Performance Exploration of Black-Start Block Loads Pick-Up Sequences for Grid-Forming Dominated Systems

After a total or partial system outage, black-start serves as a critical measure to restore the system to the normal operation. In the later stage of restoration, various types of loads will be energized, the pick-up sequences of which may affect the success probability of the black-start. In this context, a block loading strategy for the inverter-based low-inertia systems is explored, with special consideration given to the inertial support by induction motors. Through detailed analysis, it is shown that initiating induction motors at an early stage leads to improved frequency stability during subsequent loads pick-up. The advantages of prioritizing motor energization are validated from multiple perspectives, including motor starting success rate, the timing of block load pick-up, and the overall system stability. Both simulation results and hardware-in-the-loop validations confirm these observations.