A two-stage coordinated restoration scheme of hybrid AC/DC distribution grid considering cold load pickup and resilience enhancement

The ever-increasingly severe weather events have elevated the quest for resilience in distribution grids. Cold load pickup (CLPU), a common occurrence in buildings with thermostatically controlled loads (TCLs), generates a significant peak power demand when loads restart. With widespread TCLs distribution, the restoration speed and power level could be impacted by the conventional grid restoration scheme due to limited distribution generator (DG) capability and power supply paths. In this context, this paper proposes a two-stage coordinated restoration scheme based on the novel hybrid AC/DC distribution grid, encompassing the grid configuration level, information interaction level, and designed restoration flow. The typical delayed exponential model is used to characterize CLPU properties during extended outages. In the 1st stage, the contained coordinated restoration strategy decides the optimal load restoration sequence with CLPU concerned. Then, the grid loss optimization is carried out in stage 2 to generate the proper power reference for DGs and voltage source converters (VSCs) of hybrid grids. In case studies, four types of heterogeneous buildings with varied CLPU characteristics are deployed in the analyzed grid. It is verified that the proposed scheme could make effective aggregation and dispatching for multiple DGs, achieving an additional 11.3 h of total load support, a 16.5 % increase of DG utilization and an 11.7 % enhancement of the resilience index compared to the conventional restoration scheme. Furthermore, this scheme demonstrates adaptability for resilience improvement under varied temperatures and fault locations.