改进巴氏距离算法下混合级联直流输电纵联阻抗保护优化OACSTPCD

To enhance the robustness of longitudinal protection in LCC-MMC hybrid cascaded HVDC transmission systems,a longitudinal protection scheme of HVDC transmission based on longitudinal impedance and improved Bhattacharyya distance algorithm was proposed.The differ-ence of the electric capacity at the first and last ends of the protected line was quantified by com-bining the Bhattacharyya distance algorithm with longitudinal impedance protection in this scheme,and the faults inside and outside the area were determined through the quantified data.Then,the fault pole selection criterion was constructed based on the energy function to ensure the reliability of the protection.Furthermore,an improved adaptive sliding window was constructed by fractal dimension,which improved the rapidity of protection.Finally,the±800 kV LCC-MMC hybrid cascaded HVDC transmission system model of"Baijiang Project"was established on Mat-lab and PSCAD/EMTDC platforms,and the improved protection scheme was verified.Simulation results show that the proposed protection scheme can identify faults inside and outside the region quickly and reliably,correctly select fault poles and has a better resistance to transition resist-ance.