Coordination of Transmission and Distribution Systems in Load Restoration

The power distribution system is evolving in the form of an intelligent grid. The proliferation of distributed energy resources (DERs) makes the previously passive system active and more complicated. With the adoption of de-carbonization principles, large-scale coal and nuclear power plants are being gradually replaced by renewables and carbon-free DERs. With this rapid transformation, the power system operates with less inertia and minimal margins. In recent years, power systems have been facing apocalyptic weather events more frequently, and large-scale blackouts have become regular. After the complete or partial blackouts, the power system goes through different stages before it reaches the normal operating condition. The load restoration is the stage where the power system is fully established after the blackouts; however, due to the limiting ramping rates of centralized generation, the energization of large amounts of loads is delayed by some time. To mitigate the negative impact of ramping rates of centralized generation, DERs in distribution systems are proposed to serve the loads in both transmission and distribution systems in coordination with limited centralized generation in the transmission system. The problem is formulated as a centralized or integrated transmission and distribution (T$\&$D) coordination model. The modified IEEE 14 bus test case and IEEE 13 node test feeders are used to validate the proposed strategy; the results indicate the validity of the proposed model.