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petajoule avatar image
petajoule asked

ESS PV preference in a DC/AC hybrid system

How does ESS behave in a hybrid DC (Victron MPPTs)/ AC (Fronius) system with no feed-in and full batteries?

Will it regulate down the DC PV system or the AC PV system?

I would prefer the DC PV system to be regulated down, but am not sure if that is the default or configurable at all.

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2 Answers
rainerb avatar image
rainerb answered ·

Hello PetaJoule.

I have a ESS system with one Victron MPPT DC charger and a Fronius AC inverter.

But in my case I allow the Fronius to feed-in excess PV power and I disabled the feed-in function for the DC charger. So in my case only the DC charger will be regulated down.

For a Fronius inverter that is connected to the GX device, there is the function "Fronius Zero feed-in" available. If you enable this, then the Fronius is throttled down (too).


Regards

Rainer


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petajoule avatar image petajoule commented ·

Hello @RainerB.

Thanks. Yes, we're aware of the zero feed-in - that's why we do use the Fronius.

The question is just if there is a possibility to decide which one of these (MPPTs or Fronius) is regulated down preferably.

We would prefer the MPPTs to be regulated down first so the Fronius would support the internal Microgrid directly with AC (instead of the MPPT -> DC -> Quattro -> AC chain).

However, we're not aware if there is a configuration possibility to achieve this.

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chrisawp avatar image chrisawp petajoule commented ·

I have a similar situation now where the MPPT takes preference above the AC Coupled on AC-Out and not sure why the PV inverter takes up the load first before the Multi discharges and charges via the MPPT.


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Mark avatar image
Mark answered ·

There is no option or ability to formally preference/favour AC or DC coupled PV over each other (when there is excess PV).

In an ESS with both AC and DC coupled PV, with feed-in disabled and excess PV power available, in general the AC coupled PV will be used to directed power AC loads and the DC coupled PV will be used for direct battery charging.

Although the Inverter/Charger will still attempt to utilise some excess AC PV for battery charging and if the battery is fully charged, then DC coupled PV could be throttled down to zero.

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petajoule avatar image petajoule commented ·

I see - thanks.

Maybe I can achieve some sort of preference if I configure the MPPTs with slightly lower bat voltage (for bulk/absorption) than what the Quattros are configured to.

That should throttle them down at a 99% battery full, while the fronius would get throttled down by the system as last resort.

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Mark avatar image Mark ♦♦ petajoule commented ·

Note that for systems with the ESS Assistant installed, the MPPT Solar Chargers will follow the charge curve as set in VEConfigure. The charge parameters configured in the MPPT Solar Chargers are ignored in an ESS setup (Ext Control).

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