Fault Location Method for Multi-terminal Flexible DC Distribution Network Based on Control and Protection Coordination

The fault current of the flexible DC distribution network has a large impact and serious harm. By changing the control strategy of the controllable elements in the flexible DC distribution network, the fault characteristics can be changed, thereby providing support for fault protection and ranging. Therefore, this paper proposes a fault location method for multi-terminal flexible DC distribution network based on the coordination of control and protection. Firstly, a four-terminal flexible DC distribution network is taken as an example, and the fault characteristics and current limiting characteristics of the distribution network are analyzed. Secondly, the influence of the key equipment current-limiting reactor in the flexible distribution network on the fault characteristics of the DC distribution network is studied, and thereby, a two-stage control and protection coordination strategy for the DC distribution network is proposed. In the first stage of the coordination of control and protection, the current-limiting characteristics of the current-limiting reactor are used to suppress the development of the fault current and assist the fault isolation; In the second stage of the coordination of control and protection, the on-off strategy of the current-limiting reactor is controlled, a small controllable current is injected into the DC distribution network through short-term reclosing, and fault location is carried out. Finally, a four-terminal flexible DC distribution network simulation model with photovoltaic/storage is built to verify the effectiveness of the proposed method. © 2023 Science Press. All rights reserved.