Adaptive Reclosing Method for Flexible HVDC Transmission Lines

With the development of HVDC transmission, half-bridge modular multilevel converter with hybrid HVDC circuit breakers becomes one of the mainstream configuration schemes in HVDC flexible system. However, the existing reclosing strategies have some defects, such as lack of selectivity and adoption of long time delay, due to the inability to determine the arc extinction time. In order to solve the problems above, the traveling wave characteristics of both terminals of the fault line after the HVDC circuit breaker trips are analyzed in this paper. Based on the cosine similarity of the two terminals to describe the voltage traveling wave characteristics before and after the fault disappears, the paper proposed a method to detect the arc extinction time, and distinguish instantaneous fault and permanent fault. Thus an adaptive reclosing can be realized. Finally, the transient electromagnetic model of the bipolar HVDC flexible system is built in PSCAD/EMTDC. By the simulation of the fault with different locations and parameters, the effectiveness and feasibility of the adaptive reclosing method are verified.