HVdc transmission can be a key technology for inter-regional transmission needed for electricity de-carbonization, by connecting remote clean energy to load centers and by taking advantage of geographic diversity in load and generation availability. Additionally, HVdc technology offers flexibility and controllability opportunities not present in traditional ac transmission. This presentation will cover some of the technical benefits HVdc transmission can offer, in addition to the bulk power transfers across regions. The presentation will cover a continental HVdc interconnection in North American systems, showing technical benefits for frequency control, congestion management, and fast rescheduling. The presentation will also discuss modeling challenges to study large continental interconnections.