A Fault Tracing Method of Successive Commutation Failure for Multi-Infeed DC System

In order to effectively improve the transmission efficiency of energy between regions, line-commutated converter-based high-voltage direct current (LCC-HVDC) has been widely utilized for its advantages in large capacity long-distance transmission. With multiple DC systems connected to the same AC power grid, a complex multi-infeed DC (MIDC) system is formed. Compared with the traditional single infeed DC system, MIDC system has the mutual coupling between DC systems. Therefore, commutation failure (CF) at one DC system may cause successive CF of adjacent DC systems, leading to a more serious regional power loss.In order to evaluate the influence of the fault DC system by other DC systems, a fault tracing method of successive CF for MIDC system is proposed in this paper. In this method, the influence of contact impedance on the probability of successive CF can be quantitatively calculated, and the dominant DC that causes the successive CF can be obtained intuitively by comparing weight factors. Validity of this proposed method is demonstrated by building a test system in PSCAD/EMTDC.