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Powerwall 2 - Outage “Switchover” Delays?

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
8,828
9,781
Riverside Co. CA
That's the current frequencies, right? I'm looking for the max frequency TEG is set to turn off inverters

Just test it with a kill a watt by throwing your main breaker with powerwalls close to being full. The PWs will put out whatever their frequency is to turn off the solar and you can see it on your kill a watt.


I bought this thing, but if you already have a kill a watt type device you should be able to see it on there as well.

https://www.amazon.com/gp/product/B0777H8MS8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
 

wjgjr

Active Member
May 11, 2020
1,217
952
Silver Spring, MD
That's the current frequencies, right? I'm looking for the max frequency TEG is set to turn off inverters
Sorry - misunderstood. I am not aware of where you can see that setting.

As noted by @jjrandorin, you can buy a device to get the data, but you can also just monitor the URL after disconnecting the grid to see the frequency. This does not directly prove what the setting is, but it gives you a good indication.
 

BrettS

Active Member
Mar 28, 2017
2,109
2,512
Orlando, FL
Just to follow up on the frequency topic, I went ahead and tested it again this afternoon with my kill a watt. As my powerwalls got to 98% charged I could see the frequency start going up... My system seems stay around 59.9 when running off grid, so it started at about 59.9, then it went up to 60.0, then 60.1, then 60.2, 60.3, then the inverters shut off as it hit 60.4. This all happened within about a minute (It also makes me wonder if my Kill A Watt is reading a little low since it didn’t even hit 60.5 before the inverters turned off)

But this coincides with what I wrote earlier. During normal operations while you are off grid (and assuming that your inverters shut off at 60.5Hz) then the frequency should never go above 60.5Hz no matter what the max is set to. The only time you should hit the max frequency is if an outage happens when your powerwalls are fully charged. At that point it will immediately take the frequency up to the max, until the powerwalls drain a bit, then it will start the cycle where it brings the frequency up to 60.5 to shut off the inverters as it approaches a full charge again.

I can only report what happens with my system though. I’d love to see someone else try this with their system to see if they see the same results.
 

Freakyguy666

Member
May 14, 2020
60
13
USA
Just to follow up on the frequency topic, I went ahead and tested it again this afternoon with my kill a watt. As my powerwalls got to 98% charged I could see the frequency start going up... My system seems stay around 59.9 when running off grid, so it started at about 59.9, then it went up to 60.0, then 60.1, then 60.2, 60.3, then the inverters shut off as it hit 60.4. This all happened within about a minute (It also makes me wonder if my Kill A Watt is reading a little low since it didn’t even hit 60.5 before the inverters turned off)

But this coincides with what I wrote earlier. During normal operations while you are off grid (and assuming that your inverters shut off at 60.5Hz) then the frequency should never go above 60.5Hz no matter what the max is set to. The only time you should hit the max frequency is if an outage happens when your powerwalls are fully charged. At that point it will immediately take the frequency up to the max, until the powerwalls drain a bit, then it will start the cycle where it brings the frequency up to 60.5 to shut off the inverters as it approaches a full charge again.

I can only report what happens with my system though. I’d love to see someone else try this with their system to see if they see the same results.

2 questions:

1) does your PV production ramp evenly from 100% to 0% as frequency goes from 59.9 to 60.4? Or is the ramp-down uneven?

2) We know that PWs seem to be designed to allow the PV to continue production uninterrupted immediately after an outage provided the PWs are not at 97+%. However, if the PWs were below that level, I wonder if the level of charge correlates to the frequency. For example, if PWs were at 30% when outage occurs, then perhaps the frequency would remain at 60Hz immediately after an outage; however, if the PWs were are 90% when the outage occurred, perhaps the frequency would be raised to 60.3Hz to keep the PV producing albeit at a lower level?
 

BrettS

Active Member
Mar 28, 2017
2,109
2,512
Orlando, FL
2 questions:

1) does your PV production ramp evenly from 100% to 0% as frequency goes from 59.9 to 60.4? Or is the ramp-down uneven?

No, my inverters are just configured to shut off at 60.5, so they were at 100% until it hit the cutoff frequency and then they just shut off.

As I mentioned above (or maybe in another thread) it is possible to configure the solaredge inverters to ramp down as the frequency increases, but when I tried configuring this I didn’t really have any success, I think it may be possible to get it to work, but I would first need to change the shut down frequency to something higher than 60.5Hz. There’s just not enough resolution between 60Hz and 60.5Hz to really effectively ramp down.

Especially since I really wouldn’t want the ramp down to start until around 60.2Hz at a minimum since it’s possible for the frequency to vary slightly even when things are operating normally. I wouldn’t want the inverters to start ramping down and lose 20% of my solar production because the utility frequency happened to be a little high.

2) We know that PWs seem to be designed to allow the PV to continue production uninterrupted immediately after an outage provided the PWs are not at 97+%. However, if the PWs were below that level, I wonder if the level of charge correlates to the frequency. For example, if PWs were at 30% when outage occurs, then perhaps the frequency would remain at 60Hz immediately after an outage; however, if the PWs were are 90% when the outage occurred, perhaps the frequency would be raised to 60.3Hz to keep the PV producing albeit at a lower level?

It does, but the range is much narrower than what you are thinking. The frequency starts to rise at about 97/98%, so below that it will always be at 60Hz, and then from about 98% to 100% it will evenly go up from 60Hz to the max frequency.

So if the max frequency was set to 62.5Hz and the powerwalls were 100% charged the frequency would jump to 62.5Hz at the time of an outage. If the powerwalls were 98% charged the frequency would only go up a little, to around 60.2Hz. If the powerwalls were 99% charged then the frequency would go to around 61.3Hz.

It’s also worth noting that the frequency rise would be linear.. it wouldn’t jump from 60.2 at 98% right to 61.3 at 99%, it would go up to 60.3, then 60.4, then 60.4, etc as it gets closer and closer to 99%.

Finally, it’s worth noting that Tesla does not seem configure the PV systems to ramp down. Even though the powerwall and the inverters do support it Tesla just configures them to cycle on and off. As I’ve stated before, while ramping down might be a slightly more elegant solution I’m not sure that there’s really a big benefit to it.
 
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gpez

Member
Apr 25, 2019
661
538
USA
So as we keep talking about this it’s making me want to re-attempt configuring my inverters to ramp down. Despite it all I do like elegant solutions. I may try this tomorrow. If I do I’ll let you know how it goes.

In my testing last year the frequency is a function of the state of charge and current home consumption. Utility outage simulation data dump

As an example (your settings/setup may be different):

High SoC, low load = 62hz
Low SoC, low load = 60hz
High SoC, high load = 61hz
Low SoC, high load = 60hz
 

MorrisonHiker

S 100D 2021.4.18.2
Mar 8, 2015
9,665
8,920
Colorado
In my testing last year the frequency is a function of the state of charge and current home consumption. Utility outage simulation data dump

As an example (your settings/setup may be different):

High SoC, low load = 62hz
Low SoC, low load = 60hz
High SoC, high load = 61hz
Low SoC, high load = 60hz
How low was your "Low SoC"? Last year we had a 48 hour outage after a blizzard and when our Powerwalls got down to 5% they started setting the frequency to 65 Hz. This caused the PV to be shut off. Tesla told us that the higher frequency was an attempt to keep the battery temperature up during the extreme cold. Unfortunately, it also caused the PV to cycle on and off throughout the day while the grid was down. So even though we had full sunlight and had cleared 40% of our solar panels, the PV couldn't operate and the Powerwalls couldn't recharge. Tesla made some firmware updates since then and updated the firmware on our inverters as well but we haven't tested this scenario again.
 

gpez

Member
Apr 25, 2019
661
538
USA
How low was your "Low SoC"?.

Remember this was last year (many software/firmware updates ago) and with one Powerwall so YMMV. In my simulation the frequency only returned back to 60hz when the SoC reached 93.4% at 1,400w load. It was at max frequency (~62hz) all the way from 100% to 95.0%, then started dropping between 95.0% and 93.4%. If you correct for the load it seems fairly linear.

The graph in the thread I linked doesn't show the battery charge so here it is.

upload_2020-8-13_9-39-2.png



Tesla told us that the higher frequency was an attempt to keep the battery temperature up during the extreme cold.

This sounds like a nonsense answer from Tesla. I'd love to hear how frequency changes keep the battery temperature up.

 

MorrisonHiker

S 100D 2021.4.18.2
Mar 8, 2015
9,665
8,920
Colorado
Remember this was last year (many software/firmware updates ago) and with one Powerwall so YMMV. In my simulation the frequency only returned back to 60hz when the SoC reached 93.4% at 1,400w load. It was at max frequency (~62hz) all the way from 100% to 95.0%, then started dropping between 95.0% and 93.4%. If you correct for the load it seems fairly linear.

The graph in the thread I linked doesn't show the battery charge so here it is.

View attachment 575820


This sounds like a nonsense answer from Tesla. I'd love to hear how frequency changes keep the battery temperature up.
Yeah, I wasn't sure if it was true or not but I think I heard it from a couple employees at the time. They kind of equated it to revving an engine. Anyhow, we haven't taken it down to 5% in extremely cold weather since then, so I don't know if the issue was actually addressed.
 

warriorsfan

Member
Apr 7, 2021
18
9
Bay Area, CA
I have two PW2s with Gateway 2 and 6720 watt solar with SMA SunnyBoy 7000 inverter.

I was doing various power outage test scenarios by throwing the service disconnect and in most cases, the switchover to the PW2s was seamless save for flickering of some lights, my NAS server had no interruption nor any clocks.

One scenario did not have a seamless switchover:
  • During the day
  • the PW2s are 100% charged
  • PW2s are not discharging (in standby)
  • Solar panels are producing electricity
  • Home is completely powered by solar energy
  • Excess solar energy is being exported to the grid (NEM PG&E E6 plan)
  • Gateway 2 is configure with time based control.
When I simulate a grid outage by throwing the service disconnect, the solar inverter shuts off immediately as expected. However the PW2s beep as if they are resetting and the power to the entire house is lost. About 15-30 seconds later, definitely longer than just a few seconds, the PW2s start back up and power the home.

Has anyone encountered or tested this scenario?

Could this non-seamless switchover be due to the PW2s being fully charged and somehow it can’t immediately shutoff the solar inverter that was putting the house and exporting to the grid? And therefore, to prevent the solar power from overloading the fully charged PW2s, the PW2s disconnect for 15-30 sec and then turn back on.

This is bothering me because this scenario is going to be the most common for me where the batteries are 100% and solar is producing during daytime.

If the battery is not full like 90-something %, then the switchover is seamless during the simulated outage. This leads me to believe that since the solar power had someplace to go (to charge the battery), the PW2 did not have to reset to avoid being overloaded and hence the switchover is seamless.
 
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