Hybrid IGBT/IGCT-based DC-hub for interconnection of VSC/LCC future DC networks

The interest in interconnecting multiple DC grids- medium-voltage direct current/high-voltage direct current (MVDC/HVDC)- across the globe has grown significantly in recent years. This interest is primarily driven by the benefits of increased reliability and cost efficiency in power transmission systems, particularly with the growing utilisation of renewable energy resources. However, some HVDC networks are based on line commutated converters (LCC), while other MVDC/HVDC rely on voltage source converters (VSC). In this context, this paper introduces a new DC-Hub that facilitates the interconnection between multiple VSC- and LCC-based DC networks using hybrid IGBT/IGCT device technology. The proposed converter enables power reversal without interruption, promotes multi-vendor interoperability, and provides galvanic isolation. An important aspect of the design is its modularity, allowing each port to have an independent design for interfacing with the HVDC/MVDC grid without affecting the other ports. This modularity enables further port extension or elimination without requiring modifications to the remaining ports. The paper also discusses AC filter design and power flow control techniques to achieve zero reactive power circulation at rated port power, thereby reducing power losses. Finally, to validate the theoretical claims of the proposed system, both a simulation model and an experimental hardware test rig have been established.