Jack Ricard on UL-1741 and utility tapering, thoughts?

[Ampster]

The utility does care that you don't recharge batteries with lower rate off-peak, discharge batteries to backfeed grid on-peak.
That function is done somewhere, but they don't want you to do it at retail rates.

I have an ideosycrousy where my SolArk exports to the grid from my batteries, based on some settings that I am not clear on how I set had set that parameter. I do know how to control the amount and I lowered that to 1000 Watts during my 4-9 TOU period. I don;t think that will cause a red flag. Now with Daylight Savings Time I am generating solar as late as 7PM from some of my West facing panels anyway in addition to the battery export.

 

[Hedges]

I'm playing with Sunny Boy Storage, similar issues of not sticking my head up too far.

I've figured out how to charge enough to prevent export, discharge enough to prevent import, force charge from grid, force discharge to grid.

It has 2 connections for WattNode meters which use CT. Could put CT around grid connection or around GT PV connection only. (for now, CT around SBS connection in my lab, and I used an electric radiator to simulate either house loads or PV generation, simply reversing CT.)

I'm having trouble getting it to work each day, after a run of several in a row it now charges only every other day. I am able to limit discharge rate (LG recommends 0.33C for longer life than 0.5C), but DoD limits in SBS aren't working.

Once I get this working, I plan to get PTO and install it to store PV generation for export during peak rates. For now I've got discharge low enough it probably just balances house loads. (Especially when sun isn't shining.)

 

[toms]

In Australia, all grid tie inverters have to have the ability to be remotely disabled by the utility provider. They are switched off during times of peak production to stop grid over-voltage.

 

[Hedges]

Can you get around that if you just tell it zero export?
Or are you required to curtail your own production so you can buy somebody else's?

 

[941all-electric]

In Australia, all grid tie inverters have to have the ability to be remotely disabled by the utility provider. They are switched off during times of peak production to stop grid over-voltage.

That's insane to me. Do utilities do this? Are customers aware when it happens?

 

[robby]

That's insane to me. Do utilities do this? Are customers aware when it happens?

Yes it is very well known feature built into all Inverters that can be legally Grid Tied.
Your probably thinking of the output power of a single Inverter and thinking it's effects on the Utility company are Tiny.
Utility companies have to be planning for growth in Solar, if you look at Hawaii with 37% of the Islands Energy being produced by Home owners you get an idea of why they need to be able to shut it off if the Grid is being overloaded by power from thousands of Inverters.
I think the Frequency throttling starts at 62Hz and shuts off the Inverter at 66Hz. This feature does have some benefits for home owners with Inverters and Micro Inverters. It allows the systems to throttle back power on one device when there is no where to dump extra power.

 

[zanydroid]

The utility grid frequency is VERY tightly controlled. The utility is not going to shift it for some solar inverters. That would screw up people's clocks and the phasing of all the utilities power sources, including the interconnection of other grids across a wide area.

They will do it across the grid though (EDIT: as opposed to targeting some individuals / groups as enemies of the state^^^^^grid). Otherwise why did they add Frequency-Watts throttling to UL1741SA? It wasn't to give off grid plebs AC coupling capability when off-grid.

And the utility can do Volt-watts control instead of Frequency-Watts, and Volt-watts can intrinsically kick in even without utility intervention (IE switching transformer windings to adjust the frequency). EG if you are in a neighborhood with an excess of solar the local grid voltage will be higher.

EDIT: And Volt-watts can be more readily enforced on a per-neighborhood basis by adjusting the transformers upstream of the neighborhood of undesirables. So I guess you can target enemies of the <blank> this way.

Anyway I didn't click the video b/c I was pretty sure the person needs to have a reality check.

 

[Philip53]

Does anyone know when grid tied inverters began to incorporate this feature? I have a 12 year old Schneider, and I don't think it has this capability.

 

[zanydroid]

That's insane to me. Do utilities do this? Are customers aware when it happens?

A large part of 1741SB (which is required by most / all states with substantial grid-tied solar) is to provide a pathway to doing this. It requires inverters to be ready to be tied into a control API, however it does not require the full path to be defined. At the time it was standardized the security issues, among many other important details, were not addressed.

1741SA (Frequency-Watts, Volt-Watts, etc) are ways to curtail without the API path, by sending the curtailment signal via changing the electrical characteristics of the grid.

The ship has sailed, if you don't like it, you have to violate the interconnection agreement, move to a state without the requirement, or stay off-grid.

 

[zanydroid]

Does anyone know when grid tied inverters began to incorporate this feature? I have a 12 year old Schneider, and I don't think it has this capability.

Google for the adoption history for 1741SA/1741SB (or manufacturer self-attestation of compliance) for your local grid.

12 year old schneider absolutely does not. 1741SA's control scheme was probably only a twinkle in the eye of some academics at that time.

 

[Ampster]

Can you get around that if you just tell it zero export?

I think the concept is to throttle back power, so the result could be that your inverter throttles back to where it is not exporting. If you tell your inverter to zero export to avoid getting throttled back your could miss out on a lot of export opportunities.

 

[toms]

That's insane to me. Do utilities do this? Are customers aware when it happens?

Yes utilities regularly use this function - yes it is accepted practice and not a hidden feature. The sneaky thing is utilities deliberately raising grid voltage so they can shut off grid feed inverters and not have to pay people for feed-in. (this is obviously denied by utilities).

 

[Hedges]

I'd want to export all I could most of the time, drop to zero-export when requested by grid to curtail. But I think inverters will drop back to a percentage of available power, resulting in consumers purchasing power.

 

[zanydroid]

Yes utilities regularly use this function - yes it is accepted practice and not a hidden feature. The sneaky thing is utilities deliberately raising grid voltage so they can shut off grid feed inverters and not have to pay people for feed-in. (this is obviously denied by utilities).

Don’t they publicly report feed in from all sources (including solar, peaker plants, etc) and grid demand?

So they would have to cook some books/deal with a paper trail.

 

[robby]

Yes utilities regularly use this function - yes it is accepted practice and not a hidden feature. The sneaky thing is utilities deliberately raising grid voltage so they can shut off grid feed inverters and not have to pay people for feed-in. (this is obviously denied by utilities).

Are you sure that this is not some sort of Urban Myth
Inverters are constantly adjusting their output according to what the Grid is producing.

 

[zanydroid]

Are you sure that this is not some sort of Urban Myth
Inverters are constantly adjusting their output according to what the Grid is producing.

I mean literally everybody can see what the grid frequency and voltage is. Nobody is stopping you from buying an emporia and tracking it. IOW it’s pretty easy to track frequency and voltage excursions

 

[Ampster]

Yes utilities regularly use this function

As mentioned earlier it can happen at the substation inadvertently. Years ago my Xantrex went offline because the grid voltage was too high. I called SCE and they told me that they had delayed ramping down the voltage after making some kind of seasonal adjustment at my substation. It was fixed in a number of days. I don't think that old inverter had much of UL1741 in its spec because it was purchased in 2008. But it did have a limit on grid voltage.

 

[Hedges]

Google for the adoption history for 1741SA/1741SB (or manufacturer self-attestation of compliance) for your local grid.

12 year old schneider absolutely does not. 1741SA's control scheme was probably only a twinkle in the eye of some academics at that time.

SMA inverters used frequency and voltage droop for AC coupling of off-grid systems 20 years ago.

https://www.osti.gov/etdeweb/servlets/purl/20902675

https://iitime.org/new/wp-content/uploads/documents/accoupling.pdf

AC-coupling Design

One of the main considerations to AC-coupling design is the ratio between the Grid-Tie inverter (GTI) and the Battery-Based inverter (BBI).

www.greentechrenewables.com

Here are more recent products from 11 years ago.

Coupling Options For Off-Grid Solar Arrays - Sunny. SMA Corporate Blog

Substantial improvements to off-grid photovoltaic technology during the past decade have led to more choices in off-grid PV system design....

www.sma-sunny.com

So the concept and implementation was already there. Got adopted for grid use.
It seems like volts-watts makes more sense for systems on the mainland (or communications). Frequency-watts maybe for Hawaii.

But I think pagers would be a way to knock PV or loads offline.

 

[robby]

I mean literally everybody can see what the grid frequency and voltage is. Nobody is stopping you from buying an emporia and tracking it. IOW it’s pretty easy to track frequency and voltage excursions

Yes it is easy to read it, but my question is are you sure "Raising Grid Voltage" is an attempt to knock people off of Grid feeding?
With the Sol-Ark and I think most Inverters you set the Minimum and Maximum Grid Voltage it will work with and if the Grid goes above the Maximum it disconnects from the Grid and goes onto PV/Batteries only. I could just raise it to get around a problem like that.
If my settings where lower this would stop me from selling to them but it is a very clumsy method that would require the Line voltage to go past 127 V per leg on a typical system.
I think that could cause some customers closer in to the Power Substations to see even larger increase probably in the 130V or more range.
Sounds like a bad plan to me. I suspect that as @Ampster said it might just be a problem they were having.

 

[zanydroid]

So the concept and implementation was already there. Got adopted for grid use.
It seems like volts-watts makes more sense for systems on the mainland (or communications). Frequency-watts maybe for Hawaii.

Frequency-watts correlates with the concept in backup generators where if spinning generators get overloaded, their frequency will decrease, which then triggers load shedding relays. And similar probably applies to the grid. Conversely if there is a reduction in demand (from turning off loads or turning on extra grid tie inverters) the frequency will tend to go up as there is less load pushing back against the spinning generator. So there is a measure of passive safety.


Not clear whether it has been tested in practice. Maybe one of the utilities, grid operators, or energy labs has access to information about minor grid operation mistakes, and can see whether or not 1741SA actually helped.

With the Sol-Ark and I think most Inverters you set the Minimum and Maximum Grid Voltage it will work with and if the Grid goes above the Maximum it disconnects from the Grid and goes onto PV/Batteries only. I could just raise it to get around a problem like that.

If you are on-grid, generally the interconnection agreement will have some buried fine print telling you to set the inverter within a range of grid parameters, which ought to be baked in if you pick the right grid code.

EDIT: For instance SolarEdge at one point told installers to do this .

I don't think that old inverter had much of UL1741 in its spec because it was purchased in 2008.

1741 has cutoffs when voltage or frequency goes out of range. It's more of a sharp on-off.

One of the changes in 1741SA (in addition to curtailment) was seeking to make inverters fall off more gracefully (ride-through concept). Otherwise, if you have 40% grid-tie on your grid, a minor grid glitch might cause 40% of your generation capacity to fall off. Generally speaking that's a bad day.

1741 was defined when the grid-tie % was pretty low, so if 1-2% of grid tie inverters fall off, it's not as big a deal.