question

This is just a suggestion

as you have not mentioned the freq setting you have set, try increasing the freq setting to say 55hz in the assistant as I am pretty sure that all grid tie inverters have to shut down by a frequency shift, but some will also de-rate at different settings

NOTE the Multi plus can only raise the frequency if the mains input has failed.

secondly if they don't and you are stuck with them then you could install some contractors in the incoming grid tie inverter lines that are triggered on/off by setting up a assistant in the multiplus to turn the contractors off if battery voltage went above a set figure and back on again at a lower figure,

For that matter you could conect the grid tie inverters to ac2 out and use the assistant to turn this internal relay on and off based on a DC voltage trigger

Just some ideas hope they help in your setup

Hi Paul, Thanks for responding to this. I tagged @Phil_Gavin because he wrote that he has used a Solis inverter for frequency controlled AC coupling. The Solis will switch off if it sees out of range frequency, but I want to use the frequency de-rate function to optimise power from the PV inveter. That means de-rating the output gradually in respose to the state of charge of the batteries, rather then just cutting out.

It is frustrating because the Solis information shows a graph of linear power reduction from 100 to 0 % as the frequency rises from 51 - 52 Hz, which is exactly what I need it to do. When I contacted Solis they say this is only available on US models, which seems wierd.

On the Victron Multi, when you load the assistant for frequency de-rate, it tells you that this will not work when you are coupled to a grid on the AC input. That is fine, this set up is entirely off grid.

in the solis network standart setting, you need to choose the "gen50" (or gen60 for 60hz) setting, then you got the frequency derating from 50 (100%) to 54hz (0%)

it works nicely

@Yann could you please share Solis model and firmware version? Probably they support "gen50" feature for new models only or from a specific firmware version.

@Mikhail Petukhov the model I just tested is a S5-GR1P2.5K-M (2.5kW, 1mppt) but I have no idea wich firmware is running inside, and I can't see it right now (my customer is gone for some weeks)

I read somewhere the S4 models (previous generation) already have the "gen50" mode.

On the S5 I have, there is also a "manual setting" that let you define everything as you want, but there are tons of parameters wich is not clear what they are for. Nothing in the user manual about them.

@Mikhail Petukhov Here are the inverter informations I have :and from the solis monitoring, I can see : DSP version 0002, HMI version 0046, country code 54