Analytical design considerations for MVDC solid-state circuit breakers Sondre J.K. Berg, Andreas Giannakis and Dimosthenis Peftitsis NORWEGIAN UNIVERSITY OF SCIENCE AND TECHNOLOGY, NTNU Department of Electric Power Engineering O.S. Bragstads plass 2E, Trondheim, Norway Email: sondre.j.k.berg@ntnu.no, andreas.giannakis@ntnu.no, dimosthenis.peftitsis@ntnu.no Keywords ≪protection device≫, ≪faults≫, ≪power semiconductor device≫, ≪fault handling strategy≫ Abstract This paper investigates the design principles of a solid-state circuit breaker (SS CB) for medium voltage direct current (MVDC) grids. The emphasis is given on the design of the required active and passive components that employed in a SS DCCB based on analytic methodology. Several cases related to the characteristics of the current technology of power semiconductor devices have been investigated and evaluated in terms of maximum short-circuit current, maximum switch current, maximum switch voltage, clearance time, as well as, passive elements requirements. It has been shown that potential improvements of the current power semiconductor technology could lead to improved performance of SS DCCB with lower requirements for passive elements. In particular, the most significant characteristic that improves the overall SS breaker performance was found to be a potential reduce of the falling time (or increase of power dissipation) of the switches used in SS breaker. Introduction Medium Voltage (MV) direct current (DC) systems are usually used for distribution or collector systems whose requirements has previously hindered the implementation of DC grids [1]. The reasons to these hindrances are particularly related to insufficient ratings and performance of power semiconductor de- vices, as well as to their price. With the recent and future technological advances, however, this trend seems to reach a turning point. Recently, the integration of MVDC in a vast variety of applications such as micro grids [1], collector grids for offshore wind generation and solar power [2], marine vessels [3] and other industrial applications such as a mine site islanded micro grid [4] have been considered. For such applications, MVDC may enable advantages, such as easy interconnection of decentralized generation and storage devices, reduced number of electric power conversion stages, no need for synchronization, reduced ratings of cables and switch gears, no reactive voltage drop, easier implementation of high speed and variable frequency operation, no need for bulky low frequency AC transformers and fully controlled power flow [3]. One of the main challenges of implementing MVDC systems that still impedes their development is the design of proper and high-performance fault handling technology. Due to the inherently low cable inductances in the short distances related to MVDC applications, fault currents quickly rise to unaccept- able values and impose the need of very fast fault breaking mechanisms. Traditional mechanical AC circuit breakers (AC CB) are too slow to perform this action that depends on the AC systems natural zero crossing, which is not present in DC counterparts. Several different DCCB topologies have been proposed in literature. They can be categorized into, me- chanical DCCB with active/passive resonance circuit, solid-state CBs and hybrid CBs [5, 6]. The first