Adaptive Hybrid Filtering & Damping Control for Grid-Following MMC

Oscillation events between grid-following MMC (GFL-MMC) and ac systems in the medium-/high-frequency (MF/HF) range have been widely reported over recent years. To address this issue, this paper proposes an adaptive hybrid filtering and damping (AHFD) control design method to address oscillation issues within the MF/HF range. When lowpass filters with proposed designs are placed into control loops, the negative damping region in the HF range of MMC is eliminated, effectively limiting the potential oscillations to the MF range. In addition, based on online resonance detection, an active narrowband damper is automatically configured to add and adjust positive damping to MMC at the system resonance frequency in the MF range. Both the damper gain and damping range of this narrowband damper are autonomously adjusted through an adaptive tuning unit, thereby eliminating the need for prior knowledge of the MMC’s physical characteristics (i.e., its model parameters) for damper design and tuning. Electromagnetic Transient (EMT) simulation results validate the efficacy of the proposed AHFD control method in a power system involving GFL-MMC and long overhead transmission.