Study on DC Breaker Fault Current and Its Limiting Method of Multiterminal Flexible DC Distribution System

The multiterminal flexible DC (MTDC) distribution system has become a hot research topic for its advantages such as new energy load accessibility and high reliability of power supply. However, the fault current during short-circuit faults will be more complicated and serious because of the multiple operating modes and specific converter structure in MTDC distribution system. The high fault current will affect the safety of equipment and system operation. As a result, it is necessary to study the fault current generation mechanism and current limiting method of the DC distribution system. In this paper, the generation mechanism, transient characteristics, and the influencing factors of the fault current in the DC breaker during the short-circuit faults are analyzed by theoretical analysis and simulations separately based on a +/- 10 kV three-terminal flexible DC distribution system. The current limiting devices are analyzed, and its configuration position and parameter calculation method are proposed. On this basis, the parameters of the current limiting reactor and its effects on each position are analyzed by electromagnetic transient simulations. The current limiting scheme is proposed and its reliability is verified. The study results can provide some reference for overcurrent analysis and current limiting measures of the multiterminal DC distribution system.