Integrate temporal and spatial complexity reduction of MVLV-grids

[ClaraBuettner]

Rather an eDisGo task, I just created an issue to not forget that this is also needed for the eGo milestone

[MoritzSchloesser]

Temporal complexity reduction (partial scope of this issue)

This issue covers both temporal and spatial complexity reduction.
Capturing the temporal part here since it is now actionable.

Problem

A per-grid eDisGo run optimizes and reinforces over the full-year time
series (8760 steps). For the eGo milestone this is prohibitively expensive
across many MVLV grids — most of the year is uncritical, and only a handful
of load/feed-in situations actually drive reinforcement.

We want to reduce each grid to a small set of representative time intervals
before the expensive OPF/reinforce steps, and to be able to control that
reduction per run and per grid.

What eDisGo provides (openego/eDisGo#663)

The eDisGo run pipeline gains a select_timesteps task with three modes:

• manual — an explicit time series (start / periods / freq).
• auto + power_flow — the existing critical-interval scorer
  (get_most_critical_time_intervals), rolling-window feeder-max-sum.
• auto + residual_load — critical intervals derived from the residual
  load (overlying-grid dispatch distributed, no power flow), each critical
  step centered in a day-start-aligned interval.

The auto modes typically yield two disconnected intervals (a load case
and a feed-in case). The OPF runs one optimization per contiguous interval
and merges the results, so SoC state does not leak across the gap.

What eGo needs (this comment's scope)

eGo must surface this configuration and route it to the correct grid:

• a default selection block applied to every grid;
• optional per-grid overrides keyed by MV grid id (so most grids use an
  auto method while specific grids can be pinned to a manual series).

The block is injected into each grid's runner config as the top-level
timeseries_selection key, the same mechanism already used for
overlying_grid. Absent config → full-year behaviour (backward compatible).

Still open (spatial reduction)

Spatial complexity reduction of the MVLV grids is not addressed here and
remains part of this issue.

Related

• eDisGo: [FEATURE] Add configurable timestep selection for individual eDisGo grids in eGo eDisGo#663
• eGo PR: (temporal part only)