anti-islanding relay?
Thanks
