Application HER Vague Harmonic Immunity VSC HVDC Transmission

Abstract

The objective of this paper is to discuss the effectiveness of optimized modulation based on pre calculated SHE- PWM in a two-level three-phase VSC to make the ac side immune from the fluctuations of the dc link without the use of passive components. However, since the VSC studied here does not include a closed-loop controller, strategies to compensate unbalances are not addressed in this paper. Control methods based on selective harmonic elimination pulse-width modulation (SHE-PWM) techniques offer the lowest possible number of switching transitions. This feature also results in the lowest possible level of converter switching losses. For this reason, they are very attractive techniques for the voltage-source- converter-(VSC) based high-voltage dc (HVDC) power transmission systems. The paper discusses optimized modulation patterns which offer controlled harmonic immunity between the ac and dc side. The application focuses on the conventional two-level converter when its dc-link voltage contains a mix of low-frequency harmonic components. Simulation and are presented to confirm the validity of the proposed switching patterns. Simulation is carried out using Matlab software.