Analysis on characteristic of DC short‐circuit fault in multi‐terminal AC/DC hybrid distribution network

Abstract

The AC/DC hybrid distribution network takes advantage of both AC and DC technologies. It is one of the most important forms of future distribution systems. However, currently few work has been done on the topology determination of this network, and its fault behaviour of DC short-circuit fault has not been clearly investigated yet. First, the tree, radial, and ring topologies of a three-terminal AC/DC distribution network are compared. Also the characteristics of fault currents in DC circuit breakers during a DC short-circuit fault are analysed in detail. Then the equivalent circuit models during the fault are established and accurate mathematical expressions of transient fault currents are deduced. Based on this, the influence of network topologies on the characteristics of fault currents is investigated thoroughly. Moreover, a method to determine the peak values and peak times of fault currents is presented which can simplify the selection of circuit components. The simulation results show that the fault currents of the radial topology have the lowest peak values and longest peak times, and the proposed method meets the requirements of both simplicity and accuracy. Finally, the influence of the key parameters on the proposed method is investigated comprehensively.