Additional Damping Suppression Measures for Medium- and High-frequency Resonance on AC Side of MMC-HVDC Transmission System

Abstract

High-frequency resonance happened in both Luxi back-to-back high voltage direct current (HVDC) project and Chongqing-Hubei back-to-back HVDC project of China. The link delay of the modular multilevel converter based high voltage direct current (MMC-HVDC) transmission system is the key factor leading to high-frequency resonance. For the medium- and high-frequency resonance problems of the MMC-HVDC transmission system, this paper establishes a detailed impedance model from the AC side port of the MMC-HVDC transmission system based on the harmonic linearization method. And the reason why the impedance of MMC presents negative damping characteristics in the medium- and high-frequency bands is analyzed. Then, the improvement of impedance characteristics of MMC and the harmonic suppression effect by using the low-pass filter, the band-stop filter and the nonlinear filter in the voltage feedforward link are compared and analyzed. Meanwhile, three kinds of additional damping controllers are proposed, and their effects on improving the impedance characteristics of MMC are analyzed. Finally, taking the model for Guangxi side of Luxi back-to-back HVDC project as an example, the correctness of the detailed impedance model and the effectiveness of the additional damping control are verified by the electromagnetic transient simulation on PSCAD.