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awsmits avatar image
awsmits asked

Multiplus II questions for AC-coupling

I currently have a grid-tie solar system with 30 panels fed into a SolarEdge HD Wave Inverter. The panels have SolarEdge optimizers. SolarEdge inverter is 7600W.

I would like to use a Multiplus 2 (or a pair of them to gain 120/240 AC)) to set up an Ac-coupled off-grid system for battery backup. I have read that the Multiplus works well for this role. So here are my questions:

1. Can a 48V, 3000W Multiplus 2 handle the 7600W load coming from the grid-tie inverter...I have read that in "inverter mode" the Multiplus just passes the AC load, so it should. I understand that the Multiplus 3000W rating is based on generating AC power from the DC batteries when no solar or grid AC is available.

2. Can the Multiplus modify the SolarEdge grid-tie inverter output through frequency shift or other means? If so, how?

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pau1phi11ips avatar image
pau1phi11ips answered ·

1. Victron state a 1:1 rule whereby the inverter power should match the AC coupled power. See here: https://www.victronenergy.com/live/ac_coupling:start
It's possible to avoid this by not having the grid-tie solar system on the AC out and instead having it on the AC in but then you're losing the ability of it to automatically switch to off grid mode when the grid goes down.

2. The Multiplus's can do frequency shift for Fronius inverters. I don't know if this will also work for SolarEdge too. My guess is yes but not 100% sure.

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awsmits avatar image
awsmits answered ·

Thanks! I’ve read that linked page about 5 times now and get a different interpretation each time, so I’m still confused. If your interpretation is correct, I would need 3 Multiplus units, or a large Quattro?

On the same page Victron has a link to AC-coupling with SolarEdge, so I think that will work, too.

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pau1phi11ips avatar image pau1phi11ips commented ·
To be honest, you could probably get away with 2 3000W Multiplus II's in parallel. Depending on how often your 7600W array actually goes over 6000W.
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rikhf avatar image
rikhf answered ·

1 - Depends. On ACin yes. On ACout no. 1:1 rule see @pau1phi11ips answer.

2 - The SE HD inverter can only be throttled by means of frequency shift. So yes.

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awsmits avatar image
awsmits answered ·

OK, so help me understand, if grid AC is coupled to the Multiplus ACin, what happens when the grid goes down?

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