Developing Black Start Strategies in Multi-Microgrids Exploiting Smart Transformers

Aiming to increase the resilience of the distribution systems following a blackout event, this paper presents an approach for enabling a black start procedure within a multi-microgrid in which the smart transformer has a central role. Under an inverter-dominated grid, a control strategy is developed for a black start procedure, coordinating the smart transformer inverters and all distributed units located in the medium and low voltage grids. With a three-stage configuration (AC/DC/AC) the smart transformer provides the possibility for connection a storage device in the DC link. Thus, smart transformer with energy storage is envisioned as the main unit enabling black start capability within a multi-microgrid. Dynamic simulations were performed, to demonstrate the feasibility of the proposed approach when using smart transformers for service restoration in multi-microgrids.