Primary Control Effort under Fluctuating Power Generation in Realistic High-Voltage Power Networks

TL;DR

This paper analyzes how fluctuations from renewable energy sources affect grid stability, showing that in large, realistic power networks, inertia does not influence transient responses to long-term disturbances, challenging traditional assumptions.

Contribution

It introduces a modified spectral decomposition method to assess stability in inhomogeneous grids under long-term disturbances, revealing inertia's limited role.

Findings

Transient excursions are independent of inertia for long-duration disturbances.

Power fluctuations with long correlation times do not necessitate additional inertia.

The method is validated on IEEE 118-Bus and European grid models.

Abstract

Many recent works in control of electric power systems have investigated their synchronization through global performance metrics under external disturbances. The approach is motivated by fundamental changes in the operation of power grids, in particular by the substitution of conventional power plants with new renewable sources of electrical energy. This substitution will simultaneously increase fluctuations in power generation and reduce the available mechanical inertia. It is crucial to understand how strongly these two evolutions will impact grid stability. With very few, mostly numerical exceptions, earlier works on performance metrics had to rely on unrealistic assumptions of grid homogeneity. Here we show that a modified spectral decomposition can tackle that issue in inhomogeneous power grids in cases where disturbances occur on time scales that are long compared to the intrinsic time scales of the grid. We find in particular that the magnitude of the transient excursion generated by disturbances with long characteristic times does not depend on inertia. For continental-size, high-voltage power grids, this corresponds to power fluctuations that are correlated on time scales of few seconds or more. We conclude that power fluctuations arising from new renewables will not require per se the deployment of additional rotational inertia. We numerically illustrate our results on the IEEE 118-Bus test case and a model of the synchronous grid of continental Europe.