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
Hi
Yes it is still approved, but not for much longer as Victron are not retesting due the 4777-20 rules coming in. which make it tougher. This includes Aussie as well. There are some people in the coal industry behind the scenes which are pushing these tougher rules for solar connections rules, so it keeps coal going.
Did you know that installing three phase install you get no benfit from grid unless completey balanced, and you are metered per phase not net metered, In some cases you can pay more for power. As NZ and Hungry are the only countries in the world to do this, its called greedy power companies some old croines control this as there is millions of dollars at stake. And they won't change this charging method, to over come this fit single phase inverters per phase to get max benfit and return.
Regards
Rob D
NZ
Hi Paul,
Had a quick look at the new 4777.2-2020 rules regarding anti-islanding and from what i can tell, seems to me more to do with software/firmware, set points etc, not so much to do with any major physical hardware changes, isolation relays etc. So hopefully, existing systems can be upgraded through a software update.
Understand that Victron will need to reapply for certification, due this month.
Is that how you read it related to anti-islanding, or am i missing something?
Regards
Joe
Hi
There are some hardware changes required from what i have being told by Victron so that is why they are dropping NZ and Aussie.
So might have to get your self a Grid relay to suit, And also these are not update as well as i contacted my supplier about this issue and they are working on it.
This will apply to a lot of inverter out there.
Hi Rob,
I hope that whatever the solution, it's cheaper than an Anti-islanding relay, at over $1,000.
With regard to my design, attached again for easy reference, I'm using current sensors to sense current flow from and to the grid, allowing the Multiplus 2 to make decisions accordingly.
All designs that I have seen online use a smart meter, is there any benefit in investing in a meter instead, or will I get the same performance using current sensors?
Regards
Joe
Hi
If you use the Victron 3phase energy meter it will be more accurate and have better control for your whole system, this is what is have used on my clients sites.
You can get anti islanding relays for about $500.
