Transmission of electrical power through high voltage direct current (HVDC) has attracted the attention of a number of researchers in the recent years. For economic design and optimal operation, HVDC system requires a detailed simulation model. Therefore, in this paper a detailed Matlab simulation model of line commutated converter (LCC) based monpolar HVDC system, feeding a strong AC network, with a fixed capacitor (FC) as a reactive power compensator is presented. Firefly algorithm based optimal proportional integral (PI) controller has been proposed for the rectifier and the inverter control. The transient performances of the HVDC system under various AC and DC fault conditions were studied. The results show the supremacy of the firefly algorithm based optimal PI controller over the conventional PI controller. The harmonic analysis is also carried out under steady state operation to assure the quality of power supply on the inverter AC side.

Transmission of electrical energy with High Voltage Direct Current (HVDC) has provided the electric power industry with a dominant means to transmit huge quantity of electricity over very long distances. To investigate the performance, a welldeveloped current source converter based HVDC transmission system model is projected, in which the AC system represented as damped LLR equivalent and is equipped with double tuned harmonic filter to mitigate the AC-DC harmonics and the DC system is secured with rectifier current control, inverter current control, voltage control and inverter extinction angle control. The MATLAB/Simulink based simulation results validate the step response of HVDC transmission system with various controllers. Keywords: HVDC transmission systems, double tuned filter, Rectifier DC Current Control, Inverter DC Current-Voltage - Extinction Angle Control, Step response.