Trying to understand how multiple strings are connected to an inverter.

[inetdog]

Hmm, interesting point. When talking to tech support yesterday, they said that the inverter holds the voltage at an optimum 360V at all times by adjusting the voltage of the optimizers (or the optimizers adjust their voltage based on what the inverter needs, one of the two). Looking at the optimizer spec sheet, it says it's operating output voltage is 5 - 60...which mean you could have up to as many as 72 panels (per string??!!! In theory anyway? ) or as little as 6 panels.

Does that make sense?

It sure seems to, yes.

[HX_Guy]

Great presentation on how the power optimizers work, the technical stuff starts at 21:25 in the video:

If you find a link from the manufacturer please post it - not from sales companies.

[HX_Guy]

Sorry about the link. It was actually from a manufacturer rep (giving a presentation to a sales company I think). Haven't found anything nearly as detailed from SolarEdge themselves explaining how their system actually works.

Something else to share, SolarEdge (as do others I'm sure) has public monitoring accounts you can peek in on. This is an account from someone here in Phoenix, I LOVE how you can see what each panel is doing.

http://monitoring.solaredge.com/solaredge-web/public?name=John%20Emerson#layout_

Very interesting to see how the system works. The lighter the shade of blue, the more those panels are producing.
This person seems to have most panels facing south, a few facing east and some facing north(?).



You can click and see which panels are connected to which inverter/string.



Peculiar that the east facing panels are producing very very little right now, maybe they have a shade issue or what else could it be?

[bcroe]

Something else to share, SolarEdge (as do others I'm sure) has public monitoring accounts you can peek in on. This is an account from someone here in Phoenix, I LOVE how you can see what each panel is doing.

http://monitoring.solaredge.com/solaredge-web/public?name=John%20Emerson#layout_

Very interesting to see how the system works. The lighter the shade of blue, the more those panels are producing. This person seems to have most panels facing south, a few facing east and some facing north(?).

You can click and see which panels are connected to which inverter/string.

Peculiar that the east facing panels are producing very very little right now, maybe they have a shade issue or what else could it be?

For rooftop that could help. I prefer to occasionally just run around my ground mounted
system with a clamp on DC ammeter. Shadows vs output tell the story for 10 strings of
various orientations. Any failure would be obvious, with everything in pairs. Bruce Roe

[MikeG]

What about how these optimizers work?

Has anyone looked into how the optimizers work? From my understanding, the optimizers on each string need to communicate with the inverter. Does combining everything on the DC level into one input to the inverter still allow for this communication and the optimzers to work as advertised?

Also, does the input limitation of the inverter still have to cover the NEC 125% of the max output current after being combined at a fused connection in the DC combiner panel?

[inetdog]

Has anyone looked into how the optimizers work? From my understanding, the optimizers on each string need to communicate with the inverter. Does combining everything on the DC level into one input to the inverter still allow for this communication and the optimzers to work as advertised?

Also, does the input limitation of the inverter still have to cover the NEC 125% of the max output current after being combined at a fused connection in the DC combiner panel?

The optimizers and inverter either have a separate control wire for communication or more likely impose an RF signal on top of the DC to carry the information among them. The string inverter is acting as the master and is sending instructions to the individual optimizers to arrive at the optimal 360 volt input to the inverter.
And, yes, the central inverter needs to know the geometry of the optimizer array, in terms of one string or more strings and which optimizers are in which string, in order to send the right instructions.

Basically each optimizer is a DC to DC convertor which is being told by the inverter what the string current should be, and it will adjust its voltage to produce that current from the available panel power. Then the inverter more slowly adjusts the string current it is asking for to match what the panel string can produce at a set voltage of 360 volts.

[Alex115]

Question

My combiner box has 2 separate output circuits. Bruce Roe[ATTACH=CONFIG]4293[/ATTACH]

Hi Bruce

Im looking to power a VFD as well as a single phase inverter from a PV array. I would like to maximize the power from the array so don't want to separate the strings between the inverters. The combiner you mentioned....would It be work to connect 4 strings to it and have two outputs of which one is connected to the inverter and the other to the VFD? Basically both VFD and inverter has access to all the power from the array. would it not cause problems with mppt or any other problems?

Alex

[bcroe]

Hi Bruce, I'm looking to power a VFD as well as a single phase inverter from a PV array. I would like to maximize the power from the array so don't want to separate the strings between the inverters. The combiner you mentioned....would it be work to connect 4 strings to it and have two outputs of which one is connected to the inverter and the other to the VFD? Basically both VFD and inverter has access to all the power from the array. would it not cause problems with mppt or any other problems?

Alex

You can use a single output combiner box to bring your strings together. You don't want
2 different loads connected to the array at the same, otherwise the MPPT or other schemes
will fight each other instead of tracking a stable operating point. If you can't change between
one or the other ONLY, you need some kind of power reserve to stabilize things, like a grid
tie or a battery that powers the loads. Bruce Roe