Isolating the impact of trading on grid frequency fluctuations

TL;DR

This study analyzes European grid frequency data from 2011 and 2017 to isolate the impact of trading on frequency fluctuations, revealing that trading intervals influence fluctuation statistics and that shorter trading intervals may improve grid stability.

Contribution

It introduces a method to isolate trading impacts on grid frequency fluctuations and compares the effects of different trading intervals on frequency stability.

Findings

Trading at typical intervals modifies fluctuation statistics.

Large deviations are more likely near trading times.

Shorter trading intervals reduce large frequency fluctuations.

Abstract

To ensure reliable operation of power grids, their frequency shall stay within strict bounds. Multiple sources of disturbances cause fluctuations of the grid frequency, ranging from changing demand over volatile feed-in to energy trading. Here, we analyze frequency time series from the continental European grid in 2011 and 2017 as a case study to isolate the impact of trading. We find that trading at typical trading intervals such as full hours modifies the frequency fluctuation statistics. While particularly large frequency deviations in 2017 are not as frequent as in 2011, large deviations are more likely to occur shortly after the trading instances. A comparison between the two years indicates that trading at shorter intervals might be beneficial for frequency quality and grid stability, because particularly large fluctuations are substantially diminished. Furthermore, we observe that the statistics of the frequency fluctuations do not follow Gaussian distributions but are better described using heavy-tailed and asymmetric distributions, for example L\'evy-stable distributions. Comparing intervals without trading to those with trading instances indicates that frequency deviations near the trading times are distributed more widely and thus extreme deviations are orders of magnitude more likely. Finally, we briefly review a stochastic analysis that allows a quantitative description of power grid frequency fluctuations.