energylad avatar image
energylad asked

Combine 2 3-phase quattro hybrid generators

I have a 30kW Hybrid unit including DC generator, 48V Li batteries, 3 x 10kVA Quattros in 3phase. The inverters are in inverter mode only and do not charge the batteries, the generator charges the batteries, controlled by a PLC. The inverter configured to cut off at low voltage setpoint.

I'd like to combine two of these units to serve a max of 60 kVA load , 3 phase.

Can I AC couple these systems ? Connecting inverter 1 of each unit to phase 1, etc. so I'd have 2 inverters on each phase, 20 kVA per phase?

Is this possible ? How would it be configured software ?

I realise normally two DC batteries can not be used if not on same DC bus, but does it matter if the inverter never charges the batteries ?

MultiPlus Quattro Inverter ChargerAC PV Coupling3 phase48v battery
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2 Answers
Kevin Windrem avatar image
Kevin Windrem answered ·

Not an expert, but from what I understand, yes you can parallel a second Quatro to each existing phase (6 units total). All units must be the same type/size. There are sometimes issues with adding newer units to older ones.

Victron recommends all inverters use a common battery bank, so one bank connected to all 6 Quatros.

Wiring, especially the AC is critical with all identical lengths to paralleled units. This is essential in order to properly load share. In your case, you won't have AC input wiring so just make sure the output side has identical lengths to the units paralleled up on each phase.

You use the VE.Bus System Configurator (same tool you used to set up the 3-phase units).

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energylad avatar image energylad commented ·

Thanks for response. Unfortunately i have 2 battery banks is separate containers which can not be combined, that's the bit i need clarification on . Can I parallel the quattros but keep the batteries seperate if the quattro are never going to charge the batteries, only discharge them

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Kevin Windrem avatar image Kevin Windrem energylad commented ·

At the very least, the battery negatives MUST be connected together. Otherwise, you fry the VE.Bus interconnections.

A low battery condition (or any other fault) on one Quatro will shut all 6 inverters.

There is a tutorial in the Online Training section of the web site about creating systems with multiple inverters. I suggest you watch it and take the tests. Lots of good and useful stuff there.

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alan avatar image alan commented ·

Yes, can’t use separate banks. Victron recommend it for a good reason and it makes perfect sense.
The master unit controls the pulse width of the slave, the pwm pulse width dictates the voltage output of the AC sign wave. This is calculated by the micro dependent on the DC battery voltage. Using 2 batteries will result in different DC voltages which with the same PWM pulse, will result in a voltage and current differential in the AC sign wave of the two units/systems and cause current flow from one unit to another. And cause imbalance between the units.
Another reason that DC wiring in a parallel system needs to be as close as possible to symmetrical.

If you can parallel the two batteries, then this would be entirely possible.

Or yes as @Daniël Boekel (Victron Energy Staff) mentioned, a series config can work.

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @EnergyLad

This can work, and it is done by others also.

It can be difficult to to configure correctly, but as your inverters don't charge it might be easier in this case:

One set would be connected to the input of the second set, the second set you configure the maximum input current to a level that works well.

As the correct working of such a system depends on a lot of settings and site specific oddities. Please be aware that Victron cannot officially support such systems.

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energylad avatar image energylad commented ·

Thanks for info, and I understand Victron can't officially support.

So if I've units A and B which 3 inverters each in 3ph and I connect inverter B1 to the input of A1, and so on for 2nd and 3rd ph inverters won't I still be limited to the 10 kVA of the 1 inverter. I will double my energy capacity by being able to use the second batteries but not my power which is what I need. I need 20 kVA per phase.

Is my understanding correct ?

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alan avatar image alan energylad commented ·

Th second set will add power through power assist.

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