Load Transfer Optimization With Graph Characterizations on Multiple Time-Scales for Multi-Voltage Distribution Networks Against Overload Cascades

In electrified transportation, a growing number of electric vehicles (EVs) are employing super fast charging technology, which provides very high charging power over a short period. This rapid load growth from super fast charging stations makes real-time load balancing particularly challenging for multi-voltage distribution networks (DNs), i.e., high-voltage DNs (HVDNs) and medium-voltage DNs (MVDNs). To address the overload problem, we formulate the load transfer optimization (LTO) model in which we simplify power flow equations and radiality constraints using graph characterizations in HVDNs and MVDNs. Moreover, a hierarchical LTO optimization framework on multiple time-scales is developed for multi-voltage DNs. This hierarchical LTO approach reduces computational time and effort with the minimum switching cost and system loss reductions, while facilitating the load transfer coordination between distribution system operators (DSOs) on different voltage levels. Finally, this proposed hierarchical LTO approach in case study outperforms existing conventional distribution network reconfiguration (DNR) approaches in terms of computational time and effort, and also achieves the minimum switching cost than existing DNR approaches for the realistic multi-voltage DNs with high penetration of super fast charging stations.