question

Hi @Francesco Marzulli

maybe I can give you some helpful tips here.

First of all, it makes a difference, if you are going to use ESS or not.

Depending on that, you will have to set your Multis/Quattros to follow a grid code, or not - this makes a big difference.

Speaking generally, there is a big difference in AC quality, that comes from the grid, compared to AC output of a genset.

It depends on the type of generator what to expect in general:

Eg.:

Capacitor regulated: cheapest method, stable and longliving technology, not the best AC output stability.

AVR: less cheap in general, cheap regulators die easily, pretty stable and good quality AC output, better overload capabilities.

Inverter: complicated electronics, best AC output quality, engine speed is variable to output power, bad overload capability, smaller type of gensets.

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important VE.configure settings for generators:

Most important setting: AC input current limit. This sets the maximum current draw from that source. This limits the power the genset is loaded with. (There is an excel sheet around for minimum values for different units, to retain power-assist functionality)

Dynamic current limiter: this option prevents that the genset is fully loaded at once. This setting raises the draw from the input step by step, so the generator has some time to regulate

Accept wide freq. input. does exactly what it says. Useful, if the genset is not stable 50Hz.

UPS function: disable this to make the input less sensitive, for a slightly longer transfer time.

This option is recommended to be disabled on most gensets. Only the really good ones can handle UPS setting staying active.

Weak AC - input. It basically reduces power factor of the charger part, and uses another mechanism, to be able to operate with weaker AC sources. In my expierience, it is with most gensets, not neccessary to enable that.

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With these settings, I was able to operate most generators with all 3 regulation methods mentioned above at the input of a Multi.

Even cheap €250 ones from the toolstore, operate good and reliably. But performed far away from the full advertised power.

I found out, most cheaper Gensets are only able to operate continuously at maybe 60-70% of their rated power some even lower, if you use them for longer, expensive ones will most likely work at their rated COP.

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1.) No grid code set. No ESS system:

You are happy to use all options above, most gensets will work

2.) Grid code set, ESS system with Multis

Your single input is configured to follow strict grid rules. Most options are not available, Multi will export energy to input - no genset on input possible

3.) Grid code set, ESS with Quattros

Well this situation is a bit odd, if you set a grid code on a Quattro, both inputs follow the grid rules in terms of V and f. Export is disabled for the input that is set to generator in Venus - system settings. It is only possible to disable LOM on the generator input, no V and f settings are available.

Only real HQ AC output gensets are going to work on the generator input. I would not advise to go this way. There might be a possibility in future firmwares to be able to except the generator input from the grid rules - but not at this time. Additionally - you have to take care, if you have AC-PV on AC-output. The Quattros freq. shift is not going to work if the genset is accepted on Ac-in.

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Another downside with generators operating at the AC-input is, that the network type plays an important role. Most smaller gensets are isolated IT type gensets. It is not legally allowed to use them at a house installation by most local laws. You have to use a genset equipped with RCD, those are not the entry level price ones.

If a genset gets accepted on AC-in of a Multi or Quattro, the AC-output is bond to the AC-input. This means you will most propably have flickering lights and poor AC quality in your circuits, when you use lower level gensets.

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Conclusion and solution:

In my opinion, the best and eaysiest way to implement a genset in a ESS is, to DC couple the genset to the battery via an extra charger. This could be another Multi connected via a MK3 interface (for an extra VE.bus port) to the GX, or any other charger you want.

If you go this way, you will have all options available to setup your generator and most gensets are going to work. The network type of the genset doesn't play an important role, you don't have weak generator AC inside your circuits and it is also possible, to blackstart the system if you only have AC-PV and your system is missing MPPTs.

Downside of this method is the efficiency loss, if loads are consuming AC directly when the genset is running.

Don't forget to implement safety, via Allow To Charge contact when using a Lithium battery.

Hope my few cents are going to be somewhat helpful.

Have a good time.