Heterogeneities in electricity grids strongly enhance non-Gaussian features of frequency fluctuations under stochastic power input

TL;DR

This study shows that heterogeneities in electricity grids significantly increase non-Gaussian frequency fluctuations caused by stochastic wind power input, especially at weakly connected nodes, impacting grid stability.

Contribution

It demonstrates how grid heterogeneities amplify non-Gaussian frequency fluctuations due to wind power injection, highlighting the importance of considering grid structure in stability analysis.

Findings

Non-Gaussian features are more pronounced at weakly connected nodes.

Heterogeneities in grid properties are essential for non-Gaussian fluctuation emergence.

Frequency fluctuation standard deviation scales linearly with wind power injection.

Abstract

Stochastic feed-in of fluctuating renewable energies is steadily increasing in modern electricity grids and this becomes an important risk factor for maintaining power grid stability. Here we study the impact of wind power feed-in on the short-term frequency fluctuations in power grids based on an IEEE test grid structure, the swing equation for the dynamics of voltage phase angles, and a series of measured wind speed data. External control measures are accounted for by adjusting the grid state to the average power feed-in on a time scale of one minute. The wind power is injected at a single node by replacing one of the conventional generator nodes in the test grid by a wind farm. We determine histograms of local frequencies for a large number of one-minute wind speed sequences taken from the measured data and for different injection nodes. These histograms exhibit a common type of shape, which can be described by a Gaussian distribution for small frequencies and a nearly exponentially decaying tail part. Non-Gaussian features become particularly pronounced for wind power injection at locations, which are weakly connected to the main grid structure. This effect is only present when taking into account the heterogeneities in transmission line and node properties of the grid, while it disappears upon homogenizing of these features. The standard deviation of the frequency fluctuations increases linearly with the average injected wind power.