Robust Transmission Expansion Planning of Hybrid Ultra-HVAC and Ultra-HVDC Grid

With increasingly prominent "strong DC and weak AC" due to the increasing high voltage DC ( HVDC) links and renewable generation units (RGUs), the transmission expansion planning (TEP) problem has been facing a major challenge to cope with the coordination between HVDC and ultra-high voltage AC (UHVAC) /HVAC. To handle this issue, this paper proposes a multistage TEP model of hybrid ultra-HVAC and UHVAC grid. The multi-stage robust TEP model takes into account the worst case including HVDC bi-pole block and RGUs uncertainty. Based on this model, the RGUs uncertainty set and the worst-case constraints are reformulated using Wasserstein metric. Aiming to ensure tractability of the proposed model, the Benders decomposition is employed. The effectiveness of the proposed TEP model is confirmed by numerical testing on a case based on the Sichuan system.