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Bruce avatar image
Bruce asked

Fronius /Victron Quattro off grid system plus wind turbine 230vac single phase output

Hi Guys, really hoping for a unique solution here from the community. We have an isolated farmhouse that currently has a 10Kw wind turbine with single phase 230vac output. ( the original system used an inverter charger connected to wet batteries to deliver 230vac to the house load.

The client has opted for installing a PV solar array delivering about 6.2Kw peak power to a Fronius inverter which will use a Victron Quattro to source the 230vac 50Hz reference, given the house is off grid.

The Fronius has active phase control via the Victron so once the associated new lithium storage is full, the Fronius will throttle off by screwing the 50Hz.

Into this mix we want to add the output of the wind turbine..i.e. the 230vac i.e we are trying to create a micro grid for the house.

The issue we have is that the plan to use a turbine inverter with a simple 230vac output which can be managed by the Victron as the second source of AC power has been thwarted because the wind turbine inverter requires a rock steady 50Hz grid frequency and it will not tolerate even small shifts in the frequency.

Is anyone got some bright ideas how we can still have the Fronius/Victron solution and be able to integrate the other source of 230vac?

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4 Answers
Paul B avatar image
Paul B answered ·

so what happens if the frequency does move for the wind farm inverter


it must have some shut down

the frequency movements can be modified on the victron and the Fronius so maybe you can still control them within the limits of that other wind farms inverter limits


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Bruce avatar image Bruce commented ·

Hi Paul,

What had been a main determinant in our serach for answers is that an early decision was made to create a 230vac microgrid system for the farmer so that simplistically the farm was presented with 2 ac energy sources, which together would handle some of his peak loads which the existing turbine charger/inverter + battery does not cope so well.

We though we had a solution by replacing the inverter charger on the turbine output with a new 3phase to 1phase direct 230vac output inverter, which the manufacturer sells for normal on-grid operation...

We believe at the moment the Victron would happily provide the 230vac50Hz reference for this new "on-grid" inverter...however that latter can't tolerate the Victron screwing the "grid" frequency when it goes to shut off the PV Inverter when the lithium storage is full.

We really do want to avoid a DC bus if we can possibly avoid it.

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kiwi-sparky avatar image kiwi-sparky Bruce commented ·

Hi frenchbruce . I have an near identical situation. Interested to know how you solved this problem.

If you have time I would love to know the outcome of this one.

Many thanks. Elstin




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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

If you absolutely cannot have any frequency adjustment then I wouldn’t muck around with AC bus solar and just use a DC MPPT for the solar connection.

That isn’t the only solution, but I think it’s the best one. There are options to connect different charge sources on AC inputs and other AC outputs and control them with assistants before frequency shift points, but none are as robust as DC bus solar.

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Bruce avatar image Bruce commented ·

Hi Guy, thanks for your response. Our farm house solar array strings are high voltage hence our desire to employ a reliable PV inverter to give us our number 1 AC source for the microgrid....and certainly the Victron can handle that reliably and interface with a BYD B Box lithium storage unit.

The existing turbine ( a Bergy unit from the USA ) even with its existing charger /inverter and wet batteries...has been reliable but the batteries are near the end of their life, hence our reason to seek a solution that would allow the victron to charge the new Lithium storage box using 2 AC inputs while giving the farmer addition Kwatts on the microgrid.

The turbine manufacturer has offered a new on-grid type inverter which on first looks would have made life easy...i.e. this would have been a neat second AC input into the Victron box but the intolerance of this (on-grid type) inverter to any freq shift , has tripped us up..and left us searching for anwers.

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Bruce avatar image Bruce commented ·

Hi Guy,

We seem to be chasing our tail here, but we thought we had a solution with using Tristar high voltage MPPT units with a Victron Quattro and a BYD BBox but it now appears that the Tristars are incompatible. Can you explain what the issue is about?

Many thanks


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boekel avatar image
boekel answered ·

How are you controlling wind turbine output when the batteries are fully charged? It tolerates being disconnected I guess?

You could disconnect the 'wind input' above a certain SOC (say 90%) by configuring an assistant in the Quattro ('ignore AC input')

I would also opt for DC solar charging (Victron MPPT's), but it I think it can work by the 'intentional islanding'. Also, the Fronius might support throttling by the Venus (so doesn't require frequency shifting)

This frequency shifting not being allowed by the wind turbine could actually be helpful also: when you place it on the output side of the inverter, it will turn off when frequency shift is engaged.

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Bruce avatar image Bruce commented ·

Hi there Boekel, thanks for responding to our call for help. The turbine power system as it currently exists feeds a charger /inverter which does have a dump load so that surplus energy is bled off when the existing wet batteries are full..

The new system proposal would see a new ( on-grid) type inverter used to replace the old inverter/charger ...on-grid because the manufacturers intends customers to connect it to a normal power network grid. Hence our thinking that we could simply use the 230vac from this new inverter to be one of the 2 ac inputs to the Victron Quattro and the other being the AC output from the PV solar inverter...hence giving us a micro grid solution for the farmer.

However just thinking now, your comment about disconnecting the wind turbine output when the Victron engages freq shift to limit the charge to the lithium box, might be worth a second look.

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Paul B avatar image
Paul B answered ·

I would have thought Guys option of some 250 volt 100 amp MPPT units would be a good solution. if the battery bank is 48 volts then you just make two strings one for each mppt

then you dont need frequency shift at all


and if stuck morningstar have 600 volt MPPT units as well

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Bruce avatar image Bruce commented ·

Thanks Paul,

We will have a look at the Morninstar hardware option.....as we really do not want to be lifting roof modules to reconfigure the strings for low voltage outputs.

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Bruce avatar image Bruce commented ·

We got excited here for a few moments only to be knocked flat after being told that the Morningstar Tristar units are not compatible with a Quattro/BYD BBox arrangement.

Are the Victron Bluestar 250/85 MPPT units the only units that will work with the Victron Quattro/ BYD storage battery system?

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Paul B avatar image Paul B Bruce commented ·

In regards to the BYD systems I dont know you would need to do your own resurch there. but 2 x SmartSolar 250/100 mppt regs would do it but yes you would have to get the string voltage to the correct level

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