Passivity-Based Sensitivity Analysis of the Inner Current Controller in Grid-Following MMC-HVdc Applications - An Overview

With a rising amount of high voltage dc projects to be overlaid to the transmission grid, a thorough understanding of the utilized equipment regarding its impact on system stability is required. To cover this need, a passivity-based stability assessment represents one promising option to investigate the damping behavior of a converter over a wide frequency range. Assuming a converter acts in a passive manner at a certain frequency, it adds damping to the overall system and contributes to mitigate un-wanted interactions e.g. related to pre-existing ac grid resonances. By means of an encompassing analysis of the converter input-admittance, relevant system sensitivities are classified in terms of their impact on passivity characteristics and frequency ranges. Moreover, feasible system delay design criteria are determined.