Understanding the control of 12-pulse thyristor converters in VSC-based HVDC system with passive filters

This paper provides the operating scheme of a 12-pulse voltage source converter (VSC) used in high voltage DC (HVDC) system. The system used here for HVDC transmission schemes comprises only one terminals with a 12-pulse converter and a DC load of 1000MW. The design of the control structure for the triggering circuit and the technique of pulse generation and for the thyristor based converter is explained and analysed using MATLAB/SIMULINK. The effect of changing the firing pulse on the active and reactive power generation and the total harmonic distortion of the source current is analysed. The simulation results confirms the capability of HVDC converter operating with a wide range of firing angles. Then the performance of the VSC based HVDC system is analyzed with passive filters and the results are validated in MATLAB/SIMULINK environment.