The Factor 1.0 rule

Q&A and troubleshooting
, ,
21

First of all: Merry christmas!

On topic, to the thread starter: No offence, but if someone isn’t familiar with the essentials like factor 1.0 rule, i would strongly suggest him to take into account to get help from an experienced person to wire and configure your system.
From my perspective, with only less than 3kW of solar power, best option efficiencywise would be a solar charger directly connected to the battery system. It is cheap an reliable and moreover makes your system able to “black start” after a long grid loss with your battery has ran out of power. All of like 1.0 rule and many more is gone with that, the MP II will handle everything on it’s own terms.
The more complex stuff like switching or splitting between ac in and out may and will fail sometimes, don’t do that unless you’re highly experienced with these things - your initial question and even more the further ones are showing, you’re not that much into this. I’m sorry, wanna tell you this to protect you from expensive and dangerous failures.
Hint: Consider to install a rechargable battery with seperate smps for your gx devices power supply, if you have one in use. With that installed, the heart of your system keeps beating long enougth even when your ess has ran out off power until the solar power comes back alive next morning. As soon as the charger has pushed enougth energy into the system, it will restart by itself.
Good luck!

22

See, you are stating the obvious. I’m here to ask information I can’t find anywhere. The Victron distributors here in my country are of no help.

My goal is just a backup to when the grid fails. Until today, in just one occasion the grid was off for more than a couple hours. So, I’m planning for a ten hour battery backup capacity.

The only reason I’d like to use a Multiplus is because it can do AC coupling to maintain my PV in use. But there is this situation when battery runs out…

To install a DC charger I’ll need to rewire my PV system. And if I do that, I’ll not use a Victron Multiplus but a less costly UPS.

23

If you allready have an ac coupled pv, then best way is to connect the existing stuff onto the ac out 1 of the MP II. Doing so will enable your system to island while grid loss thus maintaining your connected most significant devices in your home running and continue using pv power if available.
As long as parameters in MP II for frequency shift (in your existing ac coupler for output derating respectively) are set properly, the MP II will handle the 2.6kW pv well hence you’re not going to violate the 1.0 rule.
I do not know your grid system but would guess that power outages more likely during times of low pv availability. While the actual grid feed in power does not exceed the capabilities of your MP and battery system, there will be no problem with 1.0 (not the produced pv power itself, e.g. some of it is used in home at moment of grid loss)

24

First:
The PV inverter system must be able to run in microgrid mode. Microgrid mode means it is controlled by the frequency and it should be able to go to 0 power.
If it can’t go to 0 power you have an issue.

If it cannot be controlled by the frequency, then the multiplus 2 has no fast and reliable way to stop the PV inverter.

The price between an MP2 2000 and 3000 is negligable, you need a 3000. I’ve been running an off-grid 3 phase system with generator and PV chargers, and you learn to appriciate the MP2.
However, a 2.6kW PV system doesn’t sound really big and can easily be handled by an MPPT 250/60 solar battery charger (depending on the PV setup).

But in your case: invest in that mp2 3000 and some LiFePo4 batteries. 6 months before a migration to an off grid location I did exactly that (with a 5000 though and a cerbo gx) with the LiFePo4 batteries and tested the system, and it is amazing how good it works.

You don’t need to hook up the PV to the ac-out, you will loose PV power during an outage, but you won’t notice a thing.
I have had a complete computer rack connected to my test setup and it works way better than any computer UPS I’ve ever seen.
It actually made me so mad that a computer UPS is very expensive, and doesn’t have the controls over the power use as the mp2 + cerbo gx, mp2 gx or mp2 with some kind of control.
After a power outage it can soft turn on the main, which is very important.

In my current case I use a 7.6kW 3 phase diesel gen that acts as AC-IN, but the victron sees that if all my heating turns on, my diesel gen won’t be able to provide it and quickly switches from charging to supporting on that one phase…
It takes at most a minute for the victron to synchronize phase with the generator, and then it starts loading it while tracking the frequency of the generator.

So yeah, if I know which certificates I have to get, I will be installing victron gear instead of a UPS next time in a computer rack. The run time will go from 10 minutes (which is what a UPS is rated for) to whatever I configure. When the power comes back, it will gracefully load the circuits.
I’ve seen a UPS destroy several servers because it was not graceful.

So the mp2 will be worth your money.

But for real advice we need to know what your PV installation consists of.
The mp2 is relatively cheap, but battery cables aren’t. And you have to buy pre-crimped or buy crimping tools capable of crimping 35mm^2…75mm^2 for the DC side, depending on what you are going for.
If your PV isn’t capable of microgrid it would be hard though.

1 Like
25

Thank you for your answer, very good advise!

I have 8 solar panels with 8 Enphase IQ7AM microinverters. They are compatible with Victron Multiplus AC coupling. There is even an article from Enphase on how to use both together.

Ok, my best buy would be a Multiplus II instead of an UPS. A 5kW LiFePO4 battery is enough for my loads. Later I’d try to integrate it with my Enphase system, if necessary at all.

26

This is what I understood.

How does the factor 1.0 rule work if I connect my external inverters to AC OUT1 and disable the internal charger of the multiplus (see also Way to disable AC charging). This is done by by setting “Charge Current” to “0” using VEConfigure. at the charger tab.

Will the multiplus enable the internal charger in this case automatically?

Or do I have to connect the external inverters to AC OUT2 instead?

27

@herzigwi
AC-in, AC-ou1 and AC-out2 are internally connected.
If the grid fails, AC-in gets disconnected by two relays in series to provide grid protection AR-4105 (in DE).
In normal configuration, AC-out2 gets disconnected as well, while AC-out1 will stay connected all time.
In current MP2s, the relay for AC-out2 can be controlled by the “relay assistant”, e.g. switched on and off not by grid failure but by SOC for example.
The inverter will source AC-out within milliseconds so IT equipment will not be interrupted, like with an APC Smart UPS.

About PV:
you can connect AC-PV on AC-in, which will be disconnected an grid failure.
You can connect on AC-out1+2, while will most probably remain active as the MP2 creates a high quality (island/micro) grid.
Current PV inverters have to apply a grid code which decrease power output based on increasing grid frequency defined in AR-N-4105. Though your IQ7 are expected to work with the MP2.
The power on AC-out1+2 are combined in respect to the factor 1 rule. The rule determine the peak power the MP2 can handle in case of grid failure and full batteries. The energy must be absorbed until the PV inverters have been shutdown.

You should switch your charger on to absorb the energy from the PV inverters into the battery and the MP2 electronics.

If you haven’t bought a MP2 yet, I recommend the biggest with internal certified grid protection, which is the MP2-48-5000-70. In DE it’s just 100 EUR more compared to the 3000.

If you drained your battery and MP2 has shutdown due to low battery, you PV inverters will shutdown as the micro grid created by the MP2 is missing. There is no chance to switch on the system without a grid even in the brightest sun shine.
For this “black start” condition a MPPT (PV charger) is a great solution. It will power on by PV only and charge the battery. It will even raise the DC voltage, so the MP2 starts up and creates the micro grid. The micro grid will make you PV inverters start again. Than you have all PV power available to charge your battery.

Now it’s up to your scenario analysis what you need and which effort you want to invest.

Maybe a spare MPPT and PV cable with MC4 connectors are sufficient for the black out case.

If needed you can put some medium critical loads on AC-out2 and disconnect them on a medium SOC.

I have 3x MP2 5k with 7kW Hoymiles micro inverters on AC-out1. A MPPT 150/45 with 4x440Wp is used for battery charging and black start.
Critical loads like IT, gas heating, freezer und three plugs are on AC-out1.
Non-critical loads are on AC-out2 and get disconnected on 20% SOC and reconnected on 30% by the relay assistant.

Hope this helps…

1 Like
28

Thanks, but you seem not to understand my question. Or I did not explain it in an way you can understand me.

Two of my external inverters are now connected to AC-OUT1 on multiplus II 47/5000.
To stop charging the battery the another external inverter which is connected to AC-IN, the only way was to disable the internal inverter by setting “Charge Current” to “0” using VEConfigure. at the charger tab.

My question is: If the grid fails will this burn down my multiplus because the PV inverter load at AC-OUT1 can not be directed to the battery because the internal charger ist set to zero?

The 1.0 rule only works safely because the PV inverter load can be directed to the battery before multiplus increases the fequency to shut the inverter down. In my case I have switched this off.

Maybe nobody tested this or only Victron knows if they will immediately change “Charge Current” to 70A again.

A safe way would be to change the external inverters in my configuration from AC-OUT1 to AC-OUT2. In case of grid AC-OUT2 will be disconnected and the inverter will stop immediatley because the voltage drops to zero.

29

@herzigwi
No, only save way is to connect the PV inverters on AC-in where they get disconnected in case of grid failure. But I haven’t tested it.

Using Out2 with normal behavior- disconnect on grid failure - has no advantage over AC-in.

Sorry I mixed up the thread owners posts with yours.

30

Hi, I found this topic because rule 1.0 also concerns me.

The background of this rule is to assure that Multiplus can handle AC PV power in case of grid loss. Why only in that case? Because if we have grid, sudden loss of AC load won’t affect multiplus because energy surplus will be transferred to the grid.

So we have a scenario like full power of AC PV on AC-out1 side. Theoretically after grid failure we must take care of that PV energy. But in practice, Multiplus switching time is not “immediate”, it takes some 18-20ms. During that time modern AC PV inverter switches off immediately (I was testing it on some 2 or 3 ESS systems with Victron + AC PV). And then, we have grid code (as an example, Poland where I’m located):

  • re-synchro of inverter : 60s time delay after grid frequency becomes stable
  • maximum active power incrementation 10% of nominal power per minute

plus overfrequency protection:

  • full stop of power generation after reaching 51,5Hz

In that condition, Multiplus has several minutes before AC PV inverter can cause any threat, and raising microgrid frequency will decrease or switch off power generation if needed.

Those grid rules are valid for several years AFAIR and all new PV inverters must follow those settings in order to be allowed to on-grid connection.
Which, in combination with fast PV inverter LOM sensing, makes rule 1.0 obsolete.
Once again, I’m talking about modern, new inverters. Old ones could probably act differently and then cause some danger to Multipluses.

1 Like