Possibilities and requirements on operation of future MVDC networks

After high voltage direct current (HVDC) has gained momentum, the same challenges, as the shift to distributed architecture with high renewables integration, are now causing medium voltage direct current (MVDC) to arise for distribution system. Several pilot projects are emerging worldwide to shed to light the advantages of MVDC technology. These networks are typically deployed on a dedicated area with selected composition of loads and sources under limited power. They have a configuration of a so-called soft link, being connection between two medium voltage alternative current (MVAC) networks and having couple of MVDC nodes with loads and generations. This paper focuses on different MVDC configurations for a representative suburban distribution grid. The goal is to find a technically and economically viable configuration(s) and evaluate the interest of DC technology. A technical economic assessment (TEA) is performed among three networks configurations (full AC, full DC and hybrid MVAC+LVDC) considering qualitative and quantitative key performance indicators (KPI) including converter design, control and protection aspects. The outcome of the study points out the necessity for selection of right use case for MVDC. It also highlights the advantages of a full DC architecture and the challenges for further advancement in maturity of this technology.