A Pilot Protection Scheme for MMC-HVDC Transmission Lines Based on Filtered Differential Current

Abstract

The DC side fault is a major threat to the secure operation of Modular Multilevel Converter based High Voltage Direct Current (MMC-HVDC) transmission system. Combining theoretical analysis and simulation experiment, this paper studies the fault characteristics of DC side transient voltages and currents in the MMC-HVDC double-ended transmission system in detail, and introduces the new conception of filtered differential current (FDC) to construct an effective protection criterion. Based on the transient information in FDC values, this paper proposes a novel pilot protection scheme which is able to reliably identify and classify DC side faults. The simulations implemented on real time digital simulator (RTDS) platform indicate that the proposed scheme can operate accurately and reliably under a variety of fault conditions.