Comparison of Losses and Costs between AC and MVDC Connections for New DC Resources

The proliferation of direct current (DC) resources (loads, generation, and storage) presents opportunities for new medium voltage DC (MVDC) networks that should be compared against standard alternating current (AC) connections. In this paper, we provide a point-to-point transmission analysis of AC vs. MVDC, and determine the distance at which MVDC prevails over AC in terms of total losses, and, most importantly, total costs. We further provide insights on the connection of new DC resources to existing networks with different distances, accounting for network-related costs (e.g., upgrades required or avoided), and highlighting the impact that an MVDC connection of a flexible DC resource could have on the main AC/DC converter rating, by lowering the MVDC network peak load. Our work is motivated by an application of a train MVDC network, with the possibility of connecting a solar power plant potentially equipped with a battery. We thus provide numerical illustrations centered around this application; nevertheless, our analysis remains general, and applicable to the connection of any DC resource.