Power System Restoration

Power system restoration after a major outage is a technically and organizationally challenging process. Despite all precautions taken to protect the system, restoration must still be possible. Therefore, grid operators have plans and capacities in place for this eventuality.

At the same time, the electrical energy system is undergoing a transformation: A system dominated by directly coupled electrical machines is becoming a more diverse system in which power electronics-connected generators and consumers are increasingly determining system behavior.

In this context, we examine power system restoration processes, particularly with regard to operational procedures and processes such as the start-up of generation units, the energizing of grid sections, the operation of grid islands including sudden load and generation changes, faults and short circuits, and the synchronization process of two grid islands.

Key aspects of our investigations are

• converter control,
• grid-forming control,
• inertia,
• black start capability, and
• stability of the energy system and subgrids (frequency stability, transient stability, voltage stability, small signal stability) and aspects of grid protection.

We also develop control concepts for converter-coupled systems that provide grid-stabilizing functions, paying particular attention to their specific capabilities and limitations with regard to exceptional situations and emergency operation.