A New Differential Protection for Transmission Lines Connecting Renewable Energy Sources to MMC-HVDC Converter Stations Based on Dynamic Time Warping Algorithm

There are electronic controlled power sources on both sides of the transmission line, which connects the renewable energy sources (RES) station and the modular multilevel converter high-voltage DC (MMC-HVDC) converter station. The control strategy affects the fault characteristics of the short-circuit current, making it amplitude-limited and phase-angle-controlled. The sensitivity performance of the original line differential protection decreases, and the adaptability of the protection needs to be further studied. Aiming at this problem, the fault characteristics of short-circuit current fed from the RES station and the MMC-HVDC converter station are both analyzed. And a differential protection method based on dynamic time warping is proposed. The distance matrix is constructed by calculating the Euclidean distance of the currents. Then calculate the shortest cumulative distance which is used to characterize the waveform similarity of the current and construct protection criteria based on waveform similarity. Through simulation and calculation, the effectiveness of the proposed protection method is verified, showing that the protection algorithm can sensitively identify internal and external faults.