Powerwall 2 + UPS Connundrum - and solution

[bob_p]

I called Tesla's phone support.

Yesterday, they called back and asked for the specific solar panel cutoff frequency for our system - and will get their tier 2 support to lower our off-grid/full PW frequency to support the 60.5 Hz cutoff used for our microinverters.

Hopefully this change will be made in the next week - and I'll rerun our off-grid/full PW test again to verify.

 

[Ulmo]

I called Tesla's phone support.

Yesterday, they called back and asked for the specific solar panel cutoff frequency for our system - and will get their tier 2 support to lower our off-grid/full PW frequency to support the 60.5 Hz cutoff used for our microinverters.

Hopefully this change will be made in the next week - and I'll rerun our off-grid/full PW test again to verify.

This ought to be in an advanced config screen of the app, complete with an honest truthful explanation of it that isn't dumbed down at all or skimmed over (advanced config screen, not normal).

 

[bob_p]

Agree, this should be part of the installers setup, based on the specific solar/inverters being used.

 

[gpez]

This ought to be in an advanced config screen of the app, complete with an honest truthful explanation of it that isn't dumbed down at all or skimmed over (advanced config screen, not normal).

I don't disagree though the reality is there may be local regulations or utility interconnect rules that require grid tied systems to adhere to. Additionally a misconfiguration can cause damage to other hardware, such as the inverters. Tesla has non-zero liability if they open it up, even with a disclaimer.

Agree, this should be part of the installers setup, based on the specific solar/inverters being used.

The Powerwall and gateway already know what the solar make/model is as well as having a local utility profile. Heck it knows the address of the Powerwall so with all of that data it *should* be able to make the right config decision for consumer, utility, and equipment.

 

[mspohr]

I don't disagree though the reality is there may be local regulations or utility interconnect rules that require grid tied systems to adhere to. Additionally a misconfiguration can cause damage to other hardware, such as the inverters. Tesla has non-zero liability if they open it up, even with a disclaimer.



The Powerwall and gateway already know what the solar make/model is as well as having a local utility profile. Heck it knows the address of the Powerwall so with all of that data it *should* be able to make the right config decision for consumer, utility, and equipment.

I have an Outback Skybox which adjusts the frequency to bring solar inverters on/off line. It does this dynamically. If too much power is being generated beyond what is needed for loads and battery charging, it adjusts the frequency to cause solar inverters to drop out. There is no need to set a frequency. It just adjusts the frequency until the solar input drops. If it needs more solar power to satisfy loads and battery charging, it again adjusts the frequency until the inverters kick back in.
I don't know why the Powerwall can't do the same.

 

[gpez]

I have an Outback Skybox which adjusts the frequency to bring solar inverters on/off line. It does this dynamically. If too much power is being generated beyond what is needed for loads and battery charging, it adjusts the frequency to cause solar inverters to drop out. There is no need to set a frequency. It just adjusts the frequency until the solar input drops. If it needs more solar power to satisfy loads and battery charging, it again adjusts the frequency until the inverters kick back in.
I don't know why the Powerwall can't do the same.

It does. I have my Powerwall configured to dynamically adjust production during a grid outage.

You still need to set parameters for ramp up, ramp down, min and max frequencies to match your inverter. Those vary by inverter, though less so with the UL/IEEE standards now. I guess it could "learn" by trial and error. Problem is that you could run in to some pretty dramatic problems if it didn't learn fast enough.

 

[mspohr]

It does. I have my Powerwall configured to dynamically adjust production during a grid outage.

You still need to set parameters for ramp up, ramp down, min and max frequencies to match your inverter. Those vary by inverter, though less so with the UL/IEEE standards now. I guess it could "learn" by trial and error. Problem is that you could run in to some pretty dramatic problems if it didn't learn fast enough.

Don't know why this needs to be customized for each inverter (or why people are having so many problems getting theirs set up).
I'm not sure I understand what could go wrong. If you are getting too much power from inverters, raise the frequency until they shut off. (Inverters all are set to react quickly to higher frequency.) If you need more power, lower the frequency until they start up. (Need some time delay loops since it typically takes them about 5 minutes to start up.)

 

[aesculus]

It does. I have my Powerwall configured to dynamically adjust production during a grid outage.

You still need to set parameters for ramp up, ramp down, min and max frequencies to match your inverter. Those vary by inverter, though less so with the UL/IEEE standards now. I guess it could "learn" by trial and error. Problem is that you could run in to some pretty dramatic problems if it didn't learn fast enough.

Can you share where/how you did this?

 

[JPP]

Can you share where/how you did this?

Yes, please. I get little to no info from Tesla Powerwall Support. I have twice called to have tickets opened.

 

[bob_p]

I don't recall anywhere in the paperwork submitted by our installer to our local utility a specification on the power frequency used by the TEG when operating off grid with full PowerWalls (high frequency used to turn off the solar inverters/microinverters).

Since that frequency should only be used when the system is off-grid - and once the grid is connected, the TEG re-synchronizes back to the grid's power (which provides 60Hz), it seems unlikely setting the off-grid solar power cutoff power frequency would affect the grid power at all. When grid power is installed (at least for our TEG), there is at least a 5 minute period when our system will continue to operate off-grid before the TEG resynchronizes with the grid and then switches back to grid power.

Doesn't seem to be any reason why Tesla shouldn't include this setting in the "installer" interface, allowing the solar power shutdown frequency to be set between 60.5Hz to 65Hz - especially since the default setting (65Hz) is the worst setting choice!

 

[mspohr]

I don't recall anywhere in the paperwork submitted by our installer to our local utility a specification on the power frequency used by the TEG when operating off grid with full PowerWalls (high frequency used to turn off the solar inverters/microinverters).

Since that frequency should only be used when the system is off-grid - and once the grid is connected, the TEG re-synchronizes back to the grid's power (which provides 60Hz), it seems unlikely setting the off-grid solar power cutoff power frequency would affect the grid power at all. When grid power is installed (at least for our TEG), there is at least a 5 minute period when our system will continue to operate off-grid before the TEG resynchronizes with the grid and then switches back to grid power.

Doesn't seem to be any reason why Tesla shouldn't include this setting in the "installer" interface, allowing the solar power shutdown frequency to be set between 60.5Hz to 65Hz - especially since the default setting (65Hz) is the worst setting choice!

I don't think there should be a specific set frequency set as it could be set wrong. Much better to have the Powerwall dynamically adjust the frequency until the inverters shut off.

 

[woferry]

Dynamic sounds like a really bad idea to me. That period where the PW is trying to figure out what it needs to do to stop the inverter the house voltage will be climbing beyond the usual range. I'd rather not subject everything in my house to that, especially if it could happen frequently (like an outage while the sun is up and the PWs are nearly full).

 

[mspohr]

Dynamic sounds like a really bad idea to me. That period where the PW is trying to figure out what it needs to do to stop the inverter the house voltage will be climbing beyond the usual range. I'd rather not subject everything in my house to that, especially if it could happen frequently (like an outage while the sun is up and the PWs are nearly full).

Most inverters shut off in milliseconds so not much opportunity for overvoltage

 

[woferry]

Well, one cycle is 16.7ms (1/60), so I can't see how it could possibly detect a grid frequency change any faster than that (and I'd think it probably requires multiple cycles to be sure it really was a frequency change and not just a glitch/measurement error). And if the Powerwall is going to have to try multiple frequencies to see which one the inverter requires to actually shut down, then that's multiple 16.7ms steps. It adds up pretty quickly.

 

[power.saver]

My SMA UL1741 (non -SA) inverter takes 160ms to trip on high (or low) frequency, which is about 10 cycles. I think this is typical to avoid nuisance trips from noise or spikes on the grid. Newer inverters allow this to be adjusted up to 300s. Any dynamic frequency shutoff would be hampered by these delays.

I do think that Tesla should include inverter shutdown testing as part of the commissioning process, and set the appropriate frequency so customers aren't left to find out later that things don't work during an outage when the batteries are full.

 

[bob_p]

The inverter shut off frequency is static - and can be provided by the inverter manufacturer.

Based on the configuration, that frequency can be set once.

There isn't any need for a dynamic setting.

It's likely Tesla default setting of 65Hz is way too high. 63Hz may be a better choice - and more devices are likely to accept 63Hz than 65Hz.

Unless Tesla wants to continue using their support resources to configure each TEG remotely (including 3rd party installations), this should be a setting available on the installer's web site on the TEG.

 

[mspohr]

The inverter shut off frequency is static - and can be provided by the inverter manufacturer.

Based on the configuration, that frequency can be set once.

There isn't any need for a dynamic setting.

It's likely Tesla default setting of 65Hz is way too high. 63Hz may be a better choice - and more devices are likely to accept 63Hz than 65Hz.

Unless Tesla wants to continue using their support resources to configure each TEG remotely (including 3rd party installations), this should be a setting available on the installer's web site on the TEG.

In my case, I have three different models of inverters. They have different cutoff frequencies. Some are microinverters. By having dynamic frequency shift, it's possible to have some proportional control of solar generation.

 

[HankLloydRight]

Side question -- I have just a PW2 with no solar. Does the PW still change the frequency during an outage, even though there's no need to?

 

[miimura]

Side question -- I have just a PW2 with no solar. Does the PW still change the frequency during an outage, even though there's no need to?

That's a very good question. The corollary is - does the PW change the frequency if the outage happens at night when there is no solar production?

 

[woferry]

From what I've seen, it's based purely on the battery percentage, so yes, if the battery is high enough it will shift the frequency even when the sun is down. Now whether they disable that feature in an installation w/o solar I don't know.