fix: clamp s/p_nom_max in brownfield to prevent floating-point infeasibility#2115
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lkstrp merged 4 commits intoPyPSA:masterfrom Mar 25, 2026
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…ibility When brownfield carries forward s_nom_opt from a previous horizon as s_nom_min, solver floating-point tolerance can make s_nom_min exceed s_nom_max by a tiny amount (e.g., 0.00013 MW on a 33,585 MW line). This creates an infeasible constraint that crashes the solver. Extends the fix from PRs PyPSA#840 and PyPSA#952 (which handle global transmission constraints) to also cover per-line s_nom_max and DC link p_nom_max.
fneum
approved these changes
Mar 18, 2026
When barrier solutions without crossover produce slightly imprecise p_nom_opt values, the already-retrofitted H2 pipeline capacity can marginally exceed the original pipe capacity. This makes remaining_capacity negative, setting p_nom_max < p_nom_min = 0, which causes infeasibility at the next planning horizon. Observed on 115-cluster myopic runs with BarConvTol=1e-4: H2 pipeline retrofitted ES2 7 -> FR2 1: p_nom_max = -0.000649 MW H2 pipeline retrofitted GB1 3 -> GB1 7: p_nom_max = -0.000169 MW Apply the same clip(lower=0) pattern used for AC lines and DC links.
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Changes proposed in this Pull Request
In myopic optimisation,
add_brownfield()setss_nom_minandp_nom_minfor AC lines and DC links to the previoushorizon's
s_nom_opt/p_nom_opt. Due to solver floating-point tolerance, the optimised value can slightly exceeds_nom_max, creating a per-componentmin > maxinfeasibility.I ran into this on a 50-cluster, 6-horizon sector-coupled run where an AC line (DE2 → NL2) ended up with
s_nom_minexceeding
s_nom_maxby 0.00013 MW on a 33,585 MW line — enough to make the solver declare infeasibility.PRs #840 and #952 fixed the related aggregate case (total
s_nom_minhitting the global transmission expansionlimit). This PR adds the complementary per-component fix: clamping
s_nom_max/p_nom_maxto be at leasts_nom_min/p_nom_minright after the brownfield assignment.The pattern is consistent with the existing
update_p_nom_max()in_helpers.pyand the generator clamp inadd_existing_baseyear.py, both of which already handle the same class of issue for other component types.Checklist
pixi.toml(usingpixi add <dependency-name>).config/config.default.yaml.doc/configtables/*.csv.doc/release_notes.rstis added.