DISTANCE PROTECTION ON MMC-HVDC TRANSMISSION LINES WITH SINGLE-ENDED MEASUREMENTS

MMC-HVDC grid is a promising way to incorporate a large number of renewable generations. Protection of transmission lines is essential to guarantee the safe operation of the grid during line faults. However, the protection of MMC-HVDC lines requires very high operational speed (typically within 3ms), without losing dependability and security of the protection. This paper proposes a novel distance protection for MMC-HVDC transmission lines. The method only utilizes single-ended measurements, and no communication channels between line terminals are required. First, the model of the transmission line with fault is derived, with the line resistance and inductance “seen” by the relay as the unknown variables. Afterwards, the state estimation procedure is applied to accurately estimate the resistance/inductance. Finally, the trip signal and the faulted pole are determined by comparing the calculated resistance/inductance with the relay characteristics. Numerical experiments in PSCAD/EMTDC show that the proposed method can dependably operate during internal faults within 3ms after the occurrence of the fault, and securely ignore external faults. The calculation burden of the algorithm is small to enable real-time operation of the proposed distance protection method.