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SMA Sunny Boy 7.7 AC coupled frequency watt control tuning

Mr-Sandman

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I have a Sunny Boy 7.7 that I'm AC coupling thru a Schneider XW Pro 6848.

While testing how the AC Coupling works during a grid failure, it performs well up until the point where the batteries are getting full and the XW PRO starts raising frequency. The Sunny Boy does engage active power limits and curtails generation.
The XW Pro moves the frequency slowly and the Sunny Boy doesn't seem to curtail fast enough, causing excessive voltage on the DC side. Seem like maybe the Sunny Boy needs to be more sensitive to the frequency shifts.
Another thing is it seems to only curtail about 50% of the output before the frequency gets high enough to cause the sunny boy to trip. I would like to make them get along a little better. Right now they are set to Rule 21 specs. Any suggestion on my settings for this?

The Sunny Boy's are awesome inverters with a LOT of fine tuning control, but good luck finding any good explanation of what the settings does or how to set anything.

Current Sunny Boy settings:
1642126786743.png
 
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Common issue when dealing with two different manufacturers. Sunny Boy was first to put variable power control based on freq shift. Their control was proprietary to their Sunny Island inverter. Originally the industry generic was just a full PV GT or shutdown PV GT.

There is suppose to be a standard now but not sure how well each manf. obeys standard. They don't want to make it too easy for the competition.

Not familar with all the Sunny Boy parameters but looks like you might be able to modify how soon and how much it reacts to freq shift.

My suggestions.
- Call both suppliers to see if there is firmware updates.
- Type of battery setting on XW. This effects what charge amount it allows for maximum state of charge reserve for battery PV absorption.
- Maximum state of charge allowed on XW, to give more GT absorption margin.
- Battery size. Too small AH cannot absorb as high of peak reverse current or absorb as much PV overage.

If all else fails, rig a hot water heater load dump based on a controller for battery max state of charge voltage.
 
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Thanks for the reply and suggestions.

- I do have both inverters at latest firmware.
- I'm using a custom battery setting with 300ah of EG4 LL batteries on the XW. I'm not 100% sure which charge/battery setting the XW uses to start raising frequency, I'll research that, might be able to raise or lower that to help it start sooner.

The XW documents how it raises the frequency pretty well, although I don't see anywhere to adjust how it works for the AC Output side. Plenty of adjustment on the AC Input side "grid".

The Sunny Boy setting I posted above are not very intuitive to me. I question the Active power gradient being at 50% Maybe that's why the Sunny Boy seems to never reduce it's output by more than half? I'm wondering 100% on this would help with that?
 
I run 2x Sunny Islands to a 25kWh lithium bank and an 11 kW solar system consisting of 2x Sunny Boy SB6.0-US-40 inverters.

While I have limited experience with off-grid power production because we're normally grid-tied, I did notice that the frequency shift control is a bit sluggish when I have both Sunny Boy inverters turned on. If I start the system with just a single Sunny Boy 6.0 inverter, the system seems to respond faster.. but when I turn on that second inverter, the freq shift control seems sluggish, and I experienced the same problem when my batteries hit 90% of charge. A load would turn on in the house and I'd be drawing energy FROM the batteries for about 20 seconds until the frequency shift caught up.
The last time I ran it with only a single inverter, if I remember correctly, the frequency shift was so fast no extra juice ever went in or out of the battery bank except for the normal charge tapering off as they filled up.

Next time we have a storm take out the utilities, I'm going to run just one inverter and see what happens.
 
300 AH is small battery for 7kW but you did not state how much actual PV power you are pushing. Obviously you cannot absorb more than XW power rating for maximum charging which is a bit below 6kW.

The greater the PV power back push the greater the max battery charge current and the greater the battery voltage rise. This is where the battery AH size comes into play. XW absorbs it all up to its power limit and then pulls the plug when battery voltage is exceeded. It is all it can do. With enough amps and too small a battery this can happen quickly. Also battery cabling must be large enough not to contribute to inverter DC input voltage going higher.

Looks like Sunny Boy has some settings to make it be more sensitive to freq cutback requests.

Other failsafe thing you could do is relay based on battery voltage to disconnect GT inverter feed. Sunny Boy has a remote shutdown. XW may be able to output a battery overvoltage relay control.
 
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Yes, I agree at 300ah (15kwh) my battery bank is smallish, It's used mainly for power outages, not off grid. There is 7.7kw of panels on that Sunny Boy, but they are a few years old and rarely make it to 7kw. My base load hovers around 1kw, so the XW never see's more than 6kw. Usually 5kw or less.

I'm thinking there is some adjustments I can make to make it work better with the frequency curtailment sent from the XW. The question is what adjustments exactly. Those sittings I posted I think is what controls that, I just don't know what to adjust.
 
Worst case situation is you are producing a lot of PV power and house loads are consuming most of it. Then someone switches off a heavy load, and all of a sudden XW gets hits with a massive overproduction to deal with.

This is where having the ability to pull the PV plug is good thing.
 
Yes that scenario is what is happening, load drops and the XW Sunny Boy doesn't adjust fast enough, DC voltage spikes, XW panic and raises frequency high enough to cause Sunny Boy to trip. It's working, just not ideal. It won't be in this mode often, so I can deal with the way it works now.

I'm betting though it can be improved in the settings, maybe not perfectly solved, but an improvement in how it behaves. For one I don't think the XW and Sunny boy frequency curtailment curves are the same possible, "the sunny boy never curtail more than 50% of the load when the XW is asking for full curtailment on the frequency shift for instance.
 
The freq adjustment control takes too long for an immediate back surge that cannot be handled by hybrid inverter and battery capacity. Freq adjustment power reduction is not triggered until battery voltage exceeds absorb voltage setting.

1) XW has to detect back surge from 60 Hz waveform which is relatively slow (10-20 msecs)
2) XW has to move freq, which it is not allowed to do too quickly due to possibility of supporting AC motor loads.
3) GT inverter has to detect freq shift and shut down.

All this can take up to a couple of seconds before GT power is actually shut down. Hybrid inverter DC overvoltage happens very quickly with a smaller battery so only option is for hybrid inverter to shut down to save itself. Also have to be careful of too much battery cable resistance.

You are running very close to too much PV generation capability for XW wattage and too small a battery to absorb maximum back push power.

It is a good fail safe addition to have an automatic immediate hardware controlled GT shutdown on sudden back surge overload. I believe XW Pro has ability to generate this control output. Might be good to discuss with Conext. Other option is extra load dump but GT inverter shutdown is simplier to implement.

In my opinion, when PV generation can exceed half the hybrid inverter/battery system capability this is really a necessity. Conext recommends this especially when Li-Ion batteries are used.
"Conext-XW-Pro-SW-AC-Coupling-Guide"
 
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Right, I agree, the XW is having trouble regulating the output from the Sunny Boy when the batteries are near full. I understand in my setup that may never be solved, however I'm just wondering if there is room for any improvement in the Frequency power gradient setting of the Sunny Boy. I still don't believe the scale is to 100% and matches the XW for curtailment.

Keep in mind this is not a normal mode of operation for me, only during a grid down situation would I be in this mode of operation. So it doesn't have to be perfect, just want it to work as good as it can in this setup.
 
Did you ever sort out the values that would work for you? looking at exactly this setup, SB 7.0TL schneider XW with AC coupling for battery backup.
I would have assumed that changing the active power gradient number to a higher number would have made the power from the SB decrease faster.
 
Did you ever sort out the values that would work for you? looking at exactly this setup, SB 7.0TL schneider XW with AC coupling for battery backup.
I would have assumed that changing the active power gradient number to a higher number would have made the power from the SB decrease faster.
It's been a minute since I worked on this. I'll try to remember what I changed. I think most of the configuration changes to improve this was made in the SMA Sunny Boys.

The only settings I recommend in the XW is to set your AC PV Charge SOC Limit to 90% or less as it gives the inverters plenty of time to curtail the charging without over voltage. I now have closed loop communications on my batteries and did not when I originally tested AC Coupling. I need to re-test things now. Also Schneider released a new firmware for the XW Pros recently (Release 120-240V Firmware 02.04.00 Build 0029). I installed it and it goofed up my Enhanced Grid Support for my DC coupled solar, so had to move back to previous version. However they list Improved frequency shift response time for AC Coupling as an improvement in this version. If you are only AC coupled and have no DC coupled to the Schneider this version might be a good one for you to try.

Here's what I currently have in the SMA P(f) configuration:
Screenshot 2023-04-02 at 9.35.59 PM.png

I also think I had to adjust the frequency monitoring "upper maximum and lower maximum", but can't recall. Here's those settings in case:

Screenshot 2023-04-02 at 9.50.03 PM.png
I need to retest my AC coupling, I might try to do that this week and I'll report back what I find.
 
I'd be curious to hear how it's working. I have 17 KW grid tied at the moment, and would ultimately be looking at the XW with ac coupling a remote 6.8KW array, and possibly also DC coupling the nearby array, as I can put some MC4 connectors on the pv lines from the array, and plug them into a DC charge controller (high voltage). the little array (2 kw) I would just turn off. that would leave me with max: 6.8KW remote AC coupled, 8 .4 KW on the same building DC coupled (3 arrays of 2.8KW). Planning on 4 EG4 batteries or so. I don't really need the AC coupling and the remote array, but it seems silly to go thru all the trouble and expense and not be able to charge the EV on a sunny day off grid :) It's all backup, so if the power is out for a long period of time, we would be around to do some power management (plug in or unplug the car)
 
I have 11.5kw of SMA Sunny Boy Grid tied and another 3.4kw going to the XW Pro 6848 via a their MPPT 150 60amp charge controller.
My grid tie is normally NOT going thru my XW, but on the grid side of it "it's on my shop and XW is in my house".
My XW is for backup power, but sells it's extra DC solar power to the grid. IF I have an extended grid down outage "more than a day, very unusual", I can disconnect from grid at the meter and can do some switching in the house to connect and back feed power to my entire place off the XW. The XW forms a "mini grid", the SMA grid tie inverters see it and will start pushing power, and the XW will regulate them with frequency shifting.. 11.5kw is WAY too much, so in that mode of operations I would only use one of the grid tie inverter, not both.
On a sunny day this gives me an incredible amount of power, Over 12kw and the ability to fully charge the batteries while covering the loads.
I only have 3 EG4 LL's so that's barely enough to handle that kind of power. 4 or more would be better.

I think the XW has more trouble with maintaining the batteries and doing precision charge cycles with AC Coupling. I'd encourage you to hookup a small PV array to the batteries and maybe install some switching that allows you to feed in the grid ties in an extended outage for extra power "if you need that". The XW is totally capable of handling things on it's on with enough batteries, but you could charge those batteries faster IF you needed them charged in an outage if AC Coupled.

James
 
that's really similar to what i have. Knife switch at the power pole, the 8.4 is on the barn where the XW and a SB3.0 and 5.0 are, and then a remote 7.0 with 6.8KW on it. the XW would back up the barn/shop, and have a pair of breakers with an interlock to allow backfeeding the entire property when the knife switch is locked off. do you use the closed loop communication with the EG4 batteries? I'm not sure how much difference that would make long term, I've been doing solar for 20 years, but still new to the LiFEPO4 batteries.
 
I recently "last week" got my EG4 LL V1 batteries in closed loop with the XW Pro. It was a process. If you are interested i wrote a detailed set of instruction over here: https://diysolarforum.com/threads/a...ding-new-eg4-ll-v1-firmware.52088/post-742691
Knowing the SOC is useful in the XW. It opens up the ability to better control things based on SOC instead of voltage. The issue with Lifepo4 batteries is it's hard to tell their SOC based on voltage, Especially between 10% and 90%, very flat voltage drop in that range.

With all that said, come to find out the Schneider charge controller do NOT utilize the SOC reading and are purely voltage based, so not so much help with the charging control when DC coupled. I still need to test the AC Coupling with SOC control. The option and settings are there, it might make curtailing AC Grid tie inverters a little more controllable than voltage, as voltage can spike quickly with clouds coming and going on a grid tie.
 
Something else to think about is, there is NO Solar required to run the XW Pro. It doesn't have any built in solar charge controllers, it by itself is a hybrid inverter that can do off grid or grid interactive "grid tie" inverting AND charging of the batteries from AC. The XW can charge and maintain those batteries just fine without solar OR AC coupling. And if you find yourself in an extended outage where you need those grid ties to function, you isolate from the grid and switch the XW to form a "mini grid" that a grid tie inverter will provide power and excess charge the batteries.
 
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