your place looks like it could have been an article in "HomePower" magazine
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Wall of 10 Tesla Powerwall 2 units
Looks like Tesla fixed the software issue which let the Powerwalls draw too many AMPS during a Storm Alert. It maxed out at 24 kW (240VAC at 100 AMPS) which is perfect to maximize charging without tripping the breakers. Previously, it was drawing up to 35 kW when Storm Alert activated tripping our 100 AMP breakers, making that feature useless. With 10 Powerwall 2 units, it was a software glitch as it was programmed for 100 AMPS as our home has a 200 AMPS utility service and 100 AMPS renewable energy subpanel. The batteries plus renewable energy panel cannot exceed the utility service rating. I contacted Tesla Energy a few weeks ago and put in a Service Ticket but haven't heard anything back. Communication is not great, but they fixed the problem. Now we can leave the Storm Alert function toggled on when we are away while other8running in Self Powered mode to optimize using our own renewable energy to power our home and optimize our battery backup if the National Weather Service triggers a Storm Alert without the battery system shutting down because the breakers trip from charging at too many AMPS.
CrazyRabbit
Active Member
What a huge oversight! i bet powerwall would trip the breaker dumping power to the grid as well in a grid support services, especially with solar functioning...
guess i got my answer, i thought for sure PW would have been programmed correctly for this.
my utility had me sign a agreement to not export more then 200 amps (48KW).
guess i got my answer, i thought for sure PW would have been programmed correctly for this.
my utility had me sign a agreement to not export more then 200 amps (48KW).
It was a problem which they fixed. I think part of the situation is we have an unusual system. Most don't have more than 3 Powerwalls, let alone 10. We've been told this is one of 6 six systems like this in the United States. With 3 Powerwalls, the charge/discharge rates would be 21 kW peak and 15 kW continuous. If our renewable power was via a string inverter, we might have a 200 AMP (48 kW) circuit between the Gateway and the batteries. Our turbines have their own inverters in the nacelles. Our PV uses Enphase microinverters. So some of this need to have a customized charge/discharge limit is due to adding the Powerwalls to our existing, and admittedly unusual system, all installed by third party installers. Tesla doesn't have its own crews servicing Wyoming. This was the first Powerwall installation by the company which did our project. They have installed all of our grid tied renewable energy systems since 2012. It works as it should now.
When the batteries are full and the grid is connected, excess production goes out to the grid like any net metering system. When the grid is not connected, if the batteries are full, the frequency of the AC current modulates down causing all devices feeding the renewable panel to shut down. After that, when the batteries stop below 90-96% SOC, the modulation frequency shifts back and the devices feeding the renewable panel reactivated. No dump load is needed.
The maximal power "dumped to grid" never exceeds 100 AMPS. The maximum power pulled from the grid never exceeds 200 AMPS. The batteries never dump power to the grid. Only the home draws power from the batteries, not exceeding 100 AMPS. Under Storm Watch, when activated, the batteries will not draw more than 100 AMPS from the grid.
This is how our system is set up. Others no doubt are set up differently.
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petit_bateau
Active Member
Do you not have your frequencies the wrong way around ? Ordinarily it is a rising and high frequency that provides the signal for a grid-connected inverter to stop feeding. Just think of what happens to frequency when a mechanical generator is struggling to supply a load ....
My understanding is the frequency which normally is 60Hz drops to a lower frequency when the grid is offline and the batteries are at 100% SOC. If you have a source of other information, with specific details, please post it. Thank you.
When the grid is down, the Powerwalls will maintain 60Hz until it needs to curtail generation. Curtailment is always signaled by increasing the frequency. How high it increases is a configurable parameter that only Tesla can modify. It will also ramp up the frequency relatively slowly and if your solar inverters are configured to respond to it, they will proportionally reduce their output. However, some grids require "ride-through" programming which prevents the inverters from gracefully curtailing like this. In that case, the inverters have a hard limit on frequency and will abruptly halt their output when that threshold is reached. That value could be anywhere between 60.5Hz and 62.5Hz. There are other special conditions when Tesla doesn't want the Powerwalls to take a charge off-grid, so it will raise the frequency when those conditions, like low battery temperature, occur.
Interesting. Do you have a source you can cite for your information? Just curious. I noticed when the solar PV and wind turbines shut down during a grid outage, the UPS for our computers turn on.
Lots of discussion about that in the 31 page thread about UPSs.
Powerwall 2 + UPS Connundrum - and solution
The Tesla Powerwall 2 (PW2) is an excellent protection against grid power outages, yet its design does require an additional Uninterruptible Power Supply (UPS) for any devices that are sensitive to even extremely brief power breaks. While your fridge, microwave, most lights and other devices...
teslamotorsclub.com
Long story short, make sure all your generating inverters shut down by 62.5Hz and ask Tesla to reduce the max frequency to that level. Then, UPS units that start complaining at 63Hz will remain happy with your micro-grid. The alternative is to use UPS units with a wide frequency input range (up to 70Hz) or use expensive double conversion UPS units.
That’s likely because the UPS doesn’t like the higher frequency from the PW and is having the batteries take over. Here’s a post on Reddit of someone measuring the frequency shift.
You can refer to the UL 1741 standard for how a grid tied inverter is required to respond to frequency shifts. (They have to curtail as the frequency increases, and cut-off production once it reaches a certain threshold.)
Here a graph of inverter curtailment vs frequency. Of course the PWs need to operate in the same direction of frequency change
petit_bateau
Active Member
This feature has been included in most inverters for a decade or so, see SMA inverters as grid managers for another example. The reason that the curtailment signal must be a rising frequency is to do with how rotating generators function as load increases/decreases - that is a matter of physics, not a standard. When describing it one ordinarily talks about the frequency of the voltage as that is a 'cleaner' descriptor than frequency of the current. Glad to hear your Skystreams are working well, I know the chap who designed their inverters
Does the Tesla app register the power from the turbines as coming from the grid or coming from "solar"?
The App "Solar" is the wind power and PV combined as this image illustrates.
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