Multiple Sunny Boys per Sunny Island?

[Disturbedfuel15]

Hello,

I have two sunny island 6048-us with a 72kwh battery bank. JK inverter BMS is providing comms. Zero export set by data manager m-lite. Batteries charged by grid currently.

First System Build Thread - Another 71kwh DIY

Time is of the essence but I wanted to get a thread out here that I can update and receive feedback on! You've seen this before, I think two other members on this forum have started threads for their CATL module builds. So I won't go into what they are too much other than to say each is 20s...

diysolarforum.com

I started with two SB 5.0-us-40, but now have 13.5kw of of panels, so I purchased another for a total of three 5.0-us PV inverters.

Here is the diagram I've followed, as I have Midnite Solar's master+slave SMA e-panels: https://www.midnitesolar.com/pdfs/10-485-1_REVA_DUAL_SUNNY_ISLAND_AC_COUPLED.pdf

Unfortunately, I feel short-sighted in that I didn't think of exactly how to combine the SB (sunny boy's) AC outputs. On diagrams like the one above, it simply shows it to be happening, or says 'properly combined by customer'. However, I know you can't simply take two AC-generating sources and 'combine' them, expecting them to be in phase one another. Sparks, boom, bad stuff, possibly lucky for a bit...but doesn't just 'work'..... right? Here are two examples of what I'm talking about:



Could it be the 'webbox' in the second picture that is allowing them to be combined? I have one, but found it to be redundant along with the data-manager m lite.

Thanks in advance!

 

[jpwhit]

In this case you can just simply connect the L1, L2, N wires from the Sunny Island's output to the Sunny Boy Inverters. The reason it's ok in this case is the PV inverters are designed to sync up with and augment an existing AC waveform. Being PV inverters, they are normally doing that with the grid directly. But in your case, the Sunny Island's are the AC source they will sync with. A PV inverter actually can't create an AC waveform on it own, it can only sync with and augment an existing AC waveform. This is on purpose so they can never backfeed AC power onto the grid during an outage.

 

[kommando]

I have two SB's set to Off Grid 50htz country grid code (UK grid is 50htz) and a Solax X1 Boost set to a country grid code that supports frequency shift output curtailment all connected to AC1. They only produce when they see the SI's 50htz AC it sets up when turned on, as the battery's fill up and the house load is lower than the PV output the SI increases the Frequency and above 51htz the Inverters out put is curtailed until its the same as the House load. The only stipulation is in the handbook where there is a limit to the KW of inverters that can be connected to an SI. Look that limit up and do not exceed that KW limit, if you have 2 SI's then you can have double the KW limit.

 

[Disturbedfuel15]

Amazing, thank you both @jpwhit and @kommando . I really didn't want to ship this inverter back across the country.

So with that being said, kommando, regarding your comment on the KW limit: I unfortunately have to put the panels E/W. So at any time, I'm only going to be receiving peak power from one half of the total PV array. I feel safe overpaneling a bit due to that.

 

[DIYrich]

I thought the limit is 3 sunny boys on a sunny island.

 

[kommando]

Its not the panel KW that matter but the total inverter KW but having E/W panels will drop the potential peak. My 230V SI5048 will take 12.8KW input (230V x 56A) having two SI I could have 25.6KW of inverters, the US ones will be limited by the 120V and will be much lower KW.