Improved Hausdorff Distance Based Pilot Protection for Multi-terminal HVDC system

In order to overcome the weakness of dc line protection under high impedance fault, a traveling wave similarity based pilot protection method is proposed using improved Hausdorff Distance algorithm. The issue of asynchronous data, noise and anomalies are solved with the improved Hausdorff Distance algorithm. The instantaneous frequency based wave head detection method is used to overcome the problem of delay in protection start-up. Based on this protection scheme, external fault can be distinguished from internal faults regardless of fault impedance, fault location and fault type. Moreover, the faulty pole and fault direction are recognized via ratio of transient energy at line terminals. Taking the Zhangbei high voltage dc transmission project as an example, a four-terminal ring type dc grid model is developed in PSCAD/EMTDC platform for fault simulation and the data processing is performed in MATLAB platform. Based on the theoretical analysis and simulation study, the proposed pilot protection is verified with excellent fault impedance withstanding ability and robustness against noise, abnormal data and asynchronous data.