一种混合双端直流输电线路的纵联保护新原理

A New Principle of Pilot Protection for Hybrid Double-ended Direct Curret Transmission Lines

为保证混合双端高压直流输电系统安全运行,分析了混合双端直流输电线路两端电流相似度。通过故障分析发现,区内故障时线路两端电流无明显线性关系,区外故障时线路两端电流呈线性关系。根据该差异,提出了一种基于相关系数的混合直流输电线路纵联保护方法。利用PSCAD搭建混合双端型高压直流输电线路仿真模型,输出直流输电线路区内和区外故障结果,并利用MATLAB对故障数据进行处理,进行了算法仿真。仿真结果验证了所提保护方法的正确性,该方法在实际应用中数据无需严格同步,能够快速可靠地实现故障判别,具有较强的实用性。

To ensure the safe operation of the hybrid double-ended HVDC transmission system,the current similarity between the two ends of the hybrid double-ended DC transmission line was analyzed.By analyzing the fault characteristics,it was found that the fault current on both-end lines when internal fault occurs is no obvious linear relationship,whereas the fault current on both-end lines when external fault occurs was in obvious linear relationship.According to the difference of current fault characteristics on the double-end lines when internal or external fault occurred,a pilot protection method for hybrid DC transmission lines based on correlation coefficient was proposed.The simulation model of LCC-MMC hybrid double-ended DC transmission line was built by PSCAD,which was used to output the fault data under different conditions.In addition,the fault data were processed with the MATLAB to carry out the algorithm simulation.The simulation results verify the correctness of the proposed protection method.In application,the proposed method does not require strict data synchronization on the two ends of input and output,and can identify the fault quickly and reliably with strong practicability.