XW Pro won’t AC couple

Apex

Hello All, I have two XW Pro inverters AC coupled to 12 Chilicon micros and this system is off grid. We have installed AC coupling before with XW but not with Chilicon micros. I got the system up and running and what I’m seeing is the XWs raising frequency to curtail the micros prior to reaching anywhere near bulk voltage and in fact going up high enough to kick the micros off line. Here is the rub, if the micros are producing less then 2200 watts the XW will keep Hertz at 60, as soon as the watts goes above this it Shakes off the micros. Any ideas?

BB.

Check the battery voltage at the inverter's battery terminals? Too small or too long of battery cables can give higher voltage readings at the inverter....

Bill

Apex

The cabling is less the 10’ and voltage is the same on the posts

BB.

What is the battery bank voltage at that point (GT inverters at less than 2,200 Watts)?

What is the programmed battery bank absorb voltage?

-Bill

Dave Angelini

https://solar.schneider-electric.com/xw-pro-enhancements-for-installation-with-pv-inverters-ac-coupling/

What is a chilicon? It needs to be compatible with xwp curtailment specs?

Apex

The battery bank voltage is 54V when I see the freq. start to shake off the micros with a bulk setting of 58V. The Chilicon fstop/start are programmable ( set to 100% at 60.1 and 0% at 61.5) this is adjustable and we have rule21 and antilanding set to off. So this should be in line with what the XW wants.  

Dave Angelini

Does it charge correctly if you monitor voltage, with AC coupling disabled?

 Be careful when it gets to absorb and be ready to shut down charging.

  What kind of battery? Is the system also DC coupled solar?

What does Chilcon say?

Have you considered reporting this to Schneider?   https://solar.schneider-electric.com/netsuite/

Apex

If I disable AC coupling it will charge up to 60v before I shut it down.
These are 2v AGM 1140Ah battery bank. No other charge sources.
Chilicon says the micros are following the freq curtailment and I tend to see that. 

Last time I talked to tech support they said it was the micros, but I ah e more info now.
I just tried pushing the float setting up to 56V and the XW let that happen and BatteryV went to 56. So this means that the XW will not let Bulk or 3 hours of absorb happen and goes directly to float. I have the 3stage charge programmed as well. 

Dave Angelini

Yes a common problem when you do not use known working combinations of equipment. Each manufacturer will blame the other. That is why you take a risk when doing this. I know that Enphase works with Schneider because they recommend them and I have seen them to work. SMA, Fronius, and Schneider string inverters work also.

For the life of me I do not get why one would use a micro-inverter in an offgrid only system. I understand it if you converting an existing grid system to a battery inverter. I guess there is a slight value if there is shading. I just have zero tolerance for shading offgrid, so that advantage is not there to me. Having electronics on a roof or just outside is bad also offgrid.

Offgrid is all about being independent and not having new problems. It is hard enough to solve some of the old ones.

Get them both to work on the issue, and good luck on that one!  I would just buy a schneider charge controller and sell the other stuff. Lesson learned, that kind of thing.

If you have gateway working I could remote view, take a peek at the config. It could be something else is set wrong. It takes some experience to do this, even offgrid. I would bill you for this also. Way too much going on here for a freebie.  Good Luck!

Apex

Ok here’s the latest update on this issue with the XW pro and AC coupling. Had Schneider tech look at the settings and they had no comments there. They did tell me something I had never heard before. The XW will start curtailing at minus one volt from the desired voltage. So if you set 58 volts it will start at 57 volts. They said that the micros were pulling power back to aggressively and this was the issue with not getting to bulk voltage. So yesterday I tried a test and set float at 52volts and opened up the fstop/start window in the micros to 60.1 Hz start and 61.5 Hz zero output. Yesterday was a cool clear sunny day, battery voltage never got above 52. Today I will set the float to 58 and see what happens. By the way (Dave) when our client has a round roof you design a system based on what your client wants and the azimuth limitations you have, You contact both companies, Schneider and Chilicon during the planning stage and ask them if there are any issues with compatibility. I have used both products for many projects, granted not together. I suspect this is not a compatibility issue, but a XW pro issue. As an example the current XW pro software will not run on a generator without pulling the frequency down to 45 Hz during shutdown. Schneider has a fix in the works but it shows that the new XW Pro has some issues. We have designed many systems on the edge of technology advances and this is what you have to expect if your pushing the boundaries. 

Dave Angelini

You have a good attitude on pushing the boundaries. Wish you luck !

 Most folks offgrid can't wait like your customer is. They want it all, and they want it now.

Ampster

Dave Angelini said:

https://solar.schneider-electric.com/xw-pro-enhancements-for-installation-with-pv-inverters-ac-coupling/

What is a chilicon? It needs to be compatible with xwp curtailment specs?

To add to that comment,  some older inverters do not respond to frequency/Watt signals the same. More recent versions like my Enphase IQ7's will modultate or drop off a few micros instead of all of them going off line. Older Enphase micros just drop off line all at once and then have to go through their reboot process.  I think the answer can be found in the specs of the micro inverters. I believe the modern spec is UL1741SA.

Dave Angelini

Apex,
 I just received an update notice from Schneider. Both your XWP and gateway firmware were updated over the weekend and are on the Schneider site. I will post a notice. This is for grid tie and AC couple genset issues.

Most offgrid apps do not need to rush into this. Let the Grid people test it for us 

Apex

I was not aware of the update, thanks. I sent engineering data on Monday and they are reviewing it now. 

Ampster

Most offgrid apps do not need to rush into this. Let the Grid people test it for us 

That does not make sense to me. Curtailment of AC coupled inverters is not usually an issue in an AC coupled situation when on the grid,  because the infinite load of the grid can take any output of a GT inverter. My Skybox does have a limit on the amount of kW that can be sent to the grid and that setting can be set lower. I did that as a test and the Skybox did curtail the micros and a Solaredge inverter both of which were AC coupled to the Skybox.

When I cut the breaker and put my Skybox into essentially off grid mode I observe a lot more curtailment especially when my batteries are in CV mode and the charging current is tapering. In that case there was no grid to absorb the output of my GT inverters.

My point is that I think the Schneider tech guys have it backwards in terms of when curtailment is going to be an issue. It is going to occur more often when not on the grid. At any rate it sounds like adjusting the charging parameters may be a work around. Another one would be to put some load on the system and see if they are being curtailed. 

Dave Angelini

Sorry that it does not make sense to you.... Still smokey in Santa Rosa? Nasty down here....

I tested all of this for the field validation test for Schneider and it worked great with 2 string inverters and an enphase micro.

 Did not test the equipment Apex has. Even if I did, the firmware has changed and my testing was a snapshot in time that ended in January 2019.

I still think it is nuts to AC couple offgrid unless you are part of a microgrid with many homes. Even then I would want a large percentage of the charging to be DC coupled. I have heard of and seen people fry a battery system AC coupling. It would really scare me if I had automotive type NMC lithium in my garage with AC coupling.

 Less is more for reliability offgrid !  When there are few people to help you, or they can't because of weather or fire!  You really need to be independent anyway offgrid.  Even the Sheriff can't be here alot of the time and have long given up on Cal Fire. We do it all here.

Ampster

I should have been more clear about what did not make sense. I do agree with you that AC coupling off grid is nuts. What I was referring to was Schneider's response, but maybe you have more insight. Were all the GT inverters you tested UL1741SA? I assume you were testing AC coupling for Schneider in an off grid environment? To me that is where the issues would arise since curtailment should not be an issue when on the grid for the reasons I suggested. However when the grid is down, that is when a person who invested in a hybrid inverter to leverage his GT solar investment needs AC coupling the most. I thought Schneider would see that as an important issue and to me an off grid environment would be the easiest way to simulate a grid down environment. 
I am assuming that the issue Apex is having is curtailment of the micros for unexplained reasons? We haven't heard back from Apex if changing the voltage made things better or whether adding loads reduced the curtailment. 
In the meantime the smoke has cleared in the Sonoma Valley and solar production is back to normal. The worst day was September 9th when I got less than a kiloWatt of production and ran the A/C fan half an hour on the hours to clean the air inside. It was so dark the street lights came on at 3PM, I should update one of my ealier posts with the latest iteration of my build. I got a new pack of Lithium batteries and have been running my critical loads panel in self consumption mode for two months. My hat it off to you guys who do this every day and don't have the luxury of flipping the interlock to the grid like I do when I need to reboot the inverter or rearrange some cells. 

Dave Angelini

Your assumptions are correct!  Schneider is a good company ! They did all of the testing before I was made part of the team. I am just a second set of eyes that does not have much skin in the game. I want them to succeed, but I definitely do not want any new ways to lose power, EVER !

It is not that hard offgrid BTW. Many run redundant battery/inverter systems systems. We do have the luxury of "flipping the interlock"  or AC bypass to our own "grid bypass"  You think I would do this testing on unknown products and firmware without knowing I can calmly troubleshoot with my backup power source?  You think my wife would let me???

AC coupling offgrid in a microgrid format does make sense because it has diversified sources of charging the batteries. These systems need at least 2 people on site to keep eyes on it.  I have one 32KW  XW schneider system and an Outback 45KW Radian in small clusters of 6- 8 homes. They have the ability to add more homes especially if the users play nice together. Ac coupling is great if they use loads during the day and can scale back just like anyone offgrid has to. They just depend on a genset more.

All of September has pretty much sucked if you are within 75 miles of the Creek fire. It is 30% contained in some of the most beautiful forest and mountain lake country anywhere. Bass lake, Shaver lake, and Huntington are the lake home communities. Bass lake is 2 miles from the fire today. I think there are about 10 of my clients in this mess.  My favorite bar is there,
 I think....

August was a nice month for us and we built here never expecting any help on fires. 

Ampster

I spent a week in the fifties camping around Dinky Creek and Shaver Lake. My daughter spent two weeks at a camp near Huntington Lake Then in the nineties I got a tour of the Big Creek system from SCE. Beautiful country, I am glad you are safe, 

Apex

The latest news is we did a test on Monday full sun and I was able to show Schneider in a battery voltage/current download that the inverter never did come up to bulk. The XW was holding the micros in curtailment at 61.5 for the whole day. Tech support has never address this detail as of yet. After Dave A. mentioned that the new firmware was out I read the release notes and noticed that these mention using CA rule 21 for the region codes. I was told by tech support before to use IEEE as the region code. I mentioned this to Rhodes at tech support and he said to follow the the release notes so tomorrow we will re install the official XW 1.09 firmware, we had a bootleg copy, and try this again. 

Ampster

 Apex said:

...... The XW was holding the micros in curtailment at 61.5 for the whole day. Tech support has never address this detail as of yet. 

When you say the XW was holding the micros in curtailment do you mean the micros were off? Did you notice any difference at different frequencies or did the XW just maintain frequency at 61.5?

The question I asked and never heard the answer to is whether the micros have UL1741SA compliance which I believe is similar to CA Rule 21? What model are the Chilcons? I did some research and Chilcon says Model CP-720 micros are Rule 21 compliant. 
I understand the connection between the XW and the micros with regard to curtailment is the issue. The question I had is whether the micros curtail by going off line and then go through a 3 to 5 minute reboot or whether they are compliant with Rule 21 and UL1741SA and can modulate down incrementally as frequency goes up and modulate up as frequency goes back down. If the micros can not modulate with frequency then no firmware upgrade on the Schneider side can fix that. In that case it would be a limitation of the micros. They will AC couple but it will be clunky as my hypothesis would suggest if the issue is on the micro side. 
That is why I asked Dave if the tests that he did were with UL1741SA or Rule 21 GT inverters. It sounds like they must have been Rule 21 because he said there were no issues.

I hope my hypothesis is not correct that the issue may be on the micro side and that you find a solution. Hopefully the XW can use frequency to adjust the Wattage output of the micros. 

Apex

The micros were pulled way back to 30 watts or so per micro inverter. These are the CP-720 but we have rule 21 disabled on the inverters since this is off grid. These micros can modulate output so that’s not the issue.

Ampster

Okay, what you are telling me is the micros were modulating. That dumps my hypothesis so you are on to the solution with the XW and why it was curtailing the micros that much. Thank for clarifying and satisfying my curiosity. 

Dave Angelini

What voltage Apex were you at when xw was at 61.5 hz? In float? All day??  What kind of battery?  What happens if you turn on loads to DC?     Did schneider remote view your settings/config?

Much nicer up here this am. First time this month clear in the am. They are making good progress on Creek. The structure lines held at the lakes and the structure loss stayed at 858. Going up there to help a few as soon as CHP opens up. Nobody gets near creek at night because of looting.

I was up in Santa Rosa just before the Tubbs at a wedding for my Niece. That was the biggest and nastiest fire, was....
Grew up there between raising hell in san rafael and HP in santa rosa. Fun times and no real fire worries like these days.

Ampster

Dave Angelini said:

... What happens if you turn on loads to DC?     ..........

I would try AC loads as well but perhaps that is what Dave implied. The issue is to me is, what is causing the XW to raise the frequency to curtail the micros? The AC coupling algorithm is complicated and may be different among hybrid inverters. Does your XW have a setting for the size of the battery pack? On my hybrid, when the grid is down, the battery is the only buffer so size may influence the algorithm as will  AC loads and DC voltage settings relative to DC voltage.