Fault analysis of voltage-source converter based multi-terminal HVDC transmission links

A new detection method for DC line faults in a voltage source Converter based three terminal high voltage DC (VSC-MTDC) systems is proposed in this paper. A three-terminal MTDC model is used to investigate fault behavior and detection of type of fault and the dc line of the model where fault has occurred using the simulation program MATLAB/SIMULINK. The fault clearing must be done very rapidly, to limit the effect of the fault on neighboring DC lines because of the rapid increase in DC current. However, before clearing the line, the fault location must be detected as soon as possible. A rapid fault location and detection algorithm is therefore needed. The detection method proposed in this paper uses wavelet decomposition to detect the type of fault and the line in which fault has occurred, based on local measurements. The energy of the fifth level detailed decomposed coefficients of the positive line dc current is calculated for each case of fault. The final objective is to form a decision tree by analyzing the Energy values of each case and implementing it to a MATLAB program which will accurately detect the type of fault and the dc line of the model where fault has occurred. Simulation results shows that the proposed method is simple and very effective in fault detection on the dc side of a VSC-MTDC system.