Feasibility of fast restoration of power systems by micro-grids

This study shows that with fast and flexible power electronic converter interfaces, micro-grids can quickly re-energise blacked-out transmission lines without overvoltage. After the transmission lines are re-energised, micro-grids can speed up (i) the reconnections of generators and loads; (ii) the re-synchronisation of severed transmission line sections back to the original grid. Micro-grids have active power to energise auxiliary motors of large thermal plants in black start. Faster restoration is limited by steam-turbine plants because they cannot be speeded up beyond thermodynamic constraints.