| Fault characteristics such as high harmonics, frequency offset, and weak feedback in wind power systems lead to a decline of the performance of conventional pilot protection for transmission line. To address this, the fault characteristics of wind farm are analyzed, and a gradient-energy-matched pilot protection criteria based on morphological edge-oriented operator is proposed. The multi-resolution morphological gradient(MMG) is used to extract edge information from the currents on both sides, and the gradient energy is defined to accentuate amplitude difference between the currents. By introducing dynamic time warping(DTW) as a quantitative criterion, the temporal variation effect of energy is deeply compared. Based on this, the gradient energy ratio is used to adaptively adjust the restraint quantity, further enhancing the reliability and sensitivity of the protection. Simulative results demonstrate that the proposed protection is not affected by frequency offset and weak feedback, exhibiting strong tolerance to fault transition resistance and noise, providing advantages over conventional differential protection. |
