Battery and Solar during an ice storm

[Kodemonkey]

Unfortunately, I suspect most inverters already in place don't scale back their production using FSPC, but just shutdown for a bit and then try again, and I am sure you know that! That is certainly my situation. As to dumping solar energy, the object is not to "waste" that energy but to use every precious bit of it during a power failure. In my case I have a resistance heater in one of my water tanks, that are normally heated by my geothermal system. I typically turn off the geo during a power failure, although, given the installed soft start device, it will run off of the Powerwalls, just not for long. The resistance heater allows my to use excess solar energy more gently, e.g. at 5 kW rather than 8-10 kW. Heating water is not wasted energy, but even 5 kW is too granular for managing solar over production. The Tesla coordinated charging scheme is perfect for keeping the batteries at 90 or 95% as long as the sun is shining and not allowing solar energy to be wasted or not used. Of course when the car hits 100% SOC that is another matter.

I have a friend with LG panels with micro inverters and 2 Powerwalls. His scale back production. One sunny day where he should have been producing over 10KW, he was only showing 1 or 2 KW. He was without power and his 2 PW were at 99%. So there are systems that scale back power. This is a brand new install (3 months old) from Sunrun. He has the Telsa TEG and 2 powerwalls. My Telsa install with a SE string inverter just shuts down completely.

 

[jjrandorin]

It depends on how old (or how new), your install is. My inverters installed in 2015 do not have the ability to scale production, I am fairly sure. Newly installed inverters I believe all have this ability but I dont think they are all activated to do so. Not sure what it takes to get tesla to set this up for a person (scaling) if its a tesla install.

I think @gpez figured out how to configure theirs themselves?

 

[MorrisonHiker]

I had suggested coordinated car charging to solve the solar overproduction problem on this forum some time ago, but was told it was not practical because the car might not be on the same panel that was backed up by solar. How would the app know, it was said? Fortunately it is practical and this ability is a good reason to have your EV on a panel that is backed up. Unfortunately my 8-year old Model S won't play nice with the Powerwalls, I believe.

It appears your car wouldn't be supported. I assumed it would work for all S & X but it looks like they have to be 2014 or newer:

Supported Versions

• Powerwall: 1.46+
• Tesla Mobile App: 3.10.2+
• Model 3/Model Y – North America: 2019.40.1+
• Model S/Model X (2014 and later) – North America: 2020.32+
• All Tesla Vehicles in Other Regions: 2020.40

Source: Vehicle Charging During Power Outage | Tesla Powerwall

 

[shs1]

It appears your car wouldn't be supported. I assumed it would work for all S & X but it looks like they have to be 2014 or newer:

Supported Versions

• Powerwall: 1.46+
• Tesla Mobile App: 3.10.2+
• Model 3/Model Y – North America: 2019.40.1+
• Model S/Model X (2014 and later) – North America: 2020.32+
• All Tesla Vehicles in Other Regions: 2020.40

Source: Vehicle Charging During Power Outage | Tesla Powerwall

Yep!

 

[gpez]

It depends on how old (or how new), your install is. My inverters installed in 2015 do not have the ability to scale production, I am fairly sure. Newly installed inverters I believe all have this ability but I dont think they are all activated to do so. Not sure what it takes to get tesla to set this up for a person (scaling) if its a tesla install.

I think @gpez figured out how to configure theirs themselves?

They're not usually configured with that feature enabled. If you have installer access it's simple to do. I simply called Enphase (I have IQ6s) and asked them to apply a different profile that has ramp down configured. They did so quickly and easily!

 

[shs1]

Looking at the documentation, it seems as if at least one of my SMA inverters will go with full FSPC, but I was told earlier on this forum that that was there for off grid systems and full implementation would be a violation of the agreement with PG&E, so I haven't pursued it further. I do think that "storing" excess solar energy in domestic hot water or car batteries is far better than slowing down solar production, but slowing down solar production is also far better that shutting it down!

 

[jboy210]

You don't have to do this Modern inverters have the ability to scale their production.

Now if you have a car to charge then that's great too but no need to "dump" excess power if you have your system configured to simply adjust production.

What is the facility to scale production called? I have Delta M-series inverters and wanted to see if they have this capability. I did not see any reference to FSPC in the manual if that is the mechanism.

 

[gpez]

What is the facility to scale production called? I have Delta M-series inverters and wanted to see if they have this capability. I did not see any reference to FSPC in the manual if that is the mechanism.

The Delta-M series documentation seems not complete online but I do see where other Delta inverters have this. Check out page 36 of Manual-M6A-M8A-M10A.pdf (solarcutters.com).

5.3.7.2. Power vs. Frequency Inverter will reduce output power when grid frequency rises up if this mode enabled. Users can tune the parameters in Power vs. Frequency page to change the inverter’s behavior.

 

[shs1]

FSPC stands for Frequency Shift Power Control and is, as I understand it, the mechanism via which battery systems can curtail solar production, at least historically. I would think that ideally battery systems and inverters could use some networking protocols for communications as raising frequencies can cause various devices in our homes to misbehave. You might look for a diagram like the one attached that defines the frequencies as a function of the State of Charge of the batteries.

 

[jboy210]

The Delta-M series documentation seems not complete online but I do see where other Delta inverters have this. Check out page 36 of Manual-M6A-M8A-M10A.pdf (solarcutters.com).

5.3.7.2. Power vs. Frequency Inverter will reduce output power when grid frequency rises up if this mode enabled. Users can tune the parameters in Power vs. Frequency page to change the inverter’s behavior.

OK. That sounds like the control mechanism the TEG uses to cut off the inverter when the PowerWalls get full. I watched that happen numerous times when testing off-grid operations of our Powerwall setup, so know we are OK there.

I thought this was another system I needed to deal with.

 

[gpez]

OK. That sounds like the control mechanism the TEG uses to cut off the inverter when the PowerWalls get full. I watched that happen numerous times when testing off-grid operations of our Powerwall setup, so know we are OK there.

I thought this was another system I needed to deal with.

They're actually two similar but different concepts. 5.3.7.2 Power vs Frequency and 5.3.6.4. Grid Settings

Grid settings page includes the voltage and frequency protection points. These protection points are linked to electricity regulations. If there is no any special requirement, please do not change any grid settings.

 

[shs1]

Yes, the TEG uses FSPC, raising the frequency as the Powerwall gets fully charged, and most inverters setup for grid use simply shut down when this happens. It would be better for the inverters to respond the the rising frequency by proportionally scaling back their power output rather than shutting down. That is a matter of how the inverter is configured in some cases, and the question I asked earlier is, Is it OK to so configure the inverter in a grid tied system? I was told earlier that it was not.

 

[gpez]

Is it OK to so configure the inverter in a grid tied system? I was told earlier that it was not.

(I am not a lawyer, electrician, grid expert, or code enforcer)

My understanding is that for a Powerwall system the grid tie point is actually the TEG, not the PV inverter, thus its OK to change the configuration for the PV inverter to accommodate your microgrid needs because it is "behind" the TEG from the grid's perspective. The TEG also has config options which it will respect, you shouldn't alter those.

If you have a grid tie system with no storage or additional gateway you cannot, as per your interconnect agreement, alter the inverter settings outside of the contractual bounds.

 

[shs1]

Thank you. That explains things! I'll have to discuss with my installer.

 

[Dan123]

This can happen if one has "too much PV, not enough powerwalls". You have a 12k solar system with only 2 powerwalls, and if your peak production can go as high as 11kW, in order to avoid this you either need another powerwall, or to increase your home loads if possible to prevent them being forced off because of too much power... as you found out.

Also, on a cold sunny day, the peak production can really exceed the peak production (it would be limited only by the inverter size).

 

[jboy210]

[

(I am not a lawyer, electrician, grid expert, or code enforcer)

My understanding is that for a Powerwall system the grid tie point is actually the TEG, not the PV inverter, thus its OK to change the configuration for the PV inverter to accommodate your microgrid needs because it is "behind" the TEG from the grid's perspective. The TEG also has config options which it will respect, you shouldn't alter those.

If you have a grid tie system with no storage or additional gateway you cannot, as per your interconnect agreement, alter the inverter settings outside of the contractual bounds.

That squares with my understanding of the TEG. It is a smart switch that monitors the grid, solar, and Powerwalls. Based on the settings you select in the app and the conditions (PW state of charge, solar generation, etc.) it makes decisions on how to route power from the sources to the sinks. And as mentioned before will control generation via the inverters. Hopefully, with Tesla now shipping their own inverters this means tighter integration between the TEG and Tesla inverters. Raising frequency to control the inverter is a pretty crude control mechanism.