Fault analysis of VSC HVDC systems using fuzzy logic

The detection and clearance of faults are important for safe and optimal operation of any HVDC system. A feasible method is required for protective control for secure operation of HVDC system during faults. This paper presents the identification and classification of different faults that can occur in a VSC-HVDC system with the help of a fuzzy logic method. Simulation studies of various ac side faults in the VSC-HVDC system such as single-line to ground, double-line to ground, line-line and HVDC transmission line (DC link) faults have been carried out. Based on the study, a Fuzzy Inference Engine (FIE) has been developed for the fault identification in a VSC-HVDC system. The magnitude of dq - axis voltage and current obtained from source 1 voltage and current using the Park transformation are used as input variables in the FIE. The FIE derives a fault index which is used to identify the type of fault occurrence in the HVDC system. A set of simulation results are provided to show the effectiveness of the developed FIE for the power transfer of 110%, 80%, 50%, and 30% from source 1 to source 2 through the HVDC system.