A Model-Based DC Fault Location Scheme for Multi-Terminal MMC-HVDC Systems Using a Simplified Transmission Line Representation

Accurately determining the location of DC pole-to-pole short-circuit faults in modular multilevel converter (MMC) based multi-terminal HVDC (MTDC) systems is key issue in ensuring fast power recovery. This paper proposes an effective DC fault location scheme for the MMC-MTDC that uses an estimated R-L representation of the transmission lines. By using the measured voltage and current data from both ends of the faulted DC line, the proposed fault location formulas can calculate the location of the fault with high accuracy. The simplified R-L representation greatly reduces the computation burden of the fault detection algorithm. Electromagnetic transient (EMT) simulations of a four-terminal MMC-MTDC system on PSCAD/EMTDC are used to confirm the effectiveness of the proposed approach. The results verify that the proposed scheme is robust and almost not affected by the transmitted power or the fault resistance.