# Active Distribution Grids offering Ancillary Services in Islanded and Grid-connected Mode

## TL;DR

This paper explores how active distribution grids with distributed energy resources can provide frequency control services and operate reliably in islanded mode, ensuring grid stability and resilience.

## Contribution

It introduces a centralized optimal power flow model that enables ADGs to offer ancillary services while maintaining islanded operation capabilities.

## Key findings

- The scheme can respond to various frequency control products.
- It guarantees energy capacity for critical loads in islanded mode.
- The approach is feasible on low-voltage distribution networks.

## Abstract

Future active distribution grids (ADGs) will incorporate a plethora of Distributed Generators (DGs) and other Distributed Energy Resources (DERs), allowing them to provide ancillary services in grid-connected mode and, if necessary, operate in an islanded mode to increase reliability and resilience. In this paper, we investigate the ability of an ADG to provide frequency control (FC) in grid-connected mode and ensure reliable islanded operation for a pre-specified time period. First, we formulate the operation of the grid participating in European-type FC markets as a centralized multi-period optimal power flow problem with a rolling horizon of 24 hours. Then, we include constraints to the grid-connected operational problem to guarantee the ability to switch to islanded operation at every time instant. Finally, we explore the technical and economic feasibility of offering these services on a balanced low-voltage distribution network. The results show that the proposed scheme is able to offer and respond to different FC products, while ensuring that there is adequate energy capacity at every time step to satisfy critical load in the islanded mode.