Update battery controller to consider grid interconnection limit

[nickdiorio]

With the addition of a grid interconnection limit, it will be nice to have the battery controller consider this limit when dispatching.

[cpaulgilman]

Export limiting is a common request by PV modelers, for a description see:

https://www.solaranalytics.com/us/blog/what-is-solar-export-limiting-and-how-to-find-your-lost-energy.

And this SMA article about the export limiting feature on some inverters:

https://www.sma-uk.com/solar-systems/export-limitation.html

Users want to know how much energy they lose over the year due to this limiting.

[janinefreeman]

@sjanzou @dguittet Is this complete, or still on our to-do list?

[dguittet]

This is not complete. The grid interconnection limit is applied after dispatch and not factored into the dispatch decision.

[cpaulgilman]

For battery configurations with Merchant Plant, cleared capacity requirements for both energy market and ancillary services should be considered by the automated dispatch options.

[dguittet]

I'm going to move this out of the upcoming release since I think it needs to be done in conjunction with the other grid requirements, and be part of a larger merchant plant dispatch optimization framework.

[brtietz]

While working on #658 I wrote a powerflow test that tried to push a DC battery into grid export. The result was the powerflow calculations listed grid_to_load as a negative number. It's not surprising that the powerflow calcs would need work at that level, but wanted to record the specifics here for planning purposes.

[milindsmart]

I believe this issue captures the problem I had when I tried to run the Detailed PV Model with grid limits (import - export is disallowed, a pure BTM system) and battery - the grid limits are not being respected.
Despite being kind of familiar with SAM for several years, it took me a lot of sleuthing to track this behaviour down. I suggest adding a mention somewhere. Also, is there an alternative way of limiting grid imports?

[cpaulgilman]

@milindsmart Good point. I added a note to the Help topic for the Grid Limits page to explain that battery dispatch does not consider the grid interconnection limit (but does consider grid outages). This will be available in the Fall 2022 Release of SAM.

[cpaulgilman]

https://sam.nrel.gov/forum/forum-general/4366

[brtietz]

This seems like it will be increasingly important for hybrids, so hoping to sneak it into the 2024 release.

[andreaswabbes]

I can confirm that this is a very urgent topic. An option 'charge from curtailed energy' (similar to clipped energy for DC coupled) would be brilliant. Many sites are over-dimensioned on the PV side and are looking towards batteries to avoid waiting for an expansion of grid connection.