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Frequency shift stacked at 51.5 Hz during the night

Hello. I have a three phase Qattro off-grid set-up with Pylontech batteries and SMA inverter AC coupled. Frequency shifting is lowering the solar production when battery is full but during night frequency is not recovering 50 Hz during battery discharge. It keeps 51.5 Hz value. This avoid the solar inverter to start generating when sun arises. Frequency is only recovered when generator starts because of low battery. The set-up uses the PV assitant for frequency shifting and I have check the settings many times. Can anybody help me? I've seen similar cases to mine but with no solution.

Thank you.

alejandrocortes asked
alejandrocortes published ·

2 Answers

Frequency shift not working

We have installed a few systems that have Multiplus 2s ac coupled to enphase equipment off grid. This normally works great, however we have just done this ac coupling to another site recently, all set up the same, and the frequency shifting doesn't work, the system stays at 50hz, so the multiplus attempts to overcharge the 48v lithium batteries, so we have to turn off the ac coupled system. Any ideas on why this isn't working?

craig asked
sharpener edited ·

7 Answers

MyPV AC-Thor in off-grid system - settings?


the manual ( ) says that when using AC-Thor in an off-grid system frequency shifting (PV-inverter assistent) has to be activated at the Multi.

- Is this also necessary if only DC-coupled PV is used (no PV-inverter on AC-out)?

- what are the frequency settings in the "PV-inverter" assistent? Are the default-settings ok?

Best regards

e-box asked
n-dee edited ·

6 Answers

Frequency shift for 3rd party ABB inverter causes temporary power cut

I have an 5Kw ABB Uno inverter connected to the output of the Multiplus. The ESS has some reduce power and disconnection frequencies set. But when the Multiplus tried to limit the ABB power, the power temporarily went off for a fraction of a second (enough that all my electronics restarts), and I got a Error code: #39 - PV Input shutdown.

How can I start to diagnose the problem?

The output frequency momentarily goes to 51.8Hz


The settings on the ESS are here


And I have the what I think are the equivelent frequencies on the ABB

F>> Grid over-frequency (OF) threshold (extended range) to 52.7


F> Grid over-frequency (OF) threshold (restricted range) to 50.2

de1nonly asked
fivosiv520 answered ·

1 Answer

Frequency modulation on multiplus II goes immediately to max

I have a Multiplus-II-48/5000/70. My solar panels are connected to the UPS side. I like my solar invertor to reduce output when batteries are full and grid is nog available to dump extra energy. So i use the "pc invertor support" assistent to change the Multiplus-II output freqency to signal to the solar-invertor to reduce power (frequency modulation).

The specifications for the solar-convertor are:

It starts reducing output power at 50.40 Hz. Output power will be reduced to zero at 50.72 Hz. Disconnect freqeuncy of solar-invertor is 52 Hz.

I have this problem: The multilplus raises the freqency to fast for the solar-invertor to react (or maybe it raises it to disconnect freqency immediately. Not sure because it goes very fast).

Result is that the soloar-invertor is switching off and on all the time.

The solar-invertor is a fox-ess. They Fox-Ess say that the "derating speed" of the solar-invertor is set to 20. They ask if they should make the threshold wider. But i do not exactly know what they mean by derating speed and threshold. Neither can i gave them any new values for these settings.

How to solve. Can anyone help?

pietere asked
pietere commented ·

1 Answer

Current and Frequency measurement AC In for Skylla i Charger or AC Out for Phoenix Inverter

Hello, what I need to visual the current and frequency?

I want to see on VRM / Touch 70 a few data's.

AC In from Shore/Generator to my Skylla Charger.

AC Out from my Phoenix Inverter.

Skylla I is connected with VE.CAN with the Cerbo.

Phoenix Smart is connected with VE.Direct with the Cerbo.

And is there any Tile in GUI to visual this without a Multi/Quattro?

Here is an example what I want to see, but without a Multi/Quattro.

Best regards Robert


And here is my Touch 70


Robert asked
Robert edited ·

0 Answers

No ESS assistant found - fronius PV inverter

Good evening, seeking for some help.

We installed a Fronius ECO 27.0-3 inverter with a Victron energy meter EM24, and a GX. We do not have a battery inverter installed nor do we have a battery system but want to control the Fronius grid feed via the GX. Customer will expand later on with the battery inverter that is why we wanted to install the Victron energy meter.

I am trying to setup the GX but because there is no battery inverter I cant seem to get the ESS assistant running to control grid feed.

How can I achieve this,


jacodutoit asked
Alexandra commented ·

1 Answer

Frequency Shift issues


I am having these issues with 2 systems right now. The Victron is shifting frequency, and it is locking and keeping the PV inverters off. One system it happens at 60%, and in the other, it seems to happen once the batteries are full, and it won't shift frequency back to 50 Hertz to turn the PV inverter back on when a large load is applied.

Victron Inveters are 15kva 48v Quattro. And a 5KVA Multipluss 48v. Both PV inverters are Fimer 5kw ac coupled. I have used this combination over 100 times and have not had these issues. To be clear these are 2 separate systems.

xylem89 asked
xylem89 edited ·

1 Answer

Frequency shift- Quattro 48/15000

Good day .

Is there a way to determine why the inverter is Frequency Shifting ?

Is it possible to find out were the command comes from ?

I am running 3 x 48/15000 Qauttro , 56KWh Solar MD batteries and Solar Edge 27.5 Grid tie inverter.

The Qauttro's seems to shift the frequency and the solar edge starts throttling. Is there any way to determine what will make the Qauttro's start frequency shift ?


Johannes Cronje

johannes-cronje asked
xylem89 answered ·

3 Answers

Charging Behaviour of a fronius primo configured with a quattro off grid

In the documentation detailing configuring a Fronius Primo using frequency shift there isn't much information about system operation when installed offgrid. It seems to be for ESS.

We have a 48 - 8000 Quattro configured (at present) with 2 charge controller mppt's, 15 KWh storage and a cerbo GX.

We want to add additional panels and a dual mppt ac string inverter like the Fronius Primo or SMA etc.

If the system requires no power from the Fronius or SMA part of the system, will the frequency shifting work normally with no grid connection?

esusa asked
scraggs edited ·

2 Answers

PV inverter support assistant and DVCC


I have been succesfully using the PV inverter support assistant of a Multiplus 2 to control an external heater (excess solar energy dump in off grid system) via frequency shifting. My system had lead acid batteries.

Now I changed to Pylontech batteries. Charge control is now done via DVCC.

This caused the PV inverter assistant to stop working. I can configure the assistant, and as long as I don’t plug in the VE.bus cable of the inverter in the Cerbo unit, it works: ac output frequency is increased by Multiplus, as expected.

However, as soon as I plug in the cable, and thus establish communication with the inverter, the DVCC seems to overrule the inverter and PV inverter assistant stops frequency shifting.

Is there a way to make this work?



alexander-aerts asked
alexander-aerts commented ·

1 Answer

Multiplus II ESS, GRID Freq. >50.1hz

3 Phase Multiplus II-5000 ESS, goes ofgrid, when GRID Frequency goes over 50.1Hz. These is in the morning 06:00AM.
ESS Assistant is configured for Europe/Switzerland.

phak4224 asked

0 Answers

Multiplus frequency shifting: stuck at control range maximum


I use frequency shifting by a MultiPlus 48/3000/35-50 (firmware v430, off grid) to control electrical heaters via an AC Thor controller. The idea is to maximize PV power consumption. Layout:


My MultiPlus setup is the following (full settings attached):

Charger settings:

Absorption voltage 55.50 V (absorption voltage of set MPPT = 57.4 V)
Float voltage 55.10 V (MPPT float 55.2 V)

PV inverter support assistant settings:

*) The solar converter will start reducing its output power at 50.10 Hz.
Output power will be reduced to minimum when the frequency is 51.00 Hz.
The converter will disconnect when the frequency is higher than 53.00 Hz.
*) Total installed PV inverter power is 1500 Watts.
Total installed PV panel power is 1500 Watts.

The issue is that the MultiPlus frequently gets stuck at the maximal value of the frequency control range, i.e. 51 Hz. So not at the "disconnect" value of 53 Hz, which seems to be reset according to what is written in the documentation of the PV inverter assistant (at a voltage equal to Float V - 5.2 V).

An example of this issue is shown in the graph below. At time = 0 h (midnight), the system is already stuck at 51 Hz from the previous day (green curve), despite the fact that the battery voltage is 49 V or lower (blue curve), which is well below the charger absorption voltage setting of 55.5 V (dotted blue line). I had switched off the AC Thor loads the previous day, to avoid battery draining.

In the morning I remotely reset the MultiPlus to get the frequency back at 50 Hz.

At around 12:00 pm, the system did what it should: when the battery voltage increased above +/- 55.5 V (blue curve), the frequency shifted. I switched on the loads again, and AC power was sent to the heaters by the AC Thor controller (red curve). I have two sequential heaters of different power controlled by the AC Thor, explaining the variation in AC power consumption.

One can also see that at the end of the day, around t =18 h , the system again was stuck at 51 Hz (and so power consumption maximal at 1500 W), despite the fact that there was not enough PV power available and that the battery voltage reached values as low as 48 V. This is far below the absorption (and float) voltage set for the MultiPlus charger, so one would expect the frequency to be shifted back to 50 Hz. The battery was drained to 80 %, at which time the AC loads were switched off automatically by a Multiplus relay that I programmed for this purpose.

The problem is of course this behaviour drains the battery unnecessarily.

Weirdly enough, the issue does not always happen. Many times it just works as it should (see bottom graph). I did not find any regularity, except that it seems to happen on days with alternating sunshine/clouds, and after the Multiplus returned from the "disconnect" frequency, 53 Hz in my case. Similar behaviour has been reported a few times before on this forum (mostly in the context of frequency shifting for AC coupled PV charging) but a definitive solution was not given.

Can this be solved by changing the settings somehow? I tried many charger voltage/ frequency range settings already, but always the issue pops up. Or is this inherent to the way the frequency shifting is programmed?

Thank you.


Multiplus settings: MP_settings.txt

A good (sunny) day - example of how it should work:


alexander-aerts asked
Paul B edited ·

1 Answer

Volts and hertz with Victron + pylontech

Hello. I'm new to the forum and I would like someone to help me with a question.

I have a Victron Quattro + Pylontech US2000C batteries. These batteries have a maximum charge voltage of 53.5 volts.

On the other hand, Victron says that the voltage at which the frequency starts to rise, in order to control an AC-coupled fronius inverter, is 54 volts.

The question is how can that system work, with these different tensions? it is impossible!!

Is there any way to modify the voltage at which the frequency rises, to adapt to the charging voltage of the pylontech batteries?


carlos007 asked
nickdb commented ·

3 Answers

Off-grid PV Inverter support on AC IN - respond to frequency changes

In all of my searching, I can only find configuration options to modify the behavior of Multis/Quattros by changing the frequency on the AC Output. But I'm still a novice in the Victron world, so maybe I've overlooked something?

What I'd like to achieve is change battery charge/discharge parameters based on the frequency of AC Input. As far as I can see, this isn't possible, but I'd appreciate being corrected if I'm mistaken!

My goal is to use Multi to:

  • keep SoC > XX% (or keep a minimum DC Voltage)
  • if frequency > XX, charge batteries (ideally, current increases with frequency)
  • if frequency < XX, discharge batteries (via PowerAssist or Ignore AC?)

The purpose of this is to interact with an existing off-grid system in a supportive way. Grid-tied inverters will curtail their output in response to rising frequency. To avoid "wasting" that energy, I'd like my Multis to store power in the battery, until the excess condition is gone, then give this energy back again until the batteries approach empty.

I'd prefer to use an Assistant or Virtual Switch over something like Node Red, but I don't see the functionality there. Am I missing something?

randyoo asked
randyoo edited ·

0 Answers

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