Abstract

Abstract

Distributed energy resources (DERs) are expected to provide increasingly large amounts of energy and ancillary services to the grid. However, modelling distribution-connected assets in transmission studies is a challenge due to their sheer number, and due to the low visibility in distribution grids. This work uses dynamic equivalents of active distribution networks (ADNs) to study the impact of those ADNs on the stability of a representative model of the Scottish transmission grid at the horizon 2022 and early 2030s. The dynamic equivalents are built based on dynamic simulation of a series of generic distribution systems representing small and large, rural, semiurban and urban networks, and based on UK connection requirements for DERs.

Scotland has a very high onshore and offshore wind potential and is thus frequently exporting power to the rest of GB. Based on utility expertise, transient stability related transfer boundaries are known to be close to thermal limits. This study thus focuses on the impact of ADNs on transient stability. Sensitivity studies show that the main impact comes from disconnection of legacy DERs due to limited fault ride-through capacity. The impact of DER dynamic voltage support and motor post-fault recovery is found to be less impactful due to the many (transmission-connection) sources of reactive power, especially wind farm inverters. Similarly, the impact of distribution network topology (rural vs. urban) is also found to be relatively limited. This highlights the need to better estimate ride-through capabilities of legacy DERs, and to enforce ride-through standards on new installations.

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Supplementary data

All data and algorithms are available on https://github.com/FredericSabot/CIGREpaper2024. The git will be made public after the publication of Samuel Gordon’s PhD thesis.