Planning and Design of Medium Voltage DC Grids– An Overview

Abstract

Up to now, neither technical guidelines nor experiences for public medium voltage direct current (MVDC) grids exist leading to different questions concerning the design of these grids. Therefore, this paper analyzes relevant technical options for realizing MVDC grids. Technical requirements and degrees of freedom, including grid structure, operating voltage, line configuration, possible apparatuses, grid operation, power flow controllability and protection equipment are elaborated. An optimization method which allows to consider these different options and which can be applied for developing MVDC grids is presented. For an exemplary supply task, two grids are designed. Resulting grid structures indicate that the choice of line configuration and operating voltage has a significant impact on power transmissibility and the necessary amount of power lines. By choosing an asymmetric monopole and a comparatively low operating voltage for the given supply task, a more meshed grid structure results, also to avoid voltage problems. Based on further sensitivity analyses the impact of different technical options on MVDC grid design can be investigated and knowledge concerning MVDC grids can be gained, which is essentially required for further research as well as for the development of standardizations and MVDC grid components.