Interface for fetching grid metrics: `frequency`

[sahas-subramanian-frequenz]

What's needed?

A high level interface for fetching grid frequency.

Proposed solution

This can be done in two steps:

1. A method microgrid.grid.frequency() that takes an optional component_id of a meter, from which it would stream frequency values. This value does not need to be resampled (so no need to get it from the resampler actor). If no component_id is specified, use the meter closest to the grid, in the component graph. If there are multiple meters close to the grid, pick any one that has no successors.
2. Once the microgrid API starts supporting metadata for components, a query interface around the component graph, to identify meters with the best resolution, and get their component IDs, which can be used in the methods from step 1, instead of having to specify component IDs in config files.

Use cases

No response

Alternatives and workarounds

No response

Additional context

[matthias-wende-frequenz]

I looked into the FCR specs again and it looks that we don't need very fast reaction times and thus for now it's good enough if we address 1) by just using any meter.

[leandro-lucarella-frequenz]

@matthias-wende-frequenz will talk to Tom to decide whether to resample or not.

[matthias-wende-frequenz]

@matthias-wende-frequenz will talk to Tom to decide whether to resample or not.

The verdict is that resampling is not needed.

[leandro-lucarella-frequenz]

Cool, updating the issue description (and hiding these comments as resolved to avoid the noise).