docs(pypsa): a start-up or shut-down cost may change from snapshot to snapshot, as in pypsa master

[FabianHofmann]

Prompt: "2" (run steps 1 to 3 of the PyPSA-parity plan as one workflow)

Note

The following content was generated by AI.

The six start-up and shut-down cost parameters span snapshot, as on PyPSA master (PyPSA/PyPSA#1909). The relaxed file tightens only where both costs are equal in every snapshot, now stated in the language. Rung 62 records it.

Stacks on #787 and #786. Part of #783 (step 3b, "Start-up and shut-down cost per snapshot").

Method, gate output, alternatives

What changed

• examples/pypsa.yaml: {Generator,Link,Process}_{start_up,shut_down}_cost go from [scenario, c] to [scenario, snapshot, c]. PyPSA reads the cost at the snapshot of the start or stop (optimize.py:424-432 on 02bdcbba). The objective terms already summed over snapshot, so they do not change.
• The objective still adds these costs without a snapshot or period weight. PyPSA does the same; the spec copies it, as it does since rung 48. This is the not-filed bug candidate in PyPSA parity with master: open points, new master changes and the PyPSA bugs found #783.
• examples/pypsa_linearized_uc.yaml: the Generator pair spans [snapshot, generator]. The data-prep bool Generator_partly_tightened is gone. The four tightening rows now carry count(Generator_start_up_cost != Generator_shut_down_cost, over=snapshot) == 0 in their where. That is PyPSA's (start_up_cost == shut_down_cost).all("snapshot") (constraints.py:636-641). The old description said two parameters cannot be compared in a where; the language now allows expression OP expression, so no data prep and no src/ change is needed. A where names no entry, so the condition is written in each of the four rows.
• tests/fixtures/pypsa_standard_shape.yaml: the standard frame of the six parameters gains snapshot, as rungs 45 and 60 did for their parameters.
• Rung 62 (rung_62_startup_cost_per_snapshot.py) and its record. Regenerated: fragments, gallery. Golden and schema regenerated with no diff.

Rung 62

A committable peaker that the load needs in snapshots 3 and 4. A start costs [400, 100, 900, 900, 900], a stop [300, 300, 300, 300, 0]; snapshot weights [2.0, 1.5, 1.0, 2.0, 1.0]. PyPSA master solves to 6850.0 (starts at snapshot 2, stops at snapshot 5). Probes on the same network:

change	objective
start-up cost at its mean 640	7090.0
shut-down cost at its mean 240	7050.0
start-up cost times the snapshot weight	6900.0

Failing first: on pypsa==1.3.0 the rung's build() raises AttributeError: start_up_cost at n.generators_t.start_up_cost, since the attribute is static only there.

Gates

• uv run --script examples/references/pypsa/reference.py then --check: "every rung solves to its record". Only rung_62 is new in references.json.
• pixi run lint: pass. pixi run ci: pass, 2609 tests, docs-build, compile-tex.
• The first pixi run ci failed test_a_standard_parameter_changes_frame_only_by_a_leading_scenario on the six new frames, before the fixture change.

Not done

• No new rung for the relaxed file. No rung has a unit whose start and stop costs are equal in some snapshots and not in others, so the new where has no solved reference. It needs a rung number of its own.
• PyPSA checks the equality over all of n.snapshots, the spec over its snapshot dimension. They differ only when n.optimize(snapshots=...) takes a subset.
• The optimize.py:414-429 cite in rung 48 and in scenario_opex is not re-anchored; that is the re-anchor item of PyPSA parity with master: open points, new master changes and the PyPSA bugs found #783.
• Link and Process tightening rows: out of the relaxed file's scope, as before (PyPSA parity with master: open points, new master changes and the PyPSA bugs found #783 item "pypsa_linearized_uc.yaml as a patch file").
• Nothing in PyPSA parity with master: open points, new master changes and the PyPSA bugs found #783 is ticked.

[read-the-docs-community]

Documentation build overview

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• changelog/index.html
• examples/pypsa_linearized_uc/index.html
• examples/pypsa/generator/index.html
• examples/pypsa/generator_commitment/index.html
• examples/pypsa/generator_maintenance/index.html
• examples/pypsa/line/index.html
• examples/pypsa/link/index.html
• examples/pypsa/link_commitment/index.html
• examples/pypsa/link_maintenance/index.html
• examples/pypsa/process/index.html
• and 4 more...