MPP LVX6048WP AC Coupling

[Sanwizard]

Since I am not an electrician, I am looking for advice on how to add my two MPP LVX6048WP Inverters to my existing SMA inverter system. The SMA's have been humming along since 2004, and are handling the homes needs during the day. (One 6KW and one 3KW Sunny Boys).

The sunny boys are fed by two individual roof mount strings of LG panels, that are now only putting out about 300V per string. (300V to the 3K inverter, and 300V to the 6K inverter). I know sunny islands would be the best way to go, but my finances recently changed, so I need to make use of what I already own, which are two LVX6048WP's from Ian at Watts247.com
I was one of the original purchasers on the wait list with Ian, when we were all under rhe impression the WP's were Low Freq. Inverters and could be grid tied and AC coupled.
My thoughts are adding a transfer switch to the main panel, with one feed being the grid, and the other being the MPP Inverters from an existing 100amp sub panel, kinda like a whole house generator connection I used to have via a Generac 20K.
The MPP feeds would trick the SMA's into thinking grid was on, (ac coupled) so both the MPP's and existing SMA's would supply power to the main panel.
The MPP's would be setup as off-grid mode with seperate PV arrays supplying them from a ground mount system. I would also like a way for the grid to feed the ac in on the inverters to charge the batteries during extended cloudy weather, but i am not clear on that connection( yet another sub panel?)
Any advice on if this would work, or any advice on a better solution would be greatly appreciated.

 

[RCinFLA]

LVX6048 are not capable of doing GT AC coupling on their AC output.

Trouble will occur when grid goes down. LVX6048 does not have freq shifting to control GT inverter output power.

You can put a switch on PV lines to change from GT inverters direct grid AC feed to inverter PV inputs when grid goes down. PV array voltage must be in compatible range for both GT inverter and MP Solar inverter.

 

[Sanwizard]

LVX6048 are not capable of doing GT AC coupling on their AC output.

Trouble will occur when grid goes down. LVX6048 does not have freq shifting to control GT inverter output power.

You can put a switch on PV lines to change from GT inverters direct grid AC feed to inverter PV inputs when grid goes down. PV array voltage must be in compatible range for both GT inverter and MP Solar inverter.

Thanks for the response. Nothing is grid tied today. I cancelled that contract. The SMA's simply feed the main panel during the day. I am asking if its possible to use the MPP's as the "grid source" to the SMA's via a backfed breaker into the main so the SMA's dont shut down when I turn off the main breaker. The MPP's act as grid for the SMA's, and both provide power to the main panel. Is that a doable scenario? The transfer switch assures both grid and MPP's are not on at the same time.

 

[Sanwizard]

Thanks for the response. Nothing is grid tied today. I cancelled that contract. The SMA's simply feed the main panel during the day. I am asking if its possible to use the MPP's as the "grid source" to the SMA's via a backfed breaker into the main so the SMA's dont shut down when I turn off the main breaker. The MPP's act as grid for the SMA's, and both provide power to the main panel. Is that a doable scenario? The transfer switch assures both grid and MPP's are not on at the same time.

This may be a stupid question, but can an AC loop be used to provide power to a Hybrid inverter which looks like the AC "Grid" to an SMA inverter?
I am trying to fake out the SMA's to see the grid, which is provided by the hybrid inverters, but the SMA's at the same time are used to charge the batteries through the hybrid inverter.

 

[Sanwizard]

This may be a stupid question, but can an AC loop be used to provide power to a Hybrid inverter which looks like the AC "Grid" to an SMA inverter?
I am trying to fake out the SMA's to see the grid, which is provided by the hybrid inverters, but the SMA's at the same time are used to charge the batteries through the hybrid inverter.

Ok, brain freeze on that one. That would be tying the AC output to the Input. Duh.
I am looking to not spend on new panels, and keep the SMA's intact, while adding 12KW of Inverter and 70KW of batteries I already built for my off-grid home. I moved to this new house, and the SMA's are still running great. I cannot afford Sunny Islands now, so need a way to incorporate the LVX6048WP's. There is zero documentation on AC coupling with MPP.

 

[Sanwizard]

LVX6048 are not capable of doing GT AC coupling on their AC output.

Trouble will occur when grid goes down. LVX6048 does not have freq shifting to control GT inverter output power.

You can put a switch on PV lines to change from GT inverters direct grid AC feed to inverter PV inputs when grid goes down. PV array voltage must be in compatible range for both GT inverter and MP Solar inverter.

The Inverters are the LVX6048WP variant. I asked MPP, and according to them the WP model is capable of frequency shifting with AC coupling. Their manual sucks though. No good real world wiring diagrams either. Ian at Watts247 is telling me they will work with the SMA string inverters or micro inverters, as long as its 6KW or under.

 

[Sanwizard]

The Inverters are the LVX6048WP variant. I asked MPP, and according to them the WP model is capable of frequency shifting with AC coupling. Their manual sucks though. No good real world wiring diagrams either. Ian at Watts247 is telling me they will work with the SMA string inverters or micro inverters, as long as its 6KW or under.

I finally pretty much finished the outdoor addition mechanical room for the solar inverters and batteries. That was the main first step to getting off grid. I did learn that I SUCK at roofing. Oh well, its dry now, but I am still using Nema 3 components just in case.
The inverters, generator connections, and most of the AC is done. I need to install the transfer switch and make the current main a sub panel to a new meter panel going in. The SMA inverters will be the AC source for the MPP inverters to charge the Seplos batteries.
Shout out to @upnorthandpersonal, @DanF and Andy at off grid garage for all their insights.

 

[Gib]

The AC input connections on the LVX6048WP are bidirectional. I'm using it to feed into my grid tied AC panels when there is pv or enough stored battery power and it provides idling current for the inverter at night if the batteries hit low cut off. It can also charge the batteries but I have that option turned off on mine.

 

[Gib]

Looks like you have it just about done.
Nice work!
Thanks for posting your drawings and pictures.

 

[Sanwizard]

The AC input connections on the LVX6048WP are bidirectional. I'm using it to feed into my grid tied AC panels when there is pv or enough stored battery power and it provides idling current for the inverter at night if the batteries hit low cut off. It can also charge the batteries but I have that option turned off on mine.

THANK YOU for verifiying that tidbit, which is NOT in the manual. The manual says the Gen IN connection is bi-directional, which is weird, cause who would want to send power back to your generator. My design is based on nothing being bi-directional, and running the inverters in off grid mode, while using the SMA inverters as the source for battery charging.

I have no panels connected to the MPP inverters. I would love to see your design, since it seems I can also be a grid source for the Sunny Boys if needed by simply setting the MPP's into grid tie mode. What happens to AC Out when the AC in is in bi-directional mode?

So many tests I need to run to figure out what these bad boys can do. I wish the manual was actually useful.

I also heard that the gen input to charge batteries is not supported in parallel mode? Have you tested that? I will be upgrading to the 7.31 firmware, since that is the latest available for the 2021 version of these inverters. There are no tech notes on the firmware I can find though.

 

[Gib]

I ended up with one 2021 inverter and one of the newer ones. The 2021 version isn't working at the moment but MPP is sending a board on warranty.
I have 36 455 watt panels and 30 kwh of LiFePo4 rack mount batteries. The 2021 inverter died before I got it all wired up and I have a bit of work to do before it's finished.
When it's fixed up I'd like to try running everything off the output of the two inverters, using grid power on the ac inputs to supplement when pv and battery run out. I may need to buy a third inverter but I see how well these ones work first.
I have a two way switch like yours that I'm going to install so that I can bypass the inverters if I need to.

 

[Gib]

I think that AC out gets first priority when the inverters are on grid mode. Excess power goes to batteries or grid depending on which grid mode setting you're on. That's something I'll be testing too.

 

[Sanwizard]

I ended up with one 2021 inverter and one of the newer ones. The 2021 version isn't working at the moment but MPP is sending a board on warranty.
I have 36 455 watt panels and 30 kwh of LiFePo4 rack mount batteries. The 2021 inverter died before I got it all wired up and I have a bit of work to do before it's finished.
When it's fixed up I'd like to try running everything off the output of the two inverters, using grid power on the ac inputs to supplement when pv and battery run out. I may need to buy a third inverter but I see how well these ones work first.
I have a two way switch like yours that I'm going to install so that I can bypass the inverters if I need to.

May I suggest you get an emporia energy monitor for your main panel. They work great and give you second by second updates on your energy usage. They are solar aware, so it tracks both grid and solar output. I used it to get an exact basis of my energy usage day and night, ans it also keeps my grid company honest.

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