Analysis and Experimental Research on a Novel Multi-Contact MVDC Natural Current Commutation Breaking Topology

The high performance of medium-voltage direct current (MVDC) power supply system is a pre-requisite for several industrial applications. To meet the higher voltage direct current (DC) breaking requirements in the fields of aviation, aerospace, and new energy, this article proposes a novel MVDC commutation breaking topology that combines a load-carrying branch and an arcing branch in parallel. In contrast to the conventional structure based on semiconductor devices, each branch in the proposed topology contains a mechanical contact, which provides a lower on-state loss and higher voltage-breaking capacity. Moreover, the theoretical analysis and experimental results verified the asynchronous operation of the current-loading and confirmed that the arcing branch can realize the natural commutation of the current for the breaking of overload current or short-circuit current. A detailed equivalent model that combines the micro-electrical contact theory and phase-change characteristics of the electrode material was then established to investigate the molten metal bridge and pseudo arc phenomenon of the contact area during the commutation process. The results indicated that although the presence of a molten metal bridge and pseudo arc increase the current commutation time and erosion of the electrode material, the commutation process can be conducted. Finally, based on the softening voltage of the electrode material under the rated conditions, in addition to the phase change during dynamic commutation, the roughness σ and elastic modulus E can be adjusted appropriately to achieve arc-less current commutation.