A Novel Method to Provide Harmonics Damping to VSC-HVDC Converters

This paper presents a novel method to provide harmonic damping to voltage-source converters (VSCs) applied to high voltage direct current (HVDC) transmission systems. The proposed method consists of magnetically coupling a small damping coil with a passive filter to the valve reactors. Valve reactors are connected in series with the VSC converter valves, either on the AC or DC side. So, as the added damping coil will be mutually coupled to the valve reactors, harmonic currents in the main circuit will induce currents at the corresponding frequencies in the damping circuit. The filter connected to the damping coil is designed to damp the selected range of harmonics order. The configuration and rating of passive filter/components could be varied depending upon the frequency response required. This paper further discusses the possible arrangements of the damping coil in the valve reactors to achieve enough mutual inductance. Equations to calculate the main parameters of the proposed solution are also presented. The effectiveness of the proposed solution is demonstrated through a simple test case.