Design aspects of a medium-voltage direct current (MVDC) grid for a university campus

Today's power systems use alternating current (ac) for transmission and distribution of electrical energy, although the first grids were based on direct current (dc). Due to the absence of appropriate equipment to change voltage levels dc technology did not become widely accepted and was finally ruled out by the more efficient ac infrastructure. However, as a result of considerable technical progress, high-voltage direct current (HVDC) transmission has found its way back into power systems. At lower voltage and power levels medium-voltage dc (MVDC) distribution has been proposed for offshore wind farms and industrial applications. This paper describes the design of an MVDC grid for the interconnection of high-power test benches at a university campus. Voltage control within the dc grid as well as the behavior in different fault scenarios is analyzed using numerical simulations. To assess the environmental impact of the grid the magnetic flux density emitted by the dc cable lines is calculated.