Restoring microgrids to operation following blackouts
Following blackouts, special procedures known as black starts must be implemented to quickly and safely restore power. This includes the restart of Low voltage (LV) networks connected to the main grid that did not manage to switch to an islanded mode of operation during the blackout. Experts with the Power Systems Unit of INESC Porto have developed a black start mechanism designed especially for microgrids, LV networks containing several small sources usually based on renewables. The research was supported by the Energy, Environment and Sustainable Development Programme in the context of the MICROGRIDS project. The step-by-step process relies on the main components of the microGrid control and communication systems, namely the MicroGrid central controller (MGCC), Microsource controller (MC) and Load controller (LC). The process of bootstrapping the network entails connecting sources and loads while regulating voltage and frequency. In order to deal with the slow response of some of the microsources, the INESC team recommended the inclusion of energy storage facilities to shorten the time required to restore the network. The performance of the black start mechanism as well as a procedure defined to reconnect to Medium voltage (MV) networks was evaluated during the MICROGRIDS project. Computer simulations using a platform based in MatLab/Simulink, combined with a specialised software tool addressing fast transients were essential during this phase of the project.