BUILDING THE PUZZLE OF URBAN POWER GRID RESILIENCE

With an increasing occurrence of extreme weather events and a reinforced concern on climate change, the traditional energetic model is shedding light to a new one, where renewable energy sources (RES), energy storage systems (ESS) and electrical vehicles (EV) will play a central role in defining the future smart grid. The disruption of the aforementioned technologies at a distribution level is rocketing and therefore, the path to a decentralized power system with distributed energy resources (DER) is being set.

As stated by the European Commission, all challenges related to a new energetic model must be addressed in order to make the decarbonisation objectives possible through smart, sustainable and inclusive growth. By empowering consumers and placing them at a central role, the creation of microgrids (MGs), introduced in a previous IREC blog post will take place. This transforms the distribution grid in a cluster of microgrids, in which multiple MGs are interconnected (in normal operation) and controlled with the aim of ensuring quality of service to end-users.

During an electrical blackout, resilience in the power system of a city can be measured in terms of frequency and duration of interruptions. If an outage occurs in the main grid, and there are no redundancies in the system, several loads can be left unsupplied. In most of the European cities, though, the electrical grid is highly redundant and therefore resilience is already very high. Therefore, it is interesting to go a step further and to explore future DER scenarios with the current electrical model. For this matter, the concept of MG clusterization comes into force. The on-outaged areas are able to disconnect from the main grid, creating isolated MGs which can work autonomously. Most of the times, these MGs operate independently from each other and due to the variability of energy inputs and the lack of technological adaptation, such power islands are prone to instabilities. Sudden unbalances between generation and consumption leads to the idea of connecting several MGs in order to increase the system stability.

The interconnection of MGs has the capability of either supplying energy to non-local MGs in case of energy excess or to curtail the necessary loading if generation capacity is limiting. Therefore, a communication system between local controllers of each MG is essential to develop new control techniques for network reconfigurations after a blackout. Moreover, Distributed System Operators (DSOs) and MG clusters must cooperate and coordinate once the MG is connected back to the main grid in order to ensure the quality of service.

Nowadays, MG clusterization is still at an early research state. However, with the increasing concern on decarbonisation, the scenario of decentralised power systems is gaining force.

With regards to the RESCCUE Project, self-healing or automatic reconfiguration techniques on a distribution grid with DER will be studied in order to enhance resilience.