Optimal operational planning of hybrid power plants in railway MVDC networks and comparison with standard AC connections

The proliferation of Direct Current (DC) resources presents significant challenges for their connection to the grid, but also appealing opportunities for new connection options, such as Medium Voltage DC (MVDC) networks. Railway MVDC (R-MVDC) networks are among potential candidates for new DC resource connections. As such, DC resources, e.g., solar plus battery hybrid power plants (HPPs), that are geographically located near an R-MVDC network may either connect to the latter or to the closest Alternating Current (AC) network. This paper presents a mixed integer linear programming formulation for the operational-planning problem of an HPP connected to an R-MVDC network, which takes into account the R-MVDC network constraints. Furthermore, it provides a comprehensive techno-economic analysis that compares the two connection options (AC and R-MVDC), employing the outcomes of the optimized HPP operation and a detailed breakdown of the various cost components (converters, lines, losses). The analysis is applied to the French R-MVDC network providing a first assessment for the potential of new HPP connections to the R-MVDC network, considering several HPP sizes and voltage levels.