Current limiting technique based protection strategy for an industrial DC distribution system

High fault current level causes protection difficulties in industrial DC power distribution systems because of limited interruption capability of available solid-state switches. This paper presents a protection strategy based on the integration of pulse-by-pulse current limiting technique into solid-state protection switches. The gate signal of solid-state switches is controlled using pulse-by-pulse current limiting technique to restrict the fault current level within a preset range, hence relieves the fault current withstanding and interruption requirements of solid state switches. Distribution circuit architecture is proposed to use with the protection switches, so that the loads in non-faulted parts of the system can ride through the fault current limiting process unperturbed. Commercially available solid-state switches become usable for high power density applications with the proposed protection strategy. Simulations demonstrate the effectiveness of the strategy for various fault locations to show the strategy can be used in entire DC distribution systems. Interactions between the protection switches and upstream converters with current limiting control are discussed. Also the inductance required to slow down the fault current rising speed is discussed