Effect of network configuration and load profile on efficiency of LVDC distribution network

The low voltage direct current (LVDC) distribution network is a promising solution to be considered in future smart grids. For facilitating the design of cost effective LVDC distribution networks, the total losses of the network with different configurations are evaluated and compared. The possibility to connect the customer loads asymmetrically, when the bipolar DC network is used and the fact that the customer has single-phase loads, which lead to phase-asymmetrical loading of a three-phase converter, are taken into account. According to the results presented in this paper, the highest efficiency is achieved when the ungrounded LVDC distribution network is supplied by two series connected line converters. When the length of the bipolar network is 600 m at maximum, three-phase load converters should be connected to 750 V DC with a 400V/400V isolation transformer. Instead, while the length of the DC network is over 600 m, the maximum efficiency is achieved when the unipolar network configuration is used by connecting the load converters to 1500 V DC with a 800V/400V isolation transformer.