Fronius being throttled at 08h30

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question

Stuart asked Feb 23, '24

Fronius being throttled at 08h30

I have a 90kVA system with 6 x Quattro 15kVA in three-phase - two inverters on each phase

I also have 4 x Fronius ECO27kW units populated with 20kW solar each

Additionally, I have 2 x 250/100A Victron MPPT units (each with 6kWp solar)

This is coupled to a Freedom Won battery (300kWh) with a BMS for control.

All components are linked to the CerboGX

DVCC is turned on without limiting voltage or charge to the batteries

The inverters are loaded with the PV assistant with PV inverters set at 108kWp (ie 4x 27kW ECO) and installed solar set at 80kWp (20kWp per Fronius)

At 08h30 in the morning when producing only 43kW and the batteries at 39% and at 53.20V (battery voltage) and DC voltage read ON the Quattro units is 53.52V, I see the output frequency has shifted to 51.9Hz and the Fronius production is being throttled. At the time, the CCL (Charge current limit on the battery remains at 1500A) and the charge voltage limit reamins at 55.8V

So, what is causing this throttling via the frequency shifting. I see nothing that would cause this. The battery is still happy receiving 1500A and needs 55.8V, so the system is far from those values

Thanks

Fronius charge current limit frequency

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Alexandra ♦ commented · Feb 24 at 02:21 PM

@Stuart

A possibility is heat in the inverters. Charging from AC PV is hard on them.

Alternatively the battery grid charging amps setting is low?

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Modifications Space

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Answer 1 · 2024-02-25T10:47:10Z

Stuart answered · Feb 25 at 10:47 AM

@Victron

I would enjoy to hear your take on this.

I'm happy to add more info. This is an off grid system with a generator on AC 1 IN and no input in AC2.

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nickdb ♦♦ commented · Feb 25 at 02:27 PM

Please don't directly call out to Victron staff, it is against our guidelines. If there is something that needs to be raised, the moderation team will do so, if they don't come across it themselves.

Posts that directly "@" staff without good cause are being moderated to reduce the "noise" it creates.

Thank you.

(Alex, one of the resident experts is already helping troubleshooting and if it was required, would certainly raise it)

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Stuart nickdb ♦♦ commented · Feb 25 at 03:02 PM

Hi. Sorry about this - did not mean to cause an issue.

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nickdb ♦♦ Stuart commented · Feb 25 at 03:45 PM

No stress. All good. Hopefully someone here can get you sorted.

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Alexandra ♦ commented · Feb 25 at 02:30 PM

@Stuart

So what are your grid charging amps (this affects AC PV charge as well as they are grid).

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Stuart Alexandra ♦ commented · Feb 25 at 03:01 PM

Hi. This is an off grid system. The generator charging amps is set to 40A on the AC 1 input. So 80A per phase as there are 2 x Quattro 15k on each phase.

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Stuart Stuart commented · Feb 25 at 03:05 PM

AC2 input is set to 16A but nothing is connected to the AC2 input.

And all the loads (and of course the PV inverters) are connected to AC1 OUTPUT.

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Stuart Alexandra ♦ commented · Feb 25 at 03:10 PM

Hi... The DC charging amps on each inverter is set to 200A on the "Charger " page

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Alexandra ♦ Stuart commented · Feb 25 at 03:51 PM

Ok so settings not an issue.then for DC charging. Do you have high ambient temps?

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Stuart Alexandra ♦ commented · Feb 25 at 07:19 PM

The installation (ie battery and inverters) are housed in an insulated and airconditioned room which should be keeping the room at around 24C.

So I don't think the system is getting to hot.

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Alexandra ♦ Stuart commented · Feb 27 at 01:43 PM

Can do with poor air flow. Heat buildis up in corners. Often L2 get blasted by L1 and L3.

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Answer 2 · 2024-02-27T08:05:12Z

Stuart answered · Feb 27 at 08:05 AM

Hi

Here is a screenshot of the system. It was working well, till just about 10h00, when the throttling began... I just cannot see what is causing this limiting.

a.jpg (70.2 KiB)

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nickdb ♦♦ commented · Feb 27 at 11:02 AM

Hi @Stuart , some observations.

At 10am your battery is at 32C, some of that is charging related but it is still warm.

You are running at significant power levels, that will produce heat.

I would encourage you to measure inside the room and to check outlet temps.

Every degree above 25C internal, will derate.

In that pic, each inverter will be producing near 110A of charge, once DC PCV is eliminated.

Have you measured each system to make sure the load is balanced evenly across each pair? If one is working harder than another it will cause issues.

Are any alarms being generated?

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Stuart nickdb ♦♦ commented · Feb 27 at 12:44 PM

Hi Nick - thanks for the insight.

I will get the client to check the temperatures inside the room.

I have noticed that there is a large difference between the loads on each phase. Mostly, L1 is much higher than the other two and quite often L2 is the lowest.

Earlier today, the load was:

L1 - 11.3kW

L2 - 2.8kW

L3 - 4.2kW

And incoming solar was 60W (20kW per phase). As such, L2 was "charging" at around 17kW, while L1 was only 8.7kW. So, I can start to understand now that the system would then have to start holding back the solar as L2 is "maxed out".

I have seen many "Temperature L2" warnings between 10am and 11am this morning, which match to increases in frequency.

I have now reduced DC charging Amps (in each of thr 6 Quattro 15k units) to 125A. So the system is still reducing solar (once L2 gets up to 125A) but at least its not "overshooting" and getting hot.

Ultimately, I think they will have to look at getting the three phases balance better.

Thanks again to you and Alexandra for the input.

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1709037694093.png (24.7 KiB)

nickdb ♦♦ Stuart commented · Feb 27 at 01:20 PM

It is always difficult to help on more complex issues without access, the snapshot had shown an imbalance as well, which I should have mentioned.

Phase imbalances, as well as inverter imbalances can create interesting problems, there will usually be secondary symptoms, such as temp.

I'm sure you will get it sorted.

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Alexandra ♦ nickdb ♦♦ commented · Feb 27 at 01:42 PM

Yeah the inverters are getting hot if you are seeing temp warnings. Air flow is important as well as temperature. It is common for the heat to build up in spots in the room

We have temp sensors usually between inverters. The Cerbo has neat integration with all the now. You can even temporaritly put a few ruuvis in the room and explore where the build up is.

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Stuart Alexandra ♦ commented · Feb 28 at 06:30 AM

Hi - I do think the problem is this:

The phases are not balanced, so as solar power increases, there is more energy available on L2. This then maxes out L2's charging capacity and the inverters get warm and derate. This causes the system to increase the frequency in order to lower the incoming solar power, which cannot be done on L2 alone, so ALL power is reduced - even though L1 (especially) and L3 have capacity to charge.

I can get a couple Ruuvi's and put them in - this would allow us to understand better, too.

Thanks again for your insight.

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Alexandra ♦ Stuart commented · Feb 28 at 06:48 AM

It is a possibility. Obviously fro my end it is a fair shot in the dark as I know next to nothing about the install and physical set up.

In my experience though, I have just seen on a couple of installs L2 gets the heat. For the most part it probably just needs better air flow around the inverters if the room is already air conditioned and cold.

In one system (and you can do this if you are sure nothing will fall in) you can remove the tops, or the top lids of the inverters can be lifted up a bit with some stand offs.

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