Power quality improved 18-pulse VSC based BTB HVDC system with reduced current sensors

In this paper, an improved power quality 18-pulse voltage source converter is proposed for back-to-back (BTB) high voltage direct current (HVDC) system. The proposed system is regulated using PI controller for which controller gains are selected using Ziegler Nichols approach for different transient conditions. The calculated controller gains are utilized with current regulated approach with reduced current sensor topology. This control approach ensures near unity power factor under various transient conditions such as load perturbation, voltage sag, tapped load fault at points-of-common coupling (PCC) and single-line to ground (SLG) fault at input AC mains while restricting the total harmonic distortion (THD) at AC mains current within specified limits of International standard IEEE 519. The proposed system is designed, modeled and simulated in MATLAB-Simulink environment. The simulated waveforms and power quality results are presented to validate the effectiveness of the proposed control scheme.