Help with Sunny Island Sunny Boy battery backup / grid tied PV system

[JRJR112]

I'm looking for help understanding whether my grid tied SMA PV system with battery backup is operating correctly during grid down events.

Observation: When grid is down / disconnected, the Sunny Boy inverter (on a sunny day where PV is generating (3000+ W) will not sync to the local microgrid created by the Sunny Island. The Sunny Boy shows AC Frequency error, indicating it cannot get a frequency within range from the Sunny Island microgrid.

This occurs when battery bank is at @90% or higher state of charge, the Sunny Island indicates it is in the "Float" charge state, and when load on the microgrid is about 1000 W. I have not taken the battery below 90% to test if / when the fault clears itself. In other words, when battery is sufficiently depleted that charging is required, it is possible the Sunny Island will allow a connection to the power coming from the Sunny Boy. I don't know that yet.

So, the question is whether this is normal / expected / designed behavior? Should I expect the Sunny Island to prevent syncing with the Sunny Boy until the battery is sufficiently depleted to change from "Float" to another charge state? Of should Sunny Island and Sunny Boy be always in sync regardless of State of Charge and the excess 2000W of power generated by the PV to be shed other than by a complete disconnect between the Sunny Island and Sunny Boy?

Thanks.

 

[penandpike]

You may also look at the BMS configuration. If the BMS doesn't want the batteries to be charged it will send message to the SI to shift frequency and thus prevent charging. You may also have very unbalanced battery pack. The BMS will stop charging if one cell reaches let say 3.5V so if the pack is unbalanced it may not reach 100%

 

[Consumerbot3418]

My setup is solely off-grid, so my SI ramps up the frequency as the SoC gets over 90. My SB is set to island mode, and smoothly curtails its output depending on how far the frequency gets from nominal 60.

If you’re grid-tied, you wouldn’t want to set SB to island mode. I don’t have the knowledge or experience when it comes to falling back from grid power to battery, but I’d venture to say that the behavior you’ve observed is “normal”. If the battery is full, and can’t absorb the power being generated, it could be driven to over voltage, and bad things happen. There may be a way to set up SI to change its behavior based on grid loss, and I recall seeing @Hedges post about this exact issue. I think he said SMA told him to switch to island mode, but wouldn’t put it in writing, and he was concerned about the prospect of frying a lineman…

Maybe you can find that post if you search… I don’t have time at this moment. I remember he mentioned relays banging off and on when the SI disconnected and reconnected. I’ll see if I can find the post myself, when I have some time.

 

[MurphyGuy]

When your SB (SunnyBoy) fails to sync, log into the web interface and see what the microgrid's frequency is at. As your batteries are up in the 90% SOC range, I'll bet your SI's (Sunny Islands) have the frequency up in the 61hz range, which is probably outside the limits set for a SB in grid-tie mode.

The solution to this is to get a Grid Guard Code from SMA, then use it to enter the SB's web interface settings that are not available to normal users.

In those menus, there's a drop down box setting for "Country Standard", and you will see it set to various versions of UL1741/xxx. You need the grid guard code to change it to "Island Mode 60hz". Doing so will open up the operating limits and enable frequency shift power control so the Sunny Islands can control their output by shifting your grid frequency between 60 and 62hz.

 

[Consumerbot3418]

I’d like to reiterate that a grid guard code may not be needed to change the grid country setting to island mode, based on my experience.

 

[Hedges]

Which model Sunny Boy?
The banging on and off issue I had was with SB 10000TL-US

Sunny Boy frequency-shift regulation of power output - which models work per spec?

I'd like to hear from you guys as to your experience with various model SMA Sunny Boy on Sunny Island systems. I'm not seeing them respond properly to frequency shift in "Backup" (default = UL1741 & backup = On All Phases or On, depending on model and interface.) I'm only getting it to work in...

diysolarforum.com

Did SB report what frequency it was seeing?
It is useful to have a DMM that displays frequency.

If SB is UL-1741 mode, frequency has to be 59.3 to 60.5 Hz to connect.
SI raises to 64 Hz or higher, but often goes down to 59.0 Hz to get clocks back on time. And overshoots a little below.
Since UL-1741-SA widens frequency to 58.5 Hz I don't feel bad widening it on an older inverter.

If your inverter is an older one that accepts RS-485 daughterboard, wiring to SI should let it switch to wide off-grid range.
If it is newer UL-1741-SA, setting to Rule 21 should work with SI.