Impact of Market Reforms on Deterministic Frequency Deviations in the European Power Grid

TL;DR

This study examines how the 2025 European market reform, shifting to quarter-hourly trading, affects deterministic frequency deviations in the power grid, showing reductions in typical deviations but mixed results for extreme events.

Contribution

It provides a comprehensive analysis of the impact of market design changes on frequency stability using advanced data analysis techniques.

Findings

Reduction in hourly frequency deviations post-reform

Suppression of spectral components at hourly and half-hourly scales

Mixed effects on large frequency excursions depending on metrics

Abstract

Deterministic frequency deviations (DFDs) are systematic and predictable excursions of grid frequency that arise from synchronized generation ramps induced by electricity market scheduling. In this paper, we analyze the impact of the European day-ahead market reform of 1 October 2025, which replaced hourly trading blocks with quarter-hourly blocks, on DFDs in the Central European synchronous area. Using publicly available frequency measurements, we compare periods before and after the reform based on daily frequency profiles, indicators characterizing frequency deviations, principal component analysis, Fourier-based functional data analysis, and power spectral density analysis. We show that the reform substantially reduces characteristic hourly frequency deviations and suppresses dominant spectral components at hourly and half-hourly time scales, while quarter-hourly structures gain relative importance. While the likelihood of large frequency deviations decreases overall, reductions for extreme events are less clear and depend on the metric used. Our results demonstrate that market design reforms can effectively mitigate systematic frequency deviations, but also highlight that complementary technical and regulatory measures are required to further reduce large frequency excursions in low-inertia power systems.